In-cabin airflow and thermal comfort analysis of passenger car is study about car HVAC system and modular design parameters of vent outlets. For same opening area of air vent what is effect of different shapes of vents on velocities at vent outlet, pressure drop and percentage flow distribution. Study of overall thermal comfort for 3 hours of soaking followed by 1 hour cooldown is part of study. Transient analysis and to make it faster coupling of 2 solvers FLUENT and RADTHERM was main goal of project. Total transient analysis only in fluent considering conduction, convection and radiation takes 30 days which can be solved by coupled method in RADTHEM in 1 day.