1、6.1CHAPTER 6REFRIGERANT SYSTEM CHEMISTRYRefrigerants. 6.1Chemical Reactions. 6.4Compatibility of Materials 6.10Chemical Evaluation Techniques 6.12Sustainability. 6.13YSTEM chemistry deals with chemical reactions between re-Sfrigerants, lubricants, and construction materials of various sys-tem compon
2、ents (e.g., compressor, heat transfer coils, connectingtubing, expansion device). Higher temperatures or contaminantssuch as air, moisture, and unwashed process chemicals complicatechemical interaction between components. Phase changes occur inthe refrigeration cycle, and in particular the temperatu
3、re extremes ina cycle from the highest discharge line temperature after the com-pression to the lowest evaporating temperature are of importance tothe end user. This chapter covers the chemical aspects of refriger-ants and lubricants, and their effects on materials compatibility.Detailed information
4、 on halocarbon and ammonia refrigerants isprovided in Chapters 1 and 2, respectively. Contaminant control isdiscussed in Chapter 7, and lubricants are discussed in Chapter 12.More information on various refrigerants can be found in Chapters29 and 30 of the 2009 ASHRAE HandbookFundamentals.REFRIGERAN
5、TSEnvironmental AcceptabilityRefrigerants are going through a transition because of globalenvironmental issues such as ozone depletion and climate changeconcerns. Information on available refrigerants, including thermo-dynamic and environmental properties, can be found in Chapter 29in the 2009 ASHRA
6、E HandbookFundamentals. Natural refriger-ants, including CO2(R-744), hydrocarbons, and some new candi-dates such as HFO-1234yf, are of particular interest because of theirlow global warming potential (GWP). For details, see Chapter 29 ofthe 2009 ASHRAE HandbookFundamentals.Common chlorine-containing
7、 refrigerants contribute to deple-tion of the ozone layer. A materials ozone depletion potential(ODP) is a measure of its ability, compared to CFC-11, to destroystratospheric ozone.Halocarbon refrigerants also can contribute to global warmingand are considered greenhouse gases. The global warming po
8、ten-tial (GWP) of a greenhouse gas is an index describing its ability,compared to CO2(which has a very long atmospheric lifespan), totrap radiant energy. The GWP, therefore, is connected to a particulartime scale (e.g., 100 or 500 years). For regulatory purposes, theconvention is to use the 100-year
9、 integrated time horizon (ITH).Appliances using a given refrigerant also consume energy, whichindirectly produces CO2emissions that contribute to global warm-ing; this indirect effect is frequently much larger than the refriger-ants direct effect. An appliances total equivalent warmingimpact (TEWI)
10、is based on the refrigerants direct warming poten-tial and indirect effect of the appliances energy use The life cycleclimate performance (LCCP), which includes the TEWI as well ascradle-to-grave considerations such as the climate change effect ofmanufacturing the refrigerant, transportation-related
11、 energy, andend-of-life disposal, is becoming more prevalent.Environmentally preferred refrigerants (1) have low or zeroODP, (2) provide good system efficiency, and (3) have low GWP orTEWI values. Hydrogen-containing compounds such as the hydro-chlorofluorocarbon HCFC-22 or the hydrofluorocarbon HFC
12、-134ahave shorter atmospheric lifetimes than chlorofluorocarbons(CFCs) because they are largely destroyed in the lower atmosphereby reactions with OH radicals, resulting in lower ODP and GWPvalues.Tables 1 and 2 show boiling points, atmospheric lifetimes, ODPs,GWPs, and flammabilities of new refrige
13、rants and the refrigerantsbeing replaced. ODP values were established through the MontrealProtocol and are unlikely to change. ODP values calculated usingthe latest scientific information are sometimes lower but are notused for regulatory purposes. Because HFCs do not contain chlorineatoms, their OD
14、P values are essentially zero (Ravishankara et al.1994).GWP values were established as a reference point using Inter-governmental Panel on Climate Change (IPCC 1995) assessmentvalues, as shown in Table 1, and are the official numbers used forreporting and compliance purposes to meet requirements of
15、theUnited Nations Framework Convention on Climate Change(UNFCCC) and Kyoto Protocol. However, lifetimes and GWPshave since been reviewed (IPCC 2001) and are shown in Table 2,representing the most recent published values based on an updatedassessment of the science. These values are subject to review
16、 andmay change with future reassessments, but are currently not used forregulatory compliance purposes. Table 3 shows bubble points andcalculated ODPs and GWPs for refrigerant blends, using the latestscientific assessment values.Compositional GroupsChlorofluorocarbons. CFC refrigerants such as R-12,
17、 R-11,R-114, and R-115 have been used extensively in the air-condition-ing and refrigeration industries. Because of their chlorine content,these materials have significant ODP values. The Montreal Proto-col, which governs the elimination of ozone-depleting substances,was strengthened at the London m
18、eeting in 1990 and confirmed atthe Copenhagen meeting in 1992. In accordance with this interna-tional agreement, production of CFCs in industrialized countrieswas totally phased out as of January 1, 1996. Production in devel-oping countries will be phased out in 2010, although many havealready made
19、considerable phaseout progress.Hydrochlorofluorocarbons. HCFC refrigerants such as R-22and R-123 have shorter atmospheric lifetimes (and lower ODP val-ues) than CFCs. Nevertheless, the Montreal Protocol limited devel-oped-country consumption of HCFCs beginning January 1, 1996,using a cap equal to 2.
