Heat exchange performance of ground source heat pump by water cooling method

Abstract

Ground source heat pump (GSHP) is one of saving energy systems for air conditioning. However, the GSHP is not popular in Japan because an initial cost of the GSHP is higher than an air source heat pump. This paper describes the thermal performance of the GSHP using water cooled method. This system consists of commercialized water cooling heat pump which removed a cooling tower and then attached a heat exchanger. Ground water penetrates under 6 m in depth and there is natural flow of ground water. This system exchanges the heat between ground water and the circulating water in the heat exchanger. This system uses existing two wells. One is 40 m in depth and it is used as borehole. That is expected to save the digging cost of bore hole. A casing pipe whose surface was punched like slit was inserted in the borehole. Heat exchanger is in the casing pipe. The space between the casing pipe and the borehole was filled with silica sand which was performed as filler. The other well is 30 m in depth. Well pump is in the well. The pumping head is in the wall at 24 m. The pump feeds water into 38 m point of the borehole. This pump is used to recover the temperature of underground by feeding water. The proposed system is evaluated by coefficient of performance (COP) of this system. COP is used commonly as index of the performance of GSHP.