Numerical Simulation of the Thermal Comfort in a Double Decker Train Cabin

Abstract

The project “Next Generation Train” (NGT), initiated by the German Aerospace Center (DLR), faces the question of how to reduce travel times of future trains, while also improving the safety, passenger comfort and environmental aspects [1]. Part of this project is the prediction of thermal comfort in the NGT passenger cabin consisting of an upper and a lower deck. The geometry of the middle car cabin is presented in Fig. 1. For the prediction of the thermal comfort numerous thermal sources have to be taken into account in the flow simulations, one of which is the passenger itself. In our former work [2] we studied the air flow and the thermal comfort in the upper level of train cabin. The present paper focuses on numerical simulations of the air flow including heat transport, thermal radiation and the thermal comfort of passengers in both levels of the NGT cabin. The computations have been performed by coupling solutions of the Reynolds-averaged Navier-Stokes (RANS) equations, obtained with the Computational Fluid Dynamics (CFD) code OpenFOAM, with the heat transport within the passengers' predicted with the finite-element code THESEUS-FE, developed by P+Z Engineering GmbH. With the latter one, the bodies of passengers were modelled based on various layers with different heat transport characteristics, taking into account effects like blood flow, heat transfer through skin and clothing as well as activity levels and ambient humidity. Based on these computations the thermal comfort of passengers in the cabin was simulated and analysed. In particular the thermal comfort depends on the air flow, the temperature distribution and the thermal radiation in a specific cabin configuration.