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Spin flash drying equipment is widely used in chemical, food and other fields. Drying process consumes large amounts of energy and reduction in operating cost will be extremely beneficial for the industry. Therefore, in order to improve the efficiency of spin flash dryer. A three-dimensional CFD model of the drying process was established by computational fluid dynamics, and the flow field characteristics and heat transfer mechanism of the drying process were obtained. We studied the specific effects of different parameters on the drying process, and verified the results with calcium carbonate as raw material. The experimental results are basically consistent with the simulation results. The velocity, temperature and pressure in the drying chamber near the wall are greater than those in the central region, which generally decrease with height. The speed of the cutter set has a large effect on the tangential and radial velocity, but the influence on the pressure drop is not significant. Meanwhile the temperature and velocity of inlet air have a greater impact on distribution of flow field and material drying, the variable structure improves the stability of the drying process. [ABSTRACT FROM AUTHOR]

Abstract Food materials with high moisture content were prone to occur drying shrinkage-deformation during dying process. In-depth understanding of drying shrinkage-deformation mechanism for food materials was crucial for optimizing drying parameters as well as for obtaining better quality dried foods. Therefore, the main aim of the present work was to investigate the drying shrinkage-deformation mechanism of apple slices during process of heat and mass transfer. Hot air drying experiment of freshed apple slices was conducted and the shrinkage-deformation values of apple slices were obtained by image analysis. Simultaneously, Heat-mass transfer coupled with stress-strain mathematical model were constructed and solved by COMSOL Multiphysics software. Results showed that the mathematical models of heat-mass transfer and stress-strain can be used to simulate the hot-air drying process of apple slices effectively, and the maximum relative errors of simulated value and experimental value were less than 10%. Temperature distribution and moisture distribution of apple slices during hot-air drying process were uniform. The maximum value of thermal stress and moisture stress were occurred at the middle period of the whole drying process; and the moisture stress during the whole drying process of apple slices were higher than thermal stress, which indicated that moisture stress was the main factor causing the drying shrinkage deformation of apple slices. Highlights • The heat-mass transfer and stress-strain mechanism are analyzed for creating the mathematical model. • The drying shrinkage-deformation of apple slices are obtained experimentally by image processing technology. • The heat-mass transfer and stress-strain mathematical model are numerically solved by COMSOL Multiphysics software. • Experimental and predicted values are in close agreement with each other. • Moisture stress is the main factor causing the drying shrinkage-deformation of apple slices. [ABSTRACT FROM AUTHOR]

Aiming at the problem of multilayer physical structure for the skeleton of porous media, a multiscale and multilayer structural model of heat and mass transfer processes for drying of grain packing porous media was established by applying the pore network method and multiscale theory. An experimental study on rice drying was conducted in order to validate this model. The simulation and experimental results indicated that the established model could explain the mechanical properties of rice drying well. The rate of heat transfer was faster than the rate of mass transfer and there was a higher moisture gradient inside the rice grain. The diffusion coefficient of rice embryo played an important role in the drying process, and whose effect on drying was larger than the diffusion coefficient of rice hull and chaff. The moisture was imprisoned effectively inside the rice when the diffusion coefficient of rice embryo was very small. [ABSTRACT FROM AUTHOR]