Q6. A double-glazed window, 1.5 m high and 2.5 m wide, consists of two layers of glass each 3 mm thick separated by a 20

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Q6 A Double Glazed Window 1 5 M High And 2 5 M Wide Consists Of Two Layers Of Glass Each 3 Mm Thick Separated By A 20 1 (66.16 KiB) Viewed 27 times

Q6. A double-glazed window, 1.5 m high and 2.5 m wide, consists of two layers of glass each 3 mm thick separated by a 20 mm thick air gap. The window is installed in the wall of a room in which the air temperature is maintained at 25 °C. The outer surface of the window is exposed to the ambient air which is at a temperature of 3 °C. The convection heat transfer coefficient at the room- side surface of the window is 5.7 W/m²K and that on the outer surface is 9.1 W/m²K. The thermal conductivity of the glass is 0.76 W/m K. (a) Assume that the air gap between the glass layers can be considered as a stationary layer of air of thermal conductivity 0.026 W/m K. (i) Calculate the rate of heat transfer through the window. (ii) (b) (i) (ii) (8 marks) Determine the temperatures of the room-side surface and outer side surface of the glasses. (7 marks) Calculate the rate of heat transfer for a similar sized window, with a single layer of glass, assuming that all the remaining data are unchanged. Compare this result with that obtained in 6.a.i and discuss. (8 marks) Calculate the temperatures of the room-side and outer side surfaces of the single glass. Compare these results with those obtained in 6.a.ii. and discuss. (7 marks) Continued...