Microstructural Changes Along The Water Migration Path Of Broad Bean Seeds With Heat And Mass Transfer

During During the process of dehydration,tissue cells at different positions often experience different heterogeneous structural changes,such as cell shrinkage,rupture,and pore formation,along with the diffusion and evaporation of water.The change of the cellular heterostructure will affect the moisture and temperature distribution in the material and the quality of the material.Therefore,studying the variation law of the cellular heterostructure at different positions has important guiding significance for improving the quality of the material.The phenomenon of heterogeneous transport controls the overall transport mechanism.The transport model of the biological dehydration process needs to consider the cellular-level structural heterogeneity in the thermal-mass coupling process,and because the biological tissue has a certain volume,the heterogeneity of the different heterostructures at different locations is necessary.Moisture and temperature distribution are different.However,there are limited studies considering the heterogeneous horizontal transport phenomenon during dehydration.In this paper,using the technology of heterogeneity observation and image processing,the changes of cell morphology in different positions of broad bean samples during water migration were studied,and the size parameters(relative diameter,relative circumference,relative area,area of the cells at different positions at 0 ? and 8 ? were analyzed.)and shape parameters(roundness,elongation).On the basis of experiments,organically combined biological single independent cell research and tissue-level research to develop a model based on the heterogeneous heterogeneous structure of biological food to analyze and predict the changes of water content in cells at different positions and intercellular spaces during dehydration.Then,a homogeneous tissue model of heat and mass transfer during dehydration was established,and the data were processed to study the changes of water content in cells and intercellular spaces along the water migration path from the tissue center to the tissue edge,and compared with the results of the heterogeneous model.The water distribution predicted by the two models was compared with the results obtained by SEM scanning electron microscope.Influence of coefficient and cell wall diffusion coefficient on water migration.The main research conclusions are as follows:(1)During the dehydration process,the maximum value of the size parameters(relative diameter,relative perimeter,relative area,area)at different times at 0 ? was obtained at the position immediately below the center of the cut surface of the five equal sections of the sample.The maximum value is obtained at the center of the cut surface of the sample at 8 ?.The shape parameters are distributed in a range without significant regular changes.At 0?,the circularity of cells was generally distributed in the range of0.85?0.95,and the cell elongation rate was concentrated in the distribution of 1.2?1.8.At8?,the circularity of cells was generally distributed in the range of 0.80?0.90,and the cell elongation rate was concentrated in the distribution of 1.2?1.9.(2)During the dehydration process,the temperature difference between the model considering the cell structure and the model without considering the cell is small,but the change trend of the water content in the intercellular space of the model considering the cell structure is to increase first and then decrease,and the model without considering the cell structure.has been decreasing.The change trend of intracellular water content in the two models is the same,and the numerical value is significantly different.The change of the water content of cells in the center of the tissue without considering the model is larger than that in the model considering the cell structure,and the change in the water content of cells in the edge of the tissue is smaller than that in the model considering the cell.Models that take into account cellular structure more accurately predict moisture changes.(3)Dehydration temperature,cell wall diffusion coefficient and cell diffusion coefficient have different effects on water migration in cells and intercellular spaces.The three have no significant effect on the water change of the cells at the edge of the tissue,but in other cells of the tissue,the increase of the three values will accelerate the water migration;for the intercellular space,the higher the temperature,the greater the cell wall diffusion coefficient,and the intracellular space.The faster the moisture change The increase of the cell diffusion coefficient by the same value and the decrease of the same value have the same effect on the water migration in the intercellular space.