environmental data for refrigerants

8/11/2019 Environmental Data for Refrigerants

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By JAMES M. CALM, PE,*Engineering Consultant,Great Falls, Va., andGLENN C. HOURAHAN, PE,**

Air-Conditioning and RefrigerationTechnology Institute (ARTI),Arlington, Va.

Manufacturers have com-mercialized more than 50new refrigerants (includ-ing blends) in the last de-

cade, and they are examining addi-tional candidates. Users should expecta number of new introductions as thephaseout of R-22, now the most widelyused refrigerant, approaches. A similarflurry of service fluids occurred with

the phaseouts of R-12 and R-502; R-12was the most widely used refrigerantuntil a few years ago.

This article provides two tables thatsummarize selected physical, safety, andenvironmental data for old and currentrefrigerants as well as leading candidates.The data in the two tables are the same,but they are presented in a different order.

Table 1 is sorted by refrigerant num-

bers. Table 2 contains the same infor-mation sorted by the normal boilingpoints (at atmospheric pressure) of therefrigerants. Table 1 lends itself to find-ing information on a specific refriger-ant. Table 2 rearranges the refrigerantsin coarse proximity for similar applica-tions to facilitate comparisons.

The data in these tables are taken fromtheARTI Refrigerant Database,1 which isan information system on alternative re-frigerants, associated lubricants, andtheir uses in air conditioning and refrig-

eration. The database consolidates andfacilitates access to property, compatibil-ity, safety, environmental, application,and other data.2It also provides an exten-sive bibliographic reference system.

REFRIGERANT DATA TABLESThe parameter descriptions that fol-

low are in the same sequence as pre-sented in Tables 1 and 2readingfrom the left to the right columns.

Identifiers Number shown is the standard

designation based on those assignedby or recommended for addition to

ANSI/ASHRAE Standard 34-1997,Designation and Safety Classification of Re-

fr ig erants , and pending addendathereto.3 These familiar designations areused almost universallyusually pre-ceded by R-, R, the word refriger-ant, composition-designating prefixes(for example CFC-, HCFC-, HFC-,or HC-), or manufacturer trade names. Chemical formula indicates the

molecular makeup of single-compoundrefrigerants, namely those consisting ofa single chemical substance.

Blend composition is shown for re-

frigerant blends, namely those consist-ing of two or more chemicals that aremixed to obtain desired characteristics.The composition consists of two parts.The first identifies the components inorder of increasing normal boilingpoints and are separated by slashes.The second part, which is enclosed inparentheses, indicates the mass frac-tions (as percentages) of those compo-nents in the same order.

The tables also indicate the com-mon names by which some refrigerantsare frequently identified.

Physical properties Molecular mass is a calculated value

based on the atomic weights recognizedby the International Union of Pure andApplied Chemists (IUPAC).4 It indicatesthe mass in grams of a mole of the refriger-ant or, for blends, the mass-weighted av-erage of a mole of the mixture.

Normal boiling point (NBP) is thetemperature at which liquid refrigerantwill boil at standard atmospheric pres-

Physical, Safety, and

Environmental DataFOR REFRIGERANTSThis article

was prepared for

HPAC Engineering

as a convenient

reference on

common and

selected candidate

refrigerants

*James M. Calm is an internationally recog-

nized engineering consultant in heating, air

conditioning, and refrigerating systems and an

ASHRAE Fellow. He has served as the devel-oper and administrator of the Refrigerant

Database, used to prepare the reference tables

for the article, since its inception.

**Glenn C. Hourahan is Director of Technol-

ogy of Air-Conditioning and Refrigeration Insti-

tute (ARI) and Vice President of the Air-Con-

ditioning and Refrigeration Technology Institute

(ARTI). He also heads the 21-CR research ini-

tiative, which sponsors the database effort.

Heating/Piping/AirConditioning August 1999 27HPACENGINEERING


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sure, namely 101.325 kPa (14.6959psia). The NBP and most dimensionalunits in the tables are shown in bothmetric (SI) and in-lb units of measure.The bubble point (temperature at

which a bubble first appears, hence thetemperature at which boiling begins fora blend) is shown as the NBP for blends.

Critical temperature (Tc) is thetemperature at the critical point of therefrigerant. The Tc values shown forblends are the mass-weighted averagesof the component Tcs, unless actualvalues have been determined.

Critical pressure (Pc) is the pres-sure at the critical point.

The NBP and critical properties sug-gest the application range for which anindividual refrigerant might be suitable.Those with extremely low NBP lendthemselves to ultra-low temperature re-frigeration, for example, in cryogenic ap-plications. Those with high NBPs aregenerally limited to high-temperatureapplications such as chillers. Both capac-

ity and efficiency decline in a typical va-por-compression (reverse-Rankine) cy-clethe one most commonlyusedwhen condensing temperaturesapproach the Tc. The Pc will exceed theoperating pressure except in transcriticalcycles, which are uncommon except forR-744 (carbon dioxide). It is useful tocompare relative operating pressures be-cause practical cycles usually are de-signed to condense at 70 to 90 percent of

the Tc (on an absolute basis) and, there-fore, of the Pc.

