Modeling deep-bed grain drying using Comsol Multiphysics

CFD simulations were carried out to predict the convective heat and mass transfer coefficients in the rice bed, and correlations were developed for the convective heat and mass transfer coefficients as a function of drying air flow rate. The developed correlations were used to extend the coupled CFD and diffusion model developed by ElGamal et al. (2013) for thinlayer rice drying to volumetric heat and mass transfer in a deep-bed of rice. All mathematical models were solved using the Comsol Multiphysics® simulation program v4.3 (Comsol Inc, Palo Alto), which uses the finite element method to solve the model equations. The model was used to predict the air temperature, as well as the grain moisture content and temperature at different locations of the dryer during the drying process. The theoretical predictions of moisture and temperature profiles inside a deep-bed of rice were verified by experimental data from literature

Multi-scale model for heat and mass transfer during rice drying

Grain drying is a simultaneous heat and moisture transfer problem. The modeling of such a problem is of significance in understanding and controlling the drying process. The main goal of this study was to predict the heat and mass transfer processes during deep-bed rice drying. To achieve this, first, CFD simulations were carried out to analyze the external flow and temperature fields at steady-state for a control volume of a stationary rice bed. The model was used to predict the convective heat and mass transfer coefficients in the rice bed, and correlations were developed for the convective heat and mass transfer coefficients as a function of drying air flow rate. Then, the coupled CFD and diffusion model developed by ElGamal, Ronsse, Radwan & Pieters (2013) to investigate the heat and mass transfer for thin-layer drying of rice was extended to volumetric heat and mass transfer in a deep-bed of rice using the predicted heat and mass transfer coefficients. All models were solved numerically using the finite element method. The model was used to predict the air temperature, as well as the grain moisture content and temperature at different locations of the dryer during the drying process. The theoretical predictions of moisture and temperature profiles inside a deep-bed of rice were verified by experimental data from literature. The average mean relative deviation values for the prediction of grain moisture content varied between 1.00 to 3.13%

Mixed Convective Heat Transfer Flow of a Nanofluid through a Porous Meduim in a Rectangular Cavity

We consider Convective heat and mass transfer flow of a nanofluid through a porous medium in rectangular duct. The governing equations have been solved by using Galerkin finite element analysis with linear interpolation functions The effects of nanoparticle volume fraction on all the flow characteristics have been discussed. Keywords: Nanofluid, Rectangular Duct, Galerkin Method,Porous medium

Non-Darcy Convective Heat and Mass Transfer Flow in a Vertical Channel

We make an attempt to investigate non-Darcy convective heat and Mass transfer flow of a viscous chemically reacting fluid in a vertical channel .The Brinkman Forchheimer extended Darcy equations are used in the governing linear momentum equation, which are solve numerically by using  Galerkin finite element technique. The velocity, temperature, concentration, shear stress and rate of Heat and Mass transfer are evaluated numerically for different variations .It is noticed that the temperature and concentration reduce while the velocity increases in the degenerating chemical reaction ( g>0) while in the generating case(g<0), they reduce in the entire flow region The rate of heat and mass transfer reduce and the skin friction increases on the walls with increase in g>0, while a reversed effect is noticed with  g<0. Keywords: Non-Darcy Flow, Porous Medium, Chemical reaction, Vertical Channe

Устойчивость процесса зажигания полимерного материала горячей частицей

As a result of the numerical investigation of a typical polymeric material ignition by a local energy source with limited heat content it has been determined three modes: gasification without ignition followed by pyrolysis stop, stable ignition, and unstable ignition. The mathematical model of the process takes in account conductive heat transfer and thermal decomposition in condensed phase, diffusion-convective heat and mass transfer and gaseous pyrolysis products oxidation of polymeric material in air

Устойчивость процесса зажигания полимерного материала горячей частицей

As a result of the numerical investigation of a typical polymeric material ignition by a local energy source with limited heat content it has been determined three modes: gasification without ignition followed by pyrolysis stop, stable ignition, and unstable ignition. The mathematical model of the process takes in account conductive heat transfer and thermal decomposition in condensed phase, diffusion-convective heat and mass transfer and gaseous pyrolysis products oxidation of polymeric material in air

Quassiclassical approximation of solutions of boundary convective-type problems of heat and mass transfer

In this paper we suggest the approximate method of solving the internal convective heat and mass transfer problems based on the combined use of the Laplace transform and quasiclassical approximatio

Slip Effects on Unsteady Free Convective Heat and Mass Transfer Flow with Newtonian Heating

This article investigates the effects of slip condition on free convection flow of viscous incompressible fluid past an oscillating vertical plate with Newtonian heating and constant mass diffusion. The governing equations together with imposed initial and boundary conditions are solved using the Laplace transform technique. The results for velocity, temperature and concentration are obtained and plotted for the embedded parameters. The results for skin friction, Nusselt number and Sherwood number are computed in table. It is investigated that the presence of slip parameter reduces the fluid velocity

Effect of Hall Current, Thermal Radiation, Dissipation and Chemical Reaction on Hydromagnetic Non-Darcy Mixed Convective Heat and Mass Transfer Flow Past a Stretching Sheet in the Presence of Heat Sources

We study the combined influence of Hall current, radiation  and dissipation on convective heat and mass transfer flow of a viscous electrically conducting g fluid past a stretching sheet. The equations governing the flow , heat and mass transfer have been solved by Galerkin finite element analysis with three nodded line segments. The velocity, temperature and concentration have been analysed for different values of m, N, F, g, Ec  and Q. The rate of heat and mass transfer on the plate has been evaluated numerically for different variations