Temperature Measurement of a Vehicle's Windshield Using Liquid Crystals

The impingement of air jets on a vehicle's windshield is one parameter that determines the effectiveness of the defroster's system in freeing the windshield of frost and fog. Incompressible air jets impinge upon the inner surface of the windshield and create hydrodynamic and thermal boundary layers which in turn control convective heat transfer. Therefore, understanding the heat transfer interaction between impinging air jets and an inclined windshield is of practical relevance. Experimental investigations on the temperature distribution are performed on the inner surface of the windshield for the purpose of obtaining local and average heat transfer coefficients. In this paper, the temperature distribution of a vehicle's windshield is investigated using liquid crystals. As a result, a temperature contour map is generated displaying local temperature values on the inner surface of the windshield. The strongly non-uniform air velocities at the defroster's nozzles are also measured for both the driver's and the passenger's sides.