Experimental and numerical modeling of heat conduction during freezing of foods with steep variations in properties

Fernando Zigunov¹; Flavia Zinani¹

¹ Universidade do Vale do Rio dos Sinos - UNISINOS

doi:10.20906/CPS/COB-2015-0360

Resumo

This paper aims to evaluate the physical and numerical modeling of the freezing process of foods, whose thermophysical properties experience sudden variations during phase change. The finite differences method has been used to approximate the solution of the one-dimensional transient heat conduction problem in simple geometries (flat plate, infinite cylinder and sphere) with variable thermophysical properties and subjected to heat convection. The physical properties were modeled as dependent on food composition, temperature and phase. A pilot-scale freezing tunnel was developed to provide experimental data to validate the mathematical and numerical modeling. Several foods, shapes and convection coefficients have been tested, such as sausages, potatoes and cheese. Among thermophysical properties, the apparent specific heat experienced the greatest variations during freezing. The experiments showed that mass transfer (moisture evaporation) plays an important role on food freezing, and therefore a heat transfer numerical model is not enough to predict experimental results. As a solution, mass transfer was included in the numerical model so that it was able to predict experimental results with enough accuracy, and therefore it might be considered adequate to extrapolate this method to be used on more complex problems.

Palavras-chave: food freezing; transient heat conduction; finite differences; models for food thermal properties