Non-linear Heat and Mass Transfer During Convective Drying of Kaolin Cylinder Under Non-steady Conditions

The self-consistent model of heat and mass transfer during convective drying of capillary porous media describing both the first and the second periods of drying is presented in Musielak (Wydawnictwo Politechniki Poznańskiej, seria Rozprawy, nr 386 (2004a); Chem. Process Eng. 25, 393–409 (2004b)). The results of simulations of processes in steady conditions are shown (Musielak Wydawnictwo Politechniki Poznańskiej, seria Rozprawy, nr 386 (2004a); Chem. Process Eng. 25, 393–409 (2004b)). The main aim of the present work is to compare experimental results with those from numerical simulations. Three convective drying processes have been performed experimentally. The first and the second periods of drying are considered, during which the humidity of air in the dryer changes due to evaporation. The first process is used to establish drying parameters, whereafter the two remaining processes are simulated. Good agreement between experimental and simulation results is found, both qualitative and quantitative.     

Modeling of Heat and Mass Transfer in a Fractured Porous Medium

While fractured formations are possibly the most important contributors to the production of oil worldwide, modeling fractured formations with rigorous treatments has eluded reservoir engineers in the past. To date, one of the most commonly used fractured reservoir models remains the one that was suggested by Warren and Root nearly four decades ago. In this paper, a new model for fractures embedded in a porous medium is proposed. The model considers the Navier-Stokes equation in the fracture (channel flow) while using the Brinkman equation for the porous medium. Unlike the previous approach, the proposed model does not require the assumption of orthogonality of the fractures (sugar cube assumption) nor does it impose incorrect boundary conditions for the interface between the fracture and the porous medium. Also, the transfer coefficient between the fracture and matrix interface does not need to be specified, unlike the cases for which Darcy's law is used. In order to demonstrate the usefulness of the approach, a two-dimensional model of a fractured formation is developed and numerical simulation runs conducted.

The proposed model is derived through a series of finite element modeling runs for various cases using the Navier-Stokes equation in the channel while maintaining the Brinkman equation in the porous medium. Various cases studied include different fracture orientations, fracture frequencies, and thermal and solutal constraints. The usefulness of the proposed model in modeling complex formations is discussed. Finally, a series of numerical runs also provided validity of the proposed model for the cases in which thermal and solutal effects are important. Such a study of double diffusive phenomena, coupled with forced convection, in the context of fractured formations has not been reported before.     

Solutions using the Recursive Operator Method for the Dynamic Equations of Heat and Mass Transfer in Hardening Concrete under Heat Treatment in a Heating Chamber

A recursive operator method was used to obtain a general solution of the system of linearized differential equations of heat and mass transfer in hardening concrete in a heating chamber. The solution contains arbitrary analytic functions determined from the boundary and initial conditions.     

Hydrodynamic Regimes of Heat and Mass Transfer Apparatuses with a Moving Packing

Hydrodynamic regimes of heat and mass transfer apparatuses with a moving packing are considered. Relations defining the critical velocity, the loss of momentum in the working area, and the dynamic thickness of the layer of packing elements are obtained which are necessary for engineering calculations.     

Dynamics and Heat and Mass Transfer of a Bubble Containing an Evaporating Drop

The problem of unsteady heat and mass transfer for a single bubble containing an evaporating liquefied-gas drop is considered within the spherically symmetric formulation. The numerical solution and the quasi-steady analog of the problem are obtained. The existence of two stages of the process, namely, the dynamic and thermal stages, is shown. The quasi-steady solution is a good approximation for the thermal stage.     

Heat and Mass Transfer During Vapor Absorption by a Stagnant Solution Layer

Based on simple models of nonisothermal absorption for the cases of long and short times, the effect of the heatgeneration and heatextraction rates on vapor absorption by a stagnant solution layer is analyzed. Models taking into account and ignoring the motion of the interface between the phases are considered. Results of an experimental study of steam absorption by a stagnant water/LiBr solution are described. Time dependences of temperatures at various heights inside the liquid layer and of the absorbed mass, and also temperature and concentration profiles at various times, are reported. A comparison of predicted values with experimental data is given.     

