refrigerant report 17 - hvacr.pl · r407c as substitute for r22 r410a as substitute for r22 r417a,...

A-501-17

RefRigeRant REpoRT 17

Refrigerant Report

Contents

Essential revisions/supplements vs. 16th edition

Page

334667

88

99

111111

1315161717181920202122222323

252526272930

34

36

38

This edition supersedes all previous issues.

General aspects on refrigerant developmentsIntroductionAlternative refrigerants (overview)Environmental aspectsGlobal Warming and TEWI factor Eco-Efficiency

HCFC refrigerantsR22 as transitional refrigerant

Chlorine free (HFC) refrigerantsR134a as a substitute for R12 and R22 ■ Lubricants for HFCsAlternatives to R134aR152a – an alternative to R134a (?)“Low GWP” refrigerants HFO-1234yf and HFO-1234ze(E)

Refrigerant blendsService blends as substitutes for R502 Service blends as substitutes for R12 (R500)Chlorine free R502 and R22 alternatives (blends)R404A and R507A as substitutes for R502 and R22R407A, R407B and R407F as substitutes for R502 and R22 R422A as substitute for R502 and R22 Chlorine free R22 alternatives (blends) R407C as substitute for R22R410A as substitute for R22 R417A, R417B, R422D and R438A as substitutes for R22R427A as substitute for R22R32 as substitute for R22HFO/HFC blends as HFC alternatives

Halogen free refrigerantsNH3 (Ammonia) as alternative refrigerantR723 (NH3/DME) as an alternative to NH3

R290 (Propane) as substitute for R502 and R22Propylene (R1270) as an alternative to PropaneCO2 as an alternative refrigerant and secondary fluid

Special applications

Refrigerant properties

Application ranges ■ Lubricants

General aspects on refrigerant developments

Introduction

Stratospheric ozone depletion as well asatmospheric greenhouse effect due to re-frigerant emissions have led to drasticchanges in the refrigeration and air condi-tioning technology since the beginning ofthe 1990s.

This is especially true for the area of com-mercial refrigeration and A/C plants withtheir wide range of applications. Until a fewyears ago the main refrigerants used forthese systems were ozone depleting types,namely R12, R22 and R502; for specialapplications R114, R12B1, R13B1, R13and R503 were used.

With the exception of R22 the use of thesechemicals is not allowed any more in indus-trialised countries. In the European Union,however, there is a current early phase-outfor R22 as well which shall be realised stepby step (see page 8 for explanations). The main reason for this early ban of R22contrary to the international agreement isthe ozone depletion potential although it isonly small.Since 2010, phase-out regulations goteffective in other countries as well, in theUSA for instance.

Due to this situation enormous conse-quences result for the whole refrigerationand air conditioning trade. BITZER thereforecommitted itself to taking a leading role inthe research and development of environ-mentally benign system designs.

Although the chlorine free HFC refrigerantsR134a, R404A, R507A, R407C, R410A aswell as NH3 and various hydrocarbons havealready become established, there are stillfurther tasks to perform, especially withrespect to the global warming impact. Theaim is to significantly reduce direct emis-sions caused by refrigerant loss, and indi-rect emissions through highly efficientplants.

Therefore a close co-operation exists withscientific institutions, the refrigeration andoil industries, component manufacturers aswell as a number of innovative refrigerationand air conditioning companies.

A large number of development tasks havebeen completed; an extensive range of com-pressors and equipment is already availablefor the various alternative refrigerants.

Besides the development projects BITZERactively supports legal regulations and selfcommitments concerning the responsibleuse of refrigerants as well as measures toincrease system and components’ efficiency.

The following report deals with possibilitiesfor a short and medium term change toenvironmentally benign refrigerants in medi-um and large commercial refrigeration andA/C plants. At the same time, the experi-ence which already exists is also dealt withand the resulting consequences for planttechnology.

❄ ❄ ❄

The results of serveral studies confirm thatthe vapour compression refrigeration plantsnormally used in the commercial field arefar superior to all other processes down toa cold space temperature of around -40°C.

The selection of an alternative refrigerantand the system design receives special sig-nificance, however. Besides the request forsubstances without ozone depletion poten-tial (ODP=0) especially the energy demandof a system is seen as an essential criteriondue to its indirect contribution to the green-house effect. On top of that there is thedirect global warming potential (GWP) dueto refrigerant emission.

Therefore a calculation method has beendeveloped for the qualified evaluation of asystem which enables an analysis of thetotal influence on the greenhouse effect.

In this connection the so-called “TEWI” fac-tor (Total Equivalent Warming Impact) hasbeen introduced. Meanwhile, another, moreextensive assessment method has beendeveloped under the aspect of “Eco-Efficiency”. Hereby, both ecological(such as TEWI = Total Equivalent WarmingImpact) and economical criteria are takeninto account (see also page 7).

Therefore it is possible that in future theassessment of refrigerants with regard tothe environment could differ according tothe place of installation and drive method.

A closer look on the HFC based substitutesshows, however, that the possibilities fordirectly comparable single substance refrig-erants are limited. The situation for R12with the substitute R134a is relatively fa-vourable, as it is for R502 with the alterna-tives R404A and R507A. It is more critical for alternatives to otherCFC refrigerants and also for HCFCs, e.g.R22.

The refrigerants R32, R125 and R134a areregarded as direct substitutes from the lineof HFCs. These, however, can only be usedexceptionally as a pure substance due totheir specific characteristics. Most impor-tant criteria in this concern are flammability,thermodynamic properties and global warm-ing potential. These substances are muchmore suitable as components of blendswhere the individual characteristics can bematched to the requirements according tothe mixing proportions.

Besides HFC refrigerants, Ammonia (NH3)and hydrocarbons are considered as sub-stitutes as well. The use for commercialapplications, however, is limited by strictsafety requirements.

Carbon dioxide (CO2) becomes moreimportant as an alternative refrigerant andsecondary fluid, too. Due to its specificcharacteristics, however, there are restric-tions to a general application.

In the meantime also research and testingwas performed with so-called "Low GWP”refrigerants on basis of fluoro olefins (HFO).They can in future be applied either as apure substance or as a component inblends.

The illustrations on the next pages show astructural survey of the alternative refriger-ants and a summary of the single or blend-ed substances which are now available.After that the individual subjects are dis-cussed.

Refrigerant data, application ranges andlubricant specifications are shown on pages36 to 39.

For reasons of clarity the less or only re-gionally known products are not specified inthis issue, which is not intended to implyany inferiority.

3

Alternative refrigerants – overview

Fig. 2 Alternatives for CFC refrigerants (transitional / service refrigerants)

4

Alternative Refrigerants

SingleSubstances

e.g. R134aR125R32R143aR152a

HFC– chlorine free –

„Low GWP“Refrigerants

Blends

e.g. R404AR507AR407-SerieR410AR417A7BR422A/DR427A

SingleSubstances

HFO-1234yfHFO-1234ze

Blends

HFO-1234yf/HFO-1234ze/HFC

SingleSubstances

e.g. NH3R290R1270R600aR170R744

Blends

e.g. R600a/R290

R290/R170

R723

Halogen free

SingleSubstances

e.g. R22R123R124R142b

Blends

predominantlyR22-Based

HCFC/HFC– partly chlorinated –

Medium and LongTerm Refrigerants

Transitional/ServiceRefrigerants

6

Fig. 1 General survey of the alternative refrigerants

Previous Alternativesrefrigerants

ASHRAE Trade name Composition DetailedClassification (with blends) Information

R401A MP39 DuPont R22/152a/124 pagesR401B MP66 DuPont R22/152a/124 16, 38, 39R409A FX56 Arkema/Solvay R22/124/142b

R22 – – – pagesR402A HP80 DuPont R22/125/290 8, 15,16,R502 R402B HP81 DuPont R22/125/290 36...39R408A FX10 Arkema R22/143a/125

R114 R124 – – pagesR12B1 R142b – – 34, 36...39

R13B1R13 Alternatives see Fig. 3 “Chlorine free HCFC Refrigerants”R503

Transitional / Service refrigerants 09.12

3

31

R12(R500)

The listed service refrigerants belong to the group of HCFC or contain these substances as blend component. They are therefore subject to the same legal regulations as R22(see page 8). As a result of the continued refurbishment of older installations, the importance of these refrigerants is clearly on the decline. For some of them, production has already beendiscontinued. However, for development-historic reasons of service blends, these refrigerants will continue to be covered in this Report.

Alternative refrigerants – overview

5

HFC and HFO refrigerants 09.12

Fig. 3 Alternatives for CFC and HCFC refrigerants (chlorine free HFC and HFO refrigerants)

1

R22

R12(R500)

4

7

7

7

7

7

Previous AlternativesRefrigerants

ASHRAE Trade name Composition DetailedClassification (with blends) Informationen

R134a–R152a pages

R437A ISCEON MO49 Plus DuPont R125/134a/600/601 9...11, 16, 36...39

HFO-1234yf(ze) various pages 11, 12– Opteon XP10 Du Pont– Solstice N-13 Honeywell pages 23, 24

R404A various R143a/R125/R134aR502/R22 R507A various R143a/125 pages

R422A ISCEON MO79 DuPont R125/134a/600a 17...19, 36...39

R407A Mexichem, Arkema R32/125/134aR407C various R32/125/134aR407F Performax LT Honeywell R32/125/134aR410A various R32/125R417A ISCEON MO59 DuPont R125/134a/600 pages

R417B Solkane 22L Solvay R125/134a/600 18...23, 36...39

R422D ISCEON MO29 DuPont R125/134a/600aR427A Forane 427A Arkema R32/125/143a/134aR438A ISCEON MO99 DuPont R32/125/134a/600/601a

R114 R236fa – – pagesR12B1 R227ea – – 34, 36...39

R410A various R32/125 pagesR13B1 – ISCEON MO89 DuPont R125/218/290 35, 36...39

R13 R23 – – pagesR503 R508A KLEA 508A Mexichem R23/116 35, 36...39R508B Suva 95 DuPont R23/116

Previous AlternativesRefrigerants

ASHRAE Trade name Formula DetailedClassification Information

R12 R290/600a – C3H8/C4H10 pages(R500) R600a – C4H10 27, 36...39

R717 – NH3R22 R723 – NH3 + R-E170 pages(R502) R290 – C3H8 25...29, 36...39

R1270 – C3H6

R114R600a – C4H10

pagesR12B1 34, 36...39

R13B1 no direct alternatives available

R13R170 – C2H6

pagesR503 35, 36...39

Various R744 – CO2pages30...33, 36...39

Halogen free refrigerants 09.12

Fig. 4 Alternatives for CFC and HCFC refrigerants (halogen free refrigerants)

3

3

1

1

1

1

1

1

1

2

1 2 5

Explanation of Fig. 2 to 4 Inflammable Large deviation in refrigerating capacity and Azeotrope “Low GWP” alternativesToxic pressures to the previous refrigerant In development and see page 23

Service refrigerant with zero ODP test phase

3

4

5 71

2 6

6

6

6

6

Fig. 6 Comparison of TEWI figures (example)

TEW

I x 1

03

Refrigerant charge [m]10kg 25kg 10kg 25kg

recoverylosses

300

200

100

RL

RL

RL

RL

ENERGY

ENERGY

ENERGY

ENERGY

Comparisonwith 10% higher

energy consumption

LL

RL = Impact of

leakageLL = Impact of

lossesLL LL

LL

+10%

+10%

Global Warming andTEWI Factor

As already mentioned in the introduction amethod of calculation has been developed,with which the influence upon the globalwarming effect can be judged for the opera-tion of individual refrigeration plants (TEWI = Total Equivalent Warming Impact).

All halocarbon refrigerants, including thenon-chlorinated HFCs belong to the cat-egory of the greenhouse gases. An emis-sion of these substances contributes to theglobal warming effect. The influence is how-ever much greater in comparison to CO2which is the main greenhouse gas in theatmosphere (in addition to water vapour).Based on a time horizon of 100 years, theemission from 1 kg R134a is for exampleroughly equivalent to 1430 kg of CO2(GWP100 = 1430). It is already apparent from these facts thatthe reduction of refrigerant losses must beone of the main tasks for the future.

On the other hand, the major contributor toa refrigeration plant’s global warming effectis the (indirect) CO2 emission caused byenergy generation. Based on the high per-centage of fossil fuels used in power sta-tions the average European CO2 release isaround 0.6 kg per kWh of electrical energy.A significant greenhouse effect occurs overthe lifetime of the plant as a result of this.

TEWI = TOTAL EQUIVALENT WARMING IMPACT

TEWI = ( GWP x L x n ) + ( GWP x m [ 1- α recovery ] ) + ( n x Eannual x β )

Leakage Recovery losses

direct global warming potential

Energy consumption

indirect globalwarming potential

GWP = Global warming potentialL = Leakage rate per yearn = System operating timem = Refrigerant chargeα recovery = Recycling factorEannual = Energy consumption per yearβ = CO2-Emission per kWh

[ CO2-related acc. to IPCC IV ][ kg ][ Years ][ kg ]

[ kWh ](Energy-Mix)

ExampleMedium temperature R134a

SST -10 °CSCT +40 °Cm 10 kg // 25 kgL[10%] 1 kg // 2,5 kgCAP 13,5 kW E 5 kW x 5000 h/ab 0,6 kg CO2/kWha 0,75n 15 yearsGWP 1430 (CO2 = 1)

time horizon 100 years

As this is a high proportion of the total bal-ance it is also necessary to place an in-creased emphasis upon the use of highefficiency compressors and associatedequipment as well as optimized systemcomponents, in addition to the demand for alternative refrigerants with favourable (thermodynamic) energy consumption.

When various compressor designs arecompared, the difference of indirect CO2emission (due to the energy requirement)can have a larger influence upon the totaleffect as the refrigerant losses.

A usual formula is shown in Fig. 5, theTEWI factor can be calculated and the vari-ous areas of influence are correspondinglyseparated.

In addition to this an example in Fig. 6(medium temperature with R134a) shows

Fig. 5 Method for the calculation of TEWI figures

Environmental aspects

the influence upon the TEWI value with vari-ous refrigerant charges, leakage losses andenergy consumptions.

This example is simplified based on anoverall leak rate as a percentage of therefrigerant charge. As is known the practi-cal values vary very strongly whereby thepotential risk with individually constructedsystems and extensively branched plants is especially high.

Great effort is taken worldwide to reducegreenhouse gas emissions and legal regulations have partly been developedalready. Since 2007, the "Regulation oncertain fluorinated greenhouse gases" (No. 842/2006) – which also defines strin-gent requirements for refrigeration and air-conditioning systems – has become validfor the EU. The Regulation is currentlyunder revision.

7

Environmental aspects

Eco-Efficiency

As mentioned above, an assessment basedon the specific TEWI value takes into accountthe effects of global warming during theoperating period of a refrigeration, air-con-ditioning or heat pump installation. Hereby,however, the entire ecological and economi-cal aspects are not considered.

But apart from ecological aspects, whenevaluating technologies and making invest-ment decisions, economical aspects arehighly significant. With technical systems,the reduction of environmental impact fre-quently involves high costs, whereas lowcosts often have increased ecological con-sequences. For most companies, the in-vestment costs are decisive, whereas theyare often neglected during discussionsabout minimizing ecological problems.

