A novel atmospheric freeze-dryer using vortex tube and multimode heat input: simulation and experiments

摘要

This article presents a study of a novel fixed-bed atmospheric freeze-dryer using a vortex tube to generate cryogenic temperature air for drying and multimode heat supply. A two-layer moving boundary model was developed to simulate the variation of the transient moisture content distribution in the drying product in the form of a thin slab, sublimation front temperature, location of the sublimation front and moisture content as well as temperature distribution inside the dry layer. An experimental setup was designed and fabricated to verify the predicted results. A series of experiments were conducted using rectangular and disc-shaped potato and carrot samples, as model heat-sensitive products. Effects of different modes of heat input in various combinations on the drying rate were also investigated both experimentally and numerically. Fairly good agreement was found between the predicted values and the experimental data.