Cabin thermal comfort is predominantly impacted by the interior car cabin temperature. This paper aims to investigatethe impact of the orientation of the air vents in the private car cabin on temperature distribution as car cooling mode isstarted. In contrast, the prevailing cabin temperature depends on the size of the cabin, the number and shape of the airvents and the collective flow of the entire HVAC system and the interior materials of the dashboard, trims and seats. Inthis numerical investigation the effects of solar radiation on thermal comfort in a car cabin is critically analyzed.Normally, the air vents in the car cabin are manually adjustable to control the airflow direction. Computationalfluid dynamics (CFD) investigation was performed by using FLUENT 18.0 as a solver and a CFD processordeveloped by ANSYS Inc., in which the solar load model is embedded. A three -dimension (3D) computationalmodel for the car cabin has been conducted with ICEM CFD software for good quality grid generation of more than5,000,000 grid nodes. The performance of HVAC system is characterized by air flow patterns, temperature, relativehumidity contours as well as the most commonly used comfort parameters; the predicted mean vote (PMV) and thepredicted percentage of dissatisfied (PPD) based on Fanger model. With the help of CFD simulations it is shownhere that orienting air vents with 30°provided a better thermal comfort for passengers. The work showed that thecalculated temperature near the driver increased by about 1.5°C resulting of the solar radiation. This paperdemonstrated that the impact of inlet air temperature from vents has better effect on thermal comfort instead of usinghigher air change per hour (ACH) at the same vent direction.

Key words: thermal adaptation, Thermal comfort, CFD, HVAC, Car cabin temperature, solar radiation.