refrigerant report

A-501-15

15. Edition

Refrigerant Report

Refrigerant Report

Contents Revisions/supplements vs. 14th edition Page

334667

88

1010121212

131516171718192020212222

232324252728

32

34

36

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” refrigerant HFO-1234yf

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 and R407B 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 and R422D as substitutes for R22R427A as substitute for R22

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

Introduction

General aspects on refrigerant developments

Stratospheric ozone depletion as well asatmospheric greenhouse effect due torefrigerant emissions have led to drasticchanges in the refrigeration and air con-ditioning technology since the beginningof the 90s.

This is especially true for the area of com-mercial refrigeration and A/C plants withtheir wide range of applications. Until afew years ago the main refrigerants usedfor these systems were ozone depletingtypes, namely R12, R22 and R502; forspecial applications R114, R12B1, R13B1,R13 and R503 were used.

With the exception of R22 the use ofthese chemicals is not allowed any morein industrialised countries. In the Euro-pean Union, however, there is a currentearly phase-out for R22 as well whichshall be realised step by step (see page 7for explanations). The main reason for this early ban of R22contrary to the international agreement isthe ozone depletion potential although itis only small.As from 2010, phase-out regulations willbecome effective in other countries aswell, in the USA for instance.

Due to this situation enormous conse-quences result for the whole refrigerationand air conditioning trade. BITZER there-fore committed itself to taking a leadingrole in the research and development ofenvironmentally benign system designs.

Although the chlorine free HFC refriger-ants R134a, R404A, R507A, R407C,R410A as well as NH3 and various hydro-carbons have already become estab-lished, there are still further tasks to per-form, especially with respect to the globalwarming impact. The aim is to significant-ly reduce direct emissions caused by re-frigerant loss, and indirect emissionsthrough highly efficient plants.

Therefore a close co-operation exists withscientific institutions, the refrigeration andoil industries, component manufacturersas well as a number of innovative refriger-ation and air conditioning companies.

A large number of development taskshave been completed; an extensive rangeof compressors and equipment is alreadyavailable for the various alternative refrig-erants.

Besides the development projects BITZERactively supports legal regulations andself commitments concerning the respon-sible use of refrigerants.

The following report deals with possibili-ties for a short and medium term changeto environmentally benign refrigerants inmedium and large commercial refrigera-tion and A/C plants. At the same time, theexperience which already exists is alsodealt with and the resulting consequencesfor plant technology.

❄ ❄ ❄

The results of serveral studies confirmthat the vapour compression refrigerationplants normally used in the commercialfield are far superior to all other process-es down to a cold space temperature ofaround -40°C.

The selection of an alternative refrigerantand the system design receives specialsignificance, however. Besides the requestfor substances without ozone depletionpotential (ODP=0) especially the energydemand of a system is seen as an essen-tial criterion due to its indirect contribu-tion to the greenhouse effect. On top ofthat there is the direct ozone depletionpotential (GWP) due to 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”factor (Total Equivalent Warming Impact)has been introduced. Meanwhile, another,more extensive assessment method hasbeen developed under the aspect of “Eco-Efficiency”. Hereby, both ecological(such as TEWI = Total Equivalent WarmingImpact) and economical criteria are takeninto account.

Therefore it is possible that in future theassessment of refrigerants with regard to

the environment could differ according tothe place of installation and drive method.

A closer look on the HFC based substi-tutes shows, however, that the possibili-ties for directly comparable single sub-stance refrigerants are limited. The sit-uation for R12 with the substitute R134ais relatively favourable, as it is for R502with the alternatives 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 theline of HFCs. These however can only beused exceptionally as a pure substancedue to their specific characteristics. Mostimportant criteria in this concern are flam-mability, thermodynamic properties andglobal warming potential. These sub-stances are much more suitable as com-ponents of blends where the individualcharacteristics can be matched to therequirements according to the mixing pro-portions.

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.

The illustrations on the next pages show astructural survey of the alternative refrig-erants and a summary of the single orblended substances which are now avail-able. After that the individual subjects arediscussed.

Due to the increasing interest in substi-tutes for R114, R12B1, R13B1, R13 andR503, the possible alternatives are alsoconsidered in this report.

Refrigerant data, application ranges andlubricant specifications are shown onpages 34 to 37.

For reasons of clarity the less or onlyregionally known products are not speci-fied in this issue, which is not intended toimply any inferiority.

3

4

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

Fig. 1 General survey of the alternative refrigerants

Alternative refrigerants – overview

SingleSubstances

e.g. R22R123R124R142b

Blends

predominantlyR22-Based

HCFC/HFC– partly chlorinated –

Transitional/ServiceRefrigerants

SingleSubstances

e.g. R134aR125R32R143aR152a

Blends

e.g. R404AR507AR407-SeriesR410A

HFC– chlorine free –

SingleSubstance

HFO-1234yf

Medium and LongTerm Refrigerants

“Low GWP”Refrigerants

SingleSubstances

e.g. NH3

R290R1270R600aR170R744

Blends

e.g. R600a/R290

R290/R170

R723

Halogen free

Alternative Refrigerants

Transitional / Service refrigerants 09.08

Previous Alternativesrefrigerants

ASHRAE Trade name Zusammensetzung DetailedClassification (bei Gemischten) Information

R401A MP39 DuPont R22/152a/124 pagesR401B MP66 DuPont R22/152a/124 16, 34...37R409A FX56 Arkema/Solvay R22/124/142b

R22 – – –R402A HP80 DuPont R22/125/290 pagesR502 R402B HP81 DuPont R22/125/290 8, 9, 15, 16,R403B – DuPont R22/218/290 34...37R408A FX10 Arkema R22/143a/125

R114 R124 – – pagesR12B1 R142b – – 32, 34...37

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

3

31

R12(R500)

Bisherige AlternativenKältemittel

ASHRAE Trade name Formula DetailedClassification Information

R12 R290/600a – C3H8/C4H10 pages(R500) R600a – C4H10 25, 34...37

R717 – NH3 pagesR502 R290 – C3H8 23...27, 34...37R1270 – C3H6

R717 – NH3

R22R723 – NH3 + R-E170 pagesR290 – C3H8 23...27, 34...37R1270 – C3H6

R114R600a – C4H10

pagesR12B1 32, 34...37

R13B1 no direct alternatives available

R13R170 – C2H6

pagesR503 33, 34...37

Divers R744 – CO2pages28...31, 34...37

3

3

1

1

1

1

1

1

1

1

1

1

2

2

1 2 5

5

Chlorine free (HFC) refrigerants and blends (long term alternatives) 09.08

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

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

Explanation of Fig. 2 to 4 Inflammable Large deviation in refrigerating capacity and Service refrigerant with zero ODPToxic pressures to the previous refrigerant Azeotrope

Still in development and test phase

Alternative refrigerants – overview

3 41

2 5

6

Halogen free refrigerants (long term alternatives) 09.08

Previous AlternativesRefrigerants

ASHRAE Trade name Composition DetailedClassification (with blends) Informationen

R134a–R152a pages

R12 R413A ISCEON MO49 DuPont R134a/218/600a 10...12, 16, 34...37(R500) R437A ISCEON MO49 Plus DuPont R125/134a/600/601

HFO-1234yf various page 12

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

R422A ISCEON MO79 DuPont R125/134a/600a 17...19, 34...37

R407C various R32/125/134aR410A various R32/125R417A ISCEON MO59 DuPont R125/134a/600 pages

R422D ISCEON MO29 DuPont R125/134a/600a 20...22, 34...37

R427A Forane 427A Arkema R125/R134a/R-E170

R114 R236fa – – pagesR12B1 R227ea – – 32, 34...37

R410A various R32/125 pagesR13B1 – ISCEON MO89 DuPont R125/218/290 33, 34...37

R13 R23 – – pagesR503 R508A KLEA 508A INEOS Fluor R23/116 33, 34...37R508B Suva 95 DuPont R23/116

1

R22

4

6

4

6

Fig. 6 Comparison of TEWI figures (example)

Global Warming andTEWI Factor

TE

WI

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 consumtion

LL

RL = Impact of

leakageLL = Impact of

lossesLL LL

LL

+10%

+10%

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 cate-gory of the greenhouse gases. An emis-sion of these substances contributes tothe global warming effect. The influence ishowever much greater in comparison toCO2 which is the main greenhouse gas inthe atmosphere (in addition to watervapour). Based on a time horizon of 100years, the emission from 1 kg R134a is forexample roughly equivalent to 1300 kg ofCO2 (GWP100 = 1300). It is already appar-ent from these facts that the reduction ofrefrigerant losses must be one of the maintasks for the future.

On the other hand, the major contributorto a refrigeration plant’s global warmingeffect is the (indirect) CO2 emissioncaused by energy generation. Based onthe high percentage of fossil fuels used inpower stations the average European CO2release is around 0.6 kg per kWh of elec-trical energy. A significant greenhouseeffect occurs over the lifetime of the plantas 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 ][ 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/aβ 0,6 kg CO2/kWhα 0,75n 15 yearsGWP 1300 (CO2 = 1)

time horizon 100 years

As this is a high proportion of the totalbalance it is also necessary to place anincreased emphasis upon the use of highefficiency compressors and associatedequipment as well as optimized systemcomponents, in addition to the demandfor 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 thevarious areas of influence are correspon-dingly separated.

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 withvarious refrigerant charges, leakage los-ses and energy 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 plantsis 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 andair-conditioning systems – has becomevalid for the EU.

7

Environmental aspects

Eco-Efficiency

As mentioned above, an assessmentbased on the specific TEWI value takesinto account the effects of global warmingduring the operating period of a refrigera-tion, air-conditioning or heat pump instal-lation. Hereby, however, the entire eco-logical and economical aspects are notconsidered.

But apart from ecological aspects, whenevaluating technologies and making in-vestment decisions, economical aspectsare highly significant. With technical sys-tems, the reduction of environmental im-pact frequently involves high costs,whereas low costs often have increasedecological consequences. For most com-panies, the investment costs are decisive,whereas they are often neglected duringdiscussions about minimizing ecologicalproblems.

For the purpose of a more objective as-sessment, a study* was presented in2005, using the example of supermarketrefrigeration plants to describe a conceptfor evaluating Eco-Efficiency. It is based

on the relationship between added value(a product's economic value) and the re-sulting environmental impact.With this evaluation approach, the entirelife cycle of a system is taken into ac-count in terms 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 study also confirmed that an increaseof Eco-Efficiency can be achieved by in-vesting in optimized plant equipment (min-imized operating costs). Hereby, thechoice of refrigerant and the associatedsystem technology plays an importantrole.

Eco-Efficiency can be illustrated in gra-phic representation (see example in Fig. 8). For this, the results of the Eco-Efficiency evaluation are shown on the x-axis in the system of coordinates,

whilst the results of the life cycle costanalysis are shown on the y-axis. Thisrepresentation shows clearly that a sys-tem exhibits an increasingly better Eco-Efficiency, the higher it lies in the top rightquadrant – and conversely, it becomesless efficient in the bottom left sector.

