A Combined 0D/3D Approach for Comparing Bus Passenger�s Thermal Comfort

Abstract

In Great Britain (GB) the average person living in urban environments can spend up to 55 minutes per day commuting to work, with one of the most popular methods being by bus. Therefore, it is imperative that the bus operators provide a safe and comfortable indoor environment during transit, ensuring passenger health and for encouraging customers to use their service. A common approach to ensure a thermally comfortable environment is by specifying an internal temperature setpoint that the cabin air must maintain. However, there is a lack of consensus between operators as to which temperature is the most appropriate with setpoints typically ranging from 17-21 �C. Further, there has been minimal research into using thermal comfort metrics to assess whether or not these temperatures will provide thermal satisfaction. This research aims to use a combined 0D/3D approach to compare the thermal comfort level of a seated bus passenger using Fanger�s PMV model. This will be done at 3 cabin setpoints; 17, 19 and 21 �C, and an ambient temperature of 10 �C. A dynamic lumped parameter model of a vehicle has been developed in Modelica language that assesses the energy balance between the interior air mass of the cabin and the ambient conditions, and can predict the internal air temperature and surface temperatures. A simple on/off control logic is used to control the provision of heat from the HVAC system to maintain internal cabin temperature �1 �C of the setpoint. This 0D model will be used to supply boundary conditions of surface temperatures, backflow temperatures and the mass flow of HVAC air entering the cabin to a 3D CFD simulation in ANSYS CFX. The average air velocity and temperature distribution around a manikin can then be extracted and the PMV can be computed and compared for the 3 test cases.