Thermodynamics HW Solutions 50

Thermodynamics HW Solutions 50 - Chapter 1 Basics of Heat...

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Chapter 1 Basics of Heat Transfer 1-101 Two large plates at specified temperatures are held parallel to each other. The rate of heat transfer between the plates is to be determined for the cases of still air, regular insulation, and super insulation between the plates. Assumptions 1 Steady operating conditions exist since the plate temperatures remain constant. 2 Heat transfer is one-dimensional since the plates are large. 3 The surfaces are black and thus ε = 1. 4 There are no convection currents in the air space between the plates. Properties The thermal conductivities are k = 0.00015 W/m ⋅° C for super insulation, k = 0.01979 W/m ⋅° C at -50 ° C (Table A-15) for air, and k = 0.036 W/m ⋅° C for fiberglass insulation (Table A-16). Analysis ( a ) Disregarding any natural convection currents, the rates of conduction and radiation heat transfer [] W 511 = + = + = = × = = = ° = =
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