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Safety data The first value is the occupational

exposure limit, namely the Threshold

Limit Value-Time Weighted Average(TLV-TWA) or a consistent measure.It is an indication of chronic (long-term, repeat exposure) toxicity of therefrigerant. Some of the consistent tox-icity indices are the Workplace Envi-ronmental Exposure Level (WEEL)guides or the Permissible ExposureLimits (PEL). These measures indicate

adopted limits forworkplace exposuresfor trained personnelduring typical work-days and work weeks.

Lower flamma-bility limit (LFL) isthe lowest concentra-tion at which the re-frigerant will burn inair under prescribedtest conditions. It isan indication offlammability.

Heat of combus-tion (HOC) is an in-dicator of how muchenergy the refrigerantwill release when it

burns in airassum-ing complete reac-tion to the most sta-

ble products in their vapor states.Negative values indicate endothermicreactions (those that require heat toproceed), while positive values indi-cate exothermic reactions (those thatliberate heat).

ASHRAE Standard 34 safetygroup is an assigned classification that isbased on the TLV-TWA (or consistentmeasure), LFL, and HOC. It comprisesa letter (A or B) that indicates relative

toxicity followed by a number (1, 2, or3) that indicates relative flammability.These classifications are widely used inmechanical and fire construction codesto determine requirements to promotesafe use. Most of these code provisionsare based on ASHRAE Standard 15,Safety Code for Mechanical Refrigeration.Some of the classifications are followedby lower-case letters:

dsignifies that the project com-

mittee responsible for ASHRAE Stan-dard 34, SSPC 34, has recommendeddeletion of the classification, but final ap-proval and/or publication is still pending

pindicates that the classifica-

tion was assigned on aprovisional basisrsignifies that SSPC 34 has

recommended revision or addition ofthe classification as shown, but finalapproval and/or publication is stillpendingEnvironmental data

Atmospheric lifetime (atm) is anindication of the average persistence ofthe refrigerantif it is released into theatmosphere or until it decomposes or re-acts with other chemicals.

Ozone depletion potential (ODP) isa normalized indicator, based on a value

of 1.000 for CFC-11, of the ability of re-frigerants (and other chemicals) to de-stroy stratospheric ozone molecules. Thedata shown are the modeled valuesadopted by the international scientificassessment.6 The ODPs shown for blendsare mass-weighted averages.

Global warming potential (GWP)is a similar indicator of the potency towarm the planet by action as a green-house gas. The values shown are relativeto carbon dioxide (CO2) for an integra-tion period of 100 years. Both the ODPand GWP are calculated from atm, mea-

sured chemical properties, and other at-mospheric data. The GWPs shown forblends are mass-weighted averages.

NEW DATAThe atm, ODP, and GWP values in

the tables are new data based on thelatest editions of international scien-tific assessments.6,7 The values indi-cated for blends were calculated for thenominal blend compositions.Data definitions

The values shown for the refrigerantlives are composite, atmospheric life-

times. The lifetimes can also be shownseparately for the tropospheric (loweratmosphere where we live), strato-spheric (next layer where global deple-tion of ozone is a concern), and higherlayers because the atmospheric chem-istry changes between layers.

The ODP values in the tables aremodeled ODP valuesthe most indica-tive of environmental impacts. Thereare several other ways to express ODPs,

REFRIGERANT PROPERTIES

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28 August 1999 Heating/Piping/AirConditioning

Ozone depletion potential (ODP) contrasted to global warming

(GWP) for key single-compound refrigerants, based on data from

reference 6. CFCs generally have high ODP and GWP. HCFCs

generally have much lower ODP and GWP. HFCs offer near-zeroODP, but some have comparatively high GWPs.


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including the semi-empirical ODP, time-dependent ODPs, and regulatory valuessuch as those adopted in laws or in theMontreal Protocol.

The semi-empirical ODPs are calcu-

lated values that incorporate adjust-ments for observed atmospheric mea-surements. The concept is conceptuallymore accurate, but it is difficult to mea-sure the data needed for representativeadjustments accurately. The scientificconsensus recommends use of the mod-eled values.8

The regulatory values generally are re-quired for specific purposes, but they maynot be updated with newer findings afteradoption. The ODP values listed in theannexes to the Montreal Protocol, forexample, have not been updated since

1987 for chlorofluorocarbons (CFCs)and 1992 for hydrochlorofluorocarbons(HCFCs). A note in the Protocol indi-cates that the values are estimates basedon existing knowledge and will be re-viewed and revised periodically.9

Time-dependent ODPs use chemi-cals other than CFC-11 as the refer-ence. By normalizing values to short-lived compounds, for example,short-term impacts are emphasized;long-term effects are discounted.Time-dependent ODPs are not oftencitedparticularly because the release

of ozone-depleting substances alreadyhas peaked, and the stratosphericozone layer will begin to recover in thenext few years.

