A cylindrical cavity is closed at the bottom and has an opening centered in the top surface. A cross section of this configuration is shown in the sketch. For the conditions stated below, determine the rate of radiant energy passing through the 5-mm-diameter cavity opening. What will be effective emissivity of the opening?
a. All interior surfaces are black at 600 K.
b. The bottom surface is diffuse-gray with ε = 0.6, and has a temperature of 600 K. All other surfaces are re-radiating.
c. All interior surfaces are diffuse-gray with ε = 0.6 and are at a uniform temperature of 600 K.

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(1 40 mm 3) (2) - 30 mm →