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Unformatted text preview: 19.14 (a) Calculate the heat flux through a sheet of steel 10 mm (0.39 in.) thick if the temperatures at the two faces are 300 and 100C (572 and 212F); assume steady-state heat flow. (b) What is the heat loss per hour if the area of the sheet is 0.25 m 2 (2.7 ft 2 )? (c) What will be the heat loss per hour if sodalime glass instead of steel is used? (d) Calculate the heat loss per hour if steel is used and the thickness is increased to 20 mm (0.79 in.). 19.15 (a) Would you expect Equation 19.7 to be valid for ceramic and polymeric materials? Why or why not? (b) Estimate the value for the Wiedemann Franz constant L [in -W/(K) 2 ] at room temperature (293 K) for the following nonmetals: silicon (intrinsic), glass-ceramic (Pyroceram), fused silica, polycarbonate, and polytetrafluoroethylene. Consult Tables B.7 and B.9 in Appendix B....
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- Spring '08