Air conditioning performance of a ground source heat pump that use direct expansion method

This paper summarizes the results of 240 hours of continuous cooling and heating operation of a direct-expansion type ground source heat pump with a three-branch copper-tube heat exchanger. The output power of the heat pump is 6.8 kW for cooling and 8.9 kW for heating. U-shaped underground heat exchangers with a copper pipe length of 30 m on each side were inserted into three boreholes of 30 m depth. During the cooling operation, the amount of release heat to the underground was 8.0 kW, the power consumption was 1.3 kW, and the COP was 6.0. During the heating operation, the amount of extracted heat from the underground was 7.4 kW, the power consumption was 2.2 kW, and the COP was 3.6. The effect of heat extraction and dissipation during the heating and cooling operations on the ground temperature was also investigated.