The airflow characteristics and thermal comfort evaluation in high-speed train cabin with mixing ventilation: An experimental and numerical study

The airflow characteristics and distribution in high-speed train (HST) cabins have been of great significance for the travel comfort of passengers, while the indoor dynamic airflow characteristics and overall thermal comfort are still unclear. This study first conducted a transient experiment in a real train cabin with the mixing ventilation mode. Measurements showed that the turbulence intensity of the whole airflow is between 20% and 60%. The center zone airflow has a higher turbulence kinetic energy, while the spectral characteristics are closer to the natural wind with the beta value between 1.2 and 1.8. Moreover, considering the limitations of the experiment, a corresponding numerical study was carried out. To be closer to the actual situation, the numerical simulation adopted a partitioned heat transfer wall setting, the average deviation of the airflow velocity and temperature from the experimental comparison was 0.057 m/s and 0.25 degrees C, respectively. Numerical results revealed two vortices in the seating area, a significant longitudinal airflow and an increasing temperature near the carriage ends. Then, to further analyze the compartment's thermal environment and the acceptance of airflow, thermal comfort indicators based on the airflow parameters were used. The predicted mean vote (PMV) showed the thermal comfort of the cabin is slightly cold. Predicted percentage dissatisfaction (PPD) and draught rate (DR) in the center area are barely satisfactory, more than 25% and 20%, respectively. The results of this study can provide an essential reference for the optimization design of ventilation systems in public transport.