The diagonals plotted into the system ofcoordinates represent lines of equal Eco-Efficiency. This means that systems orprocesses with different life cycle costsand environmental impacts can quite possibly exhibit the same Eco-Efficiency.

Fig. 8 Example of an Eco-Efficiency evaluation

incr

easin

g Eco

-Effi

ciency

Co

st

ad

va

nta

ge

E nv i ronmen ta l advan tage

decre

asin

g Eco

-Effi

ciency

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

* The study was compiled by Solvay ManagementSupport GmbH and Solvay Fluor GmbH, Hannover,together with the Information Centre on HeatPumps and Refrigeration (IZW), Hannover. Thework was supported by an advisory group ofexperts from the refrigeration industry.

HCFC Refrigerants

8

R22 as transitionalrefrigerant

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

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

Despite of the generally favourable prop-erties R22 is already subject to variousregional restrictions* which control theuse of this refrigerant in new systems andfor service purposes due to its ozonedepletion potential – although being low.

With regard to components and systemtechnology a number of particularities areto follow as well. Refrigerant R22 hasapproximately 55% higher refrigeratingcapacity and pressure levels in compari-son to R12. The significantly higher dis-charge gas temperature is also a criticalfactor compared to R12 (see Fig. 9) andR502.

Similar relationships in terms of thermalload are found in the comparison withHFC refrigerants R134a, R404A/R507A(pages 10 and 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

In vehicles – such as cars, trucks, busesand trains – are more problematic. Thehigher pressure and temperature levels of R22 seriously limit here the range ofapplication. Only some of the applicationscan therefore be covered.

Also critical – due to the high dischargegas temperature – are low temperatureplants especially concerning thermal sta-bility of oil and refrigerant, with the dan-ger of acid formation and copper plating.Special measures have to be adoptedtherefore, such as two stage compres-sion, controlled refrigerant injection, addi-tional cooling, monitoring of dischargegas temperature, limiting the suction gassuperheat and particularly careful in-stallation.

* Not allowed for new equipment in Germany andDenmark since 2000 January 1st 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 new ODS Regu-lation 2037/2000 of the EU commision on ozonedepleting substances. This regulation also governsthe use of R22 for service reasons within the entireEU.

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

Dis

char

ge g

as t

emp

. [˚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

Pre

ssur

e [b

ar]

Temperature [˚C]

1

25

0 60

6

15

4

10

20

-40 -20

R12

R22

R502

2

4020

Although the chlorine free substitutesR134a and R404A/R507A (Fig. 1 and 3) haveextensively made their way as substitutesfor R12 and R502, in many internationalfields R22 is still used in new installationsand for retrofitting of existing systems.

Reasons are relatively low investmentcosts, especially compared with R134asystems, but also in its large applicationrange, favourable thermodynamic proper-ties and low energy requirement. Addi-tionally there is world wide availability ofR22 and the proven components for it,which is not yet guaranteed everywherewith the chlorine free alternatives.

The latter is also true for the “zeotropic”service refrigerants (Fig. 1 and 2). More-over, they predominantly contain R22 andtherefore only make sense where pureR22 cannot be controlled due to highoperation temperatures. Related to thesemixtures special handling procedures arerequired (see section “Refrigerant blends”from page 13).

HCFC Refrigerants

9

An incomparably wide palette is avail-able from BITZER for use with R22:❏ Open and semi-hermetic reciprocat-

ing compressors from 0.37 to 74 kWnominal motor power with specialdesign features for low temperatureuse– VARICOOL semi-hermetic (up to

5.5 kW)– Single stage semi-hermetic

with (up to 60 kW)– Two stage compressors

(up to 44 kW)❏ Open and semi-hermetic screw com-

pressors from 15 to 220 kW nominalmotor power (parallel operation to620 kW) for single and two stagesystems.

Converting existing plants

Existing R12 plants can only subsequentlybe converted to R22 under restrictionswithout exchanging major components.Even if the compressor, heat exchangerand pressure vessel are suitable for oper-ation with R22, the refrigeration capacityand energy requirement (with identicalcompressor displacement) are significant-ly higher after the conversion. The tem-perature differences at the evaporator andcondenser will be much greater and ab-normal or critical operating conditionscould even occur.

The installation of a compressor with asmaller displacement (same capacity aswith R12) could on the other hand lead tounstable operation of the evaporator and

oil migration due to the reduced flowvelocities.

R502 plants can in many cases be con-verted to R22 with reasonable effort. Theindividual components must however bechecked for suitability and possibly bemodified or exchanged.In this connection the significantly lowermass flow of R22 must also be considered.

®

Supplementary BITZER information(see also http://www.bitzer.de)

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

R134a as substitute forR12 and R22

10

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

Rel

atio

n R

134a

to

R12

(=10

0%)

Evaporation [˚C]

80

110

0 10

90

100

COP

Qo

85

95

105

-30 -20 -10

t c 5

0˚C

tc 50˚C

tc 40˚C

toh 20˚C

t c 4

0˚C

Rel

atio

n R

134a

to

R22

(=10

0%)

Evapration [˚C]

50

110

10 20

70

COP

Qo

60

80

100

-20 -10 0

toh 20˚C

90

tc 40˚C

tc 50˚C

tc 50˚C

tc 40˚C

tion with low evaporating temperatures tobe considered. Comprehensive tests have demonstratedthat the performance of R134a exceedstheoretical predictions over a wide rangeof compressor operating conditions. Temperature levels (discharge gas, oil) areeven lower than with R12 and, therefore,substantially lower than R22 values. Thereare thus many potential applications inair-conditioning and medium temperaturerefrigeration plants. Good heat transfercharacteristics in evaporators and con-densers (unlike zeotropic blends) favourparticularly an economical use.

Lubricants for R134a and other HFCs

The question of a suitable lubricant forR134a (and other HFCs described in thefollowing) has been found to be a prob-lem. The traditional mineral and syntheticoils are not miscible (soluble) with R134aand are therefore only insufficiently trans-ported around the refrigeration circuit.Immiscible oil can settle out in the heatexchangers and prevent heat transfer tosuch an extent that the plant can nolonger be operated. New lubricants weredeveloped with the appropriate solubilityand have now – after a long test phase –been in use for several years. These lubri-cants are based on Polyol Ester (POE)and Polyalkylene Glycol (PAG).

They have similar lubrication characteris-tics to the traditional oils, but are more orless hygroscopic, dependent upon therefrigerant solubility. This demands special care during manu-facturing (including dehydrating), trans-port, storage and charging, to avoidchemical reactions in the plant, such ashydrolysis.

PAG based oils are especially critical withrespect to water absorption. Moreover,they have a relatively low dielectric

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-conditioningunits with good results. As well as beingused as a pure substance R134a is alsoapplied as a component of a variety ofblends (see “Refrigerant blends”, page 13).

R134a has similar thermodynamic prop-erties to R12:

Refrigeration capacity, energy require-ment, temperature properties and pres-sure levels are comparable, at least in air-conditioning and medium temperaturerefrigeration plants. This refrigerant cantherefore be used as an alternative formost R12 applications.

For some applications R134a is evenpreferred as a substitute for R22, animportant reason being the limitations tothe use of R22 in new plants. However,the lower volumetric refrigeration capacityof R134a (see Fig. 11/2) requires a largercompressor displacement than with R22.There are also limitations in the applica-

Chlorine free HFC refrigerants

11

Chlorine free HFC refrigerants

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

Pre

ssur

e [b

ar]

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)

❏ Technical Information KT-620“HFC-Refrigerant R134a”

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

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

❏ Special edition 09.04“A new generation of compact screwcompressors optimised for R134a”

strength and for this reason are not verysuitable for semi-hermetic and hermeticcompressors. They are therefore mainlyused in car A/C systems with open com-pressors, where specific demands areplaced on lubrication and optimum solu-bility is required because of the high oilcirculatation rate. In order to avoid copperplating, no copper containing materialsare used in these systems either. The rest of the refrigeration industryprefers ester oils, for which extensiveexperience is already available. Theresults are generally positive when thewater content in the oil does not muchexceed 100 ppm.

In the meantime, compressors for factorymade A/C and cooling units are increas-ingly being charged with Polyvinyl Ether(PVE) oils. Although they are even morehygroscopic than POE, on the other handthey are very resistant to hydrolysis, ther-mally and chemically stable, possessgood lubricating properties and highdielectric strength. Unlike POE they donot tend to form metal soap and thus thedanger of capillary clogging is reduced.

Resulting design and construction criteria

Suitable compressors are required forR134a with a special oil charge, andadapted 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 par-ticular care and the charging or changingof lubricant must also be done carefully.In addition relatively large driers should beprovided, which have also to be matchedto the 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 beendiscussed very controversially, severalconversion methods were recommended

and applied. Today there is a generalagreement on technically and economical-ly matching solutions.Here, the characteristics of ester oils arevery favourable. Under certain conditionsthey can be used with CFC refrigerants,they can be mixed with mineral oils andtolerate a proportion of chlorine up to afew hundred 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 also been found,with systems where the chemical stabilitywas already insufficient with R12 opera-tion e.g. with bad maintenance, smalldrier capacity, high thermal loading. Theincreased deposition of oil decompositionproducts containing chlorine often occurshere. These products are released by theworking of the highly polarized mixture ofester oil and R134a and find their way intothe compressor and regulating devices.Conversion should therefore be limited tosystems which are in a good condition.

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

In future, a new EU Directive on "Emis-sions from MAC systems” will ban the useof R134a in new systems. Several alterna-tive technologies are already being devel-oped. See the pertaining explanations onpages 12 and 31.

For mobile air-conditioning systems(MAC) with open drive compressors andhose connections in the refrigerant circuit,the risk of leakages is considerably higherthan with stationary systems. With a viewto reducing direct emissions in this appli-cation area, an EU Directive (2006/40/EC) has therefore been passed. Within thescope of the Directive, and starting 2011,type approvals for new vehicles will onlybe granted if they use refrigerants with aglobal warming potential (GWP) of lessthan 150. Consequently, this excludesR134a which has been used so far inthese systems (GWP = 1300).

Meanwhile, alternative refrigerants andnew technologies are being developedand tested. This also involved a closerexamination of the use of R152a. Sincesome time, the focus has been on spe-cially adapted CO2 plants (see page 31)as well as system solutions with socalled“low GWP” refrigerants. The latter will bedescribed in the following.

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=140).

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.

12

Chlorine free (HFC) refrigerants

The forthcoming ban on the use of R134ain mobile air-conditioning systems withinthe EU has triggered a series of researchprojects. Apart from the CO2 technology(page 31), new refrigerants with very lowGWP values and similar thermodynamicproperties as R134a have been devel-oped.

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 wereblends of various fluorinated molecules.

