Consider a 1.2-m-high and 2-m-wide glass window with a thickness of 6 mm, thermal conductivity k = 0.78 W/m·K, and emissivity ε
= 0.9. The room and the walls that face the window are maintained at 25°C, and the average temperature of the inner surface of the window is measured to be 5°C. If the temperature of the outdoors is −5°C, determine (a) the convection heat transfer coefficient on the inner surface of the window, (b) the rate of total heat transfer through the window, and (c) the combined natural convection and radiation heat transfer coefficient on the outer surface of the window. Is it reasonable to neglect the thermal resistance of the glass in this case?
1 answer:
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Answer:
t = 59.37 s
Explanation:
Given data:
thermal diffusivity
theraml conductivity = k = 22 W/m.K
h = 300 W/ m^2.K
= 25 degree C = 298 k
= 60 degree C = 333 k
= 75 degree C = 348 L
diameter d = 0.1 m
characteristics length Lc = r/3 = = 0.0166
at Bi = 0.226
Ai = 0.982
-1.187 = - 0.02t
t = 59.37 s