Numerical modeling of thermal response of a ground heat exchanger with single U-shaped tube

Based on an experimental sandbox, this article analyzes the heat transfer processes of a ground heat exchanger (GHE) system when adopting two computational fluid dynamics (CFD) modeling approaches. First, the numerical model adopted the measurement recorded inlet temperature of the heat transfer fluid (HTF) as the GHE system input condition, and the predicted HTF outlet temperature was validated against the experimental data. Second, the GHE heating load initiated the numerical simulation, and the HTF outlet temperature was overpredicted by up to 2 °C (3.6 °F), especially for the late stage where discrepancy peaked. The heat transfer analysis showed the heat transfer efficiency of the GHE system adopting the second modeling approach was around 98.5%, due to multiple reasons, including experimental and numerical uncertainties during the tests. It demonstrates the significance of adopting proper thermal boundary conditions in numerical simulations, which can contribute toward the GHE system performance assessment and optimization in real practice