A special surface coating on a square panel that is 5 m × 5 m on a side is cured by placing the panel directly under a radiant heat source having the same dimensions. The heat source is diffuse and gray and operates with a power input of 75 kW. The top surface of the healer, as well as the bottom surface of the panel, may be assumed to be well insulated, and the arrangement exists in a large room with air and wall temperatures of 25 ° C . The surface coating is diffuse and gray, with an emissivity of 0.30 and an upper temperature limit of 400 K. Neglecting convection effects, what is the minimum spacing that may be maintained between the heater and the panel to ensure that the panel temperature will not exceed 400 K? Allowing for convection effects at the coated surface of the panel, what is the minimum spacing?
A special surface coating on a square panel that is 5 m × 5 m on a side is cured by placing the panel directly under a radiant heat source having the same dimensions. The heat source is diffuse and gray and operates with a power input of 75 kW. The top surface of the healer, as well as the bottom surface of the panel, may be assumed to be well insulated, and the arrangement exists in a large room with air and wall temperatures of 25 ° C . The surface coating is diffuse and gray, with an emissivity of 0.30 and an upper temperature limit of 400 K. Neglecting convection effects, what is the minimum spacing that may be maintained between the heater and the panel to ensure that the panel temperature will not exceed 400 K? Allowing for convection effects at the coated surface of the panel, what is the minimum spacing?
Solution Summary: The author explains the minimum panel heater separation, neglecting convection, and including it.
A special surface coating on a square panel that is
5
m
×
5
m
on a side is cured by placing the panel directly under a radiant heat source having the same dimensions. The heat source is diffuse and gray and operates with a power input of 75 kW. The top surface of the healer, as well as the bottom surface of the panel, may be assumed to be well insulated, and the arrangement exists in a large room with air and wall temperatures of
25
°
C
. The surface coating is diffuse and gray, with an emissivity of 0.30 and an upper temperature limit of 400 K. Neglecting convection effects, what is the minimum spacing that may be maintained between the heater and the panel to ensure that the panel temperature will not exceed 400 K? Allowing for convection effects at the coated surface of the panel, what is the minimum spacing?
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
A furnace is of cylindrical shape with a diameter of 1.2 m and a length of 1.2 m as shown in Figure 3. The top surface has an emissivity of 0.70 and is maintained at 500 K. The bottom surface has an emissivity of 0.50 and is maintained at 650 K. The side surface has an emissivity of 0.40. Heat is supplied from the base surface at a net rate of 1400 W. Estimate the temperature of the side surface and the net rates of heat transfer between the top and the bottom surfaces, and between the bottom and side surfaces.
Determine the heat loss by radiation from an oven wall to the wall of a room to
which the oven wall is directly facing. Assume that no heat flows through the
adjacent walls, which are coated with a reradiating material. The oven wall is
square, 4 ft on one side, and is 2 ft from the room wall and parallel to it. The
oven wall is steel sheet and is at 400°F, and the wall is at 80°F and is of
asbestos board.
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