During the development and test phase itbecame obvious that not all acceptancecriteria could be met, and thus furtherexaminations with these blends were dis-continued.Consequently, DuPont* and Honeywell*bundled their research and developmentactivities in a joint venture which focusedon 2,3,3,3-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 decompo-sition in the atmosphere. This raises cer-tain concerns regarding the long-term sta-bility in refrigeration circuits under realconditions. However, extensive testinghas demonstrated the required stabilityfor mobile air-conditioning systems.

HFO-1234yf has mild flammability asmeasured by ASTM 681, but requires sig-nificantly more ignition energy thanR152a, for instance. Because of its lowflame speed, it would be expected to re-ceive a classification of "A2L” from ISO 817, and a rating of "A2” fromASHRAE. A comprehensive series of testshave proven that the mild flammabilitydoes not provide an extra risk for themobile air-conditioning application.

Toxicity investigations have shown verypositive results, as well as compatibility

tests of the plastic and elastomer materi-als and lubricants used in the refrigerationcircuit.

Operating experiences gained from labo-ratory and field trials to date allow a posi-tive assessment, particularly with regardto performance and efficiency behaviour.For the usual range of mobile air-condi-tioning operation, cooling capacity andcoefficient of performance (COP) are with-in a range of 5% compared with that ofR134a. Therefore, it is expected that sim-ple system modifications will provide thesame performance as with R134a.

Critical temperature, pressure level, va-pour density, and mass flow are also simi-lar, whereas the discharge gas tempera-ture is up to about 10 K lower.

Continuing tests of HFO-1234yf are un-derway, with a concluding assessment ofHFO-1234yf vs. R134a expected by theend of 2008.

The use of HFO-1234yf in other mobileair-conditioning applications is also beingconsidered, as well as in stationary A/Cand heat pump systems. For the latter,however, the leakage rates and thereforethe direct global warming impact are ex-tremely low. In addition, there are ques-tions regarding chemical stability duringthe generally very long running times ofsuch plants, which must be addressed.

Alternatives to R134a

R152a – an alternative to R134a (?)

“Low GWP” refrigerantHFO-1234yf

* Besides of DuPont and Honeywell also Arkemahas now launched a programme for industrialproduction of this new product (press releaseJuly 9, 2008).

13

Refrigerant blends

Refrigerant blends have been developedfor existing as well as for new plants withproperties making them comparable alter-natives to 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 twocategories:

1. Transitional or service blendsMost of these blends contain HCFC R22as the main constituent. They are prima-rily intended as service refrigerants forexisting plants with view on the phase-out of R12, R502 and other CFCs. Corresponding products are offered byvarious manufacturers, the practical ex-perience covering the necessary steps of conversion procedure are mainlyavailable.However, the same legal requirementsapply for the use and phase-out regula-tions of these blends as for R22 (see page 8).

2. Chlorine free HFC blends These are long term substitutes for therefrigerants R502, R22, R13B1 andR503. Above all, R404A, R507A, R407Cand R410A, are already being used to a great extent. One group of these HFC blends alsocontains hydrocarbon additives. The lat-ter exhibit a particularly good solubilitywith lubricants, and under certain condi-tions they allow the use of conventionaloils. In many cases, this opens up possi-bilities for the conversion of existing(H)CFC plants to chlorine-free refriger-ants (ODP = 0) without the need for anoil change.

Two and three component blends alreadyhave a long history in the refrigerationtrade. A difference is made between the socalled “azeotropes” (e.g. R502, R507A)with thermodynamic properties similar to single substance refrigerants, and“zeotropes” with “gliding” phase changes

Refrigerant blends (see also next section). The developmentof “zeotropes” was mainly concentratedon special applications in low temperatureand heat pump systems. Actual systemconstruction remained however the ex-ception.

A somewhat more common earlier prac-tice was the mixing of R12 to R22 in orderto improve the oil’s return flow and to re-duce the discharge gas temperature withhigher pressure ratios. It was also usual toadd R22 to R12 systems for improvedperformance, or to add hydrocarbons inthe extra low temperature range for a bet-ter 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 R22is available from the chlorine free singlesubstance series of alternative refriger-ants. A similar situation can be stated forR13B1 and R503.

If flammability is unacceptable, and toxi-cological certainty is required and in addi-tion, application range, COP, pressure andtemperature conditions are to be compar-able, the only substitutes which remainfor the long term, in addition to R134a forR12, 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 appli-cations 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 wasobtained for the optimizing of the mix-ing proportions and for testing suitablelubricants. Based on this data, a large

supermarket plant – with 4 semi-her-metics type 4G-20.2 in parallel – couldalready be commissioned at the start of ‘91.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 singlesubstance refrigerants with regard toevaporation and condensing processes,the phase change with zeotropic fluidsoccurs in a “gliding” form over a certainrange of temperature.

This “temperature glide” can be more orless pronounced, it is mainly dependentupon the boiling points and the percent-age proportions of the individual compo-nents. Certain supplementary definitionsare also being used, depending on theeffective values, such as “near-azeotrope”or “semi-azeotrope” for less than 1 Kglide.

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

To enable a comparison with single sub-stance refrigerants, the evaporating andcondensing temperatures have beenmostly defined as mean values. As a con-sequence the measured subcooling andsuperheating conditions (based on meanvalues) are unreal. The effective result –related to dew and bubble temperature –is less in each case.

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 com-pressor capacity, the revised standards

14

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

Pre

ssur

e

Enthalpy

Temperature glideMean condensing temperatureMean evaporating temperature

Δtgtcmtom

CC1

DD1

A A1

B B1

Isotherms

Δtg

Δtgtcm

tom

Bubbl

e Li

ne

Dew

line

Pre

ssur

e [b

ar]

Temperature [˚C]

-40 40 60-20 0 20

25

15

1

20

10

2

4

6

R404A

R502R403B

Refrigerant blends

EN12900 and ARI540 are applied. Evapo-rating and condensing temperatures referto saturated 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 subcoolingtemperatures 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 effec-tively lower temperature at the evaporatorinlet.

A further characteristic of zeotropic refrig-erants 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, with-in the evaporator and condenser/ receiverare considered 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 leakageleads to less serious changes in concen-tration than was previously thought. It isin any case certain that the following sub-stances which are dealt with here cannotdevelop any flammable mixtures, either in-side or outside the circuit. Essentially sim-ilar operating conditions and temperaturesas before can only be obtained by supple-mentary charging with the original refrig-erant in the case of a small temperatureglide.

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

❏ The plant always has to be chargedwith liquid refrigerant. When vapour istaken from the charging cylinder shiftsin concentrations 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 significanttemperature glide is not recommendedfor plants with flooded evaporators. A large concentration shift is to be expected in this type of evaporator, and as a result also in the circulating refrigerant mass flow.

15

Service blends

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

The basic component is in each caseR22, the high discharge gas temperatureof which is significantly reduced by theaddition of chlorine free substances withlow isentropic compression exponent (e.g. R125, R143a, R218). A characteristicfeature of these additives is an extraordi-narily high mass flow, which enables themixture to achieve a great similarity to R502.R290 (Propane) is added as the thirdcomponent to R402A/B and R403A/B toimprove miscibility with traditional lubri-cants as hydrocarbons have especiallygood solubility characteristics.

For these blends two variations are offeredin each case. When optimizing the blend

variaions 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)leads to limitations in the application range.

On the other hand a higher proportion ofR125 or R218, which has the effect ofreducing the discharge gas temperatureto the level of R502, results in somewhathigher cooling capacity (Fig. 16).

With regard to material compatibility theblends can be judged similarly to (H)CFCrefrigerants. The use of conventional re-frigeration oil (preferably semi or full syn-thetic) is also possible due to the R22 andR290 proportions.

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 propor-tion has (although low) an ozone depletionpotential. The additional componentsR125, R143a and R218 still have a com-paratively high global warming potential.

Resulting design criteria/Converting existing R502 plants

The compressor and the componentswhich are matched to R502 can remain inthe system in most cases. The limitationsin the application range must however beconsidered: Higher discharge gas temper-ature as for R502 with R402B**, R403A**and R408A** or higher pressure levelswith R402A** and R403B**.

Due to the good solubility characteristicsof R22 and R290 an increased dangerexists, that after conversion of the plant,possible deposits of oil decompositionproducts containing chlorine may be dis-solved and find their way into the com-pressor and regulating devices. Systemswhere the chemical stability was alreadyinsufficient with R502 operation (badmaintenance, low drier capacity, high thermal loading) are particularly at risk.

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

** Classification according to ASHRAE nomenclature *** Meanwhile, R403A (ISCEON 69S – Rhodia) is no

longer available in the market. However, for development-historic reasons of service blends,this refrigerant will continue to be covered in this report.

Service blends with thebasic component R22* assubstitutes for R502

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

Dis

char

ge g

as t

emp

. [˚C

]

Content of R218 [%]

170

0 6020 40

165

150

115

120

130

140

R40

3A

R40

3B

R502

totctoh

R22

-35°C40°C20°C

145

155

135

125

160

Com

par

ison

of p

erfo

rman

ce 110

105

100

95

90

85

[%]

totctoh

-35°C

40°C

20°C

115

Qo COP

R50

2

R40

2A (

HP

80)

R40

2B (

HP

81)

R40

3B (

69L

)

R40

3A (

69S

)

R40

8A (

FX

10)

R40

3B (

69L

)

R40

3A (

69S

)

R40

8A (

FX

10)

R50

2

R40

2A (

HP

80)

R40

2B (

HP

81)

16

The basic suitability of BITZER com-pressors has already been establishedby laboratory and field tests. Howeveras the result of a conversion is verymuch dependent upon the previouscondition of the plant (see above expla-nation), the judgement of a possibleguarantee claim must be made subjectto the examination of the compressor.

Before conversion generously dimen-sioned suction gas filters and liquid linedriers should therefore be fitted for clean-ing and after approximately 100 hoursoperation an oil change should be made;further checks are recommended.

The operating conditions with R502 (in-cluding discharge gas temperature andsuction gas superheat) should be notedso that a comparison can be made withthe values after conversion. Dependingupon the results regulating devices shouldpossibly be reset and other additionalmeasures should 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”

Although as experience already shows,R134a is also well suited for the conver-sion of existing R12 plants, the generaluse for such a “retrofit” procedure is notalways possible. Not all compressorswhich have previously been installed aredesigned for the application with R134a.In addition a conversion to R134a requiresthe possibility to make an oil change,which is for example not the case withmost hermetic type compressors.

Economical considerations also arise,especially with older plants where theeffort in converting to R134a is relatively

Service blends as substi-tutes for R12 (R500)

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”

Service blends

high. The chemical stability of such plantsis also often insufficient and therefore thechance of 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). 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 tothe major proportion of HCFC.

A further service blend is offered underthe designation R413A (ISCEON MO49 –DuPont). The constituents consist of thechlorine free substances R134a, R218,and R600a. In spite of the high R134acontent the use of conventional lubricantsis possible because of the relatively lowpolarity of R218 and the favourable solu-bility of R600a. Oil migration may, how-ever, result in systems with a high oil cir-culation rate and/or a large liquid volume inthe receiver – for example if no oil separatoris installed.

