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Showing 3 results for Simultaneous Heat and Mass Transfer

, ,
Volume 12, Issue 2 (6-2012)
Abstract

In the present study the phenomenon of drying a clay brick ceramic is analyzed. Strain–Stress equations coupled to heat and mass transfers during drying of deformable two-phase media has been modeled and both 2D and 3D arrangements have been studied. In order to compare the results, two samples with identical compositions are used for both configurations. The material is considered as a two-phase, homogeneous, isotropic, and highly shrinkable medium. The principal equations of the model, because of the shrinkage behavior are written in a Lagrangian formulation. The model is solved numerically by a finite difference method and Validation of results is achieved by comparing the numerical results with experimental data. The model being developed allows the derivation of the time and space moisture contents, strains, and stresses incurred as a result of drying. A significant difference was observed between the results obtained for the two different configurations particularly in intensity of the stress causing cracking
, ,
Volume 12, Issue 3 (8-2012)
Abstract

Drying process is influenced by a variety of parameters including the geometry of part being dried. To evaluate the effect of part geometry on drying process, and resultant defects, the process is analyzed and studied. Based on the assumption related to the porous media the governing equation of the mass transfer and static equilibrium are presented. The mechanical stresses generated by the drying strains are expressed according to the linear-elastic model. Dependence of physical and mechanical properties such as Young's modulus and diffusion coefficient as a function of moisture are considered in simulation for a chemically known ceramic material. it’s Assumed that Extended thin film evaporation is the mechanism of evaporation in constant rate period has been studied. The Von Misses criterion is used for crack anticipation in 2D and 3D drying. A significant difference was observed in possibility of crack initiation for the two different configurations. Yield stress in hygroscopic moisture has been determined experimentally. Developed model made it possible to predict the time and the place of crack initiation. Different part thicknesses were studied to examine the effect of thicknesses variations on cracking. It is observed that the danger of cracking is highest at the beginning of the drying, since the yield stress is low.
Mohsen Heydari, Khalili Khalili,
Volume 15, Issue 10 (1-2016)
Abstract

Drying of porous materials is a critical step in the production of many products such as ceramics, brick and tile. Quality of dried product is severity influenced by drying processes. The aim of the present work is modeling of convection drying of a ceramic by using diffusion model. Material properties changes such as Young's modulus and shrinkage factor to moisture content are considered in simulation. Both two and three dimensional configurations have been investigated. The model is solved numerically by a finite element method. A significant difference was observed between the results obtained for the two different configurations particularly in the intensity of the drying-induced stresses. Validation of results is achieved by comparing the numerical and experimental results. The effect of Young's modulus variation has been investigated. It was observed that drying-induced stresses are highly affected by Young's modulus variations. According to the results, none of the simulation methods, cannot be regarded as a safer method in crack prediction. The changes in Young's modulus, Has no effect on the location of maximum stress However, delays in the timing of it.

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