Field test and numerical simulation on thermal performance of a large-diameter bridge energy pile

This study focuses on investigating the heat transfer characteristics of large-diameter bridge energy piles through field tests, aiming to examine the heat exchange rate and temperature distribution of a full-scale large-diameter bridge energy pile and its surrounding soil. Additionally, a three-dimensional numerical model of this energy pile is developed and validated by comparing field measurements with simulation results. With the validated model, a parameter sensitivity analysis is conducted to explore the influence mechanism of convective heat exchange between the bridge piers on top of the pile and the surrounding air on the heat transfer characteristics of the large-diameter bridge energy pile. The results indicate that the heat exchange rate of this energy pile can reach -222.28 W/m, which is approximately 1.5 to 3.9 times that of conventional types. However, the larger diameter of the pile leads to uneven temperature distribution across the cross section. Specifically, the temperature near the heat exchange tubes is significantly higher (by around 3 ℃) than that at the central axis. Furthermore, it is observed that convective heat exchange between the bridge piers and surrounding air causes a decrease in the temperature of the piers, thereby increasing the heat exchange rate of the bridge energy pile in summer operation mode. When the heat transfer mode on the pier surface transitions from natural convection (air flow rate of 0 m/s) to forced convection (air flow rate of 5 m/s), the heat exchange rate of the bridge energy pile increases by approximately 22 W/m.