Thermodynamics HW Solutions 757

Thermodynamics HW Solutions 757 - ) ( ave , window overall...

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Chapter 9 Natural Convection 9-90 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 transfer through the window is one-dimensional. 3 Thermal properties of the windows and the heat transfer coefficients are constant. 4 Infiltration heat losses are not considered. Properties The U-factor of the window is given in Table 9-6 to be 2.13 W/m 2 . ° C. Analysis The rate of heat transfer through the window can be determined from
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Unformatted text preview: ) ( ave , window overall ave window, o i T T A U Q = & where T i and T o are the indoor and outdoor air temperatures, respectively, U overall is the U-factor (the overall heat transfer coefficient) of the window, and A window is the window area. Substituting, W 456 = = C 11.3)-)(22 m C)(20 W/m 13 . 2 ( 2 2 ave window, Q & Discussion This is the average rate of heat transfer through the window in winter 12.7 mm Metal Reflective Wood Air 22C 11.3C in the absence of any infiltration. 9-80...
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