直膨方式地中熱ヒートポンプの熱交換性能

―地中熱交換器の熱交換性能―

抄録

Ground source heat pumps (GSHPs) attract attention as one of the future energy saving system. In the conventional GSHP system, which uses an indirect heat exchange method, vertical systems use two long pipes connected by a U-shaped fitting at the bottom of a hole bored in the ground. These pipes form part of a closed loop, called the ground loop, through which a mixture of water and antifreeze circulate. In contrast, a GSHP that uses a direct expansion method circulates a mixed refrigerant through the ground loop. The purpose of this study is to investigate the heat exchanging performance of the GSHP using direct expansion method. The coefficients of performance (COP) were obtained for the direct expansion type of GSHP running in the cooling and the heating mode. The amount of heat transferred was evaluated by obtaining an enthalpy difference at the indoor unit. It was found that the COP in the cooling mode was over 12 and in the heating mode was around 7.