Hybrid Train Ventilation Systems for Summer and Winter Conditions

The HVAC system of a train is the second largest energy consumer during a train journey, requiring up to 20-30% of the total energy demand. Therefore, new technologies, such as heat pumps or demand-oriented ventilation have been tested and integrated [1]. Further, novel ventilation concepts for future high-speed trains have been investigated in recent years in the lower deck of a 1:1 scale generic train mock-up at the DLR in Gottingen within the framework of the Next Generation Train (NGT) project [2]. One main objective of this project is to improve the ventilation system in terms of thermal passenger comfort, heating and cooling performance and energy efficiency. Beside state-of-the-art micro-jet ventilation used as reference case, two novel ceiling-based ventilation concepts were investigated in previous studies: low-momentum ceiling ventilation with a trickle ceiling above the aisle and hatrack-integrated low-momentum ventilation (HLMV) with a trickle ceiling above the seats. In the present study, all three ceiling ventilation concepts were combined with cabin displacement ventilation (CDV), realized by a low-momentum air supply on floor level. The windows of the mock-up were replaced by a jacket heating/cooling system based on capillary tubes mounted on aluminum sheets to allow for the experimental simulation of winter and summer conditions. To simulate the obstructions and the heat release of real passengers, 24 thermal manikins were used. In this study, the influence of warm and cold windows on hybrid ventilation concepts with different air-mass flow distributions between ceiling and floor supply was evaluated in an experimental analysis with regard to the requirements of the standard [3]. At the conference, we are going to present the results in terms of spatial temperature homogeneity, local temperatures and velocities, temperature stratifications, heat removal efficiency as well as surface temperatures of the manikins and cabin interior (see Figure 1) under summer (a) and winter (b) conditions. First results of the present study show a high potential of the novel ventilation concepts with regard to thermal comfort improvements. The lowest energy requirement was observed for the ceiling-based ventilation concepts in case of heating and for CDV in case of cooling. [1] P. Danzer, (2017) ifv Bahn-Klimatechnik (Rail-HVAC) und Bahn-Komfort (Rail-Comfort) Fachtagung. [2] Schmeling D., Hormann H.-J., (2018) Proceedings of the 4th Int. Conf. on Railways Technology. [3] EN 13129 (2016), Railway Applications; Air Conditioning for Main Line Rolling Stock.