Prediction of Thermal Comfort Inside a Midibus Passenger Cabin Using CFD and Its Experimental Validation

This paper presents a methodology for predicting thermal comfort inside Midibus cabin with an objective to modify the Heating, Ventilation and Air Conditioning (HVAC) duct design and parametric optimization in order to have improved thermal comfort of occupant. For this purpose the bus cavity is extracted from baseline CAD model including fully seated manikins with various seating positions. Solar Load has been considered in the computational model and passenger heat load is considered as per BSR/ASHRAE 55-1992R standard. CFD simulation predicted the air temperature and velocity distribution inside passenger cabin of the baseline model. The experimental measurements have been carried out as per the guidelines set in APTA-BT-RP-003-07 standard. The results obtained from CFD and Experimental test were analysed as per EVS EN ISO7730 standard and calculated occupant comfort in terms of thermal comfort parameters like Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD). These parameters are based on seven point thermal sensation scale which defines the thermal comfort of occupant inside the passenger cabin of a bus. CFD results were found to be in good agreement with the experimental results. Based on the validation of the baseline model, duct design, layout and diffuser locations have been modified to improve thermal comfort of the occupant.