Shrinkage, porosity and density behaviour during convective drying of bio-porous material

摘要

Drying is a main process of conservation used for agricultural products and it is so essential to control its drying parameters.Bio-material will shrink during the drying process.In this study, the characteristics of drying were investigated through slices shrinkage behaviour at 40, 50 and 60 °C. Results showed that shinkage was anisotropic and best fitted by the linear model of volume. The apparent density was strongly effected by volume shrinkage , its value decreased from 1035 kg/m~3 at the initial stage of the drying to about 885 kg/m~3 at the end of the drying process.The porosity has a large value approaching 80% and most of the evaporated water during drying was replaced by gas . Drying rates were underestimated and diffusivities overesimated when drying data are not corrected for shrinkage.