Capillary Porous Media Research Articles

Features of periodic temperature profiles in filtrating capillary porous media

The behavior of temperature profiles is examined in filtrating capillary porous media which are subjected to periodic heating. Reasons are described for amplitude shift in the temperature oscillations versus the fluid filtration rate.

多孔媒体の乾燥と熱および流体輸送連成モデルの検討

多孔媒体の乾燥と熱および流体輸送連成モデルの検討

AN ANALYSIS OF DRYING IN CAPILLARY-POROUS PLANAR MEDIA

ABSTRACT Analytical solutions are developed for temperature and moisture distributions in a capillary-porous medium by using Luikov's model and applying a solution methodology based on the decoupling of simultaneous heat and mass diffusion problems. A parametric survey is made to illustrate the relative importance of various dimensionless parameters affecting drying.

An Analytical Study of the Effect of the Darcy and Fick Laws on the Sublimation of a Frozen Semi-infinite Porous Medium

Many applications of the vacuum sublimation process for freeze-drying products exist. For instance, the food, medical, and chemical industries use of the sublimation process to maintain the shape and quality of heat-sensitive products during the drying process. The application of the vacuum sublimation process has received considerable attention over the past 20 years. Theoretically, it is assumed that the vapor transfer in the dried region is governed by diffusional (Fick) flow and/or hydrodynamic (Darcy) flow. Thus vapor movement in porous media is due to the concentration and/or pressure gradients. Luikov formulated the system of equations for heat and mass transfer in the capillary-porous media which included the effect of pressure gradients and the equation of pressure field. In the present work, the authors present a more complete description of the vacuum sublimation process for which an exact analytical solution is obtained. The present formulation is based upon the Luikovf system and the fact that the vapor flow in the dried region results from both moisture concentration and pressure gradients in the porous medium.

Effect of electrolytes on thermal moisture transport in capillary-porous media

Experimental data on the effect of electrolytes upon thermal moisture mobility in quartz sand and cellulose are presented. The results are interpreted from the viewpoint of change in properties of moisture boundary layers.

Non-dimensional numbers associated with the evaporation from a capillary porous medium / Nombres sans dimensions associés à l'évaporation au sein d'un milieu poreux

ABSTRACT The different factors that produce evaporation of moisture from a capillary porous medium are being investigated. Thermodynamic measurements of the porous medium-air-water system and a mathematical model have permitted the establishment of some correlations between the principal non-dimensional numbers associated with heat and mass transfer between the evaporating water in the porous medium and the external gas stream. These correlations lead to the prediction of some important parameters such as the depth of the surface of vaporization and the exchange coefficients of the heat and mass transfer during the evaporation from a capillary porous medium.

A Non-Equilibrium Thermodynamics Approach to Transport Phenomena in Capillary Porous Media

A Non-Equilibrium Thermodynamics Approach to Transport Phenomena in Capillary Porous Media

Transport phenomena in a capillary-porous medium II. Entropy production and phenomenological equations

By means of the balance equation of internal energy and the assumption of local equilibrium there is derived the balance equation of entropy. In the entropy production such terms that have connection with the work of reactive forces, with the energy of change of mass, and with the work of binding forces also appear in addition to the usual expressions. It is shown that entropy production can be written in two equivalent ways by means of tensors of different orders. Every form of entropy production in linear area leads to a different system of phenomenological equations. Transfer relations between the two systems are found. Also an expression is found for mass flux which depends explicitly neither on the temperature gradient nor on the gradient of chemical potentials. A relationship is found between viscosity tensor and the tensor which describes the swelling of a body, and friction between a fluid and the solid phase. Dependence of dispersion coefficient on concentration is derived.

Transport phenomena in a capillary-porous medium I. The model of a capillary-porous body and a series of balance equations

The reality of a capillary-porous body is substituted by the model of a continuous viscoelastic, isotropic two-component medium (component 1 is the solid phase, component 2 is a liquid). It has been proved that if a polymolecular adsorbent layer is created, this model is physically adequate to the reality. In this paper, the balance equation of mass, the momentum, the moment of momentum, the kinetic energy, the total energy, and the internal energy are derived for this model. Since it is characteristic of an arbitrarily chosen volume of the investigated system to change its mass, the derivation of these equations is based on Mescerski's instead of on Newtonian mechanics as is usual. The binding energy, which characterizes the energy interaction in sorbent processes, is considered. Tensors are found that describe the swelling of the investigated body and the friction between the fluid and the solid phase. The results are generalized for systems confined within diathermic, soft, unscreening and semipermeable walls.

Heat and Mass Transfer in a Semi Infinite Porous Medium in Contact with Well Stirred Fluid

Unsteady transfer of heat and mass in a semi-infinite capillary-porous medium in contact with well-stirred fluid has been considered in this paper. At the interface, we have assumed the continuity of temperature and of heat flux while for mass transfer convective law has been assumed. It is also assumed that a quantity of heat, proportional to the moisture transferred at the interface, is produced with in the fluid. Some numerical results have been graphically depicted.

Application of the methods of thermodynamics of irreversible processes to the investigation of heat and mass transfer

On the basis of the phenomenological theory-the thermodynamics of irreversible processes-and of the independent results of kinetic and statistical theory, a systematic description is given of transfer phenomena: heat conduction allowing for finite rate of propagation of heat, stress relaxation in viscoelastic media, moisture transfer in capillary-porous media, and turbulent transfer processes. Some solutions are presented for the hyperbolic equation of mass transfer in porous media.