The temperature dependence of different thermo-physical properties of Golden Delicious and Granny Smith apples were studied. Regression relationships for apparent specific heat, thermal conductivity and thermal diffusivity, density changes in the unfrozen and frozen states for the two varieties of apples and the surface heat transfer coefficients associated with freezing under different conditions were discussed. The mean values of the different properties for Golden Delicious apples were (values in the parentheses are for Granny Smith apples): thermal conductivity 0.427 and 1.45 W/m2C° (0.398 and 1.22 W/n2C°); apparent specific heat, 3.69 and 1.95 kJ/kgC° (3.58 and 1.68 kJ/kgC°); and density, 845 and 788 kg/m3 (829 and 786 kg/m3), respectively, in the unfrozen and frozen states. The surface heat transfer coefficients, as determined by using Plank's equation, ranged from 12.7 W/m2C° for freezing in air to 68.4 W/m2C° for freezing in liquid nitrogen.
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