An enclosure has an inside area of 100 m 2 , and its inside surface is black and is maintained at a constant temperature. A small opening in the enclosure has an area of 0.02 m 2 . The radiant power emitted from this opening is 70 W . What is the temperature of the interior enclosure wall? If the interior surface is maintained at this temperature, but is now polished, what will be the value of the radiant power emitted from the opening?
An enclosure has an inside area of 100 m 2 , and its inside surface is black and is maintained at a constant temperature. A small opening in the enclosure has an area of 0.02 m 2 . The radiant power emitted from this opening is 70 W . What is the temperature of the interior enclosure wall? If the interior surface is maintained at this temperature, but is now polished, what will be the value of the radiant power emitted from the opening?
Solution Summary: The author calculates the shape factor of surface 1 with respect to surface 2.
An enclosure has an inside area of
100
m
2
, and its inside surface is black and is maintained at a constant temperature. A small opening in the enclosure has an area of
0.02
m
2
. The radiant power emitted from this opening is
70
W
. What is the temperature of the interior enclosure wall? If the interior surface is maintained at this temperature, but is now polished, what will be the value of the radiant power emitted from the opening?
An enclosure has an inside area of 50 m², and its inside surface is black and is maintained at a constant temperature. A small opening in
the enclosure has an area of 0.03 m². The radiant power emitted from this opening is 52 W. What is the temperature of the interior
enclosure wall, in K? If the interior surface is maintained at this temperature, but is now polished so that its emissivity is 0.15, what will
be the value of the radiant power emitted from the opening, in W?
T, =
grad =
i
K
W
Earth absorbs solar energy and radiates infrared energy. The intensity of the solar radiation incident on earth is J = 1350 Wm-2, also known as the solar constant. Assume earth’s surface (ground) temperature to be uniform at Ts, and that the ground and atmosphere are black (emissivity = 1) for infrared radiation. The radius of the earth is 6.378 x 106 m. The diagram shows the ground at the surface temperature Ts and the atmosphere, represented as a thin black layer, at temperature Ta . Suppose the atmosphere absorbs 100% of the infrared radiation emitted by the ground. Assume that the ground absorbs 47.5% of the incident solar energy, and that the atmosphere absorbs 17.5% of the incident solar energy (for a total of 65% absorbed by the planet).
Calculate the "steady state” numerical values of the earth’s ground temperature Ts and the atmospheric temperature Ta taking into account the “greenhouse effect” of atmospheric infrared absorption and emission described above.
3. Two parallel plates with a diameter of 60
cm, separated at a distance of 15 cm. The
temperature on the top surface is 4 oC and
the temperature on the bottom surface is
300 K. If all the surfaces are black, what is
the rate of heat transfer?
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