Analyses of the improvement of subway station thermal environment in northern severe cold regions

Currently, subway lines are being increasingly constructed in the northern severe cold regions of China. The average ambient temperature in this region is below −10 °C during winter. Therefore, the extreme climate and piston effect impose challenges for designers for enhancing the thermal environment of a metro station in severe cold season. In this study, one-dimensional modelling is developed using the IDA Simulation Environment (IDA) based on an actual metro line, and the results are validated by experimental data. Moreover, the thermal environment of a typical metro station in the control group, two traditional optimisation measures, and one new method are investigated in severe cold regions. The results indicate that the primary heat loss during winter is attributed to the cold air invasion caused by the piston effect from the entrances. The addition of a warm-air curtain individually at the entrance may not effectively prevent the intrusion of cold air. Furthermore, adding a door curtain can reduce the inlet air volume of the entrance, but reduce the outlet air volume of the entrance. Thus, the heat of the train brake cannot be effectively utilised to improve the station temperature. In addition, one new method using the piston wind principle was presented, and it can effectively prevent the cold wind and more effectively utilise the train braking energy to improve the temperature of the metro station. It serves as a guideline for subway environmental control system (ECS) design.