外文文献-在家用空调和热泵中用R432A替代R22的性能试验.pdf

1、Short communication Experimental performance of R432A to replace R22 in residential air-conditioners and heat pumps Ki-Jung Park, Yun-Bo Shim, Dongsoo Jung* Department of Mechanical Engineering, Inha University, Incheon 402-751, Republic of Korea a r t i c l ei n f o Article history: Received 19 Dec

2、ember 2007 Accepted 20 February 2008 Available online 4 March 2008 Keywords: Natural refrigerants Propylene Dimethylether R432A Air conditioners Heat pumps a b s t r a c t In this study, thermodynamic performance of R432A and HCFC22 is measured in a heat pump bench tes- ter under both air-conditioni

3、ng and heat pumping conditions. R432A has no ozone depletion potential and very low greenhouse warming potential of less than 5. R432A also offers a similar vapor pressure to HCFC22 for drop-in replacement. Test results showed that the coeffi cient of performance and capacity of R432A are 8.58.7% an

4、d 1.96.4% higher than those of HCFC22 for both conditions. The compressor dis- charge temperature of R432A is 14.117.3 ?C lower than that of HCFC22 while the amount of charge for R432A is 50% lower than that of HCFC22 due to its low density. Overall, R432A is a good long term drop- in environmentall

5、y friendly alternative to replace HCFC22 in residential air-conditioners and heat pumps due to its excellent thermodynamic and environmental properties. ? 2008 Elsevier Ltd. All rights reserved. 1. Introduction For the past few decades, HCFC22 has been predominantly used in residential air-condition

6、ers and heat pumps. The parties to the Montreal protocol, however, decided to phase out HCFC22 eventu- ally since it contains ozone depleting chlorine 1. Hence, the reg- ulation for HCFC production has begun from 1996 in the developed countries and for new equipment HCFC22 is not currently used in E

7、uropean Union and it can not be used in United States from 2010. For the past years, various alternatives for HCFC22 have been proposed 24 and tested 3,4 in an effort to comply with the Montreal protocol. At this time, HFC refrigerant mixtures such as R410A and R407C are used in some countries to re

8、place HCFC22 2,5. At the same time, many companies expend much effort to develop their own alternatives for HCFC22. Especially, refrigerant mixtures composed of environmentally safe pure refrigerants have gotten a special attention from the industry with the expectation of possible energy effi cienc

9、y without major changes in the system 6. These days, greenhouse warming has become one of the most important global issues and Kyoto protocol was proposed to re- solve this issue, which classifi ed HFCs as greenhouse gases 7. With this global trend in view, HFC134a will be banned in mobile air-condi

10、tioners of new vehicles from 2011 according to EU F- Gases Regulation and MAC directive which specifi cally bans the use of refrigerants having global warming potential (GWP) of more than 150 8. For reference, the GWP of HFC134a is 1300. At this time, many EU countries seriously consider the ban of

11、the use of even HFCs in residential air-conditioners and heat pumps 9. Even though HFC refrigerants of R410A and R407C are used in some sys- tems, their future is not certain since their GWPs are 17002000 which is even higher than that of HFC134a. One of the possible solutions to avoid HFCs of high

12、GWP is the use of natural refrigerants such as hydrocarbons. For the past few decades, fl ammable hydrocarbon refrigerants have been prohibited in normal air-conditioning applications due to a safety concern. These days, however, this trend is somewhat relaxed because of the environmental and energy

13、 issue. Therefore, some of the fl am- mable refrigerants have been applied to certain applications 10,11. Propane (R290) and propylene (R1270) are used for heat pumping applications in Europe 12. It is well known that hydro- carbons offer low GWPs of less than 5, low cost, availability, com- patibil

14、ity with the conventional mineral oil, and environmental friendliness 10,11. Furthermore, dimethylether (DME, RE170) is a good environmentally friendly refrigerant having excellent ther- modynamic properties 13. Recently, ASHRAE listed R432A as a possible candidate to re- place R22 14. R432A is a ne

15、ar azeotropic mixture composed of 80% propylene (R1270) and 20% dimethylether (RE170) by mass. It has no ozone depletion potential and very low GWP of less than 5. Its gliding temperature difference during phase change is 1 ?C with normal boiling point of ?46.6 ?C. Even though this is a mix- ture, h

16、eat transfer degradation is not expected since its gliding temperature difference is very small 15. In this study, thermody- namic performance of R432A was measured in an attempt to 1359-4311/$ - see front matter ? 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.applthermaleng.2008.02.019 * Co

17、rresponding author. Tel.: +82 32 860 7320; fax: +82 32 868 1716. E-mail address: dsjunginha.ac.kr (D. Jung). Applied Thermal Engineering 29 (2009) 597600 Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: examine the possibility of drop-in substitution of HCFC22

