Analytical Modeling of Temperature Fields in Extra-Long Highway Tunnels: Incorporating Vehicle Heat Dissipation

A fluid-solid coupling heat transfer model for tunnel gas is established based on the law of conservation of energy, incorporating heat generation from vehicles during tunnel operation. Via variable separation and Laplace transformation, analytical solutions for the radius of the heat-regulating circle in the tunnel envelope are derived, and the annual average and annual amplitude temperatures of tunnel gas are also calculated. On this basis, the variation law of the gas temperature field in an extra-long highway tunnel is deduced by considering the annual average and annual amplitude of gas temperature at the tunnel entrance. Results indicate that when the tunnel depth exceeds 2000 m, the tunnel temperature field can be determined solely by the annual average temperature of inlet gas, with the effect of inlet gas amplitude temperature negligible. Under the influence of inlet annual average temperature, the tunnel temperature changes most significantly at a wind speed of 5 m/s. Meanwhile, when traffic flow increases from 16000 veh/d to 22000 veh/d, the tunnel exit temperature only rises from 23 °C to 24.2 °C, meaning this factor exerts a weak impact.