Retrofit assessment of refrigerator using hydrocarbon refrigerants

This study used hydrocarbon (HC) refrigerants in a small R134a refrigerator to evaluate the refrigeration performance and feasibility of using these alternative refrigerants by conducting the no-load pull-down test and 24-hour on-load cycling test. The mixed mass ratios of the HC refrigerants, R290 and R600a, were 65% and 35% (HC₁), 50% and 50% (HC₂), and 0% and 100% (HC₃), respectively. The charged ratios were 30%, 40%, 50%, and 60% based on the charged mass of R134a for HC refrigerants. The results of the no-load pull-down test revealed that the optimal charged mass for all the HC refrigerants was 40% of that of R134a. Most of the experimental results of the HC refrigerators obtained using the optimal charged masses showed that freezer temperature and power consumption were higher than those of the R134a refrigerator. Therefore, the capillary tube lengths of R134a, HC₁, HC₂, and HC₃ were recalculated to be 2.77, 5.05, 5.34, and 5.60 m, respectively, and the recalculated capillary tube was used in the 24-hour on-load cycling test. The results of the 24-hour on-load cycling test showed that the freezer temperatures considerably decreased when the HC refrigerants were used, and that all of the HC refrigerants could be used in the R134a refrigerator after changing the capillary tube lengths. All of the HCs refrigerants yielded lower electricity consumption, lower on-time ratios, and higher energy factors (EFs) than R134a did. The EFs of HC₁, HC ₂, and HC₃ were 9.1%, 12.2%, and 42.3% higher than that of R134a, respectively. Using a higher proportion of R600a in HC refrigerants can enhance the EFs of refrigerators.