If insufficient oil return to the compressoris observed, the refrigerant manufacturerrecommends replacing part of the originaloil charge with ester oil. But from the compressor manufacturer's view, such ameasure requires a very careful examina-tion of the lubrication conditions. Forexample, if increased foam formation in the compressor crankcase is observed, a complete change to ester oil will be necessary. Moreover, under the influenceof the highly polarized blend of ester oiland HFC, the admixture of or conversionto ester oil leads to increased dissolving of decomposition products and dirt in thepipework. Therefore, generously dimen-sioned suction clean-up filters must beprovided. For further details, see the refrigerant manufacturer's “Guidelines”.

R413A will be replaced by R437A at theend of 2008. This blend contains R125,R134a, R600 and R601. R437A has similarproperties and performance as R413A, andalso zero ODP.

The application criteria for R413A are alsovalid for R437A.

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 res-tricted to changing the refrigerant (possi-bly oil) and a careful check of the super-heat setting of the expansion valve. A significant temperature glide is presentdue to the relatively large differences inthe boiling points of the individual sub-stances (Fig. 34, page 35), which demandsan exact knowledge of the saturation con-ditions (can be found from vapour tablesof refrigerant manufacturer) in order toassess the effective suction gas superheat.

In addition the application range must al-so be observed.Different refrigerant types are required forhigh and low evaporating temperatures ordistinct capacity differences must be con-sidered (data and application ranges seepages 34 to 37). 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 thanwith R12. The application limits of thecompressor should therefore be checkedbefore converting.The remaining application criteria are simi-lar to those for the substitute substancesfor R502 which have already been men-tioned.

17

Chlorine free R502 and R22 alternatives (blends)

These blends are substitutes which areabsolutely chlorine free (ODP=0) and aretherefore long term alternatives for R502as well as for R22 in medium and lowtemperature 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.Further blends were traded as „Forane“FX70 (Atofina) and “Genetron” AZ50(Allied Signal/Honeywell) or “Solkane” 507(Solvay). In the mean time HP62 and FX70have been listed in the ASHRAE nomen-clature 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 R125the flammability is effectively counteract-ed and also in the case of leakage.

A feature of all three ingredients is thevery low isentropic compression exponentwhich results in a similar, with even a ten-

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

Dis

char

ge g

as t

emp

. of R

404A

– r

elat

ive

diff

eren

ce t

o R

502

[K]

Evaporating [˚C]

-20-40 -30 -20 -10

tc 55°C

tc 40°C

toh 20°C

-10

0

+10

Com

par

ison

of p

erfo

rman

ce

100

95

90

80

[%] totctoh

-35°C

40°C

20°C

105

Qo

85

COP

R50

2

R40

4A

R50

7A

R50

2

R40

4A

R50

7A

R404A and R507A assubstitutes for R502and R22

dency to be lower, discharge gas temper-ature to R502 (Fig. 17). The efficient appli-cation of single stage compressors withlow evaporating temperatures is thereforeguaranteed.

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 differentas with azeotropes. The results obtainedso far from heat transfer measurementsshow favourable conditions.

R507A is a binary substance combinationwhich even gives an azeotropic character-istic over a relatively wide range. The con-ditions therefore tend to be even better.

The performance found in laboratory tests (Fig. 18) gives hardly any differencebetween the various substances and showa large amount of agreement with R502.This justifies the good market penetrationof these substitutes.Questions concerning material compatibil-ity are manageable; experience with otherHFCs justifies a positive assessment.POE oils can be used as lubricants; the

suitability of various alternatives is beinginvestigated as well (see pages 10 and 11).

The relatively high global warming poten-tial (GWP100 = 3260…3300) which ismainly determined by the R143a andR125 is something of a hitch. It is how-ever improved compared to R502 andwhich with regard also to the favourableenergy requirement leads to a reductionof the TEWI value. Other improvementsare possible in this respect due to furtherdeveloped system control including forexample the controlled lowering of thecondensing temperature with low ambienttemperatures.

Resulting design criteria

The system technology can be based onthe experience with R502 over a widearea. On the thermodynamic side, a heatexchanger between the suction and liquidline is recommended as this will improvethe refrigeration capacity and COP.

The availability of the refrigerants is guar-anteed.

18

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

❏ Technical Information KT-630“HFC Refrigerant Blends”

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

❏ Technical Information KT-510 “Polyolester oils forreciprocating compressors”

-and R-22

Alternatively to the earlier described sub-stitutes additional mixture versions havebeen developed based on R32 which ischlorine free (ODP=0) and flammable likeR143a.

The refrigerant R32 is also of the HFC typeand primarily seen as a candidate for R22alternatives (page 20). Due to the extentof the blend variations however comparablethermodynamic characteristics to R502can also be obtained.

Such kind of refrigerants were at first inthe market under the trade name KLEA60/61 (ICI) and are listed as R407A/R407B*in the ASHRAE nomenclature.

The necessary conditions, however, forR502 alternatives containing R32 are notquite as favourable compared to theR143a based substitutes as dealt withearlier. The boiling point of R32 is verylow at -52°C, in addition the isentropiccompression exponent is similarly high aswith R22. To match the characteristics ofR502 therefore requires relatively highproportions of R125 and R134a. The flam-mability of the R32 is thus effectively sup-

pressed, at the same time the large differ-ences in the boiling points with a highproportion of R134a leads to a larger tem-perature glide.

The main advantage of R32 is the extra-ordinarily low global warming potential(GWP100 = 650) so that even in combina-tion with R125 and R134a it is significant-ly lower than with the R143a based alter-natives mentioned above.

Measurements made with R32 containingblends do show certain capacity reduc-tions compared to R502 with low evapor-ating temperatures, the COP howevershows less deviation (Fig. 20). The TEWIvalues are relatively low, together with theadvantageous global warming potential.

Where these favourable prospects areconfirmed in real applications is subject to the system criteria.

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 tothe HFC substitutes described before; thesame applies to the lubricants.

Apart from laboratory investigationsBITZER has been co-ordinating a wideprogram of field tests to obtain the nec-essary operating experience over awide area for several years. BITZER offers the whole program ofreciprocating, scroll and screw com-pressors including the suitable oils forthese blends.

Converting existing (H)CFC plants

Experience gained in investigative pro-grams shows that qualified conversionsare possible. However, major expendituremay be necessary depending on the sys-tem design.

R407A and R407B as sub-stitutes for R502 and R22


Fig. 19 Comparison of discharge gas temperature of a semi-hermetic compressor

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

Dis

char

ge g

as te

mp.

of R

407A

/B –

rela

tive

diffe

renc

e to

R50

2 [K

]

Evaporation [˚C]

-10-40 -30 -20 -10

0

+10

+20

R407A

toh

R407B

40°Ctc

20°C

Com

par

ison

of p

erfo

rman

ce

Qo

100

95

90

75

[%] totctoh

-35°C

40°C

20°C

105

80

COP

R50

2

R40

7A

R40

7B

R50

2

R40

7A

R40

7B

19


Despite the relatively high proportion ofR125 and R134a in the R32 blends aimedat R502 characteristics, the discharge gastemperature is somewhat higher than withthe R143a based alternatives. As a resultcertain limitations occur in the applicationrange. 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 con-ditions are found. An important advantagethereby is the use of a liquid subcooler.


The experience with R502 and R22 canbe used for the plant technology in manyrespects, considering the temperatureglide as well as the difference in the thermodynamic properties. This is espe-cially the case for designing and con-structing heat exchangers and expansionvalves.The refrigerants are available. Occassion-ally, individual selection will be requiredfor the necessary components.

* Meanwhile, R407B is no longer available in themarket. Due to the historical development of HFCblends this refrigerant will, however, still be con-sidered in this Report.

BITZER offers a complete range of semi-hermetic reciprocating compressors –including suitable oil – for these blends.

Converting existing CFC plants

Practical experiences show that qualifiedconversions are possible. Compared toR22 the volumetric refrigeration capacityis nearly similar while the refrigerant massflow is only slightly higher (up to approx.15%). These are relatively favourable con-ditions for the conversion of medium andlow temperature R22 systems. The maincomponents can remain in the systemprovided that they are compatible withHFC refrigerants and ester oils. However,special requirements placed on the heatexchanger with regard to the significanttemperature glide must be considerd. Aconversion to ester oil is also necessary,

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

❏ Technical Information KT-630 “HFC Refrigerant Blends”

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

❏ Technical Information KT-510“Polyolester oils for reciprocating compressors”

Amongst other aims, R422A (ISCEONMO79 – DuPont) was developed in orderto obtain a chlorine-free refrigerant (ODP = 0) for the simple conversion ofexisting medium and low temperaturerefrigeration systems using 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 rela-tively high R134a percentage, the temper-ature glide (Fig. 34) lies higher than forR404A, but lower than other refrigerantswith the same component blends – suchas R417A and R422D (see page 22).

The adiabatic exponent, compared toR404A and R507A, is smaller and there-fore the discharge gas and oil tempera-tures of the compressor, too. Underextreme low temperature conditions thiscan be advantageous. In cases of lowpressure ratio and suction gas superheat

R422A as substitute forR502 and R22

this can be negative due to increasedrefrigerant solution if ester oil is used.

The material compatibility is comparableto the blends mentioned previously, thesame applies to the lubricants, as well.On account of the good solubility ofR600a, conventional lubricants can alsobe used under favourable circumstances.

In particular, advantages result during theconversion of existing R502 and R22 sys-tems as mentioned above. However, forplants with high oil circulation ratesand/or large 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 compressoris observed, the refrigerant manufacturerrecommends replacing part of the originaloil charge with ester oil. But from thecompressor manufacturer's view, such ameasure requires a very careful examina-tion of the lubrication conditions. Forexample, if increased foam formation inthe compressor crankcase is observed, a complete change to ester oil* will benecessary. Under the influence of thehighly polarized blend of ester oil andHFC, the admixture of or conversion toester oil leads to increased dissolving ofdecomposition products and dirt in thepipework. Therefore, generously dimen-sioned suction clean-up filters must beprovided. For further details, see the refrigerantmanufacturer's “Guidelines”.

From a thermodynamic point of view a heat exchanger between suction andliquid line is recommended, therebyimproving the cooling capacity and coefficient of performance. Besides thisthe resulting increase in operating tem-peratures leads to more favourable lubri-cating conditions (lower solubility).

* General proposal for screw compressors and liquidchillers when used with DX evaporators with inter-nally structured heat exchanger pipes. Further-more, an individual check regarding possible addi-tional measures will be necessary.

BITZER compressors are suitable forR422A. An individual selection is possible upon demand.

which leads to increased dissolving ofdecomposition products and dirt in thepipework. Therefore, generously dimen-sioned suction clean-up filters must beprovided.

