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


1 Department of Mechanical Engineering, Tafresh University, Tafresh, Iran

2 Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran


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.


1.     Aroussi, A., Hassan, A., Clayton, B., AbdulNour, B. and Rice, E., "Improving vehicle windshield defrosting and demisting", (2000), SAE Technical Paper.
2.     Wang, M., Urbank, T.M. and Sangwan, K.V., “Clear vision” automatic windshield defogging system", (2004), SAE Technical Paper.
3.     Karamjit, S., "Simulation of the windscreen defrost performance", in Star European User Conference., (2011).
4.     Skea, A.F., Harrison, R., Baxendale, A. and Fletcher, D., "Comparison of CFD simulation methods and thermal imaging with windscreen defrost pattern", (2001), SAE Technical Paper.
5.     Aroussi, A. and Aghil, S., "Characterisation of the flow field in a passenger car model", Optical Diagnostics in Engineering,  Vol. 4, No. 1, (2000), 1-15.
6.     Zolet, A., "CFD and experimental correlation of the defrost flow and vehicle windshield defogging", in 21 thBrazilian Congress of Mechanical Engineering, Natal, RN, Brazi., (2011).
7.     Croce, G., D'Agaro, P., De Angelis, A. and Mattiello, F., "Numerical simulation of windshield defogging process", Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering,  Vol. 221, No. 10, (2007), 1241-1250.
8.     Himanshu, K., Upadhyay, N., Sehgal, M., Jaraut, P., Gautam, S. and Kalra, S.K., "Feasibility study and development of refrigerator cum air conditioner", International Journal of Scientific and Research Publications,  Vol. 4, No. 12, (2014), 1-6.
9.     Tehertovskaia, N., "Simulation model for the climate at the windshield of a passenger car compartment", (2004).
10.   Guide, F.U., "Fluent 6.3 documentation", Fluent Inc,  (2007).