PROPOSAL OF A FLOW RATE CONTROL GSHP SYSTEM WITH A LINING BOREHOLE GROUND HEAT EXCHANGER

Abstract

 This study proposed a flow rate control Ground Source Heat Pump (GSHP) system with a lining borehole ground heat exchanger (LBHE) from the view point of heat storage. To identify basic thermal properties of the LBHE and its surrounding ground, Thermal Response Test (TRT) was conducted. The thermal resistance of the LBHE was 0.025 K/(W/m) from the TRT and 30% lower than the conventional LBHE. In addition, we performed an air heating experiment to examine the effectiveness of the flow rate control. As a results, the water temperature difference between inlet and outlet of the heat exchange plate was about 3℃ and proposed system can work as general GSHP system. Since third day on the experiment, water temperature in the LBHE and its surrounding ground temperatures at 5 p.m. almost recovered to the previous temperature level at 8 a.m. the following morning due to thermal recovering operation. Therefore, it was expected that proposed system enables continuous use of the shallow ground heat. Then, heat exchange rate per unit length of the LBHE was about 50 W/m and about 1.3 times larger than that of double U-tube ground heat exchanger. Consequently, it was found that proposed system can help to save storage energy in the LBHE.