Alternative refrigerants, Water Source Heat Pumps, Climate change, Numerical modeling
Regulatory changes, aimed at mitigating climate change, are forcing air-conditioning and heat pump manufacturers to change refrigerants in their products, including all Water-Source Heat Pumps (WSHPs). These changes require substantive changes to WSHP equipment design in order to continue to deliver heat pumps that meet product specifications and energy efficiency regulations. Some of the proposed low-GWP refrigerants to replace R410A, such as R452B and R454A, are zeotropic mixtures of refrigerants. Zeotropes with a significant glide may be taken advantage of in the refrigerant-to-water heat exchanger in a WSHP to improve overall system efficiency. However, there is a potential to also reduce system efficiency if not designed appropriately. This work presents a four-component heat pump model which includes a moving boundary condenser model, lumped element evaporator model, and fixed efficiency compressor model. This model was validated against the data of a R410A water-to-water heat pump operated in heating mode with an average 9.7% MAE in prediction of COP. This model was exercised using R452B and R454A and discovered that the latter provided an opportunity to increase the system COP as a result of the increased enthalpy of vaporization of the fluid. Additionally, the moderate glide that these two refrigerants produce is not significant enough to warrant significant consideration for a water-to-water heat pump.