ABSTRACT
This research investigates long-term thermal performance of a three-pile group with one or multiple thermally active piles arranged in a triangular configuration. The pile-soil heat transfer analyses account for thermally induced natural convection. For a constant inlet fluid temperature, the power output under coupled thermo-hydro flow conditions was compared with that derived from a purely conductive heat transport model. Results indicated a 10% increase in power output for a single pile and a 29% increase for a group of three piles spaced at 2.5D (where D = pile diameter) under coupled flow conditions. Additionally, numerical analysis revealed a significantly lower temperature rise in the sand layer surrounding the pile group due to the formation of thermally induced convective vortices. Such findings further highlight the importance of accounting for coupled thermo-hydro flow in analysis, design, and performance prediction of shallow geothermal energy harvesting systems.
