Reducing the undesirable effects of thermal asymmetry for a bus passengers by using airflow asymmetry under summer conditions

Improving thermal comfort in vehicles, especially in public transport due to design constraints in locating inlet diffusers, overpopulation and difference condition for passengers, is always faced with many challenges. In this paper, the effect of thermal asymmetry on the sensation of passenger inside a bus with overhead mixing ventilation system in three different air distribution patterns is studied by using the 65-nodes thermal comfort model. Moreover, the inlet air temperature has been set at the value which can maintain the passengers’ predicted mean votes within the allowable range. Also, the Airpak solver has been utilized for solving the flow and energy equations; and a numerical code has been developed for solving the local thermal comfort equations. The results show that under thermal asymmetry conditions, it is necessary to use an asymmetric air distribution in order to provide more uniform thermal sensation for the passengers. In this case, air temperature of the head segment is about 22℃ which is less about 2℃ in symmetric flow pattern. The results of 65-nodes model show that using an asymmetrical distribution pattern in the mixing ventilation system improving its performance and under the mentioned conditions, the skin temperature is closer to neutral skin temperature.