Study on heat transfer model of capillary exchanger in subway source heat pump system

Abstract In order to solve the problem of heat build-up in subway tunnels, a subway heat pump system with capillary network as front-end heat exchanger is proposed. A one-dimensional simplified plate heat transfer calculation method for capillary heat exchanger (CHE) based on surface-heat-source is proposed. Taking into consideration of the changing heat flux during heat transfer, this paper adopts step load, superposition principle, energy conservation and iterative method to establish the heat transfer model of CHE. CHE heat transfer tests were carried out at the Zhiquan Road Station of Qingdao Metro R2 line to prove this model. The results show that the max error of the model is 8.79%. In addition, the impact of such factors as inlet water temperature of CHE, the lining thermal conductivity, the thermal conductivity of surrounding rock and thermal diffusivity of the surrounding rock to the performance of the heat exchanger has been analyzed.