20

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

Fig. 22 R407C/R22 – comparison of pressure levels

Rel

atio

n R

407C

to

R22

(=10

0%)

Evaporation [˚C]

80

110

10 20

90

100

85

95

105

-20 -10 0

COP

Qo

tc 40˚C

tc 50˚C

tc 50˚C

tc 40˚C

toh 20˚C

Pre

ssur

e [b

ar]

Temperature [˚C]

-40 40 60-20 0 20

25

15

1

20

10

2

4

6

R22

R407C

Chlorine free R22 alternatives

R407C as substitutefor R22

relatively low (GWP100 = 1520), which is agood presupposition for favourable TEWIvalues.

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

Due to the properties mentioned, R407Cis preferably an R22 substitute for air-conditioning systems and (within certainlimitations) also for medium temperaturerefrigeration. In low temperature refrigera-tion, because of the high proportion ofR134a, a significant drop in cooling cap-acity and COP is to be expected. There isalso the danger of an increased R134aconcentration in the blend in evaporators,with consequential reduction in perform-ance and malfunctioning of the expansionvalve (e.g. insufficient suction gas super-heat).

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. ** Because of the high proportion (70%) of R134acontained in R407D this refrigerant cannot beregarded as an alternative to R22, but rather as a substitute to R12 for low temperature cooling.

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. R407D**/ R407E) with somewhatdiffering compositions, whose propertieshave been optimized for particular appli-cations.

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 proper-ties of R22 in terms of pressure levels,mass flow, vapour density and volumetricrefrigeration capacity is thus achieved. Inaddition, the global warming potential is

Chlorine free R22 alternatives (blends)

As the HCFC refrigerant R22 (ODP=0.05)is still widely accepted only as a transi-tional solution, a number of chlorine-free(ODP=0) alternatives have been devel-oped and tested extensively. They arealready being used on a large range ofapplications.

Experience shows, however, that none ofthese substitutes can replace the refriger-ant R22 in all respects. Amongst otherthings there are differences in the volumet-ric refrigeration capacity, restrictions inpossible applications, special requirementsin system design or also considerably dif-fering pressure levels. So various alterna-tives come under consideration accordingto the particular operating conditions.

Apart from the single-component HFCrefrigerant R134a, these are mainly blends(different compositions) of the compo-nents R32, R125, R134a, R143a, andR600(a). The following description mainlyconcerns the development and potentialapplications of these. The halogen-freesubstitutes NH3, propane and propyleneas well as CO2 should also be considered,however, specific criteria must be appliedfor their use (described from page 23).

21


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

Fig. 24 R410A/R22 – comparison of pressure levels

Rel

atio

n R

410A

to

R22

(=10

0%)

Evaporation [˚C]

80

150

10 20-20 -10 0

toh 20˚C

COP

Qo

tc 40˚C

tc 50˚C

tc 50˚C

tc 40˚C

90

140

130

120

110

100

Pre

ssur

e [b

ar]

Temperature [˚C]

-40 40 60-20 0 20

25

15

20

10

2

4

6

3

35

30

R22

R410A


With regard to system technology, previ-ous experience with R22 can only be utilized to a limited extent. The distinctivetemperature glide requires a particulardesign of the main system components,e.g. evaporator, condenser, expansionvalve. In this context it must be consid-ered that heat exchangers should prefer-ably be laid out for counterflow operationand with optimized refrigerant distribution.There are also special requirements withregard to the adjustment of regulatingdevices and service handling.

Furthermore, the use in systems withflooded evaporators is not recommendedas this would result in a severe concentra-tion shift and layer formation in the evap-orator.

In addition to laboratory investigationsBITZER was also co-ordinating a com-prehensive program of field tests fromwhich the necessary operating experi-ence could be gained over a wide area.These tests have already demonstratedclearly that reliable compressor opera-tion depends entirely on the quality anddesign of the system.

BITZER can supply a range of semi-her-metic reciprocating, screw and scrollcompressors – including suitable oil – for R407C.

Converting existing R22 plants

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

In addition to R407C, there is a nearazeotropic blend being offered with theASHRAE designation R410A. It is widelyused already, mainly in air conditioningapplications.

An essential feature indicates nearly 50%higher cooling capacity (Fig. 23) in com-

R410A as substitutefor R22

parison to R22, but with the consequenceof a proportional rise in system pressure.

At high condensing temperatures, energyconsumption/COP initially seems to beless favourable than with R22. This ismainly due to the thermodynamic proper-ties. On the other hand, very high isen-tropic efficiencies are achievable (withreciprocating and scroll compressors),whereby the differences are lower in reality.

Added to this are the high heat transfercoefficients in evaporators and con-densers determined in numerous testseries, with resulting especially favourableoperating conditions. With an optimizeddesign, it is quite possible for the systemto achieve a better overall efficiency thanwith other refrigerants.

Because of the negligible temperatureglide (< 0.2 K), the general usability canbe seen similar to a pure refrigerant.

The material compatibility is comparableto the previously discussed blends andthe same applies for the lubricants. How-ever, the pressure levels and the higherspecific loads on the system componentsneed to be taken into account.

22


R427A as a substitute for R22

This refrigerant blend was introducedsome years ago under the trade nameForane FX100 (Arkema). In the meantimeit is listed in the ASHRAE nomenclatureas R427A.

This R22 substitute is offered for the conversion of existing R22 systems forwhich a “Zero ODP” solution is requested.This refrigerant is a mixture with basecomponents R32/R125/R143a/R134a.

In spite of the blend composition basedon pure HFC refrigerants, the manufactu-rer states that a simplified conversion pro-cedure is possible. Accordingly, whenconverting from R22 to R427A, all it takesis a replacement of the original oil chargewith ester oil. Additional flushing sequen-ces are not required, as proportions of up to 15% of mineral oil and/or alkyl ben-zene have no significant effect on oil cir-culation in the system.

However, it must be taken into accountthat under the influence of the highlypolarized mixture of ester oil and HFCincreased dissolving of decompositionproducts and dirt in the pipework is caused. Therefore, generously dimen-sioned suction clean-up filters must beprovided.

An individual compressor selectionis possible upon demand.

The same as for R422A (page 19), one ofthe aims for both developments was to pro-vide chlorine-free refrigerants (ODP = 0) forthe simple conversion of existing R22 plants.

R417A was introduced to the market sev-eral years ago, and is also offered underthe trade name ISCEON MO59 (DuPont).This substitute for R22 contains the blendcomponents R125/R134a/R600, andtherefore differs considerably from e.g.R407C with a correspondingly high pro-portion of R32.

Another blend version with the same maincomponents, but with R600a as hydrocar-bon additive, was introduced early in2003 (trade name ISCEON MO29), andmeanwhile is listed as R422D in theASHRAE nomenclature. Because of itslow R134a content, the volumetric coolingcapacity as well as the pressure levels arehigher than with R417A. This results indifferent performance parameters andemphasis in the application range.

Like R407C, both refrigerants are zeo-trop-ic blends with a significant temperatureglide. In this respect the criteria describedin connection with R407C are also valid.

Despite similar refrigeration capacity thereare fundamental differences in thermody-namic properties and in oil transportbehaviour. The high proportion of R125causes a higher mass flow than withR407C, a lower discharge gas tempera-ture and a relatively high superheatingenthalpy. These properties indicate thatthere could be differences in the optimiza-tion of system components and a heatexchanger between liquid and suctionlines might be of advantage.

Despite the predominant proportion ofHFC refrigerants the use of conventionallubricants is possible to some extentbecause of the good solubility propertiesof the R600(a) constituent. R422D hasachieved particular success in supermar-ket retrofits from R22 without oil change.However, in systems with a high oil circu-

R417A and R422Das substitutes for R22

lation rate and/or a large volume of liquidin the receiver oil migration may result.

In such cases, additional measures arenecessary. For further information on oilreturn and lubricants with R417A andR422D, see the previous section on"R422A as substitute for R502 and R22”(page 19).

BITZER compressors are suitable for R417A and R422D. An individual selection is possible upon demand.


The fundamental criteria for HFC blendsalso apply to the system technology withR410A, however the extreme high pres-sure levels have to be considered (43°Ccondensing temperature already corre-sponds to 26 bar abs.).

Compressors and other system compo-nents of “standard design” have substan-tial limitations for the application of thisrefrigerant. However, due to the favou-rable properties of R410A considerableeffort is taken for the development of suitable products.

When considering to cover usual R22application ranges, the significant differ-ences in the thermodynamic properties(e.g. pressure levels mass and volumeflow, vapour density) must be evaluated.

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 anddimensions of piping and flexible tubeelements (for condensing temperatures of approx. 60°C/40 bar).

Another criterion is the relatively low criti-cal temperature of 73°C. Irrespective ofthe design of components on the highpressure side, the condensing temperatureis thus limited.

BITZER has done comprehensive research with R410A and accompaniedby a series of field tests. In the mean-time, BITZER offers two series of Octa-gon® and scroll compressors for R410A– including the suitable oil.

23

Halogen free refrigerants

The refrigerant NH3 has been used for morethan a century in industrial and larger refri-geration plants. It has no ozone depletionpotential and no direct global warmingpotential. The efficiency is at least as goodas with R22, in some areas even morefavourable; the contribution to the indirectglobal warming effect is therefore small. In addition it is incomparably low in price.Summarized, is this then an ideal refrige-rant and an optimum substitute for R22 oran alternative for HFCs!? NH3 has indeedvery positive features, which can also bemainly exploited in large refrigeration plants.

Unfortunately there are also negativeaspects, which restrict the wider use inthe commercial area or require costly andsometimes new technical developments.

A disadvantage with NH3 is the high isen-tropic exponent (NH3=1.31 / R22= 1.18 /R12=1.14), that results in a dischargetemperature which is even significantlyhigher than that of R22. Single stagecompression is therefore already subject tocertain restrictions below an evaporatingtemperature of around -10°C.

The question of suitable lubricants is alsonot satisfactorily solved for smaller plantsin some kinds of applications. The oils usedpreviously were not soluble with the refriger-ant. They must be separated with compli-cated technology and seriously limit theuse of “direct expansion evaporators” dueto the deterioration 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 remainfor years in the circuit without losing anyof its stability.

NH3 has an extraordinarily high enthalpydifference and as a result a relativelysmall circulating mass flow (approximately13 to 15% compared to R22). This featurewhich is favourable for large plants makes

NH3 (Ammonia) as alternative refrigerant

the regulation of the refrigerant injectionmore difficult 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 difficultyarises from the electrical conductivity ofthe refrigerant with higher moisture content.

Additional characteristics include toxicityand flammability, which require specialsafety measures for the construction andoperation of such plants.

Resulting design and construction criteria

Based on the present “state of technolo-gy”, industrial NH3 systems demand total-ly different plant technology, compared tousual commercial systems.

Due to the insolubility with the lubricatingoil and the specific characteristics of therefrigerant, high efficiency oil separatorsand also flooded evaporators with gravityor pump circulation are usually employed.Because of the danger to the public andto the product to be cooled, the evapora-tor often cannot be installed directly atthe cold space. The heat transport mustthen take place with a secondary refrige-rant circuit.

