The characteristics of passenger heat loss and thermal environment in a subway cabin

Due to the rapidly increasing ridership and the relatively enclosed nature of subway spaces, passenger thermal comfort has become a primary design objective. In this paper, a series of human subject studies are conducted to investigate the exchange mechanism between passenger heat and the indoor environment in a type-B subway cabin. The impact of crowding levels (ideal, reasonable, and acceptable) and ventilation modes (internal ventilation mode, IVM, and external ventilation mode, EVM) are considered. The results indicate that under the IVM condition, passenger heat loss at various crowding levels has an approximately linear impact on indoor temperature, primarily driven by radiative heat loss. In contrast, the EVM leads to high radiative and convective heat loss, and the rise in indoor temperature remains modest. Furthermore, as an important parameter in the evaluation of thermal comfort models, passenger clothing surface temperature can be obtained using an iterative calculation method, with a relative error less than 2.2% compared to experimental measurements. It is also found that while the EVM mode quickly stabilizes the indoor thermal environment, excessive heat loss at low crowding degrades passenger comfort. The outcome can serve as an important reference for proceeding investigations on optimizing cabin design in public transport.