The Influence of Heat and Moisture Transfer in Soil on the Performance of the Ground Heat Exchanger

Abstract

In this paper, a numerical heat and moisture transfer model (HMTM) and a pure conduction model (PCM) were established separately for unsaturated soil around the ground heat exchanger (GHE) and were numerically solved by finite volume method. The simulation results indicate that rejecting heat into soil can reduce moisture content in the vicinity of the borehole wall. When the initial moisture content is high, moister transfer has little effect on soil thermal properties. In this case, the results of the HMTM and the PCM are basically identical. On the contrary, when the initial moisture content is low, the thermal effect has significant influence on moisture transfer around the borehole wall, and the soil thermal properties will change correspondingly. In this case, there is a large difference between the results of these two models.