The inner and outer surfaces of a 0.5-cm thick 2-m × 2-m window glass in winter are 10°C and 3°C, respectively. If the thermal conductivity of the glass is 0.78 W/m•K, determine the amount of heat loss through the glass over a period of 5 h. What would your answer be if the glass were 1 cm thick?
What will be an ideal response?
he inner and outer surfaces of a window glass are maintained at specified temperatures. The amount of heat transfer through the glass in 5 h is to be determined.
Assumptions 1 Steady operating conditions exist since the surface temperatures of the glass remain constant at the specified values. 2 Thermal properties of the glass are constant.
Properties The thermal conductivity of the glass is given to be k = 0.78 W/m°C.
Analysis Under steady conditions, the rate of heat transfer through the glass by conduction is
Then the amount of heat transfer over a period of 5 h becomes
If the thickness of the glass doubled to 1 cm, then the amount of heat transfer will go down by half to 39,310 kJ.
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