Thermodynamics HW Solutions 921

Thermodynamics HW Solutions 921 - Chapter 12 Radiation Heat...

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Chapter 12 Radiation Heat Transfer 12-28 The base, top, and side surfaces of a furnace of cylindrical shape are black, and are maintained at uniform temperatures. The net rate of radiation heat transfer to or from the top surface is to be determined. Assumptions 1 Steady operating conditions exist 2 The surfaces are black. 3 Convection heat transfer is not considered. Properties The emissivity of all surfaces are ε = 1 since they are black. T 1 = 700 K ε 1 = 1 r 1 = 2 m T 2 = 1200 K ε 2 = 1 r 2 = 2 m T 3 = 500 K ε 3 = 1 h =2 m Analysis We consider the top surface to be surface 1, the base surface to be surface 2 and the side surfaces to be surface 3. The cylindrical furnace can be considered to be three-surface enclosure. We assume that steady-state conditions exist. Since all surfaces are black, the radiosities are equal to the emissive power of surfaces, and the net rate of radiation heat transfer
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