Chapter 4 Transient Heat Conduction4-23A number of carbon steel balls are to be annealed by heating them first and then allowing them to cool slowly in ambient air at a specified rate. The time of annealing and the total rate of heat transfer from the balls to the ambient air are to be determined. Assumptions1The balls are spherical in shape with a radius of r0= 4 mm. 2 The thermal properties of the balls are constant. 3The heat transfer coefficient is constant and uniform over the entire surface. 4 The Biot number is Bi < 0.1 so that the lumped system analysis is applicable (this assumption will be verified). PropertiesThe thermal conductivity, density, and specific heat of the balls are given to be k = 54 W/m.°C, ρ= 7833 kg/m3, and Cp= 0.465 kJ/kg.°C. AnalysisThe characteristic length of the balls and the Biot number are 1.00018.0)CW/m.54()m0013.0)(C.W/m75(m0013.06m008.066/223<=°°======
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This note was uploaded on 01/19/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.