Numerical study of the air flow through an air-conditioning unit on high-speed trains

The air-conditioning units (ACUs) on high-speed trains are responsible for cooling the passenger compartment. Insufficient condensing air flux through the ACU may lead to a suboptimal cooling and causes dangerous levels of overheating or even a shutdown of the ACU itself. In this paper, the air flow through ACU at different speeds of a high-speed train is investigated numerically. A significant drop of the condensing air flux during the train operation at higher speed is observed. This phenomenon is related to the interaction of the air flow through the ACU and the boundary layer on the roof of the train. Simulations show that the motion of the train creates a region of negative pressure above the ACU inlets and a region of positive pressure above the outlets. Thus, a particular structural optimization of the air outlets aimed at reducing the pressure buildup is proposed. The proposed numerical method can be used serve to investigate and to optimize the performance the ACUs on high-speed trains under different structural modifications.