Experimental analysis on the thermal performance of a R290 air source heat pump water heater.

In this paper, an experimental apparatus of air source heat pump water heater (ASHPWH) using R290 as working fluids was established in a climatic chamber to evaluate its performance and application feasibility. The air source heat pump water heater increased the water temperature up to 70? at working conditions of 0?, to 65 ? and 55 ? at working conditions of -7? and -15?, respectively, without coefficient of performance (COP) decreasing compared to the typical range of ASHPWH. Among all the testing conditions, the maximum discharge pressure of the compressor is 3.11MPa, the maximum discharge temperature is 98.8?, and the maximum pressure ratio is 8.1, which are in the valid operating range of the compressor. The influence of refrigerant charge and capillary tube length on the system performance were also investigated, results show that the suitable charge not only increases COP, but also reduces pressure ratio and discharge temperature.