EFFECT of VOLUME CHANGE IN FOODS ON the TEMPERATURE and MOISTURE CONTENT PREDICTIONS of SIMULTANEOUS HEAT and MOISTURE TRANSFER MODELS

TLDR

Biot numbers for heat and mass transfer and the extent of overall shrinkage with moisture loss are key factors influencing temperature and moisture predictions in food drying. The study compares temperature and moisture predictions of two simultaneous heat and moisture transfer models, one assuming volume change and one not. The first model keeps thermophysical and transport parameters constant, whereas the second treats them as temperature‑ and moisture‑dependent functions and is solved with a variable‑grid finite‑difference method, with its predictions compared to experimental drying data that includes shrinkage. The comparison revealed significant differences in predicted moisture and temperature gradients, as well as average moisture contents and temperatures, between models with and without the shrinkage assumption.

Abstract

ABSTRACT Temperature and moisture content predictions of two models of simultaneous heat and moisture transfer (SHMT) in foods with and without the assumption of volume change were compared. In the first model, thermophysical and transport parameters were kept constant. In the second model, these were taken as variable functions of temperature and moisture content. Comparison of the results of both models with and without shrinkage assumption showed that there can be significant differences in predicted moisture and temperature gradients, and average moisture contents and temperatures. Biot numbers for heat and mass transfer, and the extent of overall shrinkage with moisture loss are important factors affecting these differences. the predictions of the second model were compared to experimental drying data with shrinkage. the variable‐grid finite difference method can be used successfully to solve model equations involving volume changes.