Energy analysis of low-GWP refrigerants R513A and R516A as alternatives to R134a in heat pumps for simultaneous heating and cooling of water

Abstract

The transition to low global warming potential (GWP) refrigerants is essential in addressing climate change. This study evaluates the energy performance of low-GWP refrigerants R513A and R516A as alternatives to R134a in heat pump systems for simultaneous heating and cooling applications. Utilizing a validated mathematical model and experimental data, the study examines the thermodynamic efficiency (COP) of each refrigerant under varying operational conditions, including temperature and flow rate variations in the evaporator and condenser. The research examined two primary cases: a medium-temperature scenario (scenario 1), where the evaporator inlet temperatures of the water-glycol mixture range from 0 to 5°C, and condenser water inlet temperatures range from 35 to 40°C, simulating applications such as moderate cooling and domestic hot water heating. The high-temperature scenario (scenario 2) involves evaporator inlet temperatures between 10 to 15°C and condenser water inlet temperatures from 50 to 55°C, representing conditions suitable for waste heat recovery and industrial process heating applications. Although these temperatures overlap with other technologies like evacuated-tube solar collectors, their integration into heat pump systems underscores the versatility and scalability of these systems for diverse energy demands. In both scenarios, the mass flow rate of water was adjusted between 0.05 and 0.15 kg/s in the evaporator and condenser. The results indicate that R513A and R516A achieved comparable performance to R134a, with R516A demonstrating a slightly higher COP under high-temperature conditions. For the three fluids, the average COP in cooling mode (COPc ) was 3.3, and in heating mode (COPh ), it was 4.6 across the tested conditions. These findings highlight the potential of R513A and R516A as effective replacements for high-GWP refrigerants, supporting the transition to sustainable refrigerant technologies.