The composite wall of an oven consists of three layers, 4, B, and C of thicknesses...

 

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The composite wall of an oven consists of three layers, 4, B, and C of thicknesses 12 inch, 4 inch, and 8 inch and thermal conductivities 0.75, 0.08, and 0.50 Btu/h ft °F, respectively. The inner layer is A, and it has an inside temperature of 2000°F. The outer layer (C) is exposed to an ambient temperature of 85°F and its surface heat transfer coefficient is 1.3 Btu/h ft F. It is estimated that there is a thermal contact resistance of 0.0021 h °F/Btu between the layers A and B, and 0.0025 h F/Btu between the layers B andC (expressed on the basis of unit area of the wall). Calculate (1) the rate of heat loss from the oven per square foot of the wall area, (ii) the temperatures of the walls A and B at their junction, and the temperature jump. Draw the electrical analogue of the problem. The composite wall of an oven consists of three layers, 4, B, and C of thicknesses 12 inch, 4 inch, and 8 inch and thermal conductivities 0.75, 0.08, and 0.50 Btu/h ft °F, respectively. The inner layer is A, and it has an inside temperature of 2000°F. The outer layer (C) is exposed to an ambient temperature of 85°F and its surface heat transfer coefficient is 1.3 Btu/h ft F. It is estimated that there is a thermal contact resistance of 0.0021 h °F/Btu between the layers A and B, and 0.0025 h F/Btu between the layers B andC (expressed on the basis of unit area of the wall). Calculate (1) the rate of heat loss from the oven per square foot of the wall area, (ii) the temperatures of the walls A and B at their junction, and the temperature jump. Draw the electrical analogue of the problem.

Answer rating: 100% (QA)

A B KA075 Btu KB 008 he 05 Btu To 85 F 3D T 2000F hft F Bt... View the full answer