A New Approach in Developing Optimal Defrost/Demist Performance in a Passenger Car (TECHNICAL NOTE)


1 Mecanical Engineering, Tafresh University

2 Mecanical Engineering, Sharif University of Technology


The objective of this paper is to optimize defrost/demist performance in a vehicle. However, to initiate the problem, it is necessary to have a thorough understanding of flow behavior within the compartment. So a full-scale model of passenger compartment has been modeled and the air stream from very near to the windshield up to back of the compartment has been analyzed applying computational fluid dynamics. A computational C++ code is developed to calculate vapor film thickness glass temperature and some other parameters in different time steps. The code inputs are the air flow parameters resulted from the CFD simulation. Some different flow arrangements are prepared by changing locations of demist panels and outlet pores to evaluate defrost and demist performance. Ultimately, between 6 different cases suggested, the optimum location of demist panels and exit vents is determined. For the case in which warm air enters through left A-Pillar in addition to the bottom panel, and exits through right A-Pillar, the windshield clearance time is minimum for the same initial conditions.