Two stage compressors or screw com-pressors with generously sized oil coolers,must already be used at medium pressureratios, due to the unfavorable thermalbehaviour.

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 andthe refrigerant charge.

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

These measures significantly increase the expenditure involved for NH3 plants,especially in the medium and smallercapacity area.

Efforts are therefore being made world-wide to develop simpler systems whichcan also be used in the commercial area.

A part of the research programs is dealingwith part soluble lubricants, with the aimof improving oil circulation in the system.Simplified methods for automatic return ofnon-soluble oils are also being examinedas an alternative.

BITZER is strongly involved in theseprojects and has a large number ofcompressors operating. The experien-ces 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 manu-facturers have developed special evapo-rators, where the refrigerant charge canbe significantly 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 reservoirto absorb NH3 in case of a leak. This typeof compact unit can be installed in areaswhich were previously reserved for plantswith halogen refrigerants due to the safetyrequirements.

24


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

Dis

char

ge g

as t

emp

erat

ure

[˚C

]

Evaporation [˚C]

-40 10-20 040

60

140

100

80

tc

Δ tohη

40°C10K0,8

R290

R134a

R404A

-10-30

120R22

NH3

R723

160

180

Pre

ssur

e [b

ar]

Temperature [˚C]

1

25

0 60

6

15

4

10

20

-40 -20

2

4020

R22NH3

The previously described experienceswith the use of NH3 in commercial refrige-ration plants with direct evaporation caused further experiments on the basisof NH3 under the addition of an oil solublerefrigerant component. The main goalswere an improvement of the oil transportcharacteristics and the heat transmissionwith conventional lubricants along with areduced discharge gas temperature forthe extended application range with singlestage compressors.

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”

R723 (NH3/DME) as analternative to NH3

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 viewpo-int and presupposing an acceptable pricelevel, it is anticipated that a wider rangeof products 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 anBooster applications

❏ Open screw compressors (displace-ment 84 to 410 m3/h – with parallel operation to 2460 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 arefrigerant blend of NH3 (60%) and dime-thyl ether “DME” (40%), developed by the“Institut fuer Luft- und Kaeltetechnik,Dresden”, Germany (ILK), that has beentested in a series of real systems. As alargely inorganic refrigerant it received thedesignation R723 due to it its averagemolecular weight of 23 kg/kmol in accor-dance to the standard refrigerant nomen-clature.

DME was selected as an additional com-ponent for its properties of good solubilityand high individual stability. It has a boil-ing point of -26°C, a relatively low adia-batic exponent, is non toxic and is avail-able in a high technical standard of purity.In the given concentration NH3 and DMEform an azeotropic blend characterised bya slightly rising pressure level in compari-son to 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)and thereby allows for an extension of theapplication range to higher pressure

Conversion of existing plants

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

25


ratios. On the basis of thermodynamiccalculations a single-digit percent rise incooling capacity results when comparedto NH3. The coefficient of performance issimilar and is even more favourable athigh pressure ratios, which experimentshave confirmed. Due to the lower tem-perature level during compression an improved volumetric and isentropic ef-ficiency is also to be expected, at leastwith reciprocating compressors in case of an increasing pressure ratio.

Due to the higher molecular weight ofDME, mass flow and vapour density in-crease with respect to NH3 by nearly 50%which is of little importance to commercialplants, especially in short circuits. In clas-sical industrial refrigeration plants, how-ever, this is a substantial criterion withregard to pressure drops and refrigerantcirculation. Also from this standpoint itcan be clearly seen that in commercialapplications and especially in water chil-lers, R723 has its preferred utilisation.

The material compatibility is comparableto that of NH3. Although non-ferrousmetals (e.g. CuNi alloys, bronze, hard sol-ders) are potentially suitable, providedthat the water content in the system is ata minimum (<1000 ppm), a system designthat corresponds with typical ammoniapractise is recommended nonetheless.

As lubricant mineral oils or (preferred)poly-alpha olefin can be used. As mention-ed before the portion of DME createsimproved oil solubility and a partial misci-bility. Besides this the relatively low liquiddensity and an increased concentration ofDME in the circulating oil, positively in-fluences the oil circulation. PAG oils wouldbe fully or partly miscible with R723 fortypical applications but are not recom-mended for reasons of the chemical stabi-lity and high solubility in the compressorcrankcase (strong vapour development inthe bearings).

Tests have shown that the heat transfercoefficient at evaporation and high heatflux is improved in systems with R723 andmineral oil than when using NH3 withmineral oil.

R290 (Propane) as sub-stitute for R502 and R22

R290 (propane) can also be used as asubstitute refrigerant. As it is an organiccompound (hydrocarbon) it does not havean ozone depletion potential and a negli-gible direct global warming effect. To takeinto consideration however, is a certaincontribution to summer smog.

The pressure levels and the refrigerationcapacity are similar to R22/R502 and thetemperature behaviour is as favourable aswith R12 and R502.

There are no particular material problems.In contrast to NH3 copper materials arealso suitable, so that semi-hermetic andhermetic compressors are possible.The mineral oils usually found in a CFCsystem can be used here as a lubricantover a wide application range.

Refrigeration plants with R290 have beenin operation world-wide for many years,mainly in the industrial area – it is a “pro-ven” refrigerant.

Meanwhile R290 is also used in smallercompact systems with low refrigerantcharges like residential A/C units and heatpumps. Furthermore, a rising trend can beseen in its use with commercial refrigera-tion systems 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 beenclassified as refrigerants of “Safety GroupA3”. With the normal refrigerant chargefound in commercial plants this meansthat the system must be designed accord-ing to “flame-proof” regulations.

The use of semi-hermetic compressors inso called “hermetically sealed” systems isin this case subject to the regulations fordanger zone 2 (only seldom and shortterm risk). The demands for the safetytechnology include special devices to pro-tect against excess pressures and specialarrangements for the electrical system. Inaddition measures are required to ensurehazard free ventilation to effectively pre-vent a flammable gas mixture occurring incase of refrigerant leakage.

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.

Further characteristics are toxicity andflammability. By means of the DME con-tent, the ignition point in air diminishesfrom 15 to 6% but, despite of this, theazeotrope still remains in the safety group B2.

Resulting layout criteria

The experiences made with the NH3 com-pact systems described above can beused in the plant technology. However,adjustments in the component layout arenecessary under consideration of the high-er mass flow. Besides a suitable selec-tion of the evaporator and the expansionvalve a very stable superheat control mustbe ensured. Due to the improved oil solu-bility “wet operation” can have consider-able negative results when compared toNH3 systems with non-soluble oil.

With regards to safety regulations thesame criteria apply to installation andoperation as in the case of NH3 plants.

Suitable compressors are special NH3versions which possibly have to be adapt-ed to the mass flow conditions and to the continuous oil circulation. An oil separator is usually not necessary withreciprocating compressors.

Bitzer NH3 reciprocating compressorsare suitable for R723 in principle. Anindividual selection of prototype com-pressors is possible on demand.

26

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

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

Rel

atio

n R

290

and

R12

70 t

o R

22 (=

100%

)

Evaporation [˚C]

80

120

-40 0 10-30 -20 -10

90

110

100

Qo (R290)

COP (R1270)

COP (R290)

Qo (R1270)

tc 40˚Ctoh 20˚C

Pre

ssur

e [b

ar]

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 equipmentin special flame-proof design.


Apart from the measures mentionedabove, propane plants require practicallyno special features in the medium and lowtemperature ranges compared with ausual (H)CFC and HFC system. When siz-ing components consideration shouldhowever be given to the relatively lowmass flow (approximately 55 to 60% com-pared to R22). An advantage in connec-tion with this is the possibility to greatlyreduce the refrigerant charge.

On the thermodynamic side an internalheat exchanger between the suction andliquid line is recommended as this willimprove the refrigeration capacity andCOP.

Due to the particularly good solubility withmineral oils, it may be necessary to usean oil with lower mixing characteristics orincreased viscosity for higher suctionpressures (air-conditioning range).

In connection to this, an internal heatexchanger is also an advantage as it leadsto higher oil temperatures thus to lowersolubility with the result of an improvedviscosity.

Due to the very favourable temperaturebehaviour (Fig. 25), single stage compres-sors can be used down to approximately -40°C evaporation temperature. R290could then also be considered as a directsubstitute for R502 or an alternative forsome 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 is offered. Extension “P” with com-pressor designation – e.g. 4CC-9.2P.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.


Supplementary BITZER informationconcerning the use of R290

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

Conversion of existing CFC plants

Due to the flame-proof protection meas-ures required for an R290 plant, it wouldappear that a conversion of existing plantsis only possible in exceptional cases.

They are limited to systems, which can bemodified to meet the corresponding safe-ty regulations with an acceptable effort.

27


levels. Tests carried out by hydrocarbonmanufacturers and stability tests in realapplications show that reactivity in refrig-eration systems is practically non-exis-tent. Doubts have occasionally been men-tioned in some literature regardingpropylene’s possible carcinogenic effects.These assumptions have been disprovedby appropriate 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 refrigerationcapacity (Fig. 27). The compressor dis-placement is correspondingly lower andtherefore also the suction and high pres-sure volume flows. Because of highervapour density the mass flow is almostthe same as for R290. As liquid density isnearly identical the same applies for theliquid volume in circulation.

As with R290 the use of an internal heatexchanger between suction and liquidlines is of advantage. However, due toR1270’s higher discharge gas temperaturerestrictions are partly necessary.

For some time there has also been in-creasing interest in using propylene(propene) as a substitute for R22/R502.Due to its higher volumetric refrigerationcapacity and lower boiling temperature(compared to R290) applications in medi-um and low temperature systems, e.g. liquid chillers for supermarkets, are ofparticular interest. On the other hand,higher pressure levels (>20%) and dis-charge gas temperatures have to be takeninto consideration, thus restricting thepossible application range.

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

Propylene is also easily inflammable andbelongs to the A3 group of refrigerants.The same safety regulations are thereforeto be observed as with propane (page 25).

Due to the chemical double linkage pro-pylene is relatively reaction friendly, whichmeans that there is a danger of polymeri-zation at high pressure and temperature

Propylene (R1270) as analternative to Propane

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

28

Fig. 29/1 R744(CO2) – Pressure-/Enthalpy-Diagram

200100 300 400 500 6000

20

40

60

80

100

120

140

160

Enthalpy [kJ/kg]

Pre

ssur

e [b

ar]

31.06°C

2 Trans-critical process

Sub-critical 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

Pre

ssur

e [b

ar]

Temperature [°C]

Carbon Dioxide R744 (CO2)as an alternative refriger-ant and secondary fluid

operation for long periods. In this connec-tion it must also be noted that the heattransfer coefficients of CO2 are consider-ably higher than of other refrigerants –with the potential of very low tempera-ture differences in evaporators, condens-ers, and gas coolers. Moreover, the nec-essary pipe dimensions are very small,and the influence of the pressure drop iscomparably low. In addition, when usedas a secondary fluid, the energy demandfor circulation pumps is extremely low.

