A thermopane window consists of two pieces of glass 7 mm thick (kg = 1.4 W/m⋅K) that enclose an air space 10 mm thick (ka = 0.05 W/m. K). The window separates room air at 20°C from outside ambient air at -10°C. The convection coefficient associated with the inner (room-side) surface is hi = 10 W/m²⋅K and the convection coefficient associated with the outer(ambient) air is 80W/m²⋅K. The glass has a thermal conductivity of 0.78W/m⋅K. The thermal conductivity of the air at the average temperature of T_avg = 0.5 (20−10) = 5 °C is 0.0.02401 W/m⋅K. Neglect radiation and assume the air enclosed between the panes to be stagnant (no motion).
Determine the following:
(a) The rate of heat transfer through the window in W.
(b) The temperature at point 2 (see figure below) in degree Celsius.