Investigating on Thermal Performance of U-tube Ground Heat Exchanger with Concrete Foundation Pile between U-legs

This study employs numerical analysis through the ANSYS FLUENT to evaluate the thermal performance of a 20m vertical U-tube Ground Heat Exchanger (GHE). Utilizing polyethylene pipes with a 26 mm inner diameter and water as the heat transfer fluid at 300 K inlet temperature, and the flow rate was 2 Liter/min. The introduction of a building foundation pile between the inlet and outlet tubes of the U-tube GHE is proposed to enhance thermal performance and reduce installation costs. The investigation includes a comparison of configurations, emphasizing the effectiveness of a double U-tube setup, which demonstrates increased heat exchange rates and enhanced heat transfer efficiency due to the association of two U-tubes. The study reports a notable improvement in average heat exchange rates from 23.77 W to 27.95 W per unit vertical borehole length with the inclusion of concrete piling. Moreover, the use of two U-tubes results in a significant growth in total thermal performance, reaching about 39.15 W per unit vertical borehole length. These findings underscore the cost-effectiveness of integrating a ground source heat exchanger with a pillar, with a double U-tube design proving superior in thermal performance for compact applications compared to a single U-tube.