18、for air- conditioning and heat pumping applications. 2. Experiments 2.1. Experimental apparatus In this study, drop-in performance of R432A is measured using the similar experimental apparatus as described in Ref. 3. As seen in Fig. 1, the apparatus has the water cooled con- denser and water heated

19、evaporator with a nominal capacity of 3.5 kW. A rotary compressor designed originally for HCFC22 was used to lift the pressure while a hand expansion valve was used for regulating the mass fl ow rate. Since Ref. 3 con- tains all the details of the test apparatus, measurements, test procedures, data

20、verifi cation etc., an interested reader is referred to Ref. 3. In this paper, test procedure and test condition will be described. 2.2. Test procedure Test procedure is as follows: (1) The system was evacuated for 23 h before charging. (2) The temperatures in the chiller and heating bath were set a

21、nd the secondary heat transfer fl uid (HTF) was pumped into the evaporator and condenser, and the system was charged with a specifi c refrigerant. For R22, the system was charged with a vapor refrigerant at the compressor inlet. For R432A, the system was charged with a lower vapor pressure refrig- e

22、rant, RE170, at the compressor inlet, which was followed by a higher vapor pressure fl uid, R1270. A digital scale of 0.1 g accuracy was employed to measure the amount of charge. (3) The expansion valve was controlled, and simultaneously the amount of charge was adjusted to maintain the constant sup

23、erheat and subcooling, usually 5 ?C each, at the exits of evaporator and condenser. Nomenclature COP coeffi cient of performance GWPglobal warming potential PRpressure ratio Qcapacity (W) Ttemperature (?C) Wcompressor work (W) Subscripts ccondenser disdischarge eevaporator T T Expansion Valve Flow m

24、eter (Ref.) Filter Drier Sight Glass SLHX T T T Cond. Water/Evap. Water Heat Exchanger Condenser TP T T T T T T T T T T T T T TP T T TP T T T T T T T T T T T T T T TP Water Heater Water Chiller Evaporator Flow meter (Cond. Water) Flow meter (Evap. Water) Compressor Evap. Water Cond. Water Refrigeran

25、t T : Temperature P : Pressure TP : Thermopile SLHX : Suction Line Heat Exchanger TPTP 3-Way Valve Fig. 1. Schematic of a heat pump bench tester (Ref. 3). 598K.-J. Park et al./Applied Thermal Engineering 29 (2009) 597600 (4) When the system reached steady state for more than 1 h, data were taken eve

26、ry 30 s for more than 30 min. 2.3. Test condition To compare the performance of refrigerants correctly, a fair test condition should be employed. For this purpose, all tests were conducted with the secondary HTF temperatures fi xed in this study. For air-conditioning simulation, HTF (water/ethylene

27、glycol mixture in the evaporator and water in the condenser) temperatures at the inlet and outlet of the evaporator were set to roughly 26.0 ?C and 11.0 ?C, respectively while those at the in- let and outlet of the condenser were set to roughly 30.0 ?C and 42.0 ?C, respectively. Even though the exte

28、rnal condition was the same, the resulting saturation temperatures of HCFC22 and R432A in the evaporator and condenser were different (roughly 7 ?C and 45 ?C) due to differing heat transfer characteristics of these fl uids. For heat pumping simulation, HTF temperatures at the inlet and outlet of the

29、 evaporator were set to roughly 10.0 ?C and 1.0 ?C, respectively while those at the inlet and outlet of the con- denser were set to roughly 30.0 ?C and 39.0 ?C, respectively. Un- der this condition, the saturation temperatures of HCFC22 and R432A and in the evaporator and condenser were roughly ?7 ?

30、C and 41 ?C, respectively. In fact, for both conditions the HTF temperatures at the outlets of the evaporator and condenser varied a little bit due to the difference in capacity between two refrigerants tested. Calibrated pressure transducers of 0.1% FS accuracy, coriolis mass fl ow meters of 0.2% a

31、ccuracy, and a dig- ital power meter of 0.1% accuracy were used in the measure- ments.Inthisstudy,theuncertaintyintemperature measurement is less than 0.1 ?C. For all tests, the superheat at the evaporator exit and subco- oling at the condenser exit were kept to be 5 ?C. The amount of charge was adj

32、usted to maintain the same superheat and subco- oling under the same external condition. Finally, as for the lubri- cant, a conventional mineral oil was used for both R432A and HCFC22. 3. Results and discussion Tables 1 and 2 list various measured system parameters such as the coeffi cient of perfor

33、mance (COP), capacity, compressor work, pressure ratio, discharge temperature, and amount of charge for HCFC22 and R432A obtained under air-conditioning and heat pumping conditions respectively. For each refrigerant, tests were performed at least three times and test results agreed within 1% repeata