20、8% of the 1989 ODP weighted consumption ofCFCs plus the 1989 ODP-weighted consumption of HCFCs. TheCAP was reduced by 35% by January 1, 2004, and will be reduced by65% on January 1, 2010; 90% by January 1, 2015; 99.5% by JanuaryThe preparation of this chapter is assigned to TC 3.2, Refrigerant Syste
21、mChemistry.6.2 2010 ASHRAE HandbookRefrigeration (SI)Table 1 Refrigerant Properties: Regulatory Compliance Values Used by Governments for UNFCCC Reporting and Kyoto Protocol ComplianceRefrigerant StructureBoiling PointaCAtmospheric Lifetime,bYears ODPcGWP,ITH 100-Year Flammable?E125 CHF2OCF342.0 165
22、a15 300aNoE143 CHF2OCH2F29.dYesE143a CF3OCH324.1 5.7a5400aYes11 CC13F 23.7 50 1 4600aNo12 CCl2F229.8 102 1 10 600aNo22 CHClF240.8 12.1 0.055 1900aNo23 CHF382.1 264 11 700 No32 CH2F251.7 5.6 650 Yes113 CCl2FCClF247.6 85 0.8 6000aNo114 CClF2CClF23.6 300 1 9800aNo115 CClF2CF338.9 1700 0.6 10 300aNo116
23、CF3CF378.2 10 000 11 400aNo123 CHCl2CF327.8 1.4 0.02 120aNo124 CHClFCF312.0 6.1 0.022 620aNo125 CHF2CF348.1 32.6 2800 No134a CH2FCF326.1 14.6 1300 No142b CClF2CH39.0 18.4 0.065 2300aYes143 CH2FCHF25.0 3.8 300 Yes143a CF3CH347.2 48.3 3800 Yes152a CHF2CH324.0 1.5 140 Yes218 CF3CF2CF336.6 2600a8600aNo2
24、27ea CF3CHFCF315.6 36.5 2900 No236ea CF3CHFCHF26.5d10d9400aNo236fa CF3CH2CF31.4 209 6300 No245ca CHF2CF2CH2F 25.1 6.6 560 Yes245fa CF3CH2CHF215.1 8.8a820aNoaData from Calm and Hourahan (1999).bData from IPCC (1995).cData from Montreal Protocol 2003.dData from Chapter 5 of the 2006 ASHRAE HandbookRef
25、rigeration.Table 2 Refrigerant Properties: Current IPCC Scientific Assessment ValuesRefrigerant StructureBoiling Point,CAtmospheric Lifetime,Years ODPGWP,ITHa100-Year Flammable?bE125 CHF2OCF342.0 165c14 900 NoE143 CHF2OCH2F29.9b57 YesE143a CF3OCH324.1 5.7c750 Yes11 CHl3F 23.7 50 1 4600 No12 CCl2F229
26、.8 102 1 10 600 No22 CHClF240.8 12.1 0.055 1700 No23 CHF382.1 264 12 000 No32 CH2F251.7 5.6 550 Yes113 CCl2FCF2Cl 47.6 85 0.8 6000 No114 CClF2CClF23.6 300 1 9800 No115 ClF2CF338.9 1700 0.6 7200 No116 CF3CF378.2 10 000 11 900cNo123 CHCl2CF327.8 1.4 0.02 120 No124 CHClFCF312.0 6.1 0.022 620 No125 CHF2
27、CF348.1 32.6 3400 No134a CH2FCF326.1 14.6 1300 No142b CH3CClF29.0 18.4 0.065 2400 Yes143 CH2FCHF25.0 3.8 330 Yes143a CH3CF347.2 48.3 4300 Yes152a CH3CHF224.0 1.5 120 Yes218 CF3CF2CF336.6 2600c8600cNo227ea CF3CHFCF315.6 36.5 3500 No236ea CF3CHFCHF26.5b10b1200 No236fa CF3CH2CF31.4 209 9400 No245ca CHF
28、2CF2CH2F 25.1 6.6 640 Yes245fa CF3CH2CHF25.1 8.8c950 NoaData from IPCC (2001).bData from ASHRAE Standard 34.cData from Calm and Hourahan 1999.Refrigerant System Chemistry 6.31, 2020; and total phaseout by January 1, 2030. From 2020 to 2030,HCFCs may only be used to service existing equipment. Develo
29、pingcountries must freeze HCFC ODP consumption at 2015 levels in2016, and completely phase out by January 1, 2040.In addition to the requirements of the Montreal Protocol, severalcountries have established their own regulations on HCFC phase-out. The United States met the Montreal Protocols requirem
