Thermal Performance of an Energy Pile Group with a Deeply Penetrating U-Shaped Heat Exchanger

Abstract

This study presents a novel heat exchanger configuration, called a deeply penetrating U-shaped configuration, for energy piles. The outlet water temperature, temperature variation along the tube, and heat transfer rate are simulated and computed using Comsol Multiphysics software. The simulations are for the cooling mode. The proposed configuration is compared with traditional U-shaped and W-shaped configurations to prove its superiority. The thermal performance of the pile group is compared with that of a single pile to investigate the effects of the pile group on the heat transfer. A parametric analysis is performed to investigate the effects of several important parameters (i.e., pile spacing, pile diameter, soil type, and thermal parameters) on the heat transfer performance of an energy pile group with the proposed deeply penetrating U-shaped configuration. The results indicate that the corner pile indicates a nonnegligible heat transfer rate 6.8% and 9.9% higher than the central pile in quincuncial and squared arrangements. Purely from the standpoint of thermal performance, the pile spacing is recommended to be more than 6.8 times the pile diameter to reduce the influence of the pile group on the heat transfer capacity.