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MCS,PHD
Argosy University/ Phoniex University/
Nov-2005 - Oct-2011
Professor
Phoniex University
Oct-2001 - Nov-2016
5.147
 In a manufacturing process, stainless steel cylinders (AISI 304) initially at 600 K are quenched by submersion in an oil bath maintained at  300 K with h = 500 W/m2 · K. Each cylinder is of length 2L = 60 mm and diameter D = 80 mm. Use the ready-to-solve model in the Examples menu of FEHT to obtain the following solutions.
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doubled (h = 1000 W/m2 · K). Also, for convec-
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tion coefficients of 500 and 1000 W/m2 · K, deter- mine how long the cylinder needs to remain in the oil bath to achieve a safe-to-touch surface temper- ature of 316 K. Tabulate and comment on the results of parts (a) and (d).
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The operations manager for a metals processing plant anticipates the need to repair a large furnace and has come to you for an estimate of the time required for the furnace interior to cool to a safe working temperature. The furnace is cubical with a 16-m interior dimension and 1-m thick walls for which p = 2600 kg/m3, c = 960 J/kg · K, and k = 1 W/m · K. The operating temperature of the furnace is 900°C, and the outer surface experiences convec- tion with ambient air at 25°C and a convection coef-
ro = 40 mm
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x   L = 30 mm
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L = 30 mm
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Cylinder AISI 304
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T(0, L, t)
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Oil Bath
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T(r, x, 0) = Ti = 600 K
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T(ro, 0, t)
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T(0, 0, t)
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TÂ¥ = 300 K
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h = 500 W/m2•K
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ficient of 20 W/m2 · K.
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(a)   Use a numerical procedure to estimate the time required for the inner surface of the furnace to cool to a safe working temperature of 35°C. Hint: Consider a two-dimensional cross section of the furnace, and perform your analysis on the smallest symmetrical section.
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(b)  Anxious to reduce the furnace downtime, the operations manager also wants to know what effect circulating ambient air through the furnace would have on the cool-down period. Assume equivalent convection conditions for the  inner and outer surfaces.
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