Chapter 4 Transient Heat Conduction4-53 A hot baked potato is taken out of the oven and wrapped so that no heat is lost from it. The time the potato is baked in the oven and the final equilibrium temperature of the potato after it is wrapped are to be determined. Assumptions1The potato is spherical in shape with a diameter of 8 cm. 2 Heat conduction in the potato is one-dimensional because of symmetry about the midpoint. 3The thermal properties of the potato are constant. 4The heat transfer coefficient is constant and uniform over the entire surface. 5 The Fourier number is τ> 0.2 so that the one-term approximate solutions (or the transient temperature charts) are applicable (this assumption will be verified). PropertiesThe properties of the potato are given to be k = 0.6 W/m.°C, ρ= 1100 kg/m3, Cp= 3.9 kJ/kg.°C, and α= 1.4×10-7m2/s. Oven T∞= 170°CPotato T0= 70°C Analysis (a) The Biot number is Bihrko==°°=()(.)(.).250 0406167W/m . CmW/m. C2The constants λ1and A1corresponding to this Biot number are, from Table 4-1, 111877714113..and AThen the Fourier number and the time period become
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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.