R134a와 R1234yf를 적용한 상용탑차용 냉동시스템의 성능비교 연구

Abstract

Number of cars is increased gradually due to development of automobile industry and improvements of living level. To satisfy the demand of consumers and to solve the environment problems such global warming and depletion of the ozone layer, the development competition of eco-friendly future cars such as an electric car and hydrogen fuel cell vehicle is actively studied. Besides, shopping and eating out culture have developed rapidly and purchase of goods through On-line have increased, therefore, the demand for food of frozen and refrigeration have also increased. Recently, R134a refrigerant has been used mainly as the refrigerant of automobile air conditioning system. However, it is classified as global warming gas by the 1997 Kyoto Protocol. To substitute the R134a refrigerant, many companies tried to develop the alternative refrigerant like R1234yf refrigerant. GWP of R1234yf refrigerant is just 4 which is lower than GWP of R134a refrigerant(GWP=1430). In addition, ODP of R1234yf is 0. In this study, the performance characteristics of refrigeration system using R134a and R1234yf in a refrigeration truck was investigated and compared. As a result, the optimal charging amounts of R134a and R1234yf system were 1.4 kg and 1.3 kg, respectively. Charging amounts of R134a system were 7.2% more than that of R1234yf system. Under optimal charging amounts, COP and cooling capacity of R134a system were 2.63 and 4.23 kW, and those of R1234yf system were 2.49 and 3.93 kW, respectively. To find optimal EEV opening, EEV opening of R134a system was varied. The optimal EEV openings of R134a and R1234yf system was 60% and 50%, respectively, and COP of R134a and R1234yf system at this EEV opening was 2.69 and 2.49, respectively. When the outdoor air temperature increased from 25℃ to 35℃, the power consumption of R134a and R1234yf system increased by 8.2% and 5.5%. while cooling capacity of R134a and R1234yf system decreased by 7.9% and 6.7%, respectively. Accordingly, COP of R134a and R1234yf system decreased by 15% and 11.6%, respectively. When the indoor air temperature increased from 5℃ to 9℃, cooling capacity of R134a and R1234yf system increased by 13.1% and 6.8%, while the power consumption of R134a and R1234yf system decreased by 2.9% and 1.5%, respectively. Accordingly, COP of R134a and R1234yf system increased by 16.5% and 7.7%, respectively. As the compressor rotating speed increased from 1000 rpm to 2000 rpm, cooling capacity of R134a and R1234yf system increased by 21.7% and 18.9%, respectively, resulting in 37.5% and 35.9% decrease COP for each system. Overall, the performance of R1234yf system was lower than that of R134a system. Under various operating conditions, the performance variation rate of R134a system was higher than that of R1234yf system. Through the results of this study, it can provide the basic information on the performance of a refrigeration system in a refrigeration truck by application of alternative refrigerant.