Passenger thermal comfort in the whole departure process of high-speed railway stations: A case study with thermal experience and metabolic rate changes in summer

Passengers usually experience complex thermal experience and metabolic rate changes in the departure process of high-speed railway stations. Previous studies did not consider the variations of passenger thermal comfort during the multiple spatial transitions with those simultaneous changes. Therefore, this study aims to investigate the dynamic thermal responses of passengers in the whole departure process as well as identify their specific thermal comfort demands in different functional zones. The behavior sequences of 17,354 passengers were investigated in a typical high-speed railway station. The obtained behavior characteristics were then replicated in a sequence of five climate chambers to simulate the spatial transition process, including outdoor entrance square, security check area, concourse, waiting room, and check-in area. The variations of passengers’ thermal experience were designed with 24 temperature variation sequences using four different indoor temperature settings (24 °C, 26 °C, 28 °C, and 30 °C) and two outdoor environmental conditions of low-temperature conditions (LTCs) at 27–30 °C and high-temperature conditions (HTCs) at 32–35 °C. Thirty subjects dressed in 0.49 clo were recruited, and variations in their psychological and physiological responses were recorded throughout the experiments. The results showed that although the outdoor thermal experience resulted in passengers’ subjective perceptions to the level of very uncomfortable, it also improved their thermal adaptive capacity in the waiting room and check-in area. The stabilized time of thermal comfort vote (TCV) (5.34–14.84 min) in the waiting room was shorter than that of thermal sensation vote (TSV) (13.36–18.23 min), and the time required for heart rate and skin temperature to reach stability there concentrated in 12–20 min and 16–20 min, respectively. Moreover, quantitative relationships between neutral temperature (Tn) and specific influential factors were acquired for each functional zone. The variation ranges of Tn in security check area, concourse, waiting room, and check-in area were 23.62–24.68 °C, 24.45–25.24 °C, 25.00–25.63 °C, and 24.88 °C in LTCs and 22.40–23.10 °C, 24.09–24.68 °C, 25.05–25.86 °C, and 24.56–25.38 °C in HTCs. The corresponding 90% acceptable temperature ranges varied from 1.28 °C to 3.06 °C. This study provides references for enhancing passenger thermal comfort and optimizing the indoor environments.