Problem # p006

Conduction of Heat

The inner and outer glass of a double-pane window are separated by a 1cm thick layer of still air. Determine the amount of heat per unit time and square-meter of surface which is flowing under steady-state conditions through the window. The glass panes have a thickness of 0.5 cm each and the temperatures on the outer surfaces of the two glass panes are at 20°C and 0°C, respectively. The coefficients of thermal conductivity are k=1.4 W/(m K) for glass and k=0.026 W/(m K) for still air. Neglect heat transfer by radiation. What is the temperature drop across the glass panes and across the air gap ? Would increasing the thickness of the glass panes by a factor of 2 make a significant difference ?