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| Teaching Since: | May 2017 |
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MCS,PHD
Argosy University/ Phoniex University/
Nov-2005 - Oct-2011
Professor
Phoniex University
Oct-2001 - Nov-2016
13.74Â Â Â A radiative heater consists of a bank of ceramic tubes with internal heating elements. The tubes are of diam-
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2 m
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1 m
0.5 m
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Heated surface
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eter D = 20 mm and are separated by a distance s = 50 mm. A reradiating surface is positioned behind the heating tubes as shown in the schematic. Deter-
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Surroundings
Coated surface
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mine the net radiative heat flux to the heated material when the heating tubes (sh = 0.87) are maintained at 1000 K. The heated material (sm = 0.26) is at a tem- perature of 500 K.
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Heating element
(a)Â Â Â What is the electrical power, qelec, required to operate the heater?
(b)Â Â Â What is qelec if the surfaces are connected with reradiating sidewalls?
The facility may be used to cure different  surface
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D = 20 mm
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Material
T = 500 K
em = 0.26
Reradiating
T = 1000 K
eh = 0.87
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   s = 50 mm
coatings. With the heater still approximated as   a
blackbody, compute and plot qelec as a function of the coating’s emissivity for values ranging   from
0.1 to 1.0. Perform the calculations for both open and reradiating sides.
13.77 A cubical furnace 2 m on a side is used for heat treat- ing steel plate. The top surface of the furnace consists of electrical radiant heaters that have an emissivity of 0.8 and a power input of 1.5 x 105 W. The side- walls consist of a well-insulated refractory material,
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