A new analytical model for short-term borehole heat exchanger based on thermal resistance capacity model

The present study develops a new accurate and simple analytical method for modeling of heat transfer in borehole heat exchanger for short time periods. The thermal resistance and capacity circuit is used for derivation of the governing equations inside the borehole for single U-tube and double U-tube configurations. Also, radial heat transfer is taken into account in the ground around the borehole. The Laplace transform is used for solving the governing equations. The effects of the fluid and grout thermal capacities are considered in the present model. Unlike the previous analytical models reported in the literature, the real geometry of the borehole with single and double U-tube configurations is considered in the present model. The results of the present analytical model are compared with reference experimental measurements and numerical simulation results. It is found that the mean fluid temperature and the borehole wall temperatures obtained from the present analytical method are in very good agreement with the reference numerical results.