Thermodynamics HW Solutions 753

Thermodynamics HW Solutions 753 - Chapter 9 Natural...

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Chapter 9 Natural Convection and C 59.5 ° = ° + ° = + = ⎯→ = ) m 024 . 0 )( C . W/m 502 . 8 ( ) W 05 . 0 )( 100 ( C 35 ) ( 2 2 s s s s hA Q T T T T hA Q & & Therefore, natural convection lowers the surface temperature in this case by about 2 ° C. Special Topic: Heat Transfer Through Windows 9-80C Windows are considered in three regions when analyzing heat transfer through them because the structure and properties of the frame are quite different than those of the glazing. As a result, heat transfer through the frame and the edge section of the glazing adjacent to the frame is two-dimensional. Even in the absence of solar radiation and air infiltration, heat transfer through the windows is more complicated than it appears to be. Therefore, it is customary to consider the windows in three regions when analyzing heat transfer through them: (1) the center-of-glass , (2) the edge-of-glass , and (3) the frame regions. When the heat transfer coefficient for all three regions are known, the overall U-value of the window is determined from UU A U A
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