Investigations of Heat and Mass Transfer for Thermal Protection Materials in a Long Flight

The problem of unsteady coupled heat and mass transfer in the course of motion of a spherically blunted conical body fabricated with the use of thermal protection materials is considered. Numerical integration is applied to study the characteristics of heat and mass transfer at constant stagnation parameters (Mach number 6, altitude 15 km, and flight time 600 s), which impose severe constraints on the choice of materials for thermal protection. It is demonstrated that the use of advanced ceramic materials ensures an admissible temperature regime and maintaining the initial geometry of the body, including its motion at an angle of attack.     

Analysis of Heat and Mass Transfer in a Vertical Annular Porous Cylinder Using FEM

The present study is intended to study heat and mass transfer in a vertical annular cylinder embedded with saturated porous medium. The inner surface of cylinder is maintained at uniform wall temperature and uniform wall concentration. The governing partial differential equations are non-dimensionalised and solved by using finite element method (FEM). The porous medium is discritised using triangular elements with uneven element size. Large number of smaller-sized elements are placed near the walls of the annulus to capture the smallest variation in solution parameters. The results are reported for both aiding and opposing flows. The effects of various non-dimensional numbers such as buoyancy ratio, Lewis number, Rayleigh number, aspect ratio, etc on heat and mass transfer are discussed. The temperature and concentration profiles are presented.     

Thermodynamic Conditions of Formation of CO<Subscript>2</Subscript> Hydrate in Carbon Dioxide Injection into a Methane Hydrate Reservoir

The mechanism of replacement of methane by carbon dioxide in the hydrate in the process of CO₂ injection into a reservoir with formation of fronts of methane hydrate dissociation and carbon dioxide hydrate generation is investigated. It is found that such a replacement regime can be implemented in both low- and high-permeability reservoirs. It is shown that in the highintensity injection regime the heat flux from the well does not affect propagation of the fronts of methane hydrate dissociation and carbon dioxide hydrate generation. In this case the replacement regime is maintained by only the heat released at formation of carbon dioxide hydrate. An increase in the injection pressure may lead to suppression of methane hydrate dissociation and termination of the replacement reaction. The critical diagrams of existence of the regime of conversion of methane hydrate to carbon dioxide hydrate are constructed.     

Limits of the Inertial Particle Deposition Regime and Heat Transfer in Supersonic Viscous-Dusty-Gas Flow Past Bodies

Supersonic steady dusty-gas flow past a blunt body at moderate and large Reynolds numbers Re is considered. Using the complete Navier-Stokes equations for the carrier phase, the effect of viscosity on the limits of the inertial particle deposition regime and the two-phase flow pattern near the frontal surface of the body is studied numerically for 10² Re 10⁵. The dependence of the limits of the inertial particle deposition regime on the phase velocity slip ahead of the bow shock is investigated. For large Re, the flow near the stagnation point is studied in the boundary layer approximation. On the basis of numerical calculations over a wide range of variation of the Reynolds number and the particle inertia parameter, the maximum increase in the heat fluxes at the stagnation point due to the presence of dispersed particles in the free-stream is estimated.     

Fully Developed Forced Convection Heat Transfer in a Porous Channel with Asymmetric Heat Flux Boundary Conditions

An analytical study is performed on steady, laminar, and fully developed forced convection heat transfer in a parallel plate channel with asymmetric uniform heat flux boundary conditions. The channel is filled with a saturated porous medium, and the lower and upper walls are subjected to different uniform heat fluxes. The dimensionless form of the Darcy–Brinkman momentum equation is solved to determine the dimensionless velocity profile, while the dimensionless energy equation is solved to obtain temperature profile for a hydrodynamically and thermally fully developed flow in the channel. Nusselt numbers for the lower and upper walls and an overall Nusselt number are defined. Analytical expressions for determination of the Nusselt numbers and critical heat flux ratio, at which singularities are observed for individual Nusselt numbers, are obtained. Based on the values of critical heat flux ratio and Darcy number, a diagram is provided to determine the direction of heat transfer between the lower or upper walls while the fluid is flowing in the channel.     

Some Considerations on Modeling Heat and Mass Transfer in Porous Media

In this paper some considerations are presented about the equations needed to set up a model of the process of heat and mass transfer in porous media. A clear classification is made of the various types of equations used and of their physical meaning. Special attention is paid to the thermodynamic equilibrium equations and to their derivation since they are too often taken for granted. The importance of the various transport mechanisms (of mass and energy) is analyzed and the consequences that can arise when some term is neglected are indicated.     

