Thermodynamic Theory of Convective Drying Process of Porous Media

2002 ◽  
Author(s):  
You-Rong Li ◽  
Dan-Ling Zeng
Keyword(s):  
Mass Transfer ◽  
Heat Source ◽  
Heat And Mass Transfer ◽  
Internal Heat ◽  
Internal Heat Source ◽  
Thermodynamic Theory ◽  
Convective Drying ◽  
Internal Mass ◽  
Drying Process ◽  
Mass Source

Based on non-equilibrium thermodynamic theory and combined with the conservation laws, a comprehensive theoretical model was established to describe heat and mass transfer during convective drying process, and numerical calculation was performed. The results show that: (a) the external convective heat and mass transfer may be treated as the conductive heat transfer with internal heat source and the molecular mass diffusion with internal mass source, respectively, and the ability of heat and mass transfer mainly depends on the strength of the heat source and mass source; the higher the temperature of the drying media, the lower the strength of the internal heat source, but the higher that of the internal mass sources; (b) the evaporation of internal water takes place inside the whole material, and the molecular mass diffusion of the internal vapor is in the direction of decreasing mass transfer potential, not along the decreasing partial pressure of vapor.

Heat and Mass Transfer in Magneto-Newtonian Fluid Past a Paraboloid of Revolution with Internal Heat Source

2020 ◽  
Vol 25 (2) ◽  
pp. 254-261
Author(s):  
Naveed Ahmed ◽  
Ad nan ◽  
Umar Khan ◽  
Syed Tauseef Mohyud-Din ◽  
Ilyas Khan ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat Source ◽  
Heat And Mass Transfer ◽  
Newtonian Fluid ◽  
Internal Heat ◽  
Internal Heat Source ◽  
Paraboloid Of Revolution

scholarly journals 3D simulation on convective drying process for cylindrical tea particle using CFD software to analyze the heat and mass transfer phenomena

2020 ◽  
Author(s):  
Eflita Yohana ◽  
Nazaruddin Sinaga ◽  
Haryo Pachusadewo ◽  
M. Irfan Nugraha ◽  
M. Endy Yulianto ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
3D Simulation ◽  
Convective Drying ◽  
Drying Process

scholarly journals RESEARCH OF HEAT AND MASS TRANSFER DURING CONVECTIVE DRYING OF COLLOID CAPILLARY-POROUS MATERIALS

2020 ◽  
Author(s):  
Kateryna Slobodianiuk ◽  
◽  
Kateryna Samoilenko ◽  
Keyword(s):  
Mass Transfer ◽  
Porous Materials ◽  
Heat And Mass Transfer ◽  
Raw Materials ◽  
Biochemical Properties ◽  
The Body ◽  
Biologically Active ◽  
Convective Drying ◽  
Drying Process ◽  
Vegetable Raw Materials

The article presents a reasonable analysis and relevance of the study of the drying process of vegetable raw materials (colloidal capillary-porous materials). Drying is an energy-intensive industrial process that is defined from a technological point of view: on the one hand by heat and moisture exchange between the body surface and the environment, on the other hand by heating the body and transferring moisture inside it due to the form of moisture. One of the most effective ways to increase the shelf life of food is to dry it to equilibrium humidity. Very important are the technological parameters of the drying regimes, which, when used rationally, are able to preserve the biochemical properties and nutrients of the raw material at a high level in the obtained dry product. The study of dehydration of vegetable raw materials is widely practiced around the world, especially in countries such as Germany, France, USA, Argentina, Hungary, Brazil, Poland, Korea, China, Malaysia. However, the obtained processed products lose their biologically active components and nutrients, and the processing process is energy consuming. Therefore, the problem is relevant and needs an effective solution. In this paper, the kinetics of the drying process, thermogravimetric studies and a mathematical model for colloidal capillary-porous materials of plant origin were analyzed. According to the results of the highlighted research, the process of convective drying of colloidal capillary-porous materials was intensified above 21% due to the use of innovative step regimes. The developed beet-rhubarb composition is a colloidal capillary-porous material that stabilizes and protects at the biochemical level betanin of the beet from the effects of temperature during convective drying, has in comparison with the components of the composition lower heat of dehydration and increased thermal-stability. Prolonged high-temperature exposure causes instant complete destruction of sugars, proteins and other nutrients components. Derivatographic studies have confirmed that the use of the temperature range of 100 ° C in a stepwise mode of 100/60 ° C for the developed soybean-spinach composition is safe for biologically active substances and it is justified by experimental temperature curves. Numerical modeling of heat and mass transfer during convective drying of crushed beets and crushed soybeans using the known model by A.V. Lykov satisfactorily describes the process and can be used to model the convection drying of colloidal capillary-porous materials.

