A SYSTEMIC SIMULATION MODEL AND EXPERIMENTS ON VERTICAL GROUND HEAT EXCHANGERS IN GCHP SYSTEMS

摘要

Ground coupled heat pumps (GCHPs) are a promising new technology that has been used in recent years in Chinese market. The most important component of the GCHP systems compared to conventional air conditioning systems is the ground heat exchanger (GHE). This paper mainly presents the entire simulation model of heat transfer of GHEs in GCHPs. The explicit analytical solution of the finite line source in semi-finite medium is derived for convenient calculation of the thermal resistance outside the borehole for long time steps. The resistance inside the borehole is also better expressed accounting for the thermal interference between the two legs of the U-tube. The techniques of spatial superimposition for multiple boreholes and sequential temporal superimposition for arbitrary heating/cooling loads of the systems are also presented in this paper. The validation of the models by experiments in the actual project of GCHP system in China is carried out. The results of these tests have shown that the measured data on site agree quite well with predicted data according to the model. The simulation model is suitable for engineering applications.