저온용 R502 대체 냉매의 이론 및 실험적 평가

Theoretical and Experimental Evaluation of R502 Alternatives in Low Temperature Applications

R502 has been extensively used as a working fluid in transport refrigerating vehicles and low temperature refrigerating machines but is to be phased out by the end of 1995 due to ozone layer depletion problem. In this study, both theoretical cycle analysis and experiments were carried out to examine the best substitutes for R502. Theoretical results indicate that the alternatives available in the market today may replace R502 without significant changes in the system without suction line heat exchanger(SLHX). When the system contains a SLHX, however, COPs of the alternatives increase up to approximately 15~20% than those without the SLHX. But simultaneously, the discharge temperatures of the compressor also increrease significantly with the SLHX. Actual test results obtained from the experiment with a transport vehicle's refrigerator indicate the similar trend as those of the theoretical results. Especially, HFCs and their mixtures show lower discharge temperature than those of R502, which is one of the desirable features. Further research is needed to study the effect of the SLHX on the performance of the real machine as well as on the oil return for reliability of the system.