Consider a 1.2 m high and 1.2 m wide single-layer of glass window whose thicknes

Question

Consider a 1.2 m high and 1.2 m wide single-layer of glass window whose thickness is 8 mm and has a thermal conductivity k_glass = 1.1 W.m^-1, K^-1. The room is maintained at 200degreeC and the outside air is at minus 3degreeC. Determine: the steady state rate of heat transfer through this glass window, (10 marks) the overall heat transfer coefficient, and (8 marks) the temperature of its outer surface for a time during the day (8 marks) Assume that the heat transfer coefficients at the inner and outer surfaces of the window to be h_i = 6 W.m^-2. K^-1 and h_o = 18 W.m^-2. K^-1 respectively and disregard any heat transfer by radiation.

Explanation / Answer

a) Rate = V/R = [20-3]/[0.008/(1.1*1.2*1.2)]

= 3366 W

b) heat transfer coeffcient = (6+18)/2 = 12 W/m^2K

c) outside temp = 20 C

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