Effect of air velocity and relative humidity on passengers' thermal comfort in naturally ventilated railway coach in hot-dry indian climate.

In India, railways still continue to be the most prominent means of transport, especially non-air conditioned railway that carries around 3.5 billion people every year. Thermal comfort in these non-air-conditioned trains is predominantly influenced by windows and fans. The present study orients around the effect of fan air as well as naturally ventilated air on thermal comfort of passengers. The study is part of a field survey followed by an experimental investigation that was carried out in non-air-conditioned railway coaches during summer afternoon, with more than 1500 subjects of different gender and age category. The study significantly contributes in defining an elevated acceptable range of comfort air velocity inside a moving stock. The mean threshold air velocity where passengers responded a neutral PCV (passengers' comfort vote) is found to be 2 m/s which is much higher than conventional standards for enclosed static buildings and premises. The clear dominance of behavioral adaptation has been noticed in expression of thermal comfort by the passengers. This strengthens the idea of adopting some alternative method to deal with thermal discomfort of non–air-conditioned railway passengers. Here a novel term as 'zone of independence' (ZoI) has been defined at which the effect of air velocity becomes independent on passengers' comfort vote. This ZoI can significantly be utilized while optimization of thermal comfort in an ICF railway coach. • Thermal adaptation is more dominant in case of passengers as compared to building or office occupants. • Acceptable air velocity for thermal comfort at different relative humidity values varies within a range of 1.1 m/s to 2 m/s. • For higher humidity bands slightly lower air velocity preference has been recorded. • Need to redesigning of air velocity distribution for the existing Indian railway non-air-conditioned passenger coaches. [ABSTRACT FROM AUTHOR]