4-73 Chickens are to be chilled by holding them in agitated brine for 2.75 h. The center and surface temperatures of the
chickens are to be determined, and if any part of the chickens will freeze during this cooling process is to be assessed.
Assumptions 1 The chickens are spherical in shape. 2 Heat conduction in the chickens is one-dimensional in the radial
direction because of symmetry about the midpoint. 3 The thermal properties of the chickens are constant. 4 The heat transfer
coefficient is constant and uniform over the entire surface. 5 The Fourier number is > 0.2 so that the one-term approximate
solutions are applicable (this assumption will be verified). 6 The phase change effects are not considered, and thus the actual
the temperatures will be much higher than the values determined since a considerable part of the cooling process will occur
during phase change (freezing of chicken).
Properties The thermal conductivity, thermal diffusivity, and density of chickens are given to be k = 0.45 W/mC, =
0.1310-6 m2/s, and = 950 kg/ m3. These properties will be used for both fresh and frozen chicken.
Analysis We first find the volume and equivalent radius of the chickens: