Transient heat conduction in citrus fruits is of concern to farmers in Florida and other farmers as well. They must develop strategies to prevent freezing during cold weather.
The thermal diffusivity data are needed for this, and one way to find this information is to insert a thermocouple in the center and dip the fruit in a stirred tank of iced water at \(0{ }^{\circ} \mathrm{C}\). From the following data for a \(5.8-\mathrm{cm}\)-diameter grapefruit estimate the thermal diffusivity and compare it with that of water at \(10^{\circ} \mathrm{C}\). 

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t, min 0 5 10 15 20 25 30 35 40 45 Tc, C 20 20 19.6 18.0 15.8 13.0 10.8 8.4 7.2 5.8