Numerical study on the operating performances of a novel frost-free air-source heat pump unit using three different types of refrigerant

Air-source heat pump (ASHP) is a promising device using in residential buildings because of its energy-savings. Besides, R134a and R407C as environmental friendly refrigerant have advantage to apply into heat pump system. In this study, an investigation of a novel frost-free ASHP system, integrated with dehumidification and thermal energy storage, working with R134a and R407C as an R22 alternative, was presented. A mathematical model of the system is constructed and verified by comparison with experimental data that shows the measured results are in good accordance with the numerical ones. According to the mathematical model, the dynamic performance of the system is characterized by dehumidification and regeneration efficiency, suction and discharge pressure, COP and so on at ambient temperature of 0 °C and RH (relatively humidity) of 85%. The results show that the time for keeping the evaporator frost-free operation for R22, R407C and R134a are 29, 34 and 35 minutes, respectively. In addition, at the end of working time, the discharge pressure of compressor for R134a is 29 and 32% lower than that for R22 and R407C. What is more, at the given ambient temperature of −10 °C and RH of 85%, the average COP for R134a is 3.3 and 8.6%, respectively, which is higher than that for R22 and R407C.