Hot water supply performance of a ground source heat pump that use open-type direct expansion method

Abstract

This study aimed to investigate the performance of ground source heat pumps that use the direct expansion method for hot water supply. The cooling and heating capabilities of this type of heat pump is superior to that of a conventional ground source heat pump. Experiments were conducted using an R32 refrigerant with consideration to actual usage conditions, wherein a ground source heat pump with a depth of 30 m was inserted to an open vertical borehole with a depth of 40 m and diameter of 155.2 mm. The structure of the underground heat exchanger was U-shaped and was connected at the bottom to three copper pipes with outer diameters of 6.35 mm and one copper pipe with an outer diameter of 9.52 mm. A thermocouple was attached to one of the three copper pipes to measure the wall temperature. From the experiments, the system coefficient of performance of the water supply system including the water supply pump was calculated as 2.07.