Modelling of Two-Component Turbulent Mass and Heat Transfer in Air-Fed Pressurised Suits

In this paper the modelling of an important industrial problem is addressed, which involves the two-component turbulent flow with heat transfer that takes place inside protective clothing. The geometry of the flow boundaries is reconstructed in a CAD system from photogrammetry scan data. The overall model is sufficiently realistic to allow, after validation, design improvements to be tested. Those presented here allow the reduction of hotspots over the worker’s body surface and increase thermal comfort.     

Role of Thermal Diffusion on Heat and Mass Transfer in Porous Media

In this paper, thermal diffusion phenomena in a porous cavity are investigated. The Brinkman model, coupled with the energy and the mass balance equations was solved numerically using a finite element techniques. A two-component system was included in the model. Different models were investigated to demonstrate the importance of the Soret effect with the presence of gravity vector. We do not take into consideration the pressure effect in the thermal diffusion. Even with such simplification to the problem, results reveal that the thermal diffusion is important and drives a strong convection. A series of convection cells are observed and steady-state solutions are obtained. Asymmetric solutions are obtained for various cases of dual-porosity porous media. Variations in the gravity vector indicated that the convection patterns, as well as the role of Soret coefficient, are profoundly impacted. Finally, the importance of including thermal diffusion in petroleum reservoir simulation is discussed.     

Unsteady Natural Convection,Heat and Mass Transfer in Inclined Triangular Porous Enclosures in the Presence of Heat Source or Sink: Effect of Sinusoidal Variation of Boundary Conditions

The problem of double-diffusive convection in inclined triangular porous enclosures with sinusoidal variation of boundary conditions in the presence of heat source or sink was discussed numerically. The dimensionless governing equations of the problem were solved numerically by using finite difference method. The effects of governing parameters, namely, the dimensionless time parameter, various values of the inclination angle, Darcy number, the heat generation/absorption parameter, the buoyancy parameter and the amplitude wave length ratio on the streamlines, temperature and concentration contours as well as the velocity component in the x-direction at the triangle mid-section, the average Nusselt and Sherwood numbers at the bottom wall of the triangle for various values of aspect ratio were considered. The present results are validated by favorable comparisons with previously published results. All the results of the problem were presented in graphical and tabular forms and discussed.     

Heat and Mass Transfer on the Mixed Convection of Non-Newtonian Fluids Over a Vertical Wedge with Soret/Dufour Effects and Internal Heat Generation: Variable Wall Temperature/Concentration

Transport in Porous Media - The presented work compares the mechanical behavior from standard unconfined compressive strength and indirect tensile strength tests of natural sandstone and artificial...     

Quasi-One-Dimensional Model of Heat and Mass Transfer During Sublimation of a Molecular Crystal Plate in a Plane Channel

An unsteady quasi-one-dimensional model is constructed for the process of sublimation of a monocrystalline plate of -diketonate in a uniform flow of an indifferent gas. A method of collocations and least squares is developed for solving heat-transfer problems. In contrast to the previous variants of the method, the algorithm proposed is designed for solving unsteady equations in partial derivatives with a phase transition. Numerical calculations are performed for various regimes of sublimation of chromium -diketonate; the results are in good agreement with the data of a physical experiment.     

Heat and Mass Transfer in MHD Micropolar Flow Over a Vertical Moving Porous Plate in a Porous Medium

An analysis is presented for the problem of free convection with mass transfer flow for a micropolar fluid via a porous medium bounded by a semi-infinite vertical porous plate in the presence of a transverse magnetic field. The plate moves with constant velocity in the longitudinal direction, and the free stream velocity follows an exponentially small perturbation law. A uniform magnetic field acts perpendicularly to the porous surface in which absorbs the micropolar fluid with a suction velocity varying with time. Numerical results of velocity distribution of micropolar fluids are compared with the corresponding flow problems for a Newtonian fluid. Also, the results of the skin-friction coefficient, the couple stress coefficient, the rate of the heat and mass transfers at the wall are prepared with various values of fluid properties and flow conditions.     

DNS and Highly-Resolved LES of Heat and Mass Transfer in Two-Phase Counter-Current Condensing Flow

Flow, Turbulence and Combustion - A comprehensive study of direct-contact condensation heat transfer for turbulent, counter-current, liquid/vapour flow in a nearly horizontal channel at high...