scholarly journals Heat and mass transfer in the grain under variable conditions

2021 ◽  
pp. 84-87
Author(s):  
Mikhail Gennadievich Zagoruiko ◽  
Roman Aleksandrovich Marin
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Water Vapor ◽  
Heat And Mass Transfer ◽  
Internal Heat ◽  
Initial Moment ◽  
Dense Layer ◽  
Drying Process ◽  
Grain Moisture ◽  
Grain Surface

The article describes the drying process in the formulation of the internal problem, the main equations of internal heat and mass transfer of potentials are considered. The process of removing moisture from the surface of the grain, which is determined by the transfer of moisture and the diffusion-convective transfer of heat and moisture through the boundary layer, is studied. The movement of heat in the boundary layer was determined by the molecular thermal conductivity. It is established that the speed of the drying process depends on the rate of removal of water vapor from the surface of the grain. It was found that the change in the quality of the seed material did not depend on the absolute removal of moisture. The first drying period is shown, when the temperature of the grain surface rises from the temperature of the adiabatic air saturation, when the drying agent at the boundary of the grain surface is saturated with water vapor, and the drying speed depends on the speed of their removal from the evaporation surface. At this point, the moisture evaporated, the vapors were removed by the drying agent. At the initial moment, the movement of the evaporation line did not occur, but then it was fixed inside the grain. In the course of research, the process of removing moisture from the seeds is fast, but it has little effect on their quality. The removal of grain moisture reached up to 3 % from the upper layers of the seeds, which did not affect their quality. An analytical expression is considered for calculating the heat transfer coefficient and the drying agent velocity, taking into account the allowed moisture content, as well as the heat flux density. The permissible speed of the drying agent in a dense layer of grain is determined, which depends on the height of the layer, the specific surface of the grain, its temperature and the proportion of heat supplied to heat the material. For drying conditions typical for grain dryers, the drying speed should not exceed 0.6 m/s.

scholarly journals Cross Diffusion Effect on Linear and Nonlinear Double Diffusive Convection in a Viscoelastic Fluid Saturated Porous Layer with Internal Heat Source

Fluids ◽  
2021 ◽  
Vol 6 (5) ◽  
pp. 182
Author(s):  
A. A. Altawallbeh
Keyword(s):  
Mass Transfer ◽  
Heat Source ◽  
Viscoelastic Fluid ◽  
Internal Heat ◽  
Internal Heat Source ◽  
Cross Diffusion ◽  
Diffusive Convection ◽  
Saturated Porous Layer ◽  
Heat Parameter ◽  
Linear And Nonlinear

Double diffusive convection in a binary viscoelastic fluid saturated porous layer in the presence of a cross diffusion effect and an internal heat source is studied analytically using linear and nonlinear stability analysis. The linear stability theory is based on the normal mode technique, while the nonlinear theory is based on a minimal representation of truncated double Fourier series. The modified Darcy law for the viscoelastic fluid of the Oldroyd type is considered to model the momentum equation. The onset criterion for stationary and oscillatory convection and steady heat and mass transfer have been obtained analytically using linear and nonlinear theory, respectively. The combined effect of an internal heat source and cross diffusion is investigated. The effects of Dufour, Soret, internal heat, relaxation and retardation time, Lewis number and concentration Rayleigh number on stationary, oscillatory, and heat and mass transport are depicted graphically. Heat and mass transfer are presented graphically in terms of Nusselt and Sherwood numbers, respectively. It is reported that the stationary and oscillatory convection are significantly influenced with variation of Soret and Defour parameters. An increment of the internal heat parameter has a destabilizing effect as well as enhancing the heat transfer process. On the other hand, an increment of internal heat parameter has a variable effect on mass transfer. It is found that there is a critical value for the thermal Rayleigh number, below which increasing internal heat decreases the Sherwood number, while above it increasing the internal heat increases the Sherwood number.

