Demisting of Vehicle Air Intake Using Plane Baffles

The penetration of rainwater through the heating ventilation and air conditioning system, HVAC, of a vehicle directly affects the provision of thermal comfort within the vehicle passenger compartment. The first element of a typical HVAC system, namely the cowl box is considered. The purpose of the airway from the cowl grille openings to the air filter, immediately before the blower, is to ensure proper water separation from the incoming air stream before entry onto the air filter and onwards into the rest of the HVAC system. This is achieved by ensuring standing water within the cowl is quickly drained and that water rain droplets or water flows from the windshield and body are separated from the air stream, hence minimising the effect on the total system volumetric flow rate. An experimental study is conducted to examine the effect of plane baffles on the airflow filed within a rectangular duct. A set of plane baffle plates is placed within the cowl duct. Flow visualisation methods are used to acquire the airflow properties within the rectangular duct. The experimental observations and measurements are compared to results of numerical simulation employing the finite-volume method and assuming a fully developed flow. Good agreement is found between measured and computed velocity profiles.