Improvement of a mathematical model for freeze dryer

Freeze drying is an effective method for drying of heat sensitive materials. In this paper an extended model was developed for both phases of this process. The heat required for drying was assumed to be supplied by conduction from under the sample, because the frozen layer conductivity is greater than the conductivity of dried layer. In addition to drying process, the process of vapor freezing in condenser was also included in the model. The latter makes it possible to investigate the influence of the condenser specifications on freeze dryer performance. Further, an experimental equation was developed for using in second stage model. The developed model could successfully simulate drying data of a suspension of 20% milk solids taken in a lab scale freeze dryer.