For the purpose of a more objective as-sessment, studies* were presented in 2005and 2010, using the example of supermar-ket refrigeration plants to describe a con-cept for evaluating Eco-Efficiency. It isbased on the relationship between addedvalue (a product's economic value) and theresulting environmental impact.

With this evaluation approach, the entire lifecycle of a system is taken into account interms of:

❏ ecological performance in accordancewith the concept of Life Cycle Assess-ment as per ISO 14040,

❏ economic performance by means of a Life Cycle Cost Analysis.

This means that the overall environmentalimpact (including direct and indirect emis-sions), as well as the investment costs,operating and disposal costs, and capitalcosts are taken into account.

The studies also confirm that an increase ofEco-Efficiency can be achieved by investingin optimized plant equipment (minimizedoperating costs). Hereby, the choice of re-frigerant and the associated system tech-nology plays an important role.

Eco-Efficiency can be illustrated in graphicrepresentation (see example in Fig. 8). Forthis, the results of the Eco-Efficiency evalu-ation are shown on the x-axis in the systemof coordinates, whilst the results of the lifecycle cost analysis are shown on the y-axis.This representation shows clearly that asystem exhibits an increasingly better Eco-

Efficiency, the higher it lies in the top rightquadrant – and conversely, it becomes lessefficient in the bottom left sector.

The diagonals plotted into the system ofcoordinates represent lines of equal Eco-Efficiency. This means that systems or pro-cesses with different life cycle costs andenvironmental impacts can quite possiblyexhibit the same Eco-Efficiency.

Fig. 8 Example of an Eco-Efficiency evaluation

increasing Eco-E

fficiency

Co

st a

dva

ntag

e

E n v i r o n m e n t a l a d v a n t a g e

decreasing Eco-E

fficiency

Fig. 7 Concept of Eco-Efficiency

Life-Cycle-Cost Analysis

(including investment

costs, cost of operation,

capital costs)

Eco-Efficiency

considers

economical and ecological

aspects

Concept of Eco-Efficiency

Life Cycle Assessment

according to ISO 14040

* Study 2005: Compiled by Solvay Management Support GmbH and Solvay Fluor GmbH, Hannover,together with the Information Centre on HeatPumps and Refrigeration (IZW), Hannover.

Study 2010: Compiled by SKM ENVIROS, UK, commissioned by and in cooperation with EPEE(European Partnership for Energy and Environment).

Both projects were supported by an advisory groupof experts from the refrigeration industry.

8

HCFC Refrigerants

Fig. 9 R12/R22 – comparison of discharge gas temperatures ofa semi-hermetic compressor

Fig. 10 R12/R22/R502 – comparison of pressure levels

proximately 55% higher refrigerating cap-acity and pressure levels in comparison to R12. The significantly higher dischargegas temperature is also a critical factorcompared to R12 (see Fig. 9) and R502.

Similar relationships in terms of thermalload are found in the comparison with HFCrefrigerants R134a, R404A/R507A (pages 9and 17).

Suitable compressors are required forplants with R22, these have been avail-able and are proven for medium tempera-ture and air conditioning for a long time.

Refrigeration and air conditioning

Particularly critical – due to the high dis-charge gas temperature – are low tempera-ture plants especially concerning thermalstability of oil and refrigerant, with the dan-ger of acid formation and copper plating.Special measures have to be adoptedtherefore, such as two stage compression,controlled refrigerant injection, additionalcooling, monitoring of discharge gas tem-perature, limiting the suction gas superheatand particularly careful installation.

BITZER can supply a widespread range ofreciprocating, screw and scroll compres-sors for R22.

* Not allowed for new equipment in Germany andDenmark since January 1st, 2000 and in Swedenas of 1998.

Since January 1st, 2001 restrictions apply to theother member states of the EU as well. The meas-ures concerned are defined in the ODS Regulation1005/2009 of the EU commision on ozone depletingsubstances amended in 2009. This regulation alsogoverns the use of R22 for service reasons withinthe entire EU.

Since 2010, phase-out regulations in other countries, such as the USA, are valid. Information about the world wide R22 phase-outregulation can be found underwww.arap.org/docs/regs.html as well.

Disc

harg

e ga

s te

mp.

[˚C

]

Evaporation [˚C]

80

170

-40 0 10-30 -20 -10

90

160

150R12tc +60

R22tc +60tc +50

tc +50

tc +40

tc +40

100

110

120

130

140

Pres

sure

[ba

r]

Temperature [˚C]

1

25

0 60

6

15

4

10

20

-40 -20

R12

R22

R502

2

4020

R22 as transitional refrigerant

Although chlorine free substitutes likeR134a and R404A/R507A (Figs. 1 and 3)have extensively made their way as substi-tutes, in many international fields R22 is stillused in new installations and for retrofittingof existing systems.

Reasons are relatively low investment costs,especially compared with R134a systems,but also in its large application range, fa-vourable thermodynamic properties and low energy requirement. Additionally thereis world wide availability of R22 and theproven components for it, which is not yetguaranteed everywhere with the chlorinefree alternatives.

Despite of the generally favourable proper-ties R22 is already subject to various re-gional restrictions* which control the useof this refrigerant in new systems and forservice purposes due to its ozone deple-tion potential – although being low.

With regard to components and systemtechnology a number of particularities areto follow as well. Refrigerant R22 has ap-

9

Chlorine free HFC refrigerants

Fig. 11/1 R134a/R12 – comparison of performance data of a semi-hermetic compressor

Fig. 11/2 R134a/R22 – comparison of performance data of a semi-hermetic compressor

Rela

tion

R134

a to

R12

(=10

0%)

Evaporation [˚C]

80

110

0 10

90

100

COP

Q o

85

95

105

-30 -20 -10

t c 50˚C

tc 50˚C

tc 40˚C

toh 20˚C

t c 40˚C

Rela

tion

R134

a to

R22

(=10

0%)

Evapration [˚C]

50

110

10 20

70

COP

Q o

60

80

100

-20 -10 0

toh 20˚C

90

t c 40˚C

t c 50˚C

tc 50˚C

tc 40˚C

R22. There are also limitations in the appli-cation with low evaporating temperatures tobe considered. Comprehensive tests have demonstratedthat the performance of R134a exceedstheoretical predictions over a wide range ofcompressor operating conditions. Temperature levels (discharge gas, oil) areeven lower than with R12 and, therefore,substantially lower than R22 values. Thereare thus many potential applications in air-conditioning and medium temperature re-frigeration plants as well as in heat pumps.Good heat transfer characteristics in evapo-rators and condensers (unlike zeotropicblends) favour particularly an economicaluse.

Lubricants for R134a and other HFCs

The traditional mineral and synthetic oils arenot miscible (soluble) with R134a and otherHFCs described in the following and aretherefore only insufficiently transportedaround the refrigeration circuit.Immiscible oil can settle out in the heatexchangers and prevent heat transfer tosuch an extent that the plant can no longerbe operated. New lubricants were devel-

oped with the appropriate solubility andhave by now been in use for many years.These lubricants are based on Polyol Ester(POE) and Polyalkylene Glycol (PAG).

They have similar lubrication characteristicsto the traditional oils, but are more or lesshygroscopic, dependent upon the refriger-ant solubility. This demands special care during manufac-turing (including dehydrating), transport,storage and charging, to avoid chemicalreactions in the plant, such as hydrolysis.

PAG based oils are especially critical withrespect to water absorption. Moreover, theyhave a relatively low dielectric strength andfor this reason are not very suitable forsemi-hermetic and hermetic compressors.They are therefore mainly used in car A/Csystems with open compressors, wherespecific demands are placed on lubricationand optimum solubility is required becauseof the high oil circulatation rate. In order toavoid copper plating, no copper containingmaterials are used in these systems either. The rest of the refrigeration industry prefersester oils, for which extensive experienceis already available. The results are general-ly positive when the water content in the oildoes not much exceed 100 ppm.

R134a as substitute forR12 and R22

R134a was the first chlorine free (ODP = 0)HFC refrigerant that was tested compre-hensively. It is now used world-wide inmany refrigeration and air-conditioning unitswith good results. As well as being used asa pure substance R134a is also applied asa component of a variety of blends (see“Refrigerant blends”, page 13).

R134a has similar thermodynamic properties to R12:

Refrigeration capacity, energy requirement,temperature properties and pressure levelsare comparable, at least in air-conditioningand medium temperature refrigerationplants. This refrigerant can therefore beused as an alternative for most former R12applications.

For some applications R134a is even pre-ferred as a substitute for R22, an impor-tant reason being the limitations to the useof R22 in new plants and for service. How-ever, the lower volumetric refrigeration cap-acity of R134a (see Fig. 11/2) requires alarger compressor displacement than with

10

Chlorine free HFC refrigerants

Fig. 12 R134a/R12/R22 – comparison of pressure levels

Pres

sure

[ba

r]

Temperature [˚C]

1

25

0 60

6

15

4

10

20

-40 -20

R12

R22

R134a

2

4020

Supplementary BITZER informationconcerning the use of R134a(see also http://www.bitzer.de)

❏ Semi-hermetric reciprocating com-pressors KP-104 “ECOLINE Series”

❏ Technical Information KT-620“HFC Refrigerant R134a”

❏ Technical Information KT-510“Polyolester oils for reciprocatingcompressors”

❏ Special edition“A new generation of compact screwcompressors optimised for R134a”

In the meantime, compressors for factorymade A/C and cooling units are increasinglybeing charged with Polyvinyl Ether (PVE)oils. Although they are even more hygro-scopic than POE, on the other hand theyare very resistant to hydrolysis, thermallyand chemically stable, possess good lubri-cating properties and high dielectricstrength. Unlike POE they do not tend toform metal soap and thus the danger ofcapillary clogging is reduced.

Resulting design and construction criteria

Suitable compressors are required forR134a with a special oil charge, and adapt-ed system components.The normal metallic materials used in CFCplants have also been proven with esteroils; elastomers must sometimes be match-ed to the changing situation. This is espe-cially valid for flexible hoses where therequirements call for a minimum residualmoisture content and low permeability.

The plants must be dehydrated with partic-ular care and the charging or changing oflubricant must also be done carefully. In

addition relatively large driers should beprovided, which have also to be matched tothe smaller molecule size of R134a.

Meanwhile, many years of very positiveexperience with R134a and ester oilshave been accumulated. For this re-frigerant, BITZER offers an unequalledwide range of reciprocating, screw, andscroll compressors.

Converting existing R12 plants

At the beginning this subject had been dis-cussed very controversially, several conver-sion methods were recommended and ap-plied. Today there is a general agreementon technically and economically matchingsolutions.Here, the characteristics of ester oils arevery favourable. Under certain conditionsthey can be used with CFC refrigerants,they can be mixed with mineral oils and tol-erate a proportion of chlorine up to a fewhundred ppm in an R134a system.

The remaining moisture content has, how-ever, an enormous influence. The essentialrequirement therefore exists for very thor-

ough evacuation (removal of remainingchlorine and dehydration) and the installa-tion of generously dimensioned driers.Doubtful experience has been found, withsystems where the chemical stability wasalready insufficient with R12 operation e.g.with bad maintenance, small drier capacity,high thermal loading. The increased deposi-tion of oil decomposition products contain-ing chlorine often occurs here. These prod-ucts are released by the working of thehighly polarized mixture of ester oil andR134a and find their way into the compres-sor and regulating devices. Conversionshould therefore be limited to systemswhich are in a good condition.

Restrictions for R134a in mobile air-conditioning (MAC) systems

In future, a new EU Directive on "Emissionsfrom MAC systems” will ban the use ofR134a in new systems. Several alternativetechnologies are already being developed.See the pertaining explanations on pages11, 12 and 33.

11

Chlorine free (HFC) refrigerants

Alternatives to R134a

For mobile air-conditioning systems (MAC)with open drive compressors and hoseconnections in the refrigerant circuit, therisk of leakages is considerably higher thanwith stationary systems. With a view to re-ducing direct emissions in this applicationarea, an EU Directive (2006/40/EC) has therefore been passed. Within the scope ofthe Directive, and starting 2011, type appro-vals for new vehicles will only be granted ifthey use refrigerants with a global warmingpotential (GWP) of less than 150. Conse-quently, this excludes R134a which hasbeen used so far in these systems (GWP = 1430).

Meanwhile, alternative refrigerants and newtechnologies were developed and tested.This also involved a closer examination ofthe use of R152a.

For quite some time the automotive indus-try has agreed on so-called “Low GWP”refrigerants. The latter is dealt with as fol-lows.

The CO2 technology which was preferredfor this type of application for a long timehas not yet been introduced for differentreasons (see pages 12 and 33).

R152a – an alternative to R134a (?)

Compared to R134a, R152a is very similarwith regard to volumetric cooling capacity(approx. -5%), pressure levels (approx. -10%) and energy efficiency. Mass flow,vapour density and thus also the pressuredrop are even more favourable (approx. -40%).

R152a has been used for many years as acomponent in blends but not as a singlesubstance refrigerant till now. Especiallyadvantageous is the very low global warm-ing potential (GWP = 124).

R152a is inflammable – due to its low fluorine content – and classified in safetygroup A2. As a result, increased safetyrequirements demand individual designsolutions and safety measures along withthe corresponding risk analysis.

For this reason, the use of R152a in MACsystems is rather unlikely.

“Low GWP” refrigerants HFO-1234yf and 1234ze(E)

The ban on the use of R134a in mobile air-conditioning systems within the EU has trig-gered a series of research projects. Apartfrom the CO2 technology (page 33), newrefrigerants with very low GWP values andsimilar thermodynamic properties as R134ahave been developed.

In early 2006, two refrigerant mixtures wereintroduced under the names “Blend H”(Honeywell) and “DP-1” (DuPont). INEOSFluor followed with another version underthe trade name AC-1. In the broadestsense, all of these refrigerants were blendsof various fluorinated molecules.

During the development and test phase itbecame obvious that not all acceptance cri-teria could be met, and thus further exami-nations with these blends were discontinued.Consequently, DuPont* and Honeywell*bundled their research and developmentactivities in a joint venture which focused on2,3,3,3-tetrafluoropropene (CF3CF = CH2).This refrigerant with the name HFO-1234yfbelongs to the group of fluoro olefins withcarbon-carbon double chemical bond.

The global warming potential is extremelylow (GWP100 = 4) due to rapid decomposi-tion in the atmosphere. This raises certainconcerns regarding the long-term stabilityin refrigeration circuits under real condi-tions. However, extensive testing has dem-onstrated the required stability for mobileair-conditioning systems.

HFO-1234yf is mildly flammable as meas-ured by ASTM 681, but requires significant-ly more ignition energy than R152a, forinstance. Due to its low burning velocityand the high ignition force, it received aclassification of the new safety group “A2L”according to ISO 817. A comprehensiveseries of tests have proven that the mildflammability does not provide an extra riskfor the mobile air-conditioning application.

12

Chlorine free (HFC) refrigerants

From the group of fluoro olefins, anothersubstance under the name HFO-1234ze(E)is available, which until now has been usedpredominantly as blowing agent for polyure-thane foam and propellant. HFO-1234ze(E)differs from HFO-1234yf by having a differ-ent molecular structure. Its thermodynamicproperties also provide favourable condi-tions for the use as refrigerant. Its globalwarming potential is also very low (GWP100 = 6).

