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A significant route for water ingress into passenger cars is through the Heating, Ventilating, and Air-Conditioning (HVAC) system. The penetration of rainwater through the HVAC unit and the subsequent rise in moisture levels within the passenger compartment directly affect the provision of thermal comfort to the cabin occupants. It is speculated that up to 80% of water ingress into the cowl or engine bay is from water film movement over the bonnet of the car, and only the remaining 20% is from direct rain impact from above. Using a full-scale Climatic Wind Tunnel (CWT) facility, which incorporates accurate rain distribution modeling, it has been possible to study the movement of rainwater film over the exterior surface of the vehicle to ascertain the flow distribution of the film moving into the engine bay, into the cowl, advancing up and over the windscreen and shed to the sides and front of the vehicle.

Maintaining adequate visibility at all times, through a vehicle windshield, is critical to the safe usage of the vehicle. The ability of the windshield defrosting and demisting system to quickly and completely melt ice on the outer windshield surface and remove mist formed on the inner surface is therefore of paramount importance. The objectives of this paper are to investigate the fluid flow and heat transfer on the windshield as well the effect of the air discharge from the defroster vents on passenger comfort. The results presented are from numerical simulations validated by experimental measurements both carried out a model and full-scale. The numerical predictions compare well with the experimental measurements at both scales. The effects of the defrosting and demisting air on occupants' comfort and safety are examined.

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.

The increasing competitiveness in the automobile market has resulted in the incorporation by the manufacturers of certain features in newer cars that are deemed highly desirable by the customer. Among such features that require improvement is the thermal comfort of passengers' within the cabin. Thermal comfort is in increasing demand from motorists bound to cover more mileage driving cars than ever before. As a result, car makers are striving for improved climate conditions inside the car to meet passenger demand for more comfortable trips. The need to improve the climatic comfort within the vehicle is critical not only to passengers' comfort but also to their safety. However, to make progress in this area, a good understanding of the airflow behaviour within the vehicle interior is required. This paper, reports on a novel idea of control the air movement within the cabin by forcibly removing the air from strategically positioned vents.