Performance Assessment of Zeotropic Mixtures for Heat Pump Water Heaters

Abstract

The subcritical cycle performances of eco-friendly pure refrigerants and zeotropic mixtures for heat pump water heater systems were performed by MATLAB programs. The results indicated that pure refrigerants are often restricted in meeting criteria such as environmental protection, efficiency, and flammability. The optimal compositions of R13I1/R161/R32, R13I1/R290/R32, and R13I1/R152a/R32 zeotropic mixtures are observed at 0.5/0.3/0.2, 0.15/0.65/0.2, and 0.3/0.5/0.2 (by mass), whose temperature glides are 6.2°C, 14.3°C, and 6.7°C under the given operating conditions, respectively. Meanwhile, the optimum heating coefficients of performance (COPs) are up to 5.04, 4.83, and 5.11, resulting in 10.5%, 5.9%, and 12.1% increments, respectively, compared to R22. However, the COP of R13I1/R1270/R32 exhibits a decreasing and then increasing trend with the rise of the R13I1 mass concentration. The volumetric heat capacities of R13I1/R161/R32 (0.5/0.3/0.2), R13I1/R290/R32 (0.15/0.65/0.2), and R13I1/R152a/R32 (0.3/0.5/0.2) blends yield 121.9%, 116.9%, and 94.1% of the R22 system, respectively. On the other hand, the mixtures are significantly superior in terms of lower pressure ratios, discharge temperatures, and irreversibilities of systems in comparison with R22. Furthermore, the operating pressures of blends are similar to that of R22. Consequently, it is concluded that these three zeotropic mixtures can be superior alternatives to R22 and R134a for heat pump water heater applications.