Consider a house in Atlanta, Georgia, that is maintained at 22°C and has a total of 20 m2 of window area. The windows are double-door type with wood frames and metal spacers and have a U-factor of 2.5?W/m2•K (see Prob. 1–120 for the definition of U-factor). The winter average temperature of Atlanta is 11.3°C. Determine the average rate of heat loss through the windows in winter.
What will be an ideal response?
The windows of a house in Atlanta are of double door type with wood frames and metal spacers. The average rate of heat loss through the windows in winter is to be determined.
Assumptions 1 Steady operating conditions exist. 2 Heat losses associated with the infiltration of air through the cracks/openings are not considered.
Analysis The rate of heat transfer through the window can be determined from
where Ti and To are the indoor and outdoor air temperatures, respectively, Uoverall is the U-factor (the overall heat transfer coefficient) of the window, and Awindow is the window area. Substituting,
Discussion This is the “average” rate of heat transfer through the window in winter in the absence of any infiltration.
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