Thermodynamics HW Solutions 257

Thermodynamics HW Solutions 257 - Chapter 3 Steady Heat...

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Chapter 3 Steady Heat Conduction 3-144 The winter R -value and the U -factor of a masonry cavity wall with a reflective surface are to be determined. Assumptions 1 Steady operating conditions exist. 2 Heat transfer through the wall is one-dimensional. 3 Thermal properties of the wall and the heat transfer coefficients are constant. Properties The R-values of different materials are given in Table 3-6. The R -values of air spaces are given in Table 3-9. Analysis The schematic of the wall as well as the different elements used in its construction are shown below. Heat transfer through the air space and through the studs will meet different resistances, and thus we need to analyze the thermal resistance for each path separately. Once the unit thermal resistances and the U -factors for the air space and stud sections are available, the overall average thermal resistance for the entire wall can be determined from R overall = 1/ U overall where U overall = ( Uf area ) air space + ( Uf area ) stud
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This note was uploaded on 01/19/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

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