ABSTRACT Energy tunnels rely on underground structures and effectively utilize underground rock and soil as heat carriers to achieve green and low‐carbon energy consumption for rail transit. In energy tunnel, ground heat exchangers (GHEs) are coupled with surrounding rock and air in the tunnel for heat transfer (where tunnel air temperature is affected by train operation heat dissipation and ventilation). In order to reveal the variation laws of rock and soil temperature and air temperature in underground energy tunnels under multiple factors, clarify the dynamic thermal characteristics of energy underground structures in the process of thermal storage and release, under actual train operating conditions, a coupled heat transfer model of energy tunnels based on tunnel airflow and dynamic heat transfer of rock and soil mass was established. The research results indicate that under the operating conditions of subway trains, if ventilation is not installed, there will be overheating after 2 years of operation, which will affect the normal operation of the train. However, installing GHEs for heat extraction can control air temperature below 25°C. When the GHEs heat with air and surrounding rock at an initial temperature of 20°C, the heat transfer per unit area can reach 41.2 W/m 2 in summer and 23 W/m 2 in winter at an inlet water temperature of 7°C. When adopting alternating operation of storage and heat release, it can better maintain soil thermal balance, with a heat transfer capacity of up to 180 W/m 2 , which can be effectively used for air conditioning cooling and hot water supply in buildings.
Cao et al. (Sun,) studied this question.