Phillip Thomas Heat losses in a car in the winter

The Issue Driving home for thanksgiving I noticed that the different surfaces of my car (windows, roof, side panels) were different temperatures. I took this to mean that since both the outside temperatures and the inside temperatures were reasonably uniform that the heat loss at each must have been different. So I wanted to see where the most heat was lost and how much.

Important Dimensions and Values Interior of car modeled as 1.5 meter by 1 meter by 1 meter prism Bottom half is modeled as 5 cm fiberglass and top half is modeled as glass, top side is modeled as 3 mm thick canvas. The outside is 0 degrees Celcius, the interior temperature is 20 degrees celcius, and the car is moving at 30 m/s (67 mph).

Results The most heat is lost through the side windows followed by the roof and front windshield. The roof looses about the same q/m 2 as the windshield, but because its bigger, twice as much power is lost. Total Losses = 1939 W WattsRoofSide windowsSide PanelsWindsheild q(Watts/m 2 ) q (Watts)

Importance of Results By determining these losses, efforts can be made to minimize them by changing materials with different properties, adding addition insulation, etc. It is interesting the human body at sitting conditions will produce around 150 Watts, more if in a cool environment, however, even two passengers will not make up for the lost heat to through the surfaces mentioned. A heater will be necessary to maintain air temperature at 20 Celsius.