30、ents bybanning consumption of R-141b (primarily used as a foam-blowingagent) on January 1, 2003, and phasing out HCFC-142b (primarilyfoams) and HCFC-22 for original equipment manufacturers(OEMs) beginning January 1, 2010. Production for service needs isallowed to continue. Production and consumption
31、 of all otherHCFCs will be frozen on January 1, 2015. On January 1, 2020, pro-duction and consumption of R-22 and R-142b will be banned, fol-lowed by a ban on production and consumption of all other HCFCson January 1, 2030. As required by the Montreal Protocol, from2020 to 2030, virgin HCFCs may onl
32、y be used to service existingequipment.The European Union accelerated the schedule to reduce HCFCconsumption by 15% on January 1, 2002, 55% on January 1, 2003,70% on January 1, 2004, 75% on January 1, 2008, with total phase-out on January 1, 2010. They also implemented several use restric-tions on H
33、CFCs in air-conditioning and refrigeration equipment.U.S. and E.U. phaseout schedules allow continued, limited man-ufacture for developing-country needs or for export to other coun-tries where HCFCs are still legally used.Atmospheric studies (Calm et al. 1999; Wuebbles and Calm1997) suggest that pha
34、seout of HCFC refrigerants, with low atmo-spheric lives, low ozone depletion potentials, low global warmingpotentials, low emissions, and high thermodynamic efficiencies,will result in an increase in global warming, but have a negligibleeffect on ozone depletion.HCFC-22 is the most widely used hydro
35、chlorofluorocarbon.R-410A is now the leading alternative for HCFC-22 for new equip-ment. R-407C is another HCFC-22 replacement and can be used inretrofits as well as in new equipment. HCFC-123 is used commer-cially in large chillers.Hydrofluorocarbons. These refrigerants contain no chlorineatoms, so
36、 their ODP is zero. HFC methanes, ethanes, and propaneshave been extensively considered for use in air conditioning andrefrigeration.Fluoromethanes. Mixtures that include R-32 (difluoromethane,CH2F2) are being promoted as a replacement for R-22 and R-502.For very-low-temperature applications, R-23 (
37、trifluoromethane,CHF3) has been used as a replacement for R-13 and R-503 (Atwoodand Zheng 1991).Fluoroethanes. Refrigerant 134a (CF3CH2F) of the fluoroethaneseries is used extensively as a direct replacement for R-12 and as areplacement for R-22 in higher-temperature applications. R-125and R-143a ar
38、e used in azeotropes or zeotropic blends with R-32and/or R-134a as replacements for R-22 or R-502. R-152a is flam-mable and less efficient than R-134a in applications using suction-line heat exchangers (Sanvordenker 1992, but it is still beingconsidered for R-12 replacement. R-152a is also being con
39、sideredas a component, with R-22 and R-124, in zeotropic blends (Batemanet al. 1990; Bivens et al. 1989) that can be R-12 and R-500 alter-natives.Fluoropropanes. Desmarteau et al. (1991) identified a number offluoropropanes as potential refrigerants. R-245ca is being consid-ered as a chlorine-free r