scholarly journals MHD Heat and Mass Transfer of Chemical Reaction Fluid Flow over a Moving Vertical Plate in Presence of Heat Source with Convective Surface Boundary Condition

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
B. R. Rout ◽  
S. K. Parida ◽  
S. Panda
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Boundary Condition ◽  
Heat Source ◽  
Heat And Mass Transfer ◽  
Chemical Reaction ◽  
Internal Heat ◽  
Integration Scheme ◽  
Physical Parameters ◽  
Surface Boundary

This paper aims to investigate the influence of chemical reaction and the combined effects of internal heat generation and a convective boundary condition on the laminar boundary layer MHD heat and mass transfer flow over a moving vertical flat plate. The lower surface of the plate is in contact with a hot fluid while the stream of cold fluid flows over the upper surface with heat source and chemical reaction. The basic equations governing the flow, heat transfer, and concentration are reduced to a set of ordinary differential equations by using appropriate transformation for variables and solved numerically by Runge-Kutta fourth-order integration scheme in association with shooting method. The effects of physical parameters on the velocity, temperature, and concentration profiles are illustrated graphically. A table recording the values of skin friction, heat transfer, and mass transfer at the plate is also presented. The discussion focuses on the physical interpretation of the results as well as their comparison with previous studies which shows good agreement as a special case of the problem.

scholarly journals System modelling of non-stationary drying processes

2019 ◽  
pp. 93-106
Author(s):  
Sergey Antipov ◽  
Andrey Klyuchnikov ◽  
Viktor Panfilov
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Fluidized Bed ◽  
Practical Importance ◽  
Convective Drying ◽  
System Modelling ◽  
Drying Process ◽  
Technological Parameters ◽  
Batch Mode ◽  
Integrated Research

The kinetics of the drying process in continuous drum dryers differs from the drying of single objects in a batch mode. Drying process is affected by too many factors; hence, it is practically impossible to obtain an analyt- ical solution from the initial equations of heat and mass transfer, since the duration of drying depends on the opera- ting parameters. Therefore, it is of high theoretical and practical importance to create a highly efficient rotary drum dryer. Its design should be based on an integrated research of non-stationary processes of heat and mass transfer, hydrodynamics of fluidized beds, and drying kinetics in the convective heat supply. The experiment described in the present paper featured sunflower seeds. It was based on a systematic approach to modelling rotary convective drying processes. The approach allowed the authors to link together separate idealized models. Each model characterized a process of heat and mass transfer in a fluidized bed of wet solids that moved on a cylindrical surface. The experiment provided the following theoretical results: 1) a multimodel system for the continuous drying process of bulky mate- rials in a fluidized bed; 2) an effective coefficient of continuous drying, based on the mechanics of the fluidized bed and its continuous dehydration. The multimodel system makes it possible to optimize the drying process according to its material, heat-exchanger, and technological parameters, as well as to the technical and economic characteristics of the dryer.

Numerical Simulation Analysis of Heat and Mass Transfer during Drying of Jujubes

2012 ◽  
Vol 468-471 ◽  
pp. 2323-2327
Author(s):  
Xiao Kang Yi ◽  
Wen Fu Wu ◽  
He Lei Cui ◽  
Jun Xing Li
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Simulation Analysis ◽  
Internal Heat ◽  
Simulation Software ◽  
Drying Process ◽  
Finite Volume Discretization ◽  
Transfer Equations ◽  
Labview Program

A finite volume discretization method for solving the heat and mass transfer equations of drying jujubes was developed in this paper. Combined with the Labview program, development of a numerical simulation software for internal heat and mass transfer during drying of jujubes, and simulation of the drying process on the jujubes using the software. The results showed that the simulation results and experimental data were consistent.

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