Influence of Thermal Properties Accuracy on Transient Conduction Models

The influence of thermal properties accuracy on the heat transfer mathematical models in transient state for food was studied in this work. To pursue this objective, a model in transient state with temperature variable thermal properties was solved using the method of finite differences and the alternate implicit direction scheme to a food inside a cylindrical container under a sudden heating and cooling process, similar to a method of sterilization and/or pasteurization. The model takes into account a linear dependence of the properties with the temperature. An analysis of the behavior of the main thermal properties of the food based on temperature is presented in this article. The results showed that the prediction of the transient state model is more sensitive to perturbations in the values of volumetric heat capacity than thermal conductivity and diffusivity; however, the volumetric heat capacity varies considerably less with temperature. Models with constant properties yield minor deviations when they are evaluated at typical temperature of the cooling or heating processes. The use of the constant thermal diffusivity model with diffusivity is suggested to be evaluated at temperatures between the average and the final heating or cooling process to ensure deviations less than 5%, between the exact model and the simplified one. This solution is considerably simpler than the one obtained with the variable properties model.