Chapter 4 Transient Heat Conduction4-45An egg is dropped into boiling water. The cooking time of the egg is to be determined. Assumptions1The egg is spherical in shape with a radius of r0= 2.75 cm. 2 Heat conduction in the egg is one-dimensional because of symmetry about the midpoint. 3The thermal properties of the egg 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 thermal conductivity and diffusivity of the eggs can be approximated by those of water at room temperature to be k = 0.607 W/m.°C, α =kCp/ρ= 0.146×10-6m2/s (Table A-9). AnalysisThe Biot number is Water100°CEgg Ti= 8°C 2.36)CW/m.607.0()m0275
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