GWP values can be calculated for anydesired integration period, commonlyreferred to as the integration time hori-zon (ITH). Short ITH periods empha-size immediate effects but overlook laterimpacts, while long ITH periods incor-porate the later effects. The most com-mon GWP values, including those citedherein, are for an ITH of 100 years.Time frames

The values cited for atm, ODP, andGWP change as understanding of atmo-spheric science expands and the chemi-cal kinetics involved become better un-derstood. They also change when newermeasurements are made for both specificand reference chemicals and as model-ing of atmospheric chemistry improves.These factors have driven periodic re-views and consensus assessments by thescientific community. The data shown

in Tables 1 and 2 are based on the assess-ment published in February 1999 andconsistent recalculations for the blends.Differences in data

One reason readers may see diverging

values for environmental databeyonddifferences associated with parameterchoices and whether the data are cur-renthas to do with accuracy. Somemanufacturers and authors round off thedata, and errors propagate whenrounded values are used for blend calcu-lations. Halocarbon or absolute GWP(HGWP and AGWP, respectively) val-ues sometimes are mislabeled as GWPs.

ACKNOWLEDGMENTThe database from which the sum-

mary data in Tables 1 and 2 were ex-

tracted is a part of the HVACR Researchfor the 21st Century initiative, a researchprogram of the Air-Conditioning andRefrigeration Technology Institute.The programs primary objective is toenable marked improvements in energyefficiency through precompetitive re-search. The focal areas include: alternative equipment equipment energy efficiency indoor environmental quality (IEQ) system integration working fluids.

Innovative advancements in equip-

ment will provide some of the energy andIEQ improvements. Others will stemfrom improved integration of air-condi-tioning and refrigeration processes intobuildings and other applications. HPAC

REFERENCES1) Calm, J. M., ARTI Refrigerant

Database, Air-Conditioning and Refriger-

ation Technology Institute, Arlington,

Va., Aug. 1999. The database is available

to all interested parties; please refer to:

www.arti-21cr.org/db/qa.html.

2) Calm, J. M., Property, Safety, and Envi-

ronmental Data for Alternative Refrigerants,Proceedings of the Earth Technologies Forum

(Washington, D.C., October 1998), Alliance

for Responsible Atmospheric Policy, Arling-

ton, Va., 192-205, October 1998.

3) ANSI/ASHRAE Standard 34-1997,

Designation and Safety Classification of Re-

frigerants, American Society of Heating, Re-

frigerating, and Air-Conditioning Engi-

neers, Atlanta, Ga., 1997.

4) Coplen, T. B., and H. S. Peiser for the

International Union of Pure and Applied

Chemistry Commission on Atomic Weights

and Isotopic Abundances, History of the

Recommended Atomic Weight Values from

1882 to 1997: A Comparison of Differences

from Current Values to the Estimated Un-certainties of Earlier Values, Pure and Ap-

plied Chemistry, 70(1):237-257, 1998.

5) Calm, J. M., and D. A. Didion, Trade-

Offs in Refrigerant Selections Past, Pre-

sent, and Future, Refrigerants for the 21st

Century (proceedings of the ASHRAE/NIST

Conference, Gaithersburg, Md., October

1997), International Journal of Refrigeration,

21(4):308-321, June 1998.

6) World Meteorological Organization

(WMO), Scientific Assessment of Ozone

Depletion: 1998, chaired by D. L. Albritton,

P. J. Aucamp, G. Mgie, and R. T. Watson,

report 44, WMO Global Ozone Researchand Monitoring Project, Geneva, Switzer-

land; United Nations Environment Pro-

gram, Nairobi, Kenya; National Oceanic

and Atmospheric Administration, Wash-

ington, D.C.; National Aeronautics and

Space Administration, Washington, D.C.;

and the European Commission, Directorate

General XIIScience, Research and Devel-

opment, Brussels, Belgium; February 1999.

7) Intergovernmental Panel on Climate

Change, Climate Change (IPCC) 1995

Contribution of Working Group I to the

Second Assessment Report of the IPCC,

edited by J. T. Houghton, L. G. Meira Filho,B. A. Callander, N. Harris, A. Kattenberg,

and K. Maskell, Cambridge University Press,

Cambridge, UK, 1996.

8) World Meteorological Organization

(WMO), Scientific Assessment of Ozone

Depletion: 1991, chaired by D. L. Albritton

and R. T. Watson, report 25, WMO Global

Ozone Research and Monitoring Project,

Geneva, Switzerland; United Nations Envi-

ronment Program, Nairobi, Kenya; United

Kingdom Department of the Environment,

London, UK; National Oceanic and Atmo-

spheric Administration, Washington, D.C.;

and the National Aeronautics and SpaceAdministration, Washington, D.C.; 1991.

9) United Nations Environment Program

(UNEP), 1997 Update of the Handbook for

the International Treaties for the Protection

of the Ozone Layer, UNEP Ozone Secre-

tariat, Nairobi, Kenya, 1998.

Circle 504 on reader service card if this

article was useful; circle 505 if it was not.

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TABLE 1 Summary Physical, Safety, and Environmental Data for Refrigerants (sorted by Standard 34 Designation)

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TABLE 1 (continued)

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TABLE 2 Summary Physical, Safety, and Environmental Data for Refrigerants (sorted by Boiling Point)

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TABLE 2 (continued)

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environmental data for refrigerants

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