Numerical study on natural ventilation of equipment rooms in underground subway stations

• The energy consumption of equipment rooms in subway stations is enormous. • A study was conducted on natural ventilation of equipment rooms in subway stations. • A temperature prediction model for equipment rooms was established. • The relative error of the temperature prediction model for the equipment room is less than 8% • The piston wind inside the tunnel is beneficial for reducing the equipment room temperature. Due to concentrated heat loads and confined spaces, equipment rooms in urban rail transit systems face increasing challenges in maintaining suitable thermal conditions. This study establishes a steady-state temperature prediction model driven by thermal buoyancy to address this issue. It further evaluates the effects of ventilation opening parameters, equipment heat load, and train operation on natural ventilation performance through numerical simulations. First, a temperature calculation formula is derived based on thermal balance analysis, clarifying the physical significance of the empirical coefficients a , b , and the vent velocity v . A series of three-dimensional steady-state simulations are then conducted to investigate how variations in the vent area, height, and layout affect the temperature and velocity fields within the equipment room. Representative data are extracted to analyze airflow characteristics and steady-state temperatures under various conditions. The coefficients are obtained through regression fitting, and the wind speed term is simplified using a near-constant approximation to develop a rapid prediction model. Results show that the temperature prediction model maintains a relative error within ±8 % under typical working conditions. Further analysis reveals that the piston wind effect generated by train operation significantly influences the room temperature, providing a critical basis for model refinement and optimization.