The volumetric refrigeration capacity andpressure levels are about 75% comparedto HFO-1234yf. This makes HFO-1234ze(E)also a potential candidate for extra hightemperature systems. For further informa-tion, see page 34, “Special applications”.

With a view to the relatively simple conver-sion of mobile air-conditioning systems,this technology prevailed over the compet-ing CO2 systems.

The use of HFO-1234yf in other mobile air-conditioning applications is also being con-sidered, as well as in stationary A/C andheat pump systems. However, this musttake into account the charge limitations forthe A2(L) refrigerants (e.g. EN378), whichwill restrict their use accordingly. Additionalconcerns are those regarding the long-term stability in refrigeration circuits, giventhe usually very long life cycles of suchsystems.

For applications requiring the use of refrig-erants of safety group A1 (neither flam-mable nor toxic), R134a alternatives of low-er GWP based on HFO/HFC blends havealready been developed. They have beentested for some time in real systems. Formore information on these systems, seepage 23, “HFO/HFC blends”.

Toxicity investigations have shown verypositive results, as well as compatibilitytests of the plastic and elastomer materialsand lubricants used in the refrigeration cir-cuit.

Operating experiences gained from labora-tory and field trials to date allow a positiveassessment, particularly with regard to per-formance and efficiency behaviour. For theusual range of mobile air-conditioning oper-ation, cooling capacity and coefficient ofperformance (COP) are within a range of5% compared with that of R134a. There-fore, it is expected that simple systemmodifications will provide the same per-formance and efficiency as with R134a.

The critical temperature and pressure levelsare also similar, while the vapour densitiesand mass flows are approximately 20%higher. The discharge gas temperature withthis application is up to 10 K lower.

13

Refrigerant blends

Refrigerant blends

Refrigerant blends have been developed forexisting as well as for new plants with pro-perties making them comparable alternativesto the previously used substances.

Although the situation is now less complex,the range on offer is nevertheless still veryextensive.

It is necessary to distinguish between threecategories:

1. Transitional or service blendsMost of these blends contain HCFC R22as the main constituent. They are primarilyintended as service refrigerants forolder plants with view on the use ban ofR12, R502 and other CFCs. Corresponding products are offered byvarious manufacturers, the practical ex-perience covering the necessary steps of conversion procedure are available.

However, the same legal requirementsapply for the use and phase-out regula-tions of these blends as for R22 (seepage 8).

2. HFC blends These are substitutes for the refrigerantsR502, R22, R13B1 and R503. Above all,R404A, R507A, R407C and R410A, arealready being used to a great extent. One group of these HFC blends also con-tains hydrocarbon additives. The latterexhibit an improved solubility with lubri-cants, and under certain conditions theyallow the use of conventional oils. In manycases, this opens up possibilities for theconversion of existing (H)CFC plants tochlorine-free refrigerants (ODP = 0) with-out the need for an oil change.

3. HFO/HFC blends as successor generation of HFC refriger-ants. It concerns blends of new “LowGWP” refrigerants (e.g. R1234yf) withHFCs. The fundamental target is an addi-tional decrease of the global warmingpotential (GWP) as compared to estab-lished halogenated substances (see page 23).

Two and three component blends alreadyhave a long history in the refrigeration trade.A difference is made between the so called“azeotropes” (e.g. R502, R507A) with ther-modynamic properties similar to single sub-stance refrigerants, and “zeotropes” with“gliding” phase changes (see also next sec-tion). The development of “zeotropes” wasmainly concentrated on special applicationsin low temperature and heat pump systems.Actual system construction remained, how-ever, the exception.

A somewhat more common earlier practicewas the mixing of R12 to R22 in order toimprove the oil’s return flow and to reducethe discharge gas temperature with higherpressure ratios. It was also usual to add R22to R12 systems for improved performance,or to add hydrocarbons in the extra lowtemperature range for a better oil transport.

This possibility of specific “formulation”of certain characteristics was indeed themain starting point for the development of a new generation of blends.

As already mentioned earlier, no directlycomparable substitute for R502 and R22 isavailable from the chlorine free single sub-stance series of alternative refrigerants. Asimilar situation can be stated for R13B1and R503.

If flammability is unacceptable, and toxico-logical certainty is required and in addition,application range, COP, pressure and tem-perature conditions are to be comparable,the only remaining substitutes for manyapplications are blends.

Substitutes for R502 had first priority, as it was used in larger quantities and isalready effected by the phase-out regula-tions in many countries. The following discussion therefore, deals first with theestablished alternatives for this refrigerantand the results from the extensive applica-tions in real systems.

Another focal point are alternatives forR22.

BITZER has already accumulated ex-tensive experience with the new gener-ation of blends. Laboratory and fieldtesting was commenced at an earlystage so that basic information was

obtained for the optimizing of the mix-ing proportions and for testing suitablelubricants. Based on this data, a largesupermarket plant – with 4 BITZERsemi-hermetics in parallel – couldalready be commissioned in 1991.The use of these blends in the mostvaried systems has been state-of-the-art for many years – generally withgood experiences.

General characteristics of zeotropicblends

As opposed to azeotropic blends (e.g.R502, R507A), which behave as single sub-stance refrigerants with regard to evapora-tion and condensing processes, the phasechange with zeotropic fluids occurs in a“gliding” form over a certain range of tem-perature.

This “temperature glide” can be more orless pronounced, it is mainly dependentupon the boiling points and the percentageproportions of the individual components.Certain supplementary definitions are alsobeing used, depending on the effective val-ues, such as “near-azeotrope” or “semi-azeotrope” for less than 1 K glide.

This means in practice already a smallincrease in temperature in the evaporationphase and a reduction during condensing.In other words, based on a certain pressurethe resulting saturation temperatures differin the liquid and vapour phases (Fig. 13).

To enable a comparison with single sub-stance refrigerants, the evaporating andcondensing temperatures have been oftendefined as mean values. As a consequencethe measured subcooling and superheatingconditions (based on mean values) areunreal. The effective result – related to dewand bubble temperature – is less in eachcase.

These factors are very important whenassessing the minimum superheat at thecompressor inlet (usually 5 to 7 K) and thequality of the refrigerant after the liquid receiver.

With regard to a uniform and easily com-prehensible definition of the rated compres-sor capacity, the revised standardsEN12900 and ARI540 are applied. Evapo-

14

Fig. 13 Evaporating and condensing behavior of zeotropic blends Fig. 14 Pressure level of R404A in comparison to R502

Pres

sure

Enthalpy

Temperature glideMean condensing temperatureMean evaporating temperature

Δtgtcmtom

CC1

DD1

A A1

B B1

Isotherms

Δtg

Δtgtcm

tom

Bubble

Line

Dew

line

Pres

sure

[ba

r]

Temperature [˚C]

-40 40 60-20 0 20

25

15

1

20

10

2

4

6

R404A

R502

Refrigerant blends

rating and condensing temperatures refer tosaturated conditions (dew points).

❏ Evaporating temperature according topoint A (Fig. 13).

❏ Condensing temperature according topoint B (Fig. 13).

Also in this case the assessment of theeffective superheating and subcooling tem-peratures will be simplified.

It must however be considered that theactual refrigeration capacity of the systemcan be higher than the rated compressorcapacity. This is partly due to an effectivelylower temperature at the evaporator inlet.

A further characteristic of zeotropic refriger-ants is the potential concentration shiftwhen leakage occurs. Refrigerant loss inthe pure gas and liquid phases is mainlynon-critical. Leaks in the phase changeareas, e.g. after the expansion valve, withinthe evaporator and condenser/receiver areconsidered more significant.

It is therefore recommended that solderedor welded joints should be used in thesesections.

Extended investigations have in the mean-time shown that the effect of leakage leadsto less serious changes in concentrationthan was initially thought. It is in any casecertain that the following substances ofsafety group A1 (see page 36) which aredealt with here cannot develop any flam-mable mixtures, either inside or outside thecircuit. Essentially similar operating condi-tions and temperatures as before can onlybe obtained by supplementary chargingwith the original refrigerant in the case of asmall temperature glide.

Further conditions/recommendations con-cerning the practical handling of blendsmust also be considered:

❏ The plant always has to be charged withliquid refrigerant. When vapour is takenfrom the charging cylinder shifts in con-centrations may occur.

❏ Since all blends contain at least oneflammable component, the entry of air into the system must be avoided. A critical shift of the ignition point can occur under high pressure and evacu-ating when a high proportion of air is present.

❏ The use of blends with a significant tem-perature glide is not recommended forplants with flooded evaporators. A largeconcentration shift is to be expected inthis type of evaporator, and as a resultalso in the circulating refrigerant massflow.

15

Service blends

Service blends with thebasic component R22* as substitutes for R502

As a result of the continued refurbishmentof older installations, the importance ofthese refrigerants is clearly on the decline.For some of them, production has alreadybeen discontinued. However, for develop-ment-historic reasons of service blends,these refrigerants will continue to be cov-ered in this Report.

These refrigerants belong to the group of“Service blends” and are offered under thedesignations R402A/R402B* (HP80/ HP81– DuPont), R403A/R403B* (formerlyISCEON 69S/69L) and R408A* (“Forane”FX10 – Arkema).

The basic component is in each case R22,the high discharge gas temperature ofwhich is significantly reduced by the addi-tion of chlorine free substances with lowisentropic compression exponent (e.g.R125, R143a, R218). A characteristic fea-ture of these additives is an extraordinarilyhigh mass flow, which enables the mixtureto achieve a great similarity to R502.

R290 (Propane) is added as the third com-ponent to R402A/B and R403A/B to improve

miscibility with traditional lubricants ashydrocarbons have especially good solu-bility characteristics.

For these blends two variations are offeredin each case. When optimizing the blendvariaions with regard to identical refrigera-tion capacity as for R502 the laboratorymeasurements showed a significantly in-creased discharge gas temperature (Fig.15), which above all, with higher suctiongas superheat (e.g. supermarket use) leadsto limitations in the application range.

On the other hand a higher proportion ofR125 or R218, which has the effect of re-ducing the discharge gas temperature tothe level of R502, results in somewhat high-er cooling capacity (Fig. 16).

With regard to material compatibility theblends can be judged similarly to (H)CFCrefrigerants. The use of conventional refrig-eration oil (preferably semi or full synthetic) isalso possible due to the R22 and R290proportions.

Apart from the positive aspects there arealso some disadvantages. These sub-stances can also only be seen as alterna-tives for a limited time. The R22 proportionhas (although low) an ozone depletion poten-tial. The additional components R125,

R143a and R218 still have a comparativelyhigh global warming potential.

Resulting design criteria/Converting existing R502 plants

The compressor and the components whichare matched to R502 can remain in the sys-tem in most cases. The limitations in theapplication range must however be con-sidered: Higher discharge gas temperatureas for R502 with R402B**, R403A** andR408A** or higher pressure levels withR402A** and R403B**.

Due to the good solubility characteristics ofR22 and R290 an increased danger exists,that after conversion of the plant, possibledeposits of oil decomposition productscontaining chlorine may be dissolved andfind their way into the compressor and reg-ulating devices. Systems where the chemi-cal stability was already insufficient withR502 operation (bad maintenance, low driercapacity, high thermal loading) are particu-larly at risk.

* When using blends containing R22 legal regu-lations are to be observed, see also page 8.

** Classification according to ASHRAE nomenclature.

Fig. 15 Effect of the mixture variation upon the discharge gas temperature (example: R22/R218/R290)

Fig. 16 Comparison of the performance data of a semi-hermetic compressor

Disc

harg

e g

as te

mp.

[˚C

]

Content of R218 [%]

170

0 6020 40

165

150

115

120

130

140

R403

A

R403

B

R502

totctoh

R22

-35°C40°C20°C

145

155

135

125

160

Com

paris

on o

f per

form

ance

[%] 110

105

100

95

90

85

to

tc

toh

-35°C

40°C

20°C

115

Qo COP

R50

2

R40

2A (H

P80)

R40

2B (H

P81)

R40

3B (6

9L)

R40

3A (6

9S)

R40

8A (F

X10)

R40

3B (6

9L)

R40

3A (6

9S)

R40

8A (F

X10)

R50

2

R40

2A (H

P80)

R40

2B (H

P81)

16

Before conversion generously dimensionedsuction gas filters and liquid line driersshould therefore be fitted for cleaning andafter approximately 100 hours operation anoil change should be made; further checksare recommended.

The operating conditions with R502 (in-cluding discharge gas temperature andsuction gas superheat) should be noted sothat a comparison can be made with thevalues after conversion. Depending uponthe results regulating devices should possi-bly be reset and other additional measuresshould be taken as required.

Supplementary BITZER informationconcerning the use of retrofit blends(see also http://www.bitzer.de)

❏ Technical Information KT-650 “Retrofitting of R12 and R502refrigerating systems to alterna-tive refrigerants”

Service blends as substitutes for R12 (R500)

Although as experience already shows,R134a is also well suited for the conversionof existing R12 plants, the general use forsuch a “retrofit” procedure is not alwayspossible. Not all compressors which havepreviously been installed are designed forthe application with R134a. In addition aconversion to R134a requires the possibilityto make an oil change, which is for exam-ple not the case with most hermetic typecompressors.

Economical considerations also arise, espe-cially with older plants where the effort inconverting to R134a is relatively high. Thechemical stability of such plants is alsooften insufficient and therefore the chanceof success is very questionable.Therefore “Service blends” are also avail-able for such plants as an alternative toR134a and are offered under the designa-tions R401A/R401B (MP39/MP66 – DuPont),R409A (“Forane” FX56 – Arkema, Solvay).

Service blends

The main components are the HCFC re-frigerants R22, R124 and/or R142b. Either HFC R152a or R600a (Isobutane) is used as the third component. Operationwith traditional lubricants (preferably semior full synthetic) is also possible due to themajor proportion of HCFC.

A further service blend was offered underthe designation R413A (ISCEON49 –DuPont), but replaced by R437A by the endof 2008. However, for development-historicreasons of service blends, R413A will con-tinue to be covered in this report. The con-stituents of R413A consist of the chlorinefree substances R134a, R218, and R600a.In spite of the high R134a content the useof conventional lubricants is possible be-cause of the relatively low polarity of R218and the favourable solubility of R600a.

R437A is a blend of R125, R134a, R600and R601 with similar performance andproperties as R413A. This refrigerant alsohas zero ODP.

However, due to the limited miscibility ofR413A and R437A with mineral and alkyl-benzene oils, oil migration may result insystems with a high oil circulation rateand/or a large liquid volume in the receiver –for example if no oil separator is installed.

If insufficient oil return to the compressor isobserved, the refrigerant manufacturer rec-ommends replacing part of the original oilcharge with ester oil. But from the compres-sor manufacturer's view, such a measurerequires a very careful examination of thelubrication conditions. For example, if in-creased foam formation in the compressorcrankcase is observed, a complete changeto ester oil will be necessary. Moreover,under the influence of the highly polarizedblend of ester oil and HFC, the admixture ofor conversion to ester oil leads to increaseddissolving of decomposition products anddirt in the pipework. Therefore, generouslydimensioned suction clean-up filters must be provided. For further details, see the refrigerant manu-facturer's “Guidelines”.

