Chapter 3 Steady Heat Conduction3-144 The winter R-value and the U-factor of a masonry cavity wall with a reflective surface are to be determined. Assumptions1 Steady operating conditions exist. 2Heat transfer through the wall is one-dimensional. 3 Thermal properties of the wall and the heat transfer coefficients are constant. PropertiesThe R-values of different materials are given in Table 3-6. The R-values of air spaces are given in Table 3-9. AnalysisThe 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-factorsfor the air space and stud sections are available, the overall average thermal resistance for the entire wall can be determined from Roverall= 1/Uoverallwhere Uoverall= (Ufarea)air space+ (Ufarea)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.