Modelling the moisture and temperature distribution within an agricultural product undergoing time-varying drying schemes

摘要

A mechanistic model capable of predicting the moisture and temperature distribution of food materials during isothermal and non-isothermal drying was developed. The model incorporates both liquid and vapour migration as well as heat transfer in a food material. The model was solved numerically by the method of finite volume. Evaluation of the modelling predictions shows good agreement, for the mean moisture content, between model and experimental data up to 7.4%. The calibrated model was used to study the effect of stepwise varying of the drying air temperature on the internal product moisture and temperature distributions. The product temperature distribution shows the existence of a thermal switch that changes the direction of the thermal gradient for drying conducted with step-down varying of the inlet air temperature from 35 to 20℃. The impact of the moisture and temperature distributions on the product quality is also discussed.