Resulting design criteria/Converting existing R12 plants

Compressors and components can mostlyremain in the system. However, when us-ing R413A and R437A the suitability mustbe checked against HFC refrigerants. Theactual “retro-fit” measures are mainly re-stricted to changing the refrigerant (possiblyoil) and a careful check of the superheatsetting of the expansion valve. A significant temperature glide is presentdue to the relatively large differences in theboiling points of the individual substances(Fig. 34, page 37), which demands anexact knowledge of the saturation condi-tions (can be found from vapour tables ofrefrigerant manufacturer) in order to assessthe effective suction gas superheat.

In addition the application range must alsobe observed.Different refrigerant types are required forhigh and low evaporating temperatures ordistinct capacity differences must be con-sidered (data and application ranges seepages 36 to 39). This is due to the steepercapacity characteristic, compared to R12.

Due to the partially high proportion of R22especially with the low temperature blends,the discharge gas temperature with somerefrigerants is significantly higher than withR12. The application limits of the compres-sor should therefore be checked beforeconverting.The remaining application criteria are simi-lar to those for the substitute substancesfor R502 which have already been men-tioned.

* By using R22 containing blends the legal require-ments are to be followed, see also page 8.

Supplementary BITZER informationconcerning the use of retrofit blends(see also http://www.bitzer.de)

❏ Technical Information KT-650“Retrofitting of R12 and R502 refrigerating systems to alternativerefrigerants”

17

Chlorine free R502 and R22 alternatives (blends)

R404A and R507A assubstitutes for R502and R22

These blends are chlorine free substitutes(ODP = 0) for R502 as well as for R22 inmedium and low temperature ranges.

A composition which was already launchedat the beginning of ‘92 is known under thetrade name „Suva“ HP62 (DuPont). Longterm use has shown good results. Furtherblends were traded as „Forane“ FX70(Arkema) and “Genetron” AZ50 (Allied Sig-nal/Honeywell) or “Solkane” 507 (Solvay). In the mean time HP62 and FX70 havebeen listed in the ASHRAE nomenclature as R404A and AZ50 as R507A.

The basic components belong to the HFCgroup, where R143a belongs to the flam-mable category. Due to the combinationwith a relatively high proportion of R125 theflammability is effectively counteracted andalso in the case of leakage.

A feature of all three ingredients is the verylow isentropic compression exponent whichresults in a similar, with even a tendency tobe lower, discharge gas temperature toR502 (Fig. 17). The efficient application of

Fig. 17 R404A/R502 – comparison of discharge gas temperatures of a semi-hermetic compressor

Fig. 18 Comparison of performance data of a semi-hermetic compressor

Disc

harg

e ga

s te

mp.

of R

404A

– re

lativ

e di

ffere

nce

to R

502

[K]

Evaporating [˚C]

-20-40 -30 -20 -10

tc 55°C

tc 40°C

toh 20°C

-10

0

+10

Com

paris

on o

f per

form

ance

[%]

100

95

90

80

to

tc

toh

-35°C

40°C

20°C

105

Qo

85

COP

R50

2

R40

4A

R50

7A

R50

2

R40

4A

R50

7A

single stage compressors with low evapo-rating temperatures is therefore guaranteed.

Due to the similar boiling points for R143aand R125, with a relatively low proportionof R134a, the temperature glide with theternary blend R404A within the relevantapplication range is less than one Kelvin.The characteristics within the heat ex-changers are not therefore very different aswith azeotropes. The results obtained so farfrom heat transfer measurements showfavourable conditions.

R507A is a binary substance combinationwhich even gives an azeotropic characteris-tic over a relatively wide range. The condi-tions therefore tend to be even better.

The performance found in laboratory tests(Fig. 18) gives hardly any difference be-tween the various substances and show alarge amount of agreement with R502. Thisjustifies the good market penetration ofthese substitutes.

Questions concerning material compatibilityare manageable; experience with otherHFCs justifies a positive assessment. POEoils can be used as lubricants; the suitabilityof various alternatives is being investigatedas well (see pages 9/10).

The relatively high global warming potential(GWP100 = 3922…3985) which is mainlydetermined by the R143a and R125 issomething of a hitch. It is however improvedcompared to R502 and which with regardalso to the favourable energy requirementleads to a reduction of the TEWI value.Other improvements are possible in thisrespect due to further developed systemcontrol including for example the controlledlowering of the condensing temperaturewith low ambient temperatures.

Nevertheless there are restrictions to be ex-pected in future with the application ofR404A and R507A, namely looking at rela-tively high GWP values with resulting highshare of direct emissions in the TEWIassessment. Equally these emissions con-tribute to an unfavorable "Carbon Foot-print".

Alternatives with lower GWP are the HFCblends dealt with in the following (frompage 18) as well as HFO/HFC blends beingdeveloped and evaluated (from page 23).

Halogen free refrigerants or cascade systems using different refrigerants are also an option for specific applications(from page 25).

18

R407A/R407B/R407F as substitutes for R502 and R22

Alternatively to the earlier described substi-tutes additional mixture versions have beendeveloped based on R32 which is chlorinefree (ODP = 0) and flammable like R143a.

The refrigerant R32 is also of the HFC typeand primarily seen as a candidate for R22alternatives (page 20). However, due to ex-tent of blend variations comparable thermo-dynamic characteristics to R502 and R404A/R507A can also be obtained.

Such kind of refrigerants were at first in themarket under the trade name KLEA 60/61(ICI) and are listed as R407A/R407B* in theASHRAE nomenclature.

Honeywell has developed another blendwith the trade name Performax LT (R407Faccording to ASHRAE nomenclature) andintroduced it into the market. The R32share is ten percentage points higher thanthe one in R407A while the R125 propor-tion is lower accordingly.

The necessary conditions, however, foralternatives containing R32 are not quite asfavourable compared to the R143a basedsubstitutes as dealt with earlier. The boiling

point of R32 is very low at -52°C, in addi-tion the isentropic compression exponent iseven higher than with R22. To match thecharacteristics at the level of R404A andR507A therefore requires relatively high pro-portions of R125 and R134a. The flamma-bility of the R32 is thus effectively sup-pressed, at the same time the large differ-ences in the boiling points with a high pro-portion of R134a leads to a larger tempera-ture glide.

The main advantage of R32 is the extra-ordinarily low global warming potential(GWP100 = 675) so that even in combina-tion with R125 and R134a it is significantlylower than with the R143a based alterna-tives mentioned above (e.g. R407A,GWP100 = 2107).

Measurements made with R32 containingblends do show certain capacity reductionscompared to R404A and R507A, with lowevaporating temperatures, the COP howev-er shows less deviation (Fig. 20). The TEWIvalues are relatively low, together with theadvantageous global warming potential.

Whether these favourable conditions areconfirmed in real applications is subject to the system design.

Resulting design criteria

The system technology can be based onthe experience with R502 over a wide area.On the thermodynamic side, a heat ex-changer between the suction and liquid lineis recommended as this will improve therefrigeration capacity and COP.

The availability of the refrigerants is guaran-teed.

BITZER offers the whole program ofreciprocating, scroll and screw com-pressors for these blends.

Converting existing (H)CFC plants

Experience gained in investigative programsshows that qualified conversions are pos-sible. However, major expenditure may benecessary depending on the system de-sign.

Supplementary BITZER informationconcerning the use of HFC blends(see also http://www.bitzer.de)

❏ Technical Information KT-651 "Retro-fitting of R22 systems to alternativerefrigerants"

❏ Technical Information KT-510 “Polyolester oils for reciprocatingcompressors”


Fig. 19 R407A, R407F/R404A – comparison of discharge gas temperature of a semi-hermetic compressor

Fig. 20 Comparison of performance data of a semi-hermetic compressor

Disc

harg

e ga

s te

mp.

of R

407A

/F –

rela

tive

diffe

renc

e to

R40

4A [K

]

Evaporation [˚C]

-40 -30 -20 00

10

R407A

40°Ctc

R407F

20

30

40

50

-10

Com

paris

on o

f per

form

ance

[%]

Qo

100

95

90

75

totctoh

-10°C

45°C

20°C

105

80

COP

R40

4A

R40

7A

R40

7F

R40

4

R40

7A

R40

7F

19


An important factor is the significant tem-perature glide which can have a negativeinfluence upon the capacity/temperaturedifference of the evaporator and condenser.With regard to the material compatibility,R32 blends can be assessed similarly toR404A and R507A; the same applies to thelubricants.

Despite the relatively high proportion ofR125 and R134a in the R32 blends the dis-charge gas temperature is higher than withthe R143a based alternatives. This is inparticular valid for R407F. As a result cer-tain limitations occur in the applicationrange as well as the requirement for addi-tional cooling of compressors when operat-ing at high pressure ratios.

From this point of view, but also with re-gard to the efficiency an intelligent controlis recommended for controlled floating ofthe condensing pressure with low ambienttemperatures.

2-stage compressors can be applied veryefficiently where especially large lift condi-tions are found. An important advantagethereby is the use of a liquid subcooler.


The experience with R404A/R507A andR22 can be used for the plant technologyin many respects, considering the tempera-ture glide as well as the difference in the thermodynamic properties. This is especial-ly the case for designing and constructingheat exchangers and expansion valves.The refrigerants are available. Occassional-ly, individual selection will be required forthe necessary components.

* Meanwhile, R407B is no longer available in the mar-ket. Due to the historical development of HFCblends this refrigerant will, however, still be consid-ered in this Report.


Practical experiences show that qualifiedconversions are possible. Compared to R22the volumetric refrigeration capacity is near-ly similar while the refrigerant mass flow isonly slightly higher. These are relativelyfavourable conditions for the conversion ofmedium and low temperature R22 systems.

The main components can remain in thesystem provided that they are compatible

R422A as substitute for R502 and R22

Amongst other aims, R422A (ISCEONMO79 – DuPont) was developed in order toobtain a chlorine-free refrigerant (ODP = 0)for the simple conversion of existing mediumand low temperature refrigeration systemsusing R502 and R22.

For this, it was necessary to formulate arefrigerant with comparable performanceand energy efficiency to that of R404A,R507A, and R22, which also permits theuse of conventional lubricants.

This pertains to a zeotropic blend of thebasic components R125 and R134a with asmall addition of R600a. Due to its relativelyhigh R134a percentage, the temperatureglide (Fig. 34) lies higher than for R404A,but lower than other refrigerants with thesame component blends – such as R417Aand R422D (see page 22).

The adiabatic exponent, compared toR404A and R507A, is smaller and thereforethe discharge gas and oil temperatures ofthe compressor, too. Under extreme lowtemperature conditions this can be advan-tageous. In cases of low pressure ratio andsuction gas superheat this can be negativedue to increased refrigerant solution if esteroil is used.

The material compatibility is comparable tothe blends mentioned previously, the sameapplies to the lubricants, as well. On ac-count of the good solubility of R600a, con-ventional lubricants can also be used underfavourable circumstances.

In particular, advantages result during theconversion of existing R502 and R22 sys-tems as mentioned above. However, forplants with high oil circulation rates and/orlarge liquid charge in the receiver, it is possible for oil migration to occur – for example if no oil separator is installed.

If insufficient oil return to the compressor isobserved, the refrigerant manufacturer rec-ommends replacing part of the original oilcharge with ester oil. But from the com-pressor manufacturer's view, such a meas-ure requires a very careful examination ofthe lubrication conditions. For example, ifincreased foam formation in the compres-sor crankcase is observed, a completechange to ester oil* will be necessary. Un-der the influence of the highly polarizedblend of ester oil and HFC, the admixture ofor conversion to ester oil leads to increaseddissolving of decomposition products anddirt in the pipework. Therefore, generouslydimensioned suction clean-up filters mustbe provided. For further details, see the refrigerant man-ufacturer's “Guidelines”.

From a thermodynamic point of view a heatexchanger between suction and liquid lineis recommended, thereby improving thecooling capacity and coefficient of perform-ance. Besides this the resulting increase inoperating temperatures leads to more fa-vourable lubricating conditions (lower solu-bility).

* General proposal for screw compressors and liquidchillers when used with DX evaporators with internal-ly structured heat exchanger pipes. Furthermore, anindividual check regarding possible additional meas-ures will be necessary.

BITZER compressors are suitable forR422A. An individual selection is pos-sible upon demand.

with HFC refrigerants and ester oils. How-ever, special requirements placed on theheat exchanger with regard to the signifi-cant temperature glide must be considerd.A conversion to ester oil is also necessary,which leads to increased dissolving ofdecomposition products and dirt in thepipework. Therefore, generously dimen-sioned suction clean-up filters must beprovided.

BITZER offers a comprehensive programof semi-hermetic reciprocating compres-sors for R407A und R407F.

Supplementary BITZER informationconcerning the use of HFC blends(see also http://www.bitzer.de)

❏ Technical Information KT-651“Retrofitting of R22 systems to alternative refrigerants”

20

Fig. 21 R407C/R22 – comparison of performance data of a semi-hermetic compressor

Fig. 22 R407C/R22 – comparison of pressure levels

Rela

tion

R407

C to

R22

(=10

0%)

Evaporation [˚C]

80

110

10 20

90

100

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95

105

-20 -10 0

COP

Q o

tc 40˚C

tc 50˚C

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toh 20˚C

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[ba

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-40 40 60-20 0 20

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1

20

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R22

R407C

The high temperature glide is a disadvan-tage for usual applications which requiresappropriate system design and can have anegative influence on the efficiency of theheat exchangers (see explanations onpages 13/14).

Due to the properties mentioned, R407C ispreferably an R22 substitute for air-condi-tioning systems and (within certain limita-tions) also for medium temperature refriger-ation. In low temperature refrigeration, be-cause of the high proportion of R134a, asignificant drop in cooling capacity andCOP is to be expected. There is also thedanger of an increased R134a concentra-tion in the blend in evaporators, with con-sequential reduction in performance andmalfunctioning of the expansion valve (e.g.insufficient suction gas superheat).

Material compatibility can be assessed assimilar to that of the blends discussed pre-viously; the same applies to the lubricants.

* Previous trade names are not used any more.

R407C as substitutefor R22

Blends of the HFC refrigerants R32, R125and R134a are seen as the favourite can-didates for shortterm substitution for R22 –their performance and efficiency are verysimilar (Fig. 21). At first two blends of thesame composition have been introducedunder the trade names AC9000* (DuPont)and KLEA66* (ICI). They are listed in theASHRAE nomenclature as R407C. In themeantime there are also further blend vari-eties (e.g. R407A/R407F) with somewhatdiffering compositions, whose propertieshave been optimized for particular applica-tions (see page 18).

Unlike the R502 substitutes with identicalblend components (see pages 18/19), theR22 substitutes under consideration con-tain higher proportions of R32 and R134a. A good correspondence with the propertiesof R22 in terms of pressure levels, massflow, vapour density and volumetric refriger-ation capacity is thus achieved. In addition,the global warming potential is relatively low(GWP100 = 1774), which is a good presup-position for favourable TEWI values.

