Numerical analysis on the condenser inlet air temperature of train-mounted air conditioner when a train stops in subway station tunnel

Abstract

Thermal environment in the subway tunnels is of great importance to guarantee the operation safety of train-mounted Air Conditioner (AC). Most of the previous researches focused on the interval tunnel temperature, but in fact the air temperature in the station tunnel is higher than that of the interval tunnel since the piston wind is weaker and the heat release rate from the train is more intense. In this circumstance, studying the dynamic thermal process when a train stops in a subway station tunnel is both innovative and necessary. In this research, numerical simulation was adopted and then verified by field measurements. The model was built based on a typical island subway station and also the most widely-used form of train in China. We firstly analyzed the airflow and temperature distribution in the simulation domain. Then the dynamic process for AC condenser inlet air temperature were compared between the station with mechanical ventilation system and without mechanical ventilation system. The result indicates that the mechanical ventilation system helps to prevent the quick temperature increase when train stops in the station tunnel. Moreover, main factors including the form of airflow organization, Over Tract Exhaust (OTE) ventilation volume, and heat release rate of the AC condensers were analyzed. Further, the minimum required OTE capacity for different situations can be determined based on the correlations found in this research. For station tunnels with different dimension or train type, the methodology proposed in this research can be employed to improve the safety of subway trains.