Influence of Sub-Cooling on the Energy Performance of Two Eco-Friendly R22 Alternative Refrigerants

Abstract

In this study, the effects of sub-cooling on the various refrigeration cycle performance parameters using the alternative eco-friendly refrigerants (R432A and R433A) as working fluids were evaluated theoretically and compared with those obtained using the baseline refrigerant (R22). REFPROP 7.0 software was employed for the computation and evaluation of refrigerants properties. The results obtained showed that the thermodynamic properties of R432A and R433A matched those of R22 and they could be used as substitute for R22. The two alternative refrigerants exhibited very high thermal conductivity with average values of 59.3% and 58.0% higher than that of R22, respectively. Their condenser duties are also better than that of R22, which shows that they could perform very well as refrigerants in heat pump systems. They exhibited higher coefficient of performance (COP) and higher relative capacity index (RCI) than R22. The average COPs obtained for R432A and R433A were 12.9 and 16.7% higher than that of R22. They also exhibited lower power per ton of refrigeration (PPTR) than that of R22, but R433A emerged as the most energy efficient refrigerant among all the investigated refrigerants with average reduction in PPTR of 28.5% higher than that of R22. Generally, incorporation of sub-cooling heat exchanger in the system, greatly improved the performance of the system; it increases the COP, reduces the compressor energy input and the specific power consumption of the system. The two alternative refrigerants, consistently exhibited better performance than R22 in sub-cooling heat exchanger refrigeration system. R433A performed better than both R22 and R432A in that the highest RCI, COP, reduction in energy input, reduction in PPTR and lowest discharge temperature were obtained using R433A in the system.