Secondary Step Modeling of Freeze Drying for Different Geometrical Shapes and Heat Boundary Conditions

In recent years, freeze drying has found many applications in various industries. In this study, a dynamic model is developed to describe bonded moisture removing in freeze drying by mass and energy balance. Primary and secondary drying are distinguished. Three different geometrical shapes (slab, cylinder, sphere) of wet solid take into consideration in this mathematical modeling. Each of them subjected to three different thermal boundary conditions: constant temperature, constant heat flux and convection heat flux. Based on secondary stage of drying analysis, the percentage of bonded moisture desorbed in primary drying stage has been calculated analytically for all status. Results of computation show that for all of thermal boundary conditions, the percentage of desorbed bonded moisture in spherical sample is higher than cylindrical and removed bonded moisture percent in cylindrical sample is higher than slab.