Papers by Keyword: Coefficient of Diffusion

Paper TitlePage

Authors: Joh Yeong Yoo, Han Seung Lee, Sung Ho Tae, Moon Byung Chul
Abstract: As concrete is a type of porous materials, water or air freely permeates concrete. Therefore the durability of concrete decreases. However, porous material with a rust inhibitor may allow permeation of water into concrete. In addition, there may be permeation of water through the rust inhibitor at the location of steel frames. The objective of the study is to investigate the penetration depth of concrete under water forced conditions with pressure.
Authors: Ramón Moreira, Francisco Chenlo, L. Chaguri, Christiana Fernandes
Abstract: Many food materials must be dried in order to decrease its water activity and to increase the shelf-life. Also, rehydration operation must be carried out as previous step before consumption. Both operations are commonly employed in some industrial chestnut processing. These processes can be carried out at different temperatures and in all cases the quality of the final product can be affected. In this work, convective drying with hot air is the employed method for water removal and rehydration is carried out by immersion of chestnut in water. In both cases, mass transfer processes are governed by water diffusion in the bulk of the solid. The aim of this work is to determine experimentally the drying and rehydration kinetics of chestnut samples at different conditions of temperature and moisture content. Obtained data are modeled with a diffusional model taking into account volume variations and the corresponding values of the coefficients of diffusion of water are obtained. Analysis of the results indicates that drying/rehydration rates increase with temperature and rehydration kinetics are also depending on the initial moisture content of chestnut. Finally, leaching flow during rehydration is only important at high temperature due to starch gelatinization processes.
Authors: Ramón Moreira, Francisco Chenlo, N. Vallejo, Lionel Gerbet
Abstract: Osmotic dehydration of eggplant slices in sucrose and sodium chloride solutions at different solution concentrations, stirring levels and time of process is studied. Water loss and solids gain kinetics were experimentally determined and modelled using a diffusional model and equilibrium values were predicted by means of Azuara model. Modelling was satisfactory and involved effective coefficients of diffusion useful to quantify the different mass transfer fluxes.
Authors: Luis Mayor, Ramón Moreira, Francisco Chenlo, Alberto M. Sereno
Abstract: Osmotic dehydration experiments of pumpkin with binary aqueous solutions of sucrose, sodium chloride and ternary solutions with both solutes at 298 K were carried out. Weight reduction, water loss and solute acquisition kinetics were determined. Experimental data were fitted employing a diffusional model considering samples as spheres and the external resistance to the mass transfer negligible. The model gave as parameter of fitting an effective diffusion coefficient for each component transferred (water, sucrose and sodium chloride) for each experimental condition assayed. Correlations between the effective diffusivity and solute concentration were established for binary and ternary systems.
Authors: Fei Hou, Yu Bai, Jun Dong
Abstract: Chloride ion etching is a significant reason for the damage of the reinforced concrete structures. Diffusion effect is considered to be the main form of which the chloride ion invades into the reinforced concrete structures. Assuming infinite diffusion medium, based on the Chlorine ion diffusion equation, and accounting for the effects of temperature and moisture, models of chloride diffusion in two-dimensional infinite body with consistent coefficient of diffusion and different coefficient of diffusion in both directions are formulated .Two-dimensional chloride ion diffusion behavior was simulated, which proved the diffusion coefficient has a larger effect on the diffusion behavior of the chloride ion. Through these comparisons, we can analysis that model with different coefficient of diffusion in both directions is more suitable for the actual conditions.
Showing 1 to 5 of 5 Paper Titles