Thesis Summary: Study of a New Atmospheric Freeze Drying System Incorporating a Vortex Tube and Multimode Heat Input

摘要

Atmospheric freeze drying (AFD) in a vibro-fluidized bed dryer coupled with an adsorbent and multimode heat input is proposed for dehydration of food products. An experimental setup was designed and built to permit simultaneous application of convection, conduction and radiation heat input to the drying material above its freezing point to ensure sublimation using a vortex tube to produce low temperature dry air. Comparison with AFD using fixed bed, fluidized bed dryer, traditional vacuum freeze drying and heat pump drying were carried out to investigate the viability of this new system. A two-layer moving boundary model was developed to simulate the drying kinetics and temperature scenario of thin slab product. Fairly good agreement was found between the predicted values and the experimental data. Finally a three-dimensional (3D) CFD simulation for a vortex tube is carried out to capture the highly swirling compressible flow behavior and to gain basic understanding of temperature separation process. An experimental setup was built to validate the simulation results.