Presence Of Mass Transfer Research Articles

Investigation on interphase mass transfer coefficient of a deformable bubble with density contrast using phase-field lattice Boltzmann method

The gas–liquid mass transfer process with density contrast is modeled in this paper using a phase-field Lattice Boltzmann (LB) method. In this method, the phase-field model used to calculate the flow field and the continuous species transfer model used to calculate the concentration distribution are coupled by introducing the divergence condition of the velocity in the presence of mass transfer into the Allen-Cahn equation. For a deformable bubble rising in stagnant liquid, a two-dimensional parameter dependence study is conducted and the results indicate that an increase in initial diameter, as well as a decrease in liquid diffusion coefficient or liquid viscosity, can improve the steady-state value for the Sherwood number, whereas the distribution coefficient has a little impact on this steady-state value. Furthermore, a correlation originally proposed by Takemura and Yabe (1998) modified with a shape factor can be used to predict the steady-state Sherwood number in the numerical results.

Flooding behavior of the standard liquid–liquid extraction systems in a pilot plant L-type pulse packed extraction column: Experimental study

In this study, the two-phase pressure drop and flooding velocity were investigated in a pilot plant of a new type of extraction column entitled “L-shaped pulsed packed extraction column” using two liquid-liquid systems of butyl acetate-water and toluene-water in the presence of acetone as the mass transfer agent. The effects of operating variables, physical properties, and the presence of mass transfer on the flooding flowrate and pressure drop were considered. It is found that the pressure drop is strongly influenced not only by the flow rates of the continuous and dispersed phases, but also by the pulsation intensity. That is, increasing the values of these parameters increases the shear stresses and the flooding phenomenon to occur sooner. Surprisingly, it is observed that increasing the pulsation intensity and dispersed phase flow rate reduces the maximum throughput of the column but increasing the continuous phase flow rate enhances that. Furthermore, it is achieved that the interfacial tension is a physical property which has significant impact on the flooding and the presence of mass transfer only affect at the low pulsation intensity. Finally, a new correlation is proposed to accurately predict the flooding velocity. Good adaptation between predictions and experiments was found for all investigated operational conditions, chemical systems, and with and without mass transfer.

N2O selectivity in industrial NH3 oxidation on Pt gauze is determined by interaction of local flow and surface chemistry: A simulation study using mechanistic kinetics

Despite significanteffort spent on the investigation of catalytic oxidation of ammonia on platinum at the molecular scale, there is surprisingly little work that investigates the behavior of the established reaction mechanisms under industrial conditions in the presence of mass transfer limitations.This paper presents reactive flow simulations of ammonia oxidation on platinum gauzes under industrial operating conditions, combining a mechanistic description of the surface chemistry with the computation of the flow-, temperature- and concentration fields around the platinum wires.Overall, the simulations yield temperature- and concentration fields, as well as integral N2O selectivity in line with industrial experience and (limited available) experimental data. In particular, the simulations predict the experimentally observed decrease of the integral N2O selectivity with increasing wire diameter, increasing wire-to-wire distance, decrasing flow velocity, and increased surface area due to surface reconstruction.The main result of the paper is that the local interaction of the flow field with surface chemistry leads to a variation in the local N2O (and N2) selectivity across the gauze:•The N2O and N2 selectivity is higher on the front side of a wire than on the rear side.•A reduced N2O selectivity is observed where one wire is shadowed by another wire.•Increased N2O selectivity is observed at stagnation points where upstream wires direct the flow so that it hits a downstream wire with higher velocity.These examples show that - through the flow directing effect of the upstream wires - the selectivity on an individual wire is influenced by the presence of other wires. This observation provides a mechanistic explanation for the industrial observation that optimized gauze geometries can lead to reduced N2O formation. Understanding the effect of local mass transfer on the selectivity provides a guideline for a further rational optimization of gauze geometries for improved N2O and N2 selectivity.To analyze the robustness of the simulation results towards uncertainties in the reaction mechanism, a sensitivity analysis is performed, and the selectivity order defined as nSN2O,NH3=∂lnSN2O/∂lncNH3 (i.e. the response of the N2O selectivity SN2O to changes in the near-wall NH3 concentration cNH3) is identified as the decisive property of a reaction mechanism, that controls the response of the local selectivity to variations in the flow field. This suggests that future mechanistic work should focus on a more precise determination of this selectivity order nSN2O,NH3.

Experimental investigation on drop size distribution and mean drop size in an L-shape pulsed packed extraction column

In this study, the mean drop diameter and drop size distribution have been investigated in a pilot plant of a new type of extraction column entitled “L-shaped pulsed packed extraction column” by using two liquid systems of toluene/acetone/water and n-butyl/acetone/water in the presence of mass transfer in two directions. The effects of operational variables, physical properties and mass transfer direction have been considered on the dispersed drop size. It is found that the mean drop diameter and drop size distribution is significantly affected by the pulsation intensity and interfacial tension of liquid system. However, the phases flow rates and mass transfer direction have a weaker impact. Furthermore, it is observed that the mean drops diameter in the horizontal and vertical sections of the used column have mostly the same size and it is considered as a significant advantage. Finally, new correlations are proposed to accurately predict the mean drop size and drop size distribution. Good agreement between predictions and experiments was found for all operating conditions, chemical systems and mass transfer direction that were investigated.

Experimental investigation on dispersed phase holdup in an L-shape pulsed packed extraction column

In this study, the dispersed phase hold-up has been investigated in a pilot plant of a new type of extraction column entitled “L-shaped pulsed packed extraction column” by using two liquid systems of toluene/acetone/water and n-butyl/acetone/water in the presence of mass transfer in two directions. The effects of operational variables, physical properties and mass transfer direction have been considered on the dispersed phase hold-up. It is found that the dispersed phase hold-up is significantly affected by the pulsation intensity, dispersed phase flow rate and interfacial tