A novel 2-D ring-tubes model and numerical investigation of heat and moisture transfer around helix ground heat exchanger

Abstract As for the helix ground heat exchanger, a novel 2-D ring-tubes heat and moisture transfer model was built in this paper for the sake of efficiency and convenience. And a miniature model experiment was conducted to verify the correctness of the model. Four different soil initial water content conditions were simulated with the established model. In addition, the novel model was compared with the pure heat transfer model of which there is no moisture migration. The results indicate that increasing the initial soil water content can increase heat transfer capacity of the exchanger effectively. Three different heat transfer stages can be divided for the helix ground heat exchanger in the water flow direction. And during the design of exchanger, the proportion of entrance and exit stages should be increased for the sake of larger heat exchange capacity. Moreover, some effective measures can be conducted to increase soil water content near the entrance stage in order to avoid excessive reduction of soil water content in this area. There is a critical initial water content θcr for heat release condition to determine the applicability of the pure heat transfer model, and it’s 0.111 m3/m3 for the typical mudstone soil in Chongqing.