In the following section, a few examplesof sub-critical systems and the resultingdesign criteria are described. An addition-al section provides details on trans-criticalapplications.

Sub-critical 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 cascadesystem and if required, in combinationwith a further booster stage for lowerevaporating temperatures (Fig. 30/1). The operating conditions are always sub-critical which guarantees good efficiency

cations were marine refrigeration systems,for example. With the introduction of the“Safety Refrigerants”, CO2 became lesspopular and since the fifties had nearlydisappeared.

The main reasons for that are its relativelyunfavourable thermodynamic characteris-tics for usual applications in refrigerationand air-conditioning.The discharge pres-sure with CO2 is extremely high and thecritical temperature at 31°C (74 bar) isvery low. Depending on the heat sourcetemperature at the high pressure sidetrans-critical operations with pressuresbeyond 100 bar are required. Under theseconditions, the energy efficiency is oftenlower compared to the classic vapourcompression process (with condensation),and therefore the indirect global warmingeffect is suitably higher.

Nonetheless, there is a range of applica-tions in which CO2 can be used very eco-nomically and with favourable Eco-Effi-ciency. For example, these include sub-critically operated cascade plants, butalso trans-critical systems, in which thetemperature glide on the highpressureside can be used advantageously, or thesystem conditions permit sub-critical

CO2 has had a long tradition in the refrig-eration technology reaching far into the19th century. It has no ozone depletingpotential, a negligible direct global warm-ing potential (GWP = 1), is chemicallyinactive, non-flammable and not toxic inthe classical sense. That is why CO2 isnot subjected to the stringent demandsregarding containment as apply for HFCs(F-Gas Regulation), and flammable ortoxic refrigerants. However, compared toHFCs the lower practical limit in air has tobe considered. For closed rooms this mayrequire special safety and detection systems.

CO2 is also low in cost and there is nonecessity for recovery and disposal. Inaddition, it has a very high volumetricrefrigeration capacity, which dependingon operating conditions equates to ap-prox. 5–8 times more than R22 and NH3.

Above all, the safety relevant characteris-tics were an essential reason for the initialwidespread use. The main focus for appli-



levels. 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.


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 fora 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 con-densing of the CO2 results in the cascadecooler, and the receiver tank (accumula-tor) only serves as a supply vessel.

The extremely high volumetric refrigerationcapacity of CO2 (latent heat through thechanging of phases) leads to very lowmass flow rates and makes it possible touse small cross sectional pipe and minimalenergy needs for the circulating pumps.

For the combination with a further com-pression stage, e.g. for low temperatures,there are different solutions.

Fig. 30/1 shows a variation with an addi-tional receiver where one or more Boostercompressors will pull down to the neces-sary evaporation pressure. Likewise, thedischarge gas is fed into the cascadecooler, condenses and then carried over tothe receiver (MT). The feeding of the lowpressure receiver (LT) is achieved by alevel 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 lim-ited with a view to an even distribution ofthe injected CO2.

In the case of a system breakdown wherea high rise in pressure could occur, safetyvalves can vent the CO2 to the atmos-phere with the necessary precautions.

As an alternative to this CO2 absorbingstorage systems are used where longershut-off periods can be bridged without a critical pressure increase.

For systems in commercial applications a direct expansion version is possible aswell.

Supermarket plants with their usuallywidely branched pipe work offer an espe-cially good potential in this regard. Themedium temperature system is then car-ried out in a conventional design or with asecondary circuit and for low temperatureapplication combined with a CO2 cascadesystem (for sub-critical operation). A sys-tem example is shown in Fig. 30/2.

For a general application, however, not allrequirements can be met at the moment.It is worth considering that system tech-nology changes in many respects andspecially adjusted components are nec-essary to meet the demands.

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

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

CO Cascade2HFC (NH3 / HC)*

* only with secondary system

Simplifiedsketch

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

Simplifiedsketch

CO2

LT MT

LC

PC

CPR

MT LT

NH3 / HC /HFC

29

30


Trans-critical applications

Trans-critical processes are characterizedin that the heat rejection on the highpres-sure side proceeds isobar but not isotherm.Contrary to the condensation processduring sub-critical operation, gas cooling(de-superheating) occurs, with correspon-ding temperature glide. Therefore, theheat exchanger is described as gas cool-er. As long as operation remains abovethe critical pressure (74 bar), only high-density vapour will be transported. Con-densation only takes place after expan-sion to a lower pressure level – e.g. byinterstage expansion in an intermediatepressure receiver. Depending on the tem-perature curve of the heat sink, a systemdesigned for trans-critical operation canalso be operated sub-critically, wherebythe efficiency is better under these condi-tions. In this case, the gas cooler becomesthe condenser.

Another feature of trans-critical operationis the necessary regulation of the highpressure to a defined level. This “optimumpressure” is determined as a function ofgas cooler outlet temperature by meansof balancing between the highest possibleenthalpy difference and simultaneous min-imum compression work. It must beadapted to the relevant operating condi-tions using an intelligent modulating con-troller (see system example, Fig. 31).

As described above, under purely thermo-dynamic aspects, the trans-critical 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 thehighpressure side. However, additionalmeasures can be taken for improving effi-ciency, such as the use of expanders,ejectors, and economiser systems.Apart from that, there are applicationareas in which a trans-critical process isenergetically advantageous. These includeheat pumps for sanitary water, or dryingprocesses. With the usually very hightemperature gradients between the dis-charge temperature at the gas cooler

intake and the heat sink intake tempera-ture, a very low outlet gas temperature isachievable. This is positively influencedby the temperature glide curve and therelatively high mean temperature differ-ence between CO2 vapour and secondaryfluid. The low gas outlet temperature leadsto a particularly high enthalpy difference,and therefore to a high sys-tem COP.

Low-capacity sanitary water heat pumpsare already manufactured and used inlarge quantities. Plants for medium to higher capacities (e.g. hotels, indoorswimming pools) are still in the develop-ment and introductory phase.

Apart from these specific applications,there is also a range of developments forthe classical areas of refrigeration and air-conditioning. This also covers supermar-ket refrigeration plants, for example.Meanwhile, and following extensive labo-ratory tests, real installations with parallelcompound compressors are in operation.The operating experience and the deter-mined energy costs show promising re-sults. However, the investment costs arestill considerably higher than for classicalplants 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 heattransfer and pressure drop. On the otherhand, these installations are mostly usedin climate areas permitting very high run-ning times in sub-critical operation due tothe annual 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 techno-logy cannot be regarded as a general re-placement for plants using HFC refriger-ants.


Detailed information on this topic wouldgo beyond the scope of this publication.

High demands are made on lubricants aswell. Conventional oils are mostly not mis-cible and therefore require costly meas-ures to return the oil from the system. Onthe other hand, a strong viscosity reduc-tion with the use of a miscible and highly soluble POE must be considered.

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

BITZER is actively involved in a numberof projects. For sub-critical applicationsa range of special compressors, inclu-sive of suitable oil, can be offered.

Supplementary BITZER informationconcerning compressor selection forsub-critical CO2 systems

❏ Brochure KP-120:CO2 Compressors – Octagon®

Series

❏ Additional publications on request

31


In any case, the system and control tech-niques are substantially different fromconventional plants. Already when consid-ering pressure levels as well as volumeand mass flow ratios specially developedcomponents, controls, and safety devicesas well as suitably dimensioned pipeworkmust be provided.

The compressor technology is particularlydemanding. The special requirementsresult in a completely independent ap-proach. For example, this involves design,materials (bursting resistance), displace-ment, crank gear, working valves, lubrica-tion system, as well as compressor andmotor cooling. Hereby, the high thermalload severely limits the application for single-stage compression. Low tempera-ture cooling requires 2-stage operation,whereby separate high and low pressurecompressors are particularly advanta-geous with parallel compounded systems.

The criteria mentioned above in connec-tion with sub-critical systems apply to aneven higher degree for lubricants.

Further development is necessary in manyareas, and for most applications, trans-critical CO2 technology cannot yet be re-garded as state-of-the-art. * See page 12 for further information.

BITZER is actively involved in a series of projects. Meanwhile, compressors can be supplied for certain applications.However, an individual examination ofeach application is necessary.

CO2 in mobile air-conditioning systems

Within the scope of the long-discussedmeasures for reducing direct refrigerantemissions, and the pending ban on theuse of R134a in MAC systems*, the development of CO2 systems has beenpursued intensively since several years.

At the first glance, efficiency and there-fore the indirect emissions from CO2 sys-tems under typical ambient conditionsappear to be relatively unfavourable. Butit must be considered that present R134a

systems are less efficient than stationaryplants of the same capacity. The reasonsfor this lie in the specific installation con-ditions and the relatively high pressurelosses in pipework and heat exchangers.With CO2, pressure losses have signifi-cantly less influence. Moreover, systemefficiency is further improved by the highheat transfer coefficients in the heat ex-changers.

This is why optimized CO2 air-condition-ing systems are able to achieve effi-ciencies that are comparable to those ofR134a. Regarding the usual leakage ratesof such systems, a more favourable bal-ance is obtained in terms of TEWI.

From today's viewpoint, it is not possibleto make a clear prediction as to whetherCO2 will generally prevail in these appli-cations. Certainly, this also depends ontest results and operating experienceswith “Low GWP” refrigerants (page 12).Hereby, other aspects such as operatingsafety, costs, and global logistics will play an important role.

Fig. 31 Example of a trans-critical CO2 system

GasCooler

Evaporator

TX Device

(HX)

Compressor

HP Regulation Valve

Liquid Receiver(intermediatepressure)

Simplifiedsketch

Suplementary BITZER informationconcerning compressor selection for trans-critical CO2-systems

❏ Brochure KP-130„CO2 compressors – Octagon®-series“

❏ Additional publications upon request

32


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

Basis R13B1

Dis

char

ge g

as t

emp

erat

ure

– re

lativ

e d

iffer

ence

to

R13

B1

[K]40

30

20

10

0

-10

-30

-20

R41

0A

ISC

EO

N M

O89

totcΔto

-70°C

40°C

20K

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 use long proven lubricants, preferablymineral oils and alkyl benzenes with high viscosity.

Because of the Ozone Depleting Potential,the use of these refrigerants must certain-ly only be regarded as an interim solution(in the EU member states, the applicationin new 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 tem-peratures of the alternatives are lower(approx. -10°C) which results in larger dif-ferences in the pressure levels and refrig-eration volumetric capacities. This leadsto stronger limitations in the applicationrange concerning high evaporation andcondensing temperatures.A conversion of an existing installationwill in most cases necessitate the ex-changing of the compressor and regulat-ing devices. Owing to the lower volumeflow (higher volumetric refrigeration cap-acity), possible adjustments to the evapo-rator and the suction 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. Perfor-mance data including further designinstructions are available on request.

Due to the limited markets for systemswith extra high and low temperature appli-cations, the requirements for the develop-ment of alternative refrigerants and sys-tem components for these areas has notbeen so great.