Chlorine free R22 alternatives (blends)

Chlorine free R22 alternatives

As the HCFC refrigerant R22 (ODP = 0.05)is still widely accepted only as a transitionalsolution, a number of chlorine-free (ODP = 0)alternatives have been developed and testedextensively. They are already being used ona large range of applications.

Experience shows, however, that none ofthese substitutes can replace the refrigerantR22 in all respects. Amongst other thingsthere are differences in the volumetric re-frigeration capacity, restrictions in possibleapplications, special requirements in systemdesign or also considerably differing pres-sure levels. So various alternatives comeunder consideration according to the par-ticular operating conditions.

Apart from the single-component HFCrefrigerant R134a, these are mainly blends(different compositions) of the componentsR32, R125, R134a, R143a, and R600(a).The following description mainly concernsthe development and potential applicationsof these. The halogen-free substitutes NH3,propane and propylene as well as CO2should also be considered, however, spe-cific criteria must be applied for their use(described from page 23).

21


Fig. 23/1 R410A/R22 – comparison of performance data of a semi-hermetic compressor

Fig. 23/2 R410A/R22 – comparison of pressure levels

Rela

tion

R410

A to

R22

(=10

0%)

Evaporation [˚C]

80

150

10 20-20 -10 0

toh 20˚C

COP

Q o

tc 40˚C

tc 50˚C

tc 50˚C

tc 40˚C

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[ba

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-40 40 60-20 0 20

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R22

R410A


With regard to system technology, previousexperience with R22 can only be utilized toa limited extent. The distinctive temperatureglide requires a particular design of themain system components, e.g. evaporator,condenser, expansion valve. In this contextit must be considered that heat exchangersshould preferably be laid out for counter-flow operation and with optimized refriger-ant distribution. There are also special re-quirements with regard to the adjustment ofregulating devices and service handling.

Furthermore, the use in systems with flood-ed evaporators is not recommended as thiswould result in a severe concentration shiftand layer formation in the evaporator.

BITZER can supply a widespread rangeof semi-hermetic reciprocating, screwand scroll compressors for R407C.


A series of plants have been converted for test purposes. Because of the abovementioned criteria, however, no generalguidelines can be defined. Each case musttherefore be examined individually.

R410A as substitutefor R22

In addition to R407C, there is a near azeo-tropic blend being offered with the ASHRAEdesignation R410A. It is widely used already,mainly in air conditioning applications.

An essential feature indicates nearly 50%higher volumetric cooling capacity (Fig.23/1) in comparison to R22, but with theconsequence of a proportional rise in sys-tem pressures (Fig. 23/2).

At high condensing temperatures, energyconsumption/COP initially seems to be lessfavourable than with R22. This is mainlydue to the thermodynamic properties. Onthe other hand, very high isentropic efficien-cies are achievable (with reciprocating andscroll compressors), whereby the differ-ences are lower in reality.

Added to this are the high heat transfercoefficients in evaporators and condensersdetermined in numerous test series, withresulting especially favourable operatingconditions. With an optimized design, it isquite possible for the system to achieve abetter overall efficiency than with otherrefrigerants.

Because of the negligible temperature glide(< 0.2 K), the general usability can be seensimilar to a pure refrigerant.

The material compatibility is comparable tothe previously discussed blends and thesame applies for the lubricants. However,the pressure levels and the higher specificloads on the system components need tobe taken into account.


The fundamental criteria for HFC blendsalso apply to the system technology withR410A, however the extreme high pressurelevels have to be considered (43°C con-densing temperature already correspondsto 26 bar abs.).

Compressors and other system componentsof “R22 standard design” have substantiallimitations for the application of this refrig-erant. However, due to the favourable prop-erties of R410A considerable effort is takenfor the development of suitable products.

When considering to cover usual R22 appli-cation ranges, the significant differences inthe thermodynamic properties (e.g. pres-sure levels mass and volume flow, vapourdensity) must be evaluated.

22


This R22 substitute is offered for the con-version of existing R22 systems for which a “Zero ODP” solution is requested. This re-frigerant is a HFC mixture with base com-ponents R32/R125/R143a/R134a.

In spite of the blend composition based onpure HFC refrigerants, the manufacturerstates that a simplified conversion proced-ure is possible.

This is positively influenced by the R143aproportion. Accordingly, when convertingfrom R22 to R427A, all it takes is a re-placement of the original oil charge withester oil. Additional flushing sequences arenot required, as proportions of up to 15%of mineral oil and/or alkyl benzene have nosignificant effect on oil circulation in thesystem.

However, it must be taken into account thatunder the influence of the highly polarizedmixture of ester oil and HFC increased dis-solving of decomposition products and dirtin the pipework is caused. Therefore, gen-erously dimensioned suction clean-up filtersmust be provided.

Regarding cooling capacity, pressure levels,mass flow and vapor density R427A is rela-tively close to R22. During retrofit essentialcomponents such as expansion valves canremain in the system.Due to the high proportion of blend compo-nents with low adiabatic exponent the dis-charge gas temperature is considerablylower than with R22 which has a positiveeffect at high compression ratios.

It must be taken into account that this isalso a zeotropic blend with a distinct tem-perature glide. Therefore the criteria asdescribed in context with R407C are validhere as well.

BITZER compressors are suitable forR427A. An individual selection is pos-sible upon demand.

Supplementary information concerningthe use of HFC blends(see also http://www.bitzer.de)

❏ Technical information KT-651 “Retrofitting R22 systems to alternative refrigerants”

A refrigerant also belonging to the categoryof HFC/HC blends was introduced in 2009under the trade name ISCEON MO99(DuPont) – ASHRAE classification R438A.This formulation was selectively designedfor a higher critical temperature for applica-tions in hot climate areas. The base com-ponents are R32, R125, R134a, R600 andR601a.

Like R407C, all four substitute refrigerantsare zeotropic blends with a more or less sig-nificant temperature glide. In this respect thecriteria described in connection with R407Care also valid.

Apart from similar refrigeration capacitythere are fundamental differences in thermo-dynamic properties and in oil transport be-haviour. The high proportion of R125 caus-es with R417A/B and R422D a higher massflow than with R407C, a lower dischargegas temperature and a relatively high super-heating enthalpy. These properties indicatethat there are differences in the optimizationof system components and a heat exchangerbetween liquid and suction lines is of advan-tage.

Despite the predominant proportion of HFCrefrigerants the use of conventional lubri-cants is possible to some extent becauseof the good solubility properties of thehydrocarbon constituent. However, in sys-tems with a high oil circulation rate and/or a large volume of liquid in the receiver oilmigration may result.

In such cases, additional measures arenecessary. For further information on oilreturn and lubricants, see the previous sec-tion on “R422A as substitute for R502 andR22” (page 19).

BITZER compressors are suitable for thedescribed refrigerants.An individual selection is possible upondemand.

R427A as a substitute for R22

This refrigerant blend was introduced someyears ago under the trade name ForaneFX100 (Arkema). In the meantime it is listedin the ASHRAE nomenclature as R427A.

This also requires considerable construc-tional changes to compressors, heat ex-changers, and controls, as well as meas-ures of tuning vibrations.

In addition, safety requirements are con-cerned also affecting the quality and dimen-sions of piping and flexible tube elements(for condensing temperatures of approx.60°C/40 bar).

Another criterion is the relatively low criticaltemperature of 73°C. Irrespective of thedesign of components on the high pressureside, the condensing temperature is thuslimited.

Already very early BITZER has conduct-ed comprehensive research with R410Aand accompanied a series of projects.Meanwhile, two series of semi-hermeticreciprocating and scroll compressors forR410A are available.

R417A/417B/422D/438Aas substitutes for R22

The same as for R422A (page 19), one of theaims for these developments was to providechlorine-free refrigerants (ODP = 0) for thesimple conversion of existing R22 plants.

R417A was introduced to the market sever-al years ago, and is also offered under thetrade name ISCEON MO59 (DuPont). Thissubstitute for R22 contains the blend com-ponents R125/R134a/R600, and thereforediffers considerably from e.g. R407C with acorrespondingly high proportion of R32.

Meanwhile, a further refrigerant based onidentical components, but with a higherR125 content, has been offered under the trade name Solkane 22L (Solvay) –ASHRAE classification R417B. Due to itslower R134a content, the volumetric refrig-erating capacity as well as the pressure lev-els are higher than with R417A. This resultsin different performance parameters andemphasis in the application range.

The same applies to a further blend with thesame main components, but R600a as hy-drocarbon additive. It is offered under tradename ISCEON MO29 (DuPont) and listed asR422D in the ASHRAE nomenclature.

23

HFO/HFC blends

R32 as substitute for R22

As described earlier R32 belongs to the HFCrefrigerants group but at present is mainlyused as a component of refrigerant blendsonly. An essential barrier for the application asa pure substance at the moment is the flam-mability classification in safety group A2. Thisrequires adequate charge limitations and/oradditional safety measures, especially withinstallations inside buildings. In addition thereare very high pressure levels and dischargegas temperatures (compression index higherthan with R22 and R410A).

On the other hand R32 has favorable thermo-dynamic properties, e.g. very high evaporatingenthalpy and volumetric cooling capacity, lowvapor density (low pressure drop in pipelines),low mass flow and favorable power input forcompression. Besides that the global warmingpotential is low (GWP100 = 675).

Looking at these favorable properties andtaking into account the additional and strivedfor emission reductions, R32 will increasingly

HFO/HFC blends as HFC alternatives

Due to the decision with the use of the"Low GWP" refrigerant HFO-1234yf (seepages 11/12) in automotive air-conditioningsystems, the development of alternativesfor other mobile applications and stationarysystems has meanwhile also been initiated.

The primary goals are the formulation ofblends with significantly reduced GWPwhile maintaining similar thermodynamicproperties to those of the HFCs used pre-dominantly today.

The base component HFO-1234yf, which is the preferred candidate from the group offluoro olefins with a chemical double bond,due to its combination of properties. How-ever, HFO-1234yf is mildly flammable (safe-ty group A2L). Moreover, its volumetric re-frigerating capacity of approximately thesame level as R134a is relatively low. Suit-able substances from the HFO group with ahigher volumetric capacity – as direct alter-natives to R22, R404A, R410A, etc. – arenot available.

This, in addition to the demand for non-flammable refrigerants and/or a higher volu-metric refrigerating capacity, makes theblend of HFO-1234yf with an HFC a suit-able choice.

However, due to the properties of the HFCrefrigerants suitable as blend components,flammability and GWP are related diametric-ally to one another. In other words: Blendsas alternatives to R22, R404A, R410A, etc.that have a GWP < 500 are flammable.Some of the non-flammable substanceshave a significantly higher GWP, but at asubstantially lower level than the equivalentHFCs or HFC blends.

Currently there are two directions of devel-opment:❏ Non-flammable HFC alternatives (blends)

with GWP100 > approx. 500 – safetygroup A1. Regarding safety requirementsthese refrigerants can then be utilizedthe same way as currently used HFCs

❏ Flammable HFC alternatives (blends) withGWP100 < approx. 500 – according tothe new safety group A2L for mildly flam-mable refrigerants. See also explanationson page 11.

Abb. 24 R32/R410A – comparison of performance and operating data of a scroll compressor

Rela

tive

com

paris

on [%

]

Qo

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totcΔtoh

5°C50°C10 K110

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40

50

pc qm

Disc

harg

e ga

s te

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ratu

re [°

C]

Qo Cooling capacityCoefficient of performanceCondensing pressureRefrigerant mass flow

COPpcqm

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R32

R41

0A

R32

R41

0A

also be used as a refrigerant in factory pro-duced systems (A/C units and heat pumps)with low refrigerant charges. Concerning safe-ty requirements the regulations (e.g. accord-ing to EN 378) for A2 refrigerants are still validalthough it was proven in flammability teststhat the necessary ignition energy is very highand the flame speed is low. Based on theseproperties R32 (like HFO 1234yf and 1234ze)has been put into the new safety group A2Laccording to ISO 817.

To what extent the safety demands for A2Lrefrigerants (as opposed to A2) can be relie-ved in future is not known today. Numeroustests and risk analyses are required for that.

In conjunction with development pro-jects BITZER is also carrying out cor-responding investigations with R32. Further information on demand.

24

HFO/HFC blends

Among others this group of refrigerants isthen subject to charge limitations accord-ing to today's requirements for A2 refriger-ants

To what extent the safety demands for A2Lrefrigerants (as opposed to A2) can berelieved in future is unclear today. Numer-ous tests and risk analyses are required forthat.

Non-flammable R134a alternatives

For R134a alternatives the starting pointfor a development of non-flammableblends is most favorable.

For them, GWP values =/< 600 can beachieved. This is less than half comparedwith R134a (GWP100 = 1430). In addition tothat, this type of blend versions can haveazeotropic properties, which is why theycan be used like pure refrigerants.

For quite some time a blend has been test-ed on a large scale in real systems – thiswas developed by DuPont, and is calledOpteon® XP-10 (formerly DR-11). Resultsavailable today are promising.Meanwhile Honeywell provides an R134alternative called Solstice N-13 which, how-ever, differs in terms of blend composition.

Both options have cooling capacity, powerinput, and pressure levels similar to R134a.As a result components and system tech-nology can be taken over. Just minorchanges like e.g. superheat adjustment ofthe expansion valves is necessary.

Polyolester oils are suitable lubricantswhich must meet special requirements,e.g. for the utilization of additives.

Very favorable perspectives arise in super-market applications in the Medium Tem-perature range in a cascade with CO2 forLow Temperature, just as in liquid chillerswith higher refrigerant charges where theuse of flammable or toxic refrigerants wouldrequire comprehensive safety measures.

BITZER is strongly involved in theseprojects and has already gained impor-tant knowledge in the use of these re-frigerants. An individual compressor selection ispossible on demand.

Alternatives for R22/R407C,R404A/R507A and R410A

Since the available HFO molecules (HFO-1234yf und HFO-1234ze) show a consider-ably smaller volumetric cooling capacitycompared to the above mentioned HFCrefrigerants, for the particular alternativesrelatively large HFC proportions with highvolumetric cooling capacity must be added.The potential list of candidates is ratherlimited. R32 with relative low GWP is oneoption. A negative aspect is its flammability(A2L) whereby adding larger proportions inorder to limit the GWP to values < 500 letthe blend to remain mildly flammable (safe-ty group A2L).

On the other hand, when formulating as anon-flammable blend a relatively large pro-portion of refrigerants with high fluoric con-tent must be added which allows the flam-mability to be suppressed. A drawbackhere is the relatively high GWP of thesechemicals. This leads to the fact that non-flammable alternatives for R22/R407C and R404A/R507A show GWP100 valuesabove 1000 up to approx. 1300. Com-pared to R404A/R507A, however, thismeans a reduction down to a third.

For R410A there is no non-flammable alter-native on the horizon. This requires a highproportion of R32 in order to reach the nec-essary volumetric cooling capacity.

All blend options described above show amore or less distinct temperature glide dueto significant boiling point differences. Thesame criteria apply as described in contextwith R407C.

Beyond that the discharge gas temperatureof the R404A/R507A alternatives is in partconsiderably higher compared to the corre-sponding HFC blends.

