Yuejin Yuan

Fractal Pore Network Simulation on the Drying of Porous Media

Based on the knowledge of fractal geometry, physics of flow through porous media, and transport process principle, a fractal pore network model for the drying process of a natural porous body was established in this article. This model takes various factors into consideration, such as liquid-phase flow, vapor-phase diffusion, temperature gradient, and pore microstructure characteristic. The drying dynamics characteristics of potato slices were obtained by the simulation of a fractal pore network model. The simulation results of the fractal pore network model were contrasted with those of a regular one and the experimental data, respectively. The wet patches were observed on the potato slices during the drying experiments, and it was validated by the drying simulation. The results indicate that the drying kinetics from the fractal pore network model, as well as the distributions of moisture and temperature inside the porous body, are more consistent with that of the drying experiments than that of the regular one, and the throat size distribution in the pore network of the porous media has a notable influence on the drying process.

Multiscale and multilayer structural modeling and simulation on drying of grain packing porous media

ABSTRACT 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.

Optimization of Processing Parameters for Lettuce Vacuum Osmotic Dehydration Using Response Surface Methodology

Abstract In order to obtain the optimal technological parameters of lettuce vacuum osmotic dehydration, the effects of osmotic temperature, slice thickness, sucrose concentration, and vacuum degree on the vacuum osmotic dehydration were explored. The lettuce water loss rate and solid gain rate decreased with the increase of slice thickness and vacuum degree, and increased with the increase of sucrose concentration and osmotic temperature. Response surface methodology was applied to analyze the influence of the four influential factors on the evaluated parameters and the optimization of lettuce vacuum osmotic dehydration was studied. The results indicated that, within the experimental scope, the optimized technological parameters of lettuce vacuum osmotic dehydration are the temperature of 28°C, the slice thickness of 2 mm, sucrose concentration of 47%, the vacuum degree of 22 kPa, and the water loss rate and solid gain rate are 72.16% and 11.82%, respectively.

Heat–Mass Transfer Coupled with Stress–Strain Model and Simulation for Vacuum Shelling of Chestnuts

In order to investigate the vacuum shelling mechanisms of the chestnut, a mathematical model incorporating heat and mass transfer and stress–strain was developed for the process of vacuum shelling chestnuts by applying the heat and mass transfer theory, elasticity theory, and finite element method. The model was validated by comparing simulation and experimental results. The simulation results showed the transient temperature, moisture, and pressure gradient along the chestnut shell and the resulting thermal, moisture, and pressure difference stresses. It was found that shell cracking is more likely in the shell edge and the moisture stress played a dominant role in the vacuum shelling process. The effect of vacuum was also investigated in this article.