40、eplacement for R-11. Evaluation by Doerret al. (1992) showed that R-245ca is stable and compatible with keycomponents of the hermetic system. However, Smith et al. (1993)demonstrated that R-245ca is slightly flammable in humid air atroom temperature. Keuper et al. (1996) investigated R-245ca per-for
41、mance in a centrifugal chiller; they found that the refrigerantmight be useful in new equipment but posed some problems whenused as a retrofit for R-11 and R-123 machines. R-245fa is used asa chlorine-free replacement for R-11 and R-141b in foams, and isbeing considered as a refrigerant and commerci
42、alized in organicRankine-cycle and waste-heat-recovery systems. R-236fa has beencommercialized as a replacement for R-114 in naval centrifugalchillers.Fluoroethers. Booth (1937), Eiseman (1968), Kopko (1989),ONeill (1992), ONeill and Holdsworth (1990), and Wang et al.(1991) proposed these compounds
43、as refrigerants. Fluoroethers areusually more physiologically and chemically reactive than fluori-nated hydrocarbons. Fluorinated ethers have been used as anesthet-ics and convulsants (Krantz and Rudo 1966; Terrell et al. 1971a,1971b). Reactivity with glass is characteristic of some fluoro-ethers (D
44、oerr et al. 1993; Gross 1990; Simons et al. 1977). Misakiand Sekiya (1995, 1996) investigated 1-methoxyperfluoropropane(boiling point 34.2C) and 2-methoxyperfluoropropane (boilingpoint 29.4C) as potential low-pressure refrigerants. Bivens andMinor (1997) reviewed the status of fluoroethers currently
45、 underTable 3 Properties of Refrigerant BlendsaRefrig-erant CompositionBubblePoint,bC ODPcGWP,d 100-Year ITH401A (22/152a/124)/(53/13/34) 33.3 0.027 1100401B (22/152a/124)/(61/11/28) 34.9 0.028 1200401C (22/152a/124)/(33/15/52) 28.4 0.025 900402A (125/C3H8/22)/(60/2/38) 49.0 0.013 2700402B (125/C3H8
46、/22)/(38/2/60) 47.0 0.020 2300403A (C2H6/22/218)/(5/75/20) 47.8 0.026 3000403B (C2H6/22/218)/(5/56/39) 49.2 0.019 4300404A (125/143a/134a)/(44/52/4) 46.2 0 3800405A (22/152a/142b/C318)/(45/7/5.5/42.5)32.9 0.018 5200406A (22/600a/142b)/(55/4/41) 32.7 0.036 1900407A (32/125/134a)/(20/40/40) 45.3 0 200
47、0407B (32/125/134a)/(10/70/20) 46.8 0 2700407C (32/125/134a)/(23/25/52) 43.6 0 1700407D (32/125/134a)/(15/15/70) 39.5 0 1500407E (32/125/134a)/(25/15/60) 42.9 0 1400408A (125/143a/22)/(7/46/47) 44.6 0.016 3000409A (22/124/142b)/(60/25/15) 34.7 0.039 1500409B (22/124/142b)/(65/25/10) 35.6410A (32/125
48、)/(50/50) 51.4 0 2000411A (R-1270/22/152a)/(1.5/87.5/11.0)39.5 0.030 1500411B (1270/22/152a)/(3/94/3) 41.6 0.032 1600412A (22/218/142b)/(70/5/25) 38.0 0.035 2200413A (218/134a/600a)/(9/88/3) 30.6 0 1900414A (22/124/600a/142b)/(51/28.5/4/16.5)34.0 0.032 1400414B (22/124/600a/142b)/(50/39/1.5/9.5)32.9
49、 0.031 1300415A (22/152a)/(82/18) 37.5 0.028 1400415B (22/152a)/(25/75) 27.7 0.009 500416A (134a/124/600)/(59/39.5/1.5) 23.4 0.010 1000417A (125/134a/600)/(46.6/50/3.4) 38.0 0.000 2200418A (290/22/152a)/(1.5/96/2.5) 41.2 0.33 1600500 (12/152a)/(73.8/26.2) 33.6 0.605 7900502 (22/115)/(48.8/51.2) 45.2 0.221 4500503 (23/13)/(40.1/59.9) 88.8 0.599 13 000507A (125/143a)/(50/50) 46.7 0 3900508A (23/116)/(39/61) 87.4 0 12 000508B (23/116)/(46/54) 87.0 0 12 000509A (22/218)/(44/56) 49.8 0.015 5600aData from IPCC