Meanwhile blend variants have initially beendeveloped by DuPont and Honeywell whichare already being tested in different projects.Among those are the following refrigerantswhich are still designated by their tradenames:

Actual Alternative AlternativeRefrigerant DuPont Honeywell

Non-flammable alternatives (GWP100 =/> 1000)

R22/R407C * N-20 (A1)R404A/507A DR-33 (A1) N-40 (A1)

Flammable alternatives (GWP100 < 500)

R22/R407C DR-3 (A2L) L-20 (A2L)R404A/507A DR-7 (A2L) L-40 (A2L)R410A DR-5 (A2L) L-41 (A2L)

* Not published

For testing the “Low GWP” refrigerantsAHRI (USA) has initiated an internationaltest program entitled “Alternative Refriger-ants' Evaluation Program (AREP)”. In thisconnection additional development pro-ducts of other manufacturers (Arkema,Mexichem, among others) as well as halo-gen free refrigerants are investigated andevaluated.

The investigations in the scope of AREPhave still not been finalized which alsoapplies to additional test programs. There-fore no evaluation on suitability and longterm chemical stability of the various pro-ducts is possible yet.

25

Halogen free refrigerants

NH3 (Ammonia) as alternative refrigerant

The refrigerant NH3 has been used for morethan a century in industrial and larger re-frigeration plants. It has no ozone depletionpotential and no direct global warming po-tential. The efficiency is at least as good aswith R22, in some areas even more favour-able; the contribution to the indirect globalwarming effect is therefore small. In addition it is incomparably low in price.Summarized, is this then an ideal refrigerantand an optimum substitute for R22 or analternative for HFCs!? NH3 has indeed verypositive features, which can also be mainlyexploited in large refrigeration plants.

Unfortunately there are also negative as-pects, which restrict the wider use in thecommercial area or require costly andsometimes new technical developments.

A disadvantage with NH3 is the high isen-tropic exponent (NH3 = 1.31 / R22 = 1.19 /R134a = 1.1), that results in a dischargetemperature which is even significantly hig-her than that of R22. Single stage compres-sion is therefore already subject to certainrestrictions below an evaporating tempera-ture of around -10°C.

The question of suitable lubricants is also notsatisfactorily solved for smaller plants insome kinds of applications. The oils usedpreviously were not soluble with the refriger-ant. They must be separated with compli-cated technology and seriously limit the useof “direct expansion evaporators” due to thedeterioration in the heat transfer.

Special demands are made on the thermalstability of the lubricants due to the highdischarge gas temperatures. This is espe-cially valid when automatic operation is considered where the oil should remain foryears in the circuit without losing any of itsstability.

NH3 has an extraordinarily high enthalpydifference and as a result a relatively smallcirculating mass flow (approximately 13 to15% compared to R22). This feature which

is favourable for large plants makes theregulation of the refrigerant injection moredifficult with small capacities.

A further criteria which must be consideredis the corrosive action on copper contain-ing materials; pipe lines must therefore be made in steel. Apart from this the de-velopment of motor windings resistant toNH3 is also hindered. Another difficulty arises from the electrical conductivity of the refrigerant with higher moisture content.

Additional characteristics include toxicityand flammability, which require special safe-ty measures for the construction and oper-ation of such plants.

Resulting design and construction criteria

Based on the present “state of technology”,industrial NH3 systems demand totally diffe-rent plant technology, compared to usualcommercial systems.

Due to the insolubility with the lubricatingoil and the specific characteristics of therefrigerant, high efficiency oil separatorsand also flooded evaporators with gravity or pump circulation are usually employed.Because of the danger to the public and tothe product to be cooled, the evaporatoroften cannot be installed directly at the coldspace. The heat transport must then takeplace with a secondary refrigerant circuit.

Two stage compressors or screw compres-sors with generously sized oil coolers, mustalready be used at medium pressure ratios,due to the unfavorable thermal behaviour.

Refrigerant lines, heat exchangers and fit-tings must be made of steel; larger sizepipe lines are subject to examination by acertified inspector.

Corresponding safety measures and alsospecial machine rooms are required de-pending upon the size of the plant and therefrigerant charge.

The refrigeration compressor is usually of“open” design, the drive motor is a separ-ate component.

These measures significantly increase the expenditure involved for NH3 plants,especially in the medium and smaller cap-acity area.

Efforts are therefore being made world-wideto develop simpler systems which can alsobe used in the commercial area.

A part of the research programs is dealingwith part soluble lubricants, with the aim ofimproving oil circulation in the system. Sim-plified methods for automatic return of non-soluble oils are also being examined as analternative.

BITZER is strongly involved in theseprojects and has a large number ofcompressors operating. The experi-ences up to now have revealed thatsystems with part soluble oils are diffi-cult to govern. The moisture content inthe system has an important influenceon the chemical stability of the circuitand the wear of the compressor. Be-sides, high refrigerant dilution in the oil(wet operation, insufficient oil tempera-ture) leads to strong wear on the bear-ings and other moving parts. This isdue to the enormous volume changewhen NH3 evaporates in the lubricatedareas.These developments are being done ona widely used program. The emphasisis also on alternative solutions for non-soluble lubricants.

Besides to this various equipment manufac-turers have developed special evaporators,where the refrigerant charge can be signifi-cantly reduced.

In addition to this there are also solutionsfor the “sealing” of NH3 plants. This dealswith compact liquid chillers (charge below50 kg), installed in a closed container andpartly with an integrated water reservoir toabsorb NH3 in case of a leak. This type ofcompact unit can be installed in areaswhich were previously reserved for plantswith halogen refrigerants due to the safetyrequirements.

26


Fig. 25 Comparison of discharge gas temperatures Fig. 26 NH3/R22 – comparison of pressure levels

Disc

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-40 10-20 040

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Δtohh

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120R22

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R22NH3

R723 (NH3/DME) as an alternative to NH3

The previously described experiences withthe use of NH3 in commercial refrigerationplants with direct evaporation caused fur-ther experiments on the basis of NH3 un-der the addition of an oil soluble refrigerantcomponent. The main goals were an im-provement of the oil transport characteristicsand the heat transmission with conventionallubricants along with a reduced dischargegas temperature for the extended applica-tion range with single stage compressors.

It is still too early to give a final judgementconcerning the extended use of compactNH3 systems, in place of plants with HFCrefrigerants and mainly conventional tech-nology. From the purely technical view-pointand presupposing an acceptable pricelevel, it is anticipated that a wider range ofproducts will become available.

The production program from BITZERtoday includes an extensive selectionof optimized NH3 compressors forvarious types of lubricants:

❏ Single stage open reciprocatingcompressors (displacement 19 to152 m3/h with 1450 rpm) for air-con-ditioning, medium temperature andBooster applications

❏ Open screw compressors (displace-ment 84 to 535 m3/h – with parallel operation to 3200 m3/h – with 2900rpm) for air-conditioning, mediumand low temperature cooling.Options for low temperature cooling:– Single stage operation– Economiser operation– Booster operation

The result of this research project is a re-frigerant blend of NH3 (60%) and dimethylether “DME” (40%), developed by the “Insti-tut fuer Luft- und Kaeltetechnik, Dresden”,Germany (ILK), that has been applied in aseries of real systems. As a largely inorgan-ic refrigerant it received the designationR723 due to it its average molecular weightof 23 kg/kmol in accordance to the stan-dard refrigerant nomenclature.

DME was selected as an additional compo-nent for its properties of good solubility andhigh individual stability. It has a boiling pointof -26°C, a relatively low adiabatic expo-nent, is non toxic and is available in a hightechnical standard of purity.In the given concentration NH3 and DMEform an azeotropic blend characterised bya slightly rising pressure level in comparisonto pure NH3. The boiling point lies at -36.5°C (NH3 -33.4°C), 26 bar (abs.) ofcondensing pressure corresponds to58.2°C (NH3 59.7°C).

The discharge gas temperature in air-con-ditioning and medium temperature rangesdecrease by about 10 to 25 K (Fig. 25) andthereby allows for an extension of the appli-cation range to higher pressure ratios. Onthe basis of thermodynamic calculations a

Conversion of existing plants

The refrigerant NH3 is not suitable for theconversion of existing (H)CFC plants; theymust be constructed completely new withall components.

Supplementary BITZER informationconcerning the application of NH3(see also http://www.bitzer.de)

❏ Technical Information KT-640“Application of Ammonia (NH3)as an alternative refrigerant”

27


single-digit percent rise in cooling capacityresults when compared to NH3. The coeffi-cient of performance is similar and is evenmore favourable at high pressure ratios,which experiments have confirmed. Due tothe lower temperature level during com-pression an improved volumetric and isen-tropic efficiency is also to be expected, atleast with reciprocating compressors incase of an increasing pressure ratio.

Due to the higher molecular weight of DME,mass flow and vapour density increase withrespect to NH3 by nearly 50% which is oflittle importance to commercial plants, es-pecially in short circuits. In classical indus-trial refrigeration plants, however, this is asubstantial criterion with regard to pressuredrops and refrigerant circulation. Also fromthis standpoint it can be clearly seen that incommercial applications and especially inwater chillers, R723 has its preferred utilisa-tion.

The material compatibility is comparable tothat of NH3. Although non-ferrous metals(e.g. CuNi alloys, bronze, hard solders) arepotentially suitable, provided that the watercontent in the system is at a minimum (< 1000 ppm), a system design that cor-responds with typical ammonia practise is recommended nonetheless.

As lubricant mineral oils or (preferred) poly-alpha olefin can be used. As mentioned be-fore the portion of DME creates improvedoil solubility and a partial miscibility. Besidesthis the relatively low liquid density and anincreased concentration of DME in the cir-culating oil, positively influences the oil cir-culation. PAG oils would be fully or partlymiscible with R723 for typical applicationsbut are not recommended for reasons ofthe chemical stability and high solubility inthe compressor crankcase (strong vapourdevelopment in the bearings).

Tests have shown that the heat transfer co-efficient at evaporation and high heat flux isimproved in systems with R723 and mineraloil than when using NH3 with mineral oil.

Further characteristics are toxicity and flam-mability. By means of the DME content, theignition point in air diminishes from 15 to6% but. Despite of this, the azeotrope still

R290 (Propane) as substitute for R502 and R22

R290 (propane) can also be used as a sub-stitute refrigerant. As it is an organic com-pound (hydrocarbon) it does not have anozone depletion potential and a negligibledirect global warming effect. To take intoconsideration however, is a certain contri-bution to summer smog.

The pressure levels and the refrigerationcapacity are similar to R22 and the tem-perature behaviour is as favourable as withR134a.

There are no particular material problems.In contrast to NH3 copper materials arealso suitable, so that semi-hermetic andhermetic compressors are possible. Themineral oils usually found in a HCFC systemcan be used here as a lubricant over a wideapplication range.

Refrigeration plants with R290 have been inoperation world-wide for many years, main-ly in the industrial area – it is a “proven”refrigerant.

Meanwhile R290 is also used in smallercompact systems with low refrigerant char-ges like residential A/C units and heatpumps. Furthermore, a rising trend can beseen in its use with commercial refrigerationsystems and chillers.

Propane is offered also as a mixture withIsobutane (R600a) or Ethan (R170). Thisshould obtain a good performance matchwith halocarbon refrigerants. Pure Isobu-tane is mostly intended as a substitute forR12 in small plants (preferably domesticrefrigerators).

The disadvantage of hydrocarbons is thehigh flammability, and therefore been classi-fied as refrigerants of “Safety Group A3”.With the normal refrigerant charge found incommercial plants this means that the sys-tem must be designed according to “flame-proof” regulations.

The use of semi-hermetic compressors inso called “hermetically sealed” systems is inthis case subject to the regulations for dan-ger zone 2 (only seldom and short term risk).The demands for the safety technologyinclude special devices to protect againstexcess pressures and special arrangementsfor the electrical system. In addition meas-ures are required to ensure hazard free ven-tilation to effectively prevent a flammablegas mixture occurring in case of refrigerantleakage.

The design requirements are defined bystandards (e.g. EN378, Draft DIN 7003) andmay vary in different countries. For systemsapplied within the EU an assessment ac-cording to the EC Directive 94/9/EC (ATEX)may become necessary as well.

remains in the safety group B2, but mayreceive a different classification in case of arevised assessment.

Resulting layout criteria

The experiences made with the NH3 com-pact systems described above can be usedin the plant technology. However, adjust-ments in the component layout are neces-sary under consideration of the higher massflow. Besides a suitable selection of theevaporator and the expansion valve a verystable superheat control must be ensured.Due to the improved oil solubility “wet ope-ration” can have considerable negative re-sults when compared to NH3 systems withnon-soluble oil.

With regards to safety regulations the samecriteria apply to installation and operationas in the case of NH3 plants.

Suitable compressors are special NH3 ver-sions which possibly have to be adapted tothe mass flow conditions and to the con-tinuous oil circulation. An oil separator isusually not necessary with reciprocatingcompressors.

Bitzer NH3 reciprocating compressorsare suitable for R723 in principle. Anindividual selection of specificallyadapted compressors is possible ondemand.

28


Fig. 27 R290/R1270/R22 – comparison of performance data of a semi-hermetic compressor

Fig. 28 R290/R1270/R22 – comparison of pressure levels

Rela

tion

R290

and

R12

70 to

R22

(=10

0%)

Evaporation [˚C]

80

120

-40 0 10-30 -20 -10

90

110

100

Q o (R290)

COP (R1270)

COP (R290)

Q o (R1270)

tc 40˚Ctoh 20˚C

Pres

sure

[ba

r]

Temperature [˚C]

1

25

0 60

6

15

4

10

20

-40 -20

2

4020

R22

R1270

R290

With open compressors this will possiblylead to a classification in zone 1. Zone 1demands, however, electrical equipment inspecial flame-proof design.


Apart from the measures mentioned above,propane plants require practically no specialfeatures in the medium and low tempera-ture ranges compared with a usual (H)CFCand HFC system. When sizing componentsconsideration should however be given tothe relatively low mass flow (approximately55 to 60% compared to R22). An advan-tage in connection with this is the possibili-ty to greatly reduce the refrigerant charge.

On the thermodynamic side an internal heatexchanger between the suction and liquidline is recommended as this will improvethe refrigeration capacity and COP.

Due to the particularly good solubility withmineral oils, it may be necessary to use anoil with lower mixing characteristics or in-creased viscosity for higher suction pres-sures (air-conditioning range).

In connection to this, an internal heatexchanger is also an advantage as it leadsto higher oil temperatures thus to lower solubility with the result of an improved viscosity.

Due to the very favourable temperaturebehaviour (Fig. 25), single stage compres-sors can be used down to approximately -40°C evaporation temperature. R290 couldthen also be considered as an alternativefor some of the HFC blends.

On demand a palette of semi-hermeticreciprocating compressors is availablefor R290. Due to the individual require-ments a specifically equipped compres-sor version is offered. Inquires and orders need a distinstiveindication to R290. The handling of theorder does include an individual agree-ment between the contract partners.Open reciprocating compressors arealso available for R290, together with acomprehensive program of flame-proofaccessories which may be required.

Conversion of existing plants with R22or HFC

Due to the flame-proof protection measuresrequired for an R290 plant, it would appearthat a conversion of existing plants is onlypossible in exceptional cases.

