A Method for Determination of Porosity Change from Shrinkage Curves of Deformable Materials

Abstract

Among the numerous models developed to predict the shrinkage of materials during drying, the model developed by Katekawa and Silva [1] Katekawa , M.E. ; Silva , M.A. Study of porosity behavior in convective drying of bananas . In Proceedings of the 14th International Drying Symposium (IDS 2004) , Sao-Paulo , Brazil , August 22–25 , 2004 ; B , 1427 – 1434 . [Google Scholar] gives a general relationship between shrinkage and porosity with a limited number of parameters such as initial density of the wet product, true density of the solid phase, and true density of the liquid phase. A graphical interpretation of this model is proposed to visualize the changes of porosity by comparing the experimental shrinkage curve with an ideal one. Four examples are given to illustrate the applicability of the model using different materials (carrot, banana, xerogel, and sludge), two types of the solvent (water, isopropanol), and two drying technologies (convective drying, freeze drying). Porosity calculations were found to be very consistent and complementary with porosity measurements.