Thermodynamics HW Solutions 318

# Thermodynamics HW Solutions 318 - Chapter 4 Transient Heat...

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Chapter 4 Transient Heat Conduction 4-43 A rib is roasted in an oven. The heat transfer coefficient at the surface of the rib, the temperature of the outer surface of the rib and the amount of heat transfer when it is rare done are to be determined. The time it will take to roast this rib to medium level is also to be determined. Assumptions 1 The rib is a homogeneous spherical object. 2 Heat conduction in the rib is one-dimensional because of symmetry about the midpoint. 3 The thermal properties of the rib 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 the rib are given to be k = 0.45 W/m. ° C, ρ = 1200 kg/m 3 , C p = 4.1 kJ/kg. ° C, and α = 0.91 × 10 -7 m 2 /s. Analysis ( a ) The radius of the roast is determined to be Oven 163 ° C Rib, 4.5 ° C m 08603 . 0
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