Question

To defrost ice accumulated on the outer surface of a car windshield, warm air is blown over the inner surface of the windshield. Consider windshield thickness is 5 mm and its thermal conductivity is 1.4 w/(m.K). The outside ambient temperature is -10c and the convection heat transfer coefficient is 200 w/(m2.K), while the ambient temperature inside the car is 25c. Determine the value of the convection heat transfer coefficient for the warm air blowing over the inner surface of the windshield necessary to cause the accumulated ice to begin melting.

Answer 1

Explanation:

To defrost ice accumulated on the outer surface of an automobile windshield, warm air is blown over the inner surface of the windshield. Consider an automobile windshield (kw = 1.4 W/m·K) with an overall height of 0.5 m and thickness of 5 mm. The outside air (1 atm) ambient temperature is − 20°C and the average airflow velocity over the outer windshield surface is 80 km/h, while the ambient temperature inside the automobile is 25°C . Determine the value of the convection heat transfer coefficient, for the warm air blowing over the inner surface of the windshield, necessary to cause the accumulated ice to begin melting. Assume the windshield surface can be treated as a flat plate surface.