HVAC Defrost System Assessment through 1D and 3D Simulation during Concept Development

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. The validation results are presented by comparing the CFD predicted windshield de-icing patterns with the windshield de-icing tunnel test. The present CFD windshield de-icing simulations demonstrated reasonable agreement with available test data within the error of 10%. The prediction of defrost duct outlet temperature through 1D simulation numerical method will aid in getting the results quickly without carrying out the vehicle testing during early design cycle. By employing this methodology, CFD simulation results could be analyzed and it helps to optimize the defrost duct in a robust way during the early design stages of the program.