They are limited to systems, which can bemodified to meet the corresponding safetyregulations with an acceptable effort.

Supplementary BITZER informationconcerning the use of R290

❏ Technical Information KT-660“Application of Propane with semi-hermetic reciprocating compressors”

29


means that there is a danger of polymeri-zation at high pressure and temperaturelevels. Tests carried out by hydrocarbonmanufacturers and stability tests in realapplications show that reactivity in refriger-ation systems is practically non-existent.Doubts have occasionally been mentionedin some literature regarding propylene’spossible carcinogenic effects. These as-sumptions have been disproved by appro-priate studies.


With regard to system technology, experi-ence gained from the use of propane canwidely be applied to propylene. However,component dimensions have to be altereddue to higher volumetric refrigeration cap-acity (Fig. 27). The compressor displace-ment is correspondingly lower and thereforealso the suction and high pressure volumeflows. Because of higher vapour density themass flow is almost the same as for R290.As liquid density is nearly identical the sameapplies for the liquid volume in circulation.

Propylene (R1270) as an alternative to Propane

For some time there has also been in-creasing interest in using propylene(propene) as a substitute for R22 or HFC.Due to its higher volumetric refrigerationcapacity and lower boiling temperature(compared to R290) applications in mediumand low temperature systems, e.g. liquidchillers for supermarkets, are of particularinterest. On the other hand, higher pressurelevels (> 20%) and discharge gas tempera-tures have to be taken into consideration,thus restricting the possible applicationrange.

Material compatibility is comparable withpropane, as is the choice of lubricants.

Propylene is also easily inflammable andbelongs to the A3 group of refrigerants. Thesame safety regulations are therefore to beobserved as with propane (page 27).

Due to the chemical double linkage pro-pylene is relatively reaction friendly, which

As with R290 the use of an internal heatexchanger between suction and liquid lines isof advantage. However, due to R1270’s high-er discharge gas temperature restrictions arepartly necessary.

BITZER has carried out a series of investigations with R1270. In additionthere are experiences with the operation in real plants. An indivdual compressorselection is possible upon demand.

30

Fig. 29/1 R744(CO2) – pressure-/enthalpy-diagram

200100 300 400 500 6000

20

40

60

80

100

120

140

160

Enthalpy [kJ/kg]

Pres

sure

[bar

]

31.06°C

2Transcritical process

Subcritical process

R744 (CO2)

Fig. 29/2 R744(CO2)/R22/R404A – comparison of pressure levels

0

80

0 80

60

50

70

-60 4020

40

30

20

10

-40 -20 60

Critical temperature 31.06 ˚C

CO2

R404A

R22

Pres

sure

[bar

]

Temperature [°C]

temperature differences in evaporators,condensers, and gas coolers. Moreover, the necessary pipe dimensions are verysmall, and the influence of the pressuredrop is comparably low. In addition, whenused as a secondary fluid, the energy de-mand for circulation pumps is extremely low.

In the following section, a few examples ofsubcritical systems and the resulting designcriteria are described. An additional sectionprovides details on transcritical applications.

Subcritical applications

From energy and pressure level points ofview, very beneficial applications can beseen for industrial and larger commercialrefrigeration plants. For this, CO2 can beused as a secondary fluid in a cascade sys-tem and if required, in combination with afurther booster stage for lower evaporatingtemperatures (Fig. 30/1).

The operating conditions are always sub-critical which guarantees good efficiencylevels. In the most favourable applicationrange (approx. -10 to -50°C), pressures are still on a level where already existingcomponents or items in development, e.g.for R410A, can be matched with accept-able effort.

Refrigerants”, CO2 became less popularand since the 1950’s had nearly disap-peared.

The main reasons for that are its relativelyunfavourable thermodynamic characteristicsfor usual applications in refrigeration andair-conditioning.The discharge pressurewith CO2 is extremely high and the criticaltemperature at 31°C (74 bar) is very low.Depending on the heat source temperatureat the high pressure side transcritical oper-ations with pressures beyond 100 bar arerequired. Under these conditions, the ener-gy efficiency is often lower compared to theclassic vapour compression process (withcondensation), and therefore the indirectglobal warming effect is suitably higher.

Nonetheless, there is a range of applica-tions in which CO2 can be used very eco-nomically and with favourable Eco-Efficien-cy. For example, these include subcriticallyoperated cascade plants, but also transcrit-ical systems, in which the temperature glideon the highpressure side can be used ad-vantageously, or the system conditions permit subcritical operation for long periods.In this connection it must also be notedthat the heat transfer coefficients of CO2are considerably higher than of other re-frigerants – with the potential of very low

Carbon Dioxide R744 (CO2) as an alternative refrigerant and secondary fluid

CO2 has had a long tradition in the refri-geration technology reaching far into the19th century. It has no ozone depletingpotential, a negligible direct global warmingpotential (GWP = 1), is chemically inactive,non-flammable and not toxic in the classi-cal sense. That is why CO2 is not subject-ed to the stringent demands regardingcontainment as apply for HFCs (F-GasRegulation), and flammable or toxic re-frigerants. However, compared to HFCsthe lower practical limit in air has to beconsidered. For closed rooms this mayrequire special safety and detection systems.

CO2 is also low in cost and there is no nec-essity for recovery and disposal. In ad-dition, it has a very high volumetric refriger-ation capacity, which depending on oper-ating conditions equates to approx. 5 – 8times more than R22 and NH3.

Above all, the safety relevant characteristicswere an essential reason for the initial wide-spread use. The main focus for applicationswere marine refrigeration systems, for ex-ample. With the introduction of the “Safety


31


For the high temperature side of such acascade system, a compact cooling unitcan be used, whose evaporator serves onthe secondary side as the condenser forCO2. Chlorine-free refrigerants (NH3, HCsor HFCs) are suitable.

With NH3 the cascade heat exchangershould be designed so that the dreadedbuild-up of ammonium carbonate is pre-vented in the case of leakage. This tech-nology has been applied in breweries for a long time.

A secondary circuit for larger plants withCO2 could be constructed utilising, to awide extent, the same principles for a lowpressure pump circulating system, as isoften used with NH3 plants. The essentialdifference exists therein, that the condens-ing of the CO2 results in the cascade cool-er, and the receiver tank (accumulator) onlyserves as a supply vessel.

The extremely high volumetric refrigerationcapacity of CO2 (latent heat through thechanging of phases) leads to very low massflow rates and makes it possible to usesmall cross sectional pipe and minimal en-ergy needs for the circulating pumps.

For the combination with a further compres-sion stage, e.g. for low temperatures, thereare different solutions.

Fig. 30/1 shows a variation with an addition-al receiver where one or more Booster com-pressors will pull down to the necessaryevaporation pressure. Likewise, the dischargegas is fed into the cascade cooler, condens-es and then carried over to the receiver (MT).The feeding of the low pressure receiver (LT)is achieved by a level control device.Instead of classical pump circulation thebooster stage can also be built as a so-called LPR system. The circulation pump is thus not necessarybut the number of evaporators is then limit-ed with a view to an even distribution of theinjected CO2.

In the case of a system breakdown where ahigh rise in pressure could occur, safetyvalves can vent the CO2 to the atmospherewith the necessary precautions.As an alternative to this, additional coolingunits for CO2 condensation are also usedwhere longer shut-off periods can bebridged without a critical pressure increase.

For systems in commercial applications adirect expansion version is possible as well.

Supermarket plants with their usually widelybranched pipe work offer an especiallygood potential in this regard. The mediumtemperature system is then carried out in aconventional design or with a secondarycircuit and for low temperature applicationcombined with a CO2 cascade system (forsubcritical operation). A system example isshown in Fig. 30/2.

For a general application, however, not allrequirements can be met at the moment. Itis worth considering that system technolo-gy changes in many respects and speciallyadjusted components are necessary tomeet the demands.

The compressors, for example, must beproperly designed because of the highvapour density and pressure levels (par-ticularly on the suction side). There are also specific requirements with regard tomaterials. Furthermore only highly dehy-drated CO2 must be used.

High demands are made on lubricants aswell. Conventional oils are mostly not misci-ble and therefore require costly measuresto return the oil from the system. On theother hand, a strong viscosity reductionwith the use of a miscible and highly solublePOE must be considered.

Fig. 30/2 Conventional refrigeration system combined with CO2 low temperature cascade

CO Cascade2HFC (NH3 / HC)*

* only with secondary system

Fig. 30/1 Casacde system with CO2 for industrial applications

CO2

LT MT

LC

PC

CPR

MT LT

NH3 / HC /HFC

Simplifiedsketch

Simplifiedsketch


32

Another feature of transcritical operation isthe necessary regulation of the high pres-sure to a defined level. This “optimum pres-sure” is determined as a function of gascooler outlet temperature by means of bal-ancing between the highest possible en-thalpy difference and simultaneous mini-mum compression work. It must be adapt-ed to the relevant operating conditionsusing an intelligent modulating controller(see system example, Fig. 31).

As described above, under purely thermo-dynamic aspects, the transcritical operat-ing mode appears to be unfavourable interms of energy efficiency. In fact, this istrue for systems with a relatively high tem-perature level of the heat sink on the high-pressure side. However, additional meas-ures can be taken for improving efficiency,such as the use of expanders, ejectors, andeconomiser systems.Apart from that, there are application areasin which a transcritical process is energe-tically advantageous. These include heatpumps for sanitary water, or drying proces-ses. With the usually very high temperaturegradients between the discharge tempera-ture at the gas cooler intake and the heatsink intake temperature, a very low outletgas temperature is achievable. This is posi-tively influenced by the temperature glidecurve and the relatively high mean tempera-ture difference between CO2 vapour andsecondary fluid. The low gas outlet tempera-ture leads to a particularly high enthalpy difference, and therefore to a high systemCOP.

Low-capacity sanitary water heat pumpsare already manufactured and used in largequantities. Plants for medium to highercapacities (e.g. hotels, indoor swimmingpools) are still in the development and intro-ductory phase.

Apart from these specific applications, thereis also a range of developments for theclassical areas of refrigeration and air-con-ditioning. This also covers supermarketrefrigeration plants, for example. Mean-while, and following extensive laboratorytests, real installations with parallel com-pound compressors are in operation to alarger scale. The operating experience andthe determined energy costs show promis-ing results. However, the investment costsare still considerably higher than for classi-cal plants with HFCs and direct expansion.

On the one hand, the reasons for thefavourable energy costs lie in the highdegree of optimized components and thesystem control, and also in the previouslydescribed advantages regarding heat trans-fer and pressure drop. On the other hand,these installations are mostly used in cli-mate areas permitting very high runningtimes in subcritical operation due to theannual ambient temperature profile.

Insofar, but also in view of the very de-manding technology and the high require-ments placed on the qualification of plan-ners and service personnel, CO2 technologycannot be regarded as a general replace-ment for plants using HFC refrigerants.


Detailed information on this topic would gobeyond the scope of this publication. In anycase, the system and control techniquesare substantially different from conventionalplants. Already when considering pressurelevels as well as volume and mass flowratios specially developed components,controls, and safety devices as well as suitably dimensioned pipework must beprovided.

Further development work is necessary,also with regard to the adaptation oftechnical standards and safety require-ments.

For subcritical CO2 applicationsBITZER already offers a wide range ofspecial compressors.

Supplementary BITZER informationconcerning compressor selection forsubcritical CO2 systems

❏ Brochure KP-120CO2 Compressors for subcriticalapplications

❏ Additional publications on request

Transcritical applications

Transcritical processes are characterized inthat the heat rejection on the highpressureside proceeds isobar but not isotherm.Contrary to the condensation process dur-ing subcritical operation, gas cooling (de-superheating) occurs, with correspondingtemperature glide. Therefore, the heatexchanger is described as gas cooler. Aslong as operation remains above the criti-cal pressure (74 bar), only high-densityvapour will be transported. Condensationonly takes place after ex-pansion to alower pressure level – e.g. by interstageexpansion in an intermediate pressurereceiver. Depending on the temperaturecurve of the heat sink, a system designedfor transcritical operation can also be oper-ated subcritically, whereby the efficiency isbetter under these conditions. In this case,the gas cooler becomes the condenser.


33

The compressor technology is particularlydemanding. The special requirements resultin a completely independent approach. For example, this involves design, materials(bursting resistance), displacement, crankgear, working valves, lubrication system, aswell as compressor and motor cooling.Hereby, the high thermal load severely limitsthe application for single-stage compres-sion. Low temperature cooling requires 2-stage operation, whereby separate highand low pressure compressors are particu-larly advantageous with parallel compound-ed systems.

The criteria mentioned above in connectionwith subcritical systems apply to an evenhigher degree for lubricants.

Further development is necessary in manyareas, and for most applications, transcriti-cal CO2 technology cannot yet be regardedas state-of-the-art.

For transcritical CO2 applications,BITZER already offers a wide range ofspecial compressors.Their use is aimed at specific applica-tions, therefore individual examinationand assessment are required. * See page 11 for further information.

CO2 in mobileair-conditioning systems

Within the scope of the long-discussedmeasures for reducing direct refrigerantemissions, and the ban on the use ofR134a in MAC systems* within the EU, the development of CO2 systems has beenpursued intensively since several years.

At the first glance, efficiency and thereforethe indirect emissions from CO2 systemsunder typical ambient conditions appear tobe relatively unfavourable. But it must beconsidered that present R134a systemsare less efficient than stationary plants ofthe same capacity. The reasons for this liein the specific installation conditions andthe relatively high pressure losses in pipe-work and heat exchangers. With CO2,

pressure losses have significantly less influ-ence. Moreover, system efficiency is furtherimproved by the high heat transfer coeffi-cients in the heat exchangers.

This is why optimized CO2 air-condition-ing systems are able to achieve efficienciesthat are comparable to those of R134a.Regarding the usual leakage rates of suchsystems, a more favourable balance isobtained in terms of TEWI.

From today's viewpoint, it is not yet pos-sible to make a prediction as to whetherthe CO2 technology can in the long run be-come established in this application. Cer-tainly, this also depends on experienceswith “Low GWP” refrigerants (page 11)which in the meantime are partially intro-duced by the automotive industrie. Hereby,other aspects such as operating safety,costs, and global logistics will play animportant role.

Fig. 31 Example of a transcritical CO2 system

GasCooler

Evaporator

TX Device

(HX)

Compressor

HP Regulation Valve

Liquid Receiver(intermediatepressure)

Suplementary BITZER information concerning compressor selection for transcritical CO2-systems

❏ Brochure KP-130CO2 compressors for transcriticalapplications

❏ Additional publications upon request

Simplifiedsketch


34


R124 and R142b as substitutes forR114 and R12B1

Instead of the refrigerants R114 andR12B1 predominately found in the past inhigh temperature heat pumps and cranecabin A/C installations, the HCFC R124and R142b can be used as alternatives innew installations.With these gases it is also possible to uselong proven lubricants, preferably mineraloils and alkyl benzenes with high viscosity.

Because of the Ozone Depleting Potential,the use of these refrigerants must certainlyonly be regarded as an interim solution (inthe EU member states, the application innew systems is no longer allowed). Theflammability of R142b should also be con-sidered with the resulting safety implica-tions (refrigerant group A2).

