Chapter 4 Transient Heat Conduction4-55E The center temperature of oranges is to be lowered to 40°F during cooling. The cooling time and if any part of the oranges will freeze during this cooling process are to be determined. Assumptions1 The oranges are spherical in shape with a radius of r0=1.25 in = 0.1042 ft. 2 Heat conduction in the orange is one-dimensional in the radial direction because of the symmetry about the midpoint. 3 The thermal properties of the orange are constant. 4 The 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 thermal conductivity and thermal diffusivity of oranges are given to be k = 0.26 Btu/h⋅ft⋅°F and α= 1.4×10-6ft2/s. Analysis First we find the Biot number:BiBtu / h.ft . F)ft0.26 Btu / h.ft. C2==°°=hrk046125 121843(.(. /).
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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.