Study on the Performance Evaluation of Domestic Hot Water Supply System using Storage Tank : Experiments and Analyses on the Operation Control Modes of CO_2 Heat Pump Water Heaters

Abstract

This paper describes the performance of CO_2 heat pump water heaters. Experiments were carried out for the same hot water demands by using the modified M1 mode. The results showed that the value of HPCOP for each heat pump was in the following range: 3.1-5.0 in summer, 3.2-4.4 in the middle season, and 2.4-3.9 in winter. The value of SCOP for each heat pump was in the following range: 2.2-3.9 in summer, 1.9-3.7 in the middle season, and 1.8-3.1 in winter. The value of SCOP was high when the temperature of the output hot water from the HP unit was low. However, it is necessary to pay attention to the hot water shortage. The result of a simplified annual prediction based on the experiments showed that the value of SCOP was in the range 1.8-3.7.