Personalized air exhaust combined with mixing ventilation for environmental management and airborne droplets in a train cabin

The enclosed space and high passenger density in high-speed train cabins pose substantial challenges in providing a safe, healthy, and comfortable indoor environment, especially during pandemics such as COVID-19 and influenza. High ventilation rates, while beneficial in reducing pathogen transmission, may compromise airflow field quality and result in great energy consumption. Therefore, understanding the tradeoffs between transmission risk, thermal comfort, and energy saving is critical for devising cabin ventilation systems. As the primary method of regulating indoor environments, heating, ventilation, and air conditioning systems are central to this study, which proposes an improved personalized ventilation mode that combines personalized exhaust with various supply air strategies. The results indicate that the personalized exhaust mode considerably reduces the longitudinal spread of particles and rapidly decreases their concentration in the air. When paired with a higher proportion of airflow entering the cabin through sidewall air outlets, the airflow primarily diffuses upward. The proposed mode enhances thermal comfort, balances energy consumption and air quality, and delivers significant performance improvements, including a 22.4% increase in energy utilization efficiency and over a 23.3% reduction in suspended droplets. This study provides a theoretical foundation for optimizing high-speed train cabin ventilation systems in the post-pandemic era.