On the estimation of thermophysical properties in nonlinear heat-conduction problems

The influence of thermophysical property variations on the resulting temperature fields is investigated with reference to quasilinear heat-conduction problems. Both theoretical and experimental evidence is produced to show that errors in the calculation of temperature distributions, brought about by an inaccurate estimate of thermal properties, are small if approximate heat capacities, even exhibiting large local differences with respect to the actual ones in a small range of temperatures, retain enthalpy variations and if the integral across the whole working temperature interval of the absolute value of the difference between approximate and actual thermal conductivities is small. Then the practical relevance of these results is pointed out with reference to freezing and thawing processes of biological materials whose thermal coefficients vary sharply over the phase change zone, where only mean values of thermophysical properties can be easily measured.