34、bility. 3.1. Coeffi cient of performance In refrigeration and air-conditioning, COP is a measure of en- ergy effi ciency for a given device charged with a specifi c refriger- ant. Hence, it is important to examine, fi rst of all, the COP of R432A against HCFC22. As listed in Tables 1 and 2, the COP

35、of R432A is 8.58.7% higher than that of HCFC22 under both condi- tions. One of the reasons for the improved effi ciency is the decrease in pressure ratio (PR) across the compressor. As listed in Tables 1 and 2, the PR of R432A decreased 9.7% as compared to that of HCFC22. The decreased pressure rati

36、o in turn results in a decrease in compressor work, which was also seen in Tables 1 and 2. Test results demonstrate that R432A is a good alternative to replace HCFC22 in air-conditioners and heat pumps from the standpoint of energy effi ciency. 3.2. Capacity The capacity is as important as COP in re

37、frigeration. Tables 1 and 2 show the evaporator cooling capacity, Qefor air-conditioning and the condenser heating capacity, Qcfor heat pumping as well as changes in capacity (difference in Qeand difference in Qc) of R432A as compared to HCFC22 for a given compressor. R432A showed 1.96.4% higher cap

38、acity under both conditions. Especially, the capacity difference between R432A and HCFC22 was larger under heat pumping condition. This is a good feature considering the inherent problem of heat pumps that the heating capacity de- creases as the outdoor temperature decreases. Test results indicate t

39、hat R432A is a good drop-in replacement without requiring ma- jor changes in compressor. In fact, resizing and redesigning of com- pressors is very costly and the drop-in feature of R432A is very advantageous from the viewpoint of manufacturing cost. 3.3. Compressor discharge temperatures The lifeti

40、me and reliability of the system as well as the stability of the refrigerant and lubricant should be considered when alter- native refrigerants are considered. These characteristics can be examined indirectly by measuring the compressor discharge tem- perature (Tdis). As listed in Tables 1 and 2, R4

41、32A showed 14.1 17.3 ?C decrease in discharge temperature. From this observation, it can be safely concluded that R432A would be appropriate from the viewpoint of system reliability and refrigerant stability. 3.4. Refrigerant charge Most of the hydrocarbons have smaller density than that of the halo

42、carbons and hence the amount of charge decreases signifi - cantly with hydrocarbons 10. As listed in Tables 1 and 2, R432A Table 1 Test results for HCFC22 and R432A under air-conditioning condition RefrigerantsCOPDifference in COP (%)Qe(W)Difference in Qe(%)W (W)Difference in W (%)PRTdis(?C)Charge (

43、g) HCFC223.41373410962.9984.71300 R432A3.708.538061.91028?6.22.7070.6650 Table 2 Test results for HCFC22 and R432A under heat pumping condition RefrigerantsCOPDifference in COP (%)Qc(W)Difference in Qc(%)W (W)Difference in W (%)PRTdis(?C)Charge (g) HCFC223.6834729434.2794.11350 R432A4.008.736936.492

44、3?2.13.8676.8650 K.-J. Park et al./Applied Thermal Engineering 29 (2009) 597600599 showed a decrease in charge of 50.051.9% as compared to HCFC22. This will help alleviate further the direct emission of refrigerant which is responsible for the greenhouse warming. 4. Conclusions In this study, thermo

45、dynamic performance of R432A and HCFC22 was measured in a breadboard type heat pump/air-condi- tioner under typical air-conditioning and heat pumping conditions. Various performance characteristics were measured and following conclusions were drawn. (1) The COP of R432A is 8.58.7% higher than that o

46、f HCFC22. (2) The capacity of R432A is 1.96.4% higher than that of HCFC22. (3) The compressor discharge temperature of R432A is 14.1 17.3 ?C lower than that of HCFC22. (4) The amount of charge for R432A is 50% lower than that of HCFC22 due to its low density. (5) R432A is a good long term drop-in en

47、vironmentally friendly alternative refrigerant to replace HCFC22 in residential air- conditioners and heat pumps due to its excellent thermody- namic and environmental properties. Acknowledgements This study was supported by MK Chemical, Inc. and Inha University. References 1 United Nations Environm

48、ental Programme, Montreal Protocol on Substances that Deplete the Ozone Layer, Final act, United Nations, New York, 1987. 2 A. Cavallini, Working fl uids for mechanical refrigeration, Int. J. Refrigeration 19 (1996) 485496. 3 D. Jung, Y. Song, B. Park, Performance of HCFC22 alternative refrigerants, Int. J. Refrigeration 23 (2000) 466474. 4 K. Park, D. Jung, Performance of alternative refrigerants for residential air- cond