45. Study on Heat Transfer of Soil Thermal Recovery of Ground Source Heat Pump System

The imbalance of heat extracted from the soil by the ground heat exchangers (GHEs) in winter, and rejected into it in summer is expected to affect the long-term performance of ground source heat pump (GSHP) in areas of southern China. This chapter presents a new operation mode to resolve this problem that in summer night the intermittent operation of GHEs with the cooling tower as the supplemental heat rejecter of GSHP system and in transition seasons the coupling operation of cooling tower combined with the GHEs. The practical analytical model of GHEs based on the line-source theory is established. The computer program based on established model is developed to do the feasibility analysis under the proposed operating mode for a GSHP system in Nanjing of southern China. The results indicate that the imbalance problem of the rejected/extracted heat for the GSHP system in Nanjing of southern China is effectively resolved. In addition, under the proposed operating mode the COP of heat pump unit can be improved, design capacity of cooling tower can be reduced and utilization rate of cooling tower throughout the year can also be increased. The results can improve the energy efficiency of GSHP system.