Study on heat transfer law between wall and airflow in high-temperature and high-humidity railway tunnels with fractures

In order to explore the heat transfer essence between the surrounding rock and the internal airflow in the high-temperature and high-humidity railway tunnels, an experimental platform for simulated tunnels is designed and built, and a ventilation and heat transfer model in the tunnel is established according to the similarity theory by using simulation software. Based on the consistency between the numerical simulation results and the experimental simulation results, the effects of the virgin rock temperature, inlet airflow temperature and velocity on the unstable heat transfer coefficient and heat transfer in the dry tunnels and the fractured porous and humid tunnels are analysed. The results show that the unstable heat transfer coefficient of fractured porous and humid surrounding rocks increases with the increase of inlet airflow temperature and velocity, and virgin rock temperature. The unstable heat transfer coefficient of dry surrounding rocks is almost not affected by the virgin rock temperature and inlet airflow temperature, and increases with the increase of inlet airflow velocity. When other parameters are the same, the unstable heat transfer coefficient and heat transfer of fractured porous and humid surrounding rocks are greater than those of dry surrounding rocks. Therefore, when studying the environment of fractured railway tunnels, the influence of fracture water and seepage water must be considered.