Performance assessment of R1234ze(E) as a low GWP substitute to R410A in fin-and-tube heat exchangers

Several energy efficiency regulations worldwide are forcing air conditioning and heat pump manufacturers to replace the halogenated refrigerants currently used in these systems, such as R410A, with more climate friendly alternatives that have a lower Global Warming Potential (GWP). This study explores how the performance of R1234ze(E) compares for an R410A based fin-and-tube evaporator coil. A total of 36 experiments were completed for both refrigerants, by means of a high-fidelity experimental facility, to validate a segment-by-segment heat exchanger model. For R410A, the mean absolute percent error between the experimental and simulated capacity was found to be 0.9%, and it was 1.4% for R1234ze(E). Simulations were then carried out, using the model, with R1234ze(E), where the fin density and refrigerant circuitry of the original heat exchanger were altered independently. By increasing the fin density from 15 to 20 fins per inch (FPI), the capacity increased by 4.9%, and refrigerant side pressure drop decreased by 4.5%. For the refrigerant circuitry optimizations, a maximum increase in capacity of 5.6% was observed when compared to the baseline, but at the expense of 7.5 times higher pressure drop. Alternatively, a separate circuitry resulted in a 38% pressure drop reduction and 2.5% reduction in capacity. The results demonstrated the relative sensitivity of capacity and refrigerant side pressure drop for R1234ze(E) on only two heat exchanger geometrical parameters. This sensitivity suggests potential for additional optimizations to heat exchanger designs for low-GWP refrigerants by performing further parametric analysis on heat exchanger geometry.