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The windshield defrosting performance is a very important requirement for the vehicle safety because it affects directly the driver’s visibility during driving. The defrosting process in the vehicle is carried out by blowing hot air from the HVAC (Heating Ventilation and Air conditioning) through the defrost duct system. Computational Fluid Dynamics (CFD) is used to numerically simulate the vehicle defroster performance with the available defrost duct outlet temperature and coolant temperature data from the vehicle testing. This paper describes the 1D modelling of complete HVAC system configuration to find out the defrost duct outlet temperature and through the CFD, transient defrost simulation was carried out to simulate the ice melting process over the windshield at various time step. In the CFD simulation, shell modelling analysis method is followed to predict the de-icing phenomenon over the vehicle windshield.

In recent years clearing the mist on side windows is one of the main criterions for all OEMs for providing comfort level to the person while driving. Visibility through the side windows will be poor when the mist is not cleared to the desired level. “Windows fog up excessively/don't clear quickly” is one of the JD Power question to assess the customer satisfaction related to HVAC performance. In a Mobile Air Conditioning System, HVAC demister duct and outlet plays an important role for removing the mist formation on vehicle side window. Normally demister duct and outlet design is evaluated by the target airflow and velocity achieved at driver and passenger side window. The methodology for optimizing the demister outlet located at side door trim has been discussed. Detailed studies are carried out for creating a parametric modeling and optimization of demister outlet design for meeting the target velocity.