Heat Transfer Performance of an Energy Tunnel in a Cold Region through Numerical Simulation

This research develops a numerical model to simulate the thermal performance of energy tunnels in cold regions, with validation through laboratory-scale model tests. Using the Daban Mountain Tunnel as a prototype, a full-scale numerical model incorporating energy tunnel technology was constructed to perform a detailed parametric study. Key factors such as wind speed, seasonal temperature variations, and design/operational parameters were examined to assess their influence on the heat exchange efficiency at the tunnel portal. The findings reveal that: (1) the temperature of the heat transfer fluid at the inlet and the insulation layer thickness considerably affect heat transfer efficiency in the entrance segment of cold-region energy tunnels; (2) wind speed at the tunnel entrance also notably affects heat transfer performance—when wind speed increases from 2.5 to 4.5 m/s, the heat exchange efficiency rises by 94.6%, but further increases beyond 4.5 m/s only lead to a 5.1% improvement due to convective saturation; and (3) from the perspective of engineering application, the influence of wind speed on heat transfer efficiency cannot be ignored in the design of cold-region energy tunnels.