Assessment of transient thermal comfort characteristics in an underground metro station

Abstract

This paper presents the results of a thermal comfort evaluation of an underground metro station located in a composite climate zone of India (New Delhi). The evaluation comprised real-time monitoring of indoor thermal comfort during winter and summer seasons accompanied by subjective thermal comfort surveys. This study extends the existing field study protocols to transport buildings, which are characterised by dynamic passenger flow. Parameters such as dry bulb temperature (Ti), globe temperature (Tg), relative humidity (RH) and air velocity (Va) were measured using a thermal comfort monitoring system. In addition, spatial variation of Ti, Tg and RH were monitored using lab-assembled Arduino kits. Subjective surveys comprised of transverse responses collected from 360 users and 360 sequential thermal experience responses collected form 60 users. The subjective responses were collected separately for boarding and alighting sequences using an android-based application developed by the team. Transient thermal comfort was estimated using Relative Warmth Index (RWI). A comparative analysis of mean RWI indicates a gradual and uniform change along the alighting sequence of passenger flow. However, the variation of mean RWI is non-uniform and undulated along the boarding sequence. RWI varied from 0.26 at platform to 0.45 at the walkway along the alighting sequence. It varied from 0.3 at concourse to 0.51 at the ticket lobby along the boarding sequence. The neutral temperature (Ti) obtained through thermal sensation vote (TSV) is 30.3°C. The variation in TSV between alighting and boarding passengers were found to be statistically significant at platform, concourse and walkway. A strong positive correlation was obtained between TSValighting and RWI (R =0.52) as well as TSVboarding and RWI (R =0.53). An RWI value of 0.14 corresponded with mean neutral TSV for the alighting sequence while it was 0.33 for the boarding sequence. The passengers exhibited higher level of tolerance to heat discomfort than that predicted by RWI. Acceptable thermal limits along the alighting and boarding sequence of the metro station are presented. © 2018 Proceedings of 10th Windsor Conference: Rethinking Comfort.