The Study On Mass Transfer Problem In Drying Process Of Cortex Resistance Material

In the different ways drying process of many kinds of plant material, there is a common problem of the cortical resistance dominant, which is the cortical tissue of material is usually the key factor in restricting heat and mass transfer process. The common features is that the mass transfer resistance of the epidermis is high, which limits large amounts of water in the internal organization of material come through. However, due to the lack of the physical parameters of cortex itself to mass transfer, previous studies tend to deal with the cortical and endoplasmic overall of material as a continuous homogeneous medium. There is a lack of the necessary research to them in the performance differences and the resulting of mass transfer process.This paper takes the combination of theoretical study and experimental study as technology roadmap. Based on the topical biological materials having cortical resistance dominant mass transfer characteristics. A partition diffusion model is developed between the cortex and the endoplasmic and a solution for this model is put forward. I make a deeper understand about mass-transfer mechanism happened inside the cortical tissue. And through making quantitative representations to the transfer performance of the cortex itself, it reveals that the cortical tissue is one of the most important mass transfer resistances in the drying process.In this paper, the topical biological materials having cortical resistance dominant mass transfer characteristics is divided into the endoplasmic area and cortical areas. And i make a partition diffusion model on the hypothesis that different diffusion coefficients and boundary conditions. Moreover, I use MATLAB calculation and simulation. From the simulation results, it can be seen that the water of cortical surface dry quickly when considering cortical impact, but the water in the endoplasmic dry slowly due to the obstruction of the cortical tissue proliferation. The smaller the diffusion rates of the cortex, that is to say, the stronger the resistance of the cortex, the more difficult water diffusion and penetration in the endoplasmic. Furthermore, the mass transfer mechanism and cortex resistance of a variety of biological material are studied, and the corresponding cortex resistance mass transfer model is developed. I take hot air drying experiment of the grapes which having cortical resistance dominant mass transfer characteristics, and obtain cortical resistance dominant mass transfer characteristics with dealing with experimental data.I obtain materials for the experiments using different approach, such as peeled grapes, grapes having the skins, grapes which was treated with alkaline solution. I assume the peeled grapes and grapes having the skin to be homogeneous, continuous medium and respectively obtain diffusion coefficient and equivalent diffusion coefficient. I calculate and fit the a partition diffusion model through putting the obtained endoplasmic diffusion coefficient and the equivalent diffusion coefficient of the completed grapes. So determined multiple between the endoplasmic and cortical diffusion coefficient. At last, the diffusion coefficient of grapes skin.The research of this subject is mass transfer mechanism and model of the topical biological materials having cortical resistance dominant mass transfer characteristics in the drying process. It provides theoretical support for hot-air drying process of grapes by studying the drying characteristics of seedless grapes. This topic serves Typical Plant Fruit Cortical Tissue During Drying Mechanism Of Mass Transfer. Moreover, professor Zhang Shiwei from Northeastern University is responsible for this project and it is supported by the National Natural Science Foundation of China (Grant No.51176027).