Resulting design criteria/Converting existing plants

In comparison to R114 the boiling tempera-tures of the alternatives are lower (approx. -10°C) which results in larger differences inthe pressure levels and refrigeration volu-metric capacities. This leads to strongerlimitations in the application range concern-ing high evaporation and condensing tem-peratures.A conversion of an existing installation willin most cases necessitate the exchangingof the compressor and regulating devices.Owing to the lower volume flow (higher vol-umetric refrigeration capacity), possibleadjustments to the evaporator and the suc-tion line will be required.

Over the previous years BITZER com-pressors have been found to be wellsuited with R124 and R142b in actualinstallations. Depending on perform-ance data and compressor type modifi-cations are necessary, however. Per-formance data including further designinstructions are available on request.

Chlorine free substitutes for special applications

Due to the limited markets for systems withextra high and low temperature applica-tions, the requirements for the developmentof alternative refrigerants and system com-ponents for these areas has not been sogreat.

In the meantime a group of alternatives forthe CFC R114 and Halon R12B1 (high tem-perature), R13B1, R13 and R503 (extra lowtemperature) were offered as the replace-ments. With closer observations it has beenfound that the thermodynamic properties ofthe alternatives differ considerably from thesubstances used untill now. This can causecostly changes especially with the conver-sion of existing systems.

Alternatives for R114 and R12B1

At present R227ea and R236fa are regard-ed as the prefered substitutes. R227ea cannot be seen as a full replace-ment. Recent research and field tests haveshown favourable results, but with normalsystem technology the critical temperatureof 102°C limits the condensing temperatu-res to about 85..90°C.

R236fa provides the more favourable con-ditions at least in this regard – the criticaltemperature is above 120°C. A disadvan-tage, however, is the smaller volumetricrefrigeration capacity. This is similar to R114and with that 40% below the performance ofR124 which is widely used for extra hightemperature applications today.

In the meantime, an azeotropic blend ofR365mfc and a perfluoropolyether has alsobeen developed. It is available under thetrade name Solkatherm SES36 (Solvay). Itsboiling temperature (at 1.013 bar) is 36.7 °C,and the critical temperature is 177.4°C.

The preferred application areas will there-fore be heat pumps in process technology,and Organic Rankine Cycles (ORC).

Refrigerant R600a (Isobutane) will be aninteresting alternative where the safety reg-ulations allow the use of hydrocarbons(Group A3). With a critical temperature of135°C, condensing temperatures of 100°Cand more are within reach.

The volumetric refrigeration capacity isalmost identical to R124.

The "Low GWP" refrigerant HFO-1234ze(E)can also be regarded as a potential candi-date for extra high temperature applica-tions. Compared to R124, its cooling cap-acity is higher by 10 to 20% and its pres-sure level by about 25%. At an identicalcooling capacity, the mass flow differs onlyslightly. Its critical temperature is 107°C,which would enable an economical opera-tion up to a condensing temperature ofabout 90°C. However, like HFO-1234yf,HFO-1234ze(E) is mildly flammable and willtherefore be classified in the new safetygroup A2L. The corresponding safety regu-lations must be observed.

However, until now no sufficient operatingexperience is available, which is why anassessment of the suitability of this refriger-ant for long-term use is not yet possible.

For high temperature heat pumps and spe-cial applications in the field of high tem-peratures DuPont has presented an HFObased refrigerant called DR-2.

The critical temperature is at 171°C, theboiling temperature at 33.4°C. This enablesan operation at condensing temperaturesfar above 100°C for which only purpose-built compressors and system componentscan be used.

DR-2 has a GWP < 10 but is not flammableaccording to tests carried out so far. There-fore a classification in safety group A1 canbe expected.

A more intensive evaluation is not yet pos-sible.

35


Fig. 32 R13B1/HFC alternatives – comparison of discharge gas temperatures of a 2-stage compressor

Basis R13B1

Disc

harg

e ga

s te

mpe

ratu

re –

rela

tive

diffe

renc

e to

R13

B1 [K

]

40

30

20

10

0

-10

-30

-20

R41

0A

ISC

EON

MO

89

to

tc

Δtoh

-70°C

40°C

20 K

In addition to this, the steep fall of pressurelimits the application at very low tempera-tures and may require a change to a cas-cade system with for example R23 in thelow temperature stage.

Lubrication and material compatibility areassessed as being similar to the other HFCblends.

Alternatives for R13 and R503

The situation is more favourable with thesesubstances as R23 and R508A/R508B canalready replace R13 and R503. RefrigerantR170 (Ethane) is also suitable when thesafety regulations allow the use of hydro-carbons (Group A3).

Due to the partly steeper pressure curve ofthe alternative refrigerants and the higherdischarge gas temperature of R23 com-

Alternatives for R13B1

Besides R410A, ISCEON MO89 (DuPont)can be regarded as potential R13B1 sub-stitute. With R410A a substantially higherdischarge gas temperature is to be con-sidered when compared to R13B1 whichrestricts the application range even in 2-stage compression systems to a greaterextent.

ISCEON MO89 is a mixture of R125 andR218 with a small proportion of R290. Dueto the properties of the two main compo-nents, density and mass flow are relativelyhigh and discharge gas temperature is verylow. Liquid subcooling is of particular ad-vantage.

Both of the mentioned refigerants have rel-atively high pressure levels and are there-fore limited to 40 through 45°C condensingtemperature with the usually applied 2-stagecompressors. They also show less capacitythan R13B1 at evaporating temperaturesbelow -60°C.

pared with R13, differences in performanceand application ranges for the compres-sors must be considered. Individual adap-tation of the heat exchangers and controlsis also necessary.

As lubricants for R23 and R508A/B, polyolester oils are suitable, but these must bematched for the special requirements atextreme low temperatures.

R170 has also good solubility with conven-tional oils, however an adaptation to thetemperature conditions will be necessary.

BITZER has already carried out investi-gations and also collected experienceswith several of the substitutes mention-ed, performance data and instructionsare available on request.Due to the individual system technolo-gy for these special installations, con-sultation with BITZER is necessary.

Refrigerant Properties

36

R22R124R142b

R402A R402BR408A

R134aR152aR125R143aR32

R227eaR236fa

R23

R404AR507A R407AR407FR422A

R437A

R407CR417AR417BR422DR427AR438A

R410A

ISCEON MO89

R508AR508B

HFO-1234yfHFO-1234ze(E)Opteon XP-10Solstice N-13

R717R723R600aR290R1270

R170

R744

Time horizon 100 years – according toIPCC IV (2007)Values in brackets according toIPCC III (2001) ➔ reference data in EN378-1: 2012, Annex E– also basis for EU Regulation 842/2006

N/A Data not yet published.

Alternative refrigerant has larger deviation in refrigerating capacity and pressureAlternative refrigerant has larger deviation below -60°C evaporating temperature

Also proposed as a component in R290/600a-Blends (direct alternative to R12)

Classification according to EN378-1 and ASHRAE 34

According to EN 378-1: 2012, Annex E

0,0550,0220,065

0,0210,0330,0310,026

0

0

0

0

1810 (1700)609 (620)

2310 (2400)

2788 (2690)2416 (2310)3152 (3020)

1430 (1300)124 (120)

3500 (3400)4470 (4300)

675 (550)

3220 (3500)9810 (9400)

14800 (12000)

3922 (3780)3985 (3850)2107 (1990)1825 (1705)3143 (3040)

1805 (1680)

1774 (1650)2346 (2240)

29202729 (2620)2138 (2010)2264 (2150)

2088 (1980)

3805

13214 (11940)13396 (11950)

46

<600<600

08333

3

1

Composition(Formula)

Substitute for

ODP

[R11=1,0]

GWP(100a)

[CO2=1,0]

Practicallimit

[kg/m3]

Safetygroup

Application range

5

HCFC/HFC Service-Blends

HFC Single-component Refrigerants

HFC Blends

Halogen free Refrigerants

HFO and HFO/HFC Blends

0.30.11

0.066

0.330.320.41

0.250.0270.39

0.0560.061

0.590.59

0.68

0.520.530.330.290.29

0,08

0.310.150.070.260.280.08

0.44

N/A

0.230.2

0.058N/A0.35N/A

0.00035N/A

0.0110.0080.008

0.008

0.07

A1A1A1

A1A1A1

A1A2A1A2

A2(L)

A1A1

A1

A1A1A1A1A1

A1

A1A1A1A1A1A1

A1

N/A

A1A1

A2(L)A2(L)A1A1

B2B2A3A3A3

A3

A1

09.12

CHClF2CHClFCF3CCIF2CH3

R22/125/290R22/125/290R22/143a/125

CF3CH2FCHF2CH3CF3CHF2CF3CH3CH2F2

CF3-CHF-CF3CF3-CH2-CF3

CHF3

R143a/125/134aR143a/125R32/125/134aR32/125/134aR125/134a/600a

R125/134a/600/601

R32/125/134aR125/134a/600R125/134a/600R125/134a/600aR32/125/143a/134aR32/125/134a/600/601a

R32/125

R125/218/290

R23/116R23/116

CF3CF=CH2CF3CH=CHFN/AN/A

NH3NH3/R-E170C4H10C3H8C3H6

C2H6

CO2

R502 (R12 )

R114 , R12B1

R12 (R500)

R502

R13 (R503)

R503

R22 (R13B1 )

R22

R22 (R502)

R22 (R502)R22 (502)R114, R12B1R22 (R502)R22 (R502)

R13, R503

various

R12B1, R114R114

R12 (R22 )mainly usedas partcomponentsfor blends

seepage 38

seepage 38

seepage 38

seepage 38

seepage 39

R13B1

Refrigerant type

HCFC-Refrigerants

3

3

4

5

6

5 6

4

5

1

1

1

1

1

1

2

2

2

These statements are valid subject to reservations; they are based on information published by various refrigerant manufacturers.Fig. 33 Characteristics of CFC alternatives (continued on Fig. 34)

R134aseepages11 and 23

Refrigerant Properties

37

-41-11-10

-49-47-44

-26-24-48-48-52

-16-1

-82

-47-47-46-46-49

-33

-44-39-45-45-43-42

-51

-55

-86-88

-30-18-29-24

-33-37-12-42-48

-89

-57

Valid for single stage compressors

Data on request (operating conditionsmust be given)

Triple point at 5,27 bar

Stated performance data are average valuesbased on calorimeter tests.

Rounded values

Total glide from bubble to dew line – based on 1 bar (abs.) pressure.Real glide dependent on operatingconditions.Approx. values in evaporator:H/M 70%; L 60% of total glide

Reference refrigerant for these values is stated in Fig. 33 under the nomina-tion “Substitute for” (column 3)Letter within brackets indicates operating conditionsH High temp (+5/50°C)M Medium temp (-10/45°C)L Low temp (-35/40°C)

R22R124R142b

R402A R402BR408A

R134aR152aR125R143aR32

R227eaR236fa

R23

R404AR507A R407AR407FR422A

R437A

R407CR417AR417BR422DR427AR438A

R410A

ISCEON MO89

R508AR508B

HFO-1234yfHFO-1234ze(E)Opteon XP-10Solstice N-13

R717R723R600aR290R1270

R170

R744

09.12

Fig. 34 Characteristics of CFC alternatives

Refrigeranttype

3

3

4

5

6

6

1

2

Boilingtemperature

[°C]

Temperatureglide[K]

Criticaltemperature

[°C]

Cond. temp.at 26 bar(abs) [°C]

Refr.capacity

[%]

Dischargegas temp.

[K]

Lubricant(compressor)

1 2 1 1 3 3

000

2.02.30.6

00000

00

0

0.70

6.66.42.5

3.6

7.45.6 3.44.57.16.6

<0.2

4.0

00

000

0,4

00000

0

0

96122137

758383

101113667378

102>120

26

7371838372

95

878775818780

72

70

1314

9511098

106

1331311359792

32

31

63105110

535658

8085515642

96117

1

5554565756

75

586858626463

43

50

-3-3

82927885

6058

1147061

3

-11

80 (L)

109 (L)99 (L)98 (L)

97 (M)N/AN/AN/AN/A

105 (M)107 (M)

98 (M)104 (M)100 (M)

108 (M)

100 (H)97 (H)95 (M)90 (M)90 (M)88 (M)

140 (H)

99 (M)

102 (M)88 (M)

100 (M)105 (M)N/A 89 (M)

112 (M)

+35

~0+16+10

-8N/AN/AN/AN/A

-34-34-19-11-39

-7

-8-25-37-36-20-27

-4

-14

-7-6

+60+35N/A-25-20

seepage 39

5

5 5

5

5

5

5

5

5

5

5

5 5

4 4

55

5

HCFC/HFC Service-Blends

HFC Single-component Refrigerants

HFC Blends

Halogen free Refrigerants

HFO and HFO/HFC Blends

HCFC-Refrigerants

38

-100-80-60-40-2002040

R124 ● R142b

R401A ● R409A

R401B

R22

R402B

R402A ● R403B ● R408A

Evaporation °CApplication with limitations

2-stage

2-stage

Evaporation °C-100-80-60-40-2002040

R227ea ● R236fa

R134a ● XP-10 ● N-13

R407C ● R417A

R410A

R23 ● R508A ● R508B

Condensing temperature limitedApplication withlimitations

Compressors for high pressure 42 bar

CASCADE

2-stage

2-stage

2-stage

1

2

ISCEON MO89

R437A

R404A ● R507A

R407A ● R407F ● R417BR422A ● R422D ● R427A ● R438A

12

2

2

Transitional/Service refrigerants

Fig. 35 Application ranges for HCFC’s and Service Blends

HFC and HFO refrigerants

Fig. 36 Application ranges for HFC refrigerants and blends (ODP = O)

Application ranges

39

R290 ● R1270

-100-80-60-40-2002040

R600a

R170

Evaporation °C

NHR723*

3

CO2

Application with limitations

CASCADE

2-stage

– see pages 29...32 –

2-stage

2-stage

* see information on pages 25/26

(H)CFC

NH ● R7233

Service blends with R22

HFC + blends

Hydrocarbons VG VG VG

+VG

+VG

VG

Especially critical with moisture

Possible higher basic viscosity

Good suitability

Application with limitations Not suitable

Further information see pages 10/11 and explanations for the particular refrigerants.

VG VG

Suitability dependant on system design

HFC/HC blends

HFO+HFO/HFC blends

Min

eral

oil

(MO

)

Alky

l-be

nzen

e(A

B)

Min

eral

oil

+ al

kyl-

benz

ene

Poly

-alp

ha-

olef

in (P

AO)

Poly

oles

ter (

POE)

Poly

viny

l-et

her

(PVE

)

Poly

-gl

ycol

(PAG

)

Hyd

rocr

acke

dm

iner

al o

il

Traditional oils New lubricants

Application ranges ■ Lubricants


Fig. 37 Application ranges for halogen free refrigerants

Lubricants

Fig. 38 Lubricants for compressors

Subject to change // 09.2012

Bitzer Kühlmaschinenbau GmbHEschenbrünnlestraße 15 // 71065 Sindelfingen // Germany

Tel +49 (0)70 31 932-0 // Fax +49 (0)70 31 932-147 [email protected] // www.bitzer.de

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