Modeling and simulation of parametric sensitivity in primary freeze-drying of foodstuffs

A mathematical model depicting the influence of operating parameters on unsteady drying rate in primary freeze-drying operation for two food stuffs viz. paneer and mango has been presented. The dynamic model based on a semi-deterministic approach involving two major operating parameters, viz., radiator temperature and chamber pressure, has been validated over a chamber pressure ranging from 0.05 to 0.001 mbar and for a radiant heat source temperature ranging from 293 to 323 K keeping the physical shape of the material unaltered. The model equations proposed are free from simulation constants like the effective diffusivity and the Knudsen diffusivity which are difficult to evaluate. The surface temperature profile of the material during the course of primary freeze-drying has also been presented by applying the model equation for drying rate in the unsteady state one-dimensional energy balance equation. Experimental results fit appreciably well with the simulated data. It is expected that the model equations can be used for estimation of unsteady drying rate vis-à-vis dried layer temperature–time history for similar foodstuffs if physical properties viz. specific gravity, porosity, thermal conductivity, specific heat are known.