Thermodynamics HW Solutions 325

Thermodynamics HW Solutions 325 - Properties The properties...

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Chapter 4 Transient Heat Conduction 4-49E Whole chickens are to be cooled in the racks of a large refrigerator. Heat transfer coefficient that will enable to meet temperature constraints of the chickens while keeping the refrigeration time to a minimum is to be determined. Assumptions 1 The chicken is a homogeneous spherical object. 2 Heat conduction in the chicken is one- dimensional because of symmetry about the midpoint. 3 The thermal properties of the chicken 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).
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Unformatted text preview: Properties The properties of the chicken are given to be k = 0.26 Btu/h.ft. ° F, ρ = 74.9 lbm/ft 3 , C p = 0.98 Btu/lbm. ° F, and α = 0.0035 ft 2 /h. Analysis The radius of the chicken is determined to be Refrigerator T ∞ = 5 ° F Chicken T i = 72 ° F ft 2517 . 4 ) ft 06676 . ( 3 4 3 3 4 ft 06676 . lbm/ft 9 . 74 lbm 5 3 3 3 3 3 3 = = = ⎯→ ⎯ = = = = ⎯→ ⎯ = π ρ V r r V m V V m o o From Fig. 4-15b we have 75 . 1 1 1 75 . 5 45 5 35 = = ⎪ ⎪ ⎭ ⎪ ⎪ ⎬ ⎫ = = = − − = − − ∞ ∞ o o o o o hr k Bi r r r x T T T T Then the heat transfer coefficients becomes F . Btu/h.ft 0.590 2 ° = ° = = ft) 2517 . ( 75 . 1 ) F Btu/h.ft. 26 . ( 75 . 1 o r k h 4-36...
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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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