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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 thermal comfort of passengers within a vehicle is often the main objective for the climate control engineer; however, the need to maintain adequate visibility through the front and side windows of a vehicle is a critical aspect of safe driving. This paper compares the performance of the side window defrosting and demisting mechanism of several current model vehicles. The study highlights the drawbacks of current designs and points the way to improved passive defrosting mechanisms. The investigation is experimental and computational. The experiments are carried out using full-scale current vehicle models. The computational study, which is validated by the experiments, is used to perform parametric investigation into the side window defrosters performance. The results show that the current designs of the side-defroster nozzles give maximum airflow rates in the vicinity of the lower part of the window, which yields unsatisfactory visibility.

This paper examines the prevailing fluid flow and heat transfer on the windshield of a full–scale vehicle and examines ways of promoting efficient de–icing and demisting. It establishes that present methods of defrosting and demisting windshields are inefficient; since the first area cleared is below the driver's eye level and even this result only occurs some considerable time after the blower has been switched on. The complexity of the windshield topography and the defroster nozzle geometry yield inadequate flow mixing, poor momentum interchange and consequently dead flow zones in critical visibility areas. This study explores ways of improving the defrosting and demisting process through passive means and using the existing air handling system of the vehicle. The results presented are from numerical simulations validated by experiment.