Thermodynamics HW Solutions 389

Thermodynamics HW Solutions 389 - Chapter 4 Transient Heat...

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Chapter 4 Transient Heat Conduction 4-120 Large food slabs are cooled in a refrigeration room. Center temperatures are to be determined for different foods. Assumptions 1 Heat conduction in the slabs is one-dimensional since the slab is large relative to its thickness and there is thermal symmetry about the center plane. 3 The thermal properties of the slabs 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). Properties The properties of foods are given to be k = 0.233 W/m. ° C and α = 0.11 × 10 -6 m 2 /s for margarine, k = 0.082 W/m. ° C and α = 0.10 × 10 -6 m 2 /s for white cake, and k = 0.106 W/m. ° C and α = 0.12 × 10 -6 m 2 /s for chocolate cake. Analysis ( a ) In the case of margarine, the Biot number is Air T = 0 ° C Margarine, T i = 30 ° C 365 . 5 ) C W/m. 233 . 0 ( ) m
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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.

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