Only a few years ago a group of alterna-tives for the CFC R114 and Halon R12B1(high temperature), R13B1, R13 and R503(extra low temperature) were offered as thereplacements. With closer observations ithas been found that the thermodynamicproperties of the alternatives differ con-siderably from the substances used untillnow. This can cause costly changes espe-cially with the conversion of existing sys-tems.

Chlorine free substitutes for special applications

Alternatives for R114 and R12B1

At present R227ea and R236fa are regard-ed as the prefered substitutes. R227eacannot be seen as a full replacement.Recent research and field tests have shownfavourable results, but with normal systemtechnology the critical temperature of102°C limits the condensing temperaturesto 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 toR114 and with that 40% below the perfor-mance of R124 which is widely used forextra high temperature applications today.

In the meantime, an azeotropic blend ofR365mfc and a perfluoropolyether hasalso been developed. It is available underthe trade name Solkatherm SES36(Solvay). Its boiling temperature (at 1.013bar) is 36.7 °C, and the critical tempera-ture is 177.4°C. The preferred applicationareas will therefore be heat pumps inprocess technology, and Organic RankineCycles (ORC).

33

In addition to this, the steep fall of pres-sure limits the application at very lowtemperatures and may require a changeto a cascade system with for exampleR23 in the low temperature stage.

Lubrication and material compatibility areassessed as being similar to the otherHFC blends.

The situation is more favourable withthese substances as R23 and R508A/R508B can already replace R13 and R503.Refrigerant R170 (Ethane) is also suitablewhen the safety regulations allow the useof hydrocarbons (Group A3).

Due to the partly steeper pressure curveof the alternative refrigerants and thehigher discharge gas temperature of R23compared with R13, differences in per-formance and application ranges for thecompressors must be considered. Individ-ual adaptation of the heat exchangers andcontrols is also necessary.

As lubricants for R23 and R508A/B, poly-ol ester oils are suitable, but these mustbe matched for the special requirementsat extreme low temperatures.

R170 has also good solubility with con-ventional oils, however an adaptation tothe temperature conditions will be nec-essary.

BITZER has already carried out investi-gations and also collected experienceswith several of the substitutes mentioned,performance data and instructions areavailable on request.Due to the individual system technologyfor these special installations, consul-tation with BITZER is necessary.

Refrigerant R600a (Isobutane) will be aninteresting alternative where the safetyregulations 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.

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.Due to the properties of the two maincomponents, density and mass flow arerelatively high and discharge gas temper-ature is very low. Liquid subcooling is ofparticular advantage.

Both of the mentioned refigerants haverelatively high pressure levels and aretherefore limited to 40 through 45°C con-densing temperature. They also show lesscapacity than R13B1 at evaporating tem-peratures below -60°C.


Alternatives for R13B1 Alternatives for R13 and R503

Time horizon 100 years – according toIPCC II (1996) ➔ basis for Kyoto protocol

Values in brackets according to IPCC III (2001)➔ reference data in EN 378-1: 2008, Annex E – also basis for EC Regulation 842/2006

N/A Data not yet available

34

Alternative refrigerant has larger deviation in refrigerating capacity and pressure

Alternative refrigerant has larger deviation below -60°C evaporating temperature

These statements are valid subject to reservations; they are based on information published by various refrigerant manufacturers.

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, Annex E

09.08

Fig. 33 Characteristics of CFC alternatives (continued on Fig. 34)

3

4

5

61

2

Refrigerant Properties

0.0550.0220.065

0.0370.040.048

0.0210.0330.0310.026

0

0

0

1500 (1700)470 (620)

1800 (2400)

970 (1130)1060 (1220)1290 (1540)

2250 (2690)1960 (2310)3570 (4310)2650 (3020)

1300 (1300)140 (120)

2800 (3400)3800 (4300)650 (550)

2900 (3500)6300 (9400)

11700 (12000)

3260 (3780)3300 (3850)1770 (1990)2280 (2700)2530 (3040)

1770 (1920)1570 (1680)

1520 (1650)1950 (2240)2230 (2620)1830 (2010)

1720 (1980)

3090 (N/A)

11860 (11940)11850 (11950)

08333

3

1

R22R124R142b

R401AR401BR409A

R402A R402BR403BR408A

R134aR152aR125R143aR32

R227eaR236fa

R23

R404AR507A R407A(R407B)R422A

R413AR437A

R407CR417AR422DR427A

R410A

ISCEON MO89

R508AR508B

R717R723R600aR290R1270

R170

R744

Composition(Formula)

Substitute for

ODP

[R11=1.0]

GWP(100a)

[CO2=1.0]

Practicallimit

[kg/m3]

Safetygroup

Application range

5

HFCFC/HFC Service-Blends (Transitional Alternatives)

HFC – chlorine free – Refrigerants (Long Term Alternatives)

HFC – chlorine free – Blends (Long Term Alternatives)

Halogen free Refrigerants (Long Term Alternatives)

0.30.110.066

0.30.340.16

0.330.320.410.41

0.250.0260.390.0560.061

0.490.59

0.68

0.480.490.330.350.29

0.07N/A

0.310.150.260.28

0.44

N/A

0.220.2

0.00035N/A

0.0110.0080.008

0.008

0.07

A1A1A1

A1A1A1

A1A1A1A1

A1A2A1A2A2

A1A1

A1

A1A1A1A1A1

A2A1

A1A1A1A1

A1

N/A

A1A1

B2B2A3A3A3

A3

A1

CHClF2CHClFCF3CCIF2CH3

R22/152a/124R22/152a/124R22/142b/124

R22/125/290R22/125/290R22/218/290R22/143a/125

CF3CH2FCHF2CH3CF3CHF2CF3CH3CH2F2

CF3-CHF-CF3CF3-CH2-CF3

CHF3

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

R134a/218/600aR125/134a/600/601

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

R32/125

R125/218/290

R23/116R23/116

NH3NH3/R-E170C4H10C3H8C3H6

C2H6

CO2

R502 (R12 )

R114 , R12B1

R12 (R500)

R12 (R500)

R502

R13 (R503)

R503

R22 (R13B1 )

R22

R502, R22

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

R13, R503

Diverse

R12B1, R114R114

R12 (R22 )mainly usedas partcomponentsfor blends

seepage 36

seepage 36

seepage 36

seepage 36

sieheSeite 37

R13B1

Refrigerant type

HCFC-Refrigerants

3

5 6

4

5

1

1

1

1

1

2

2

Refrigerant Properties

35

Fig. 34 Characteristics of CFC alternatives

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 opera-ting conditionsH High temp (+7/55°C)M Medium temp (-10/40°C)L Low temp (-35/40°C)

09.08

3 4

5

6

1

2

-41-11-10

-33-35-34

-49-47-51-44

-26-24-48-48-52

-16-1

-82

-47-47-46-48-49

-35-33

-44-43-45-43

-51

-55

-86-88

-33-37-12-42-48

-89

-57

R22R124R142b

R401AR401BR409A

R402A R402BR403BR408A

R134aR152aR125R143aR32

R227eaR236fa

R23

R404AR507A R407A(R407B)R422A

R413AR437A

R407CR417AR422DR427A

R410A

ISCEON MO89

R508AR508B

R717R723R600aR290R1270

R170

R744

HFCFC/HFC Service-Blends (Transitional Alternatives)

HFC – chlorine free – Refrigerants (Long Term Alternatives)

HFC – chlorine free – Blends (Long Term Alternatives)

Halogen free Refrigerants (Long Term Alternatives)

Refrigeranttype

HCFC-Refrigerants

3

6

Boilingtemperature

[°C]

Temperatureglide[K]

Criticaltemperature

[°C]

Cond. temp.at 26 bar(abs) [°C]

Refr.capacity

[%]

C.O.P

[%]

Dischargegas temp.

[K]

Lubricant(compressor)

1 2 1 1 3 3

88

1009899

10098100100

103N/AN/AN/AN/A

98989698

100100

95

95

105106N/A102101

000

6,46,08,1

2,02,31,20,6

00000

00

0

0,70

6,64,42,5

6,93,6

7,45,6 4,57,1

<0,2

4,0

00

00000

0

0

96122137

108106107

75839083

101113667378

102>120

26

7371837672

10195

87908187

72

70

1314

1331311359792

32

31

63105110

807775

53565458

8085515642

96117

1

5554565356

7675

58686264

43

50

-3-3

60581147061

3

-11

80 (L)

107 (M)108 (L)

109 (M)

109 (L)99 (L)

112 (L)98 (L)

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

99 (L)102 (L)78 (L)93 (L)

105 (M)108 (M)

100 (H)97 (H)

142 (7/40°C)

100 (M)105 (M)

N/A 89 (M)

112 (M)

+35

+13+18+7

~0+16~0+10

-8N/AN/AN/AN/A

-9-10+11-2

-8-7

-8-25

-6

+60+35N/A-25-20

seepage 37

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5 5 5

5 5 5

5 5 5

4 4 4

5

5 5 5

-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

R404A ● R507AR407A ● R422A

R407C ● R417AR422D • R427A

R410A

R23 ● R508A ● R508B

Compressors for high pressure 42 bar

Condensing temperature limited

Application withlimitations

Depending on system design also suitable for low temp. applications

CASCADE

2-stage

2-stage

2-stage

1

2

3

2

3

3

3ISCEON MO89

R413A ● R437A

1

36

Transitional/Service refrigerants

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

Chlorine free HFC refrigerants and blends

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

Application ranges

R290 ● R1270

-100-80-60-40-2002040

R600a

R290/600a

R170

Evaporation °C

CO2

Application with limitations

CASCADE

2-stage

– see page 28...32 –

2-stage

2-stage

* see information on page 23/24

3NHR723*

(H)CFC

NH ● R7233

Service blends with R22

HFC + blends

Hydrocarbons

Traditional oils

VG VG VG

+VG

+VG

Min

eral

oil

VG

Especially critical with moisture

Possible higher basic viscosity

Good suitability

Application with limitations Not suitable

(MO

)

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

VG VG

Suitability dependant on system design

HFC/HC blends

New lubricants

Alk

yl-

ben

zene

(AB

)

Min

eral

oil

+ a

lkyl

-b

enze

ne

Pol

y-al

pha

-ol

efin

(PA

O)

Pol

yol

este

r (P

OE

)

Pol

yvin

yl-

ethe

r(P

VE

)

Pol

y-gl

ycol

(PA

G)

Hyd

rocr

acke

dm

iner

al o

il

Application ranges ■ Lubricants

37


Fig. 37 Application ranges for halogen free refrigerants

Lubricants

Fig. 38 Lubricants for compressors

Änd

erun

gen

vor

beh

alte

n / S

ubje

ct to

cha

nge

/ Tou

tes

mod

ifi ca

tions

rés

ervé

es 0

8.08

Bitzer Kühlmaschinenbau GmbHEschenbrünnlestraße 15

71065 Sindelfingen, Germany tel +49 (0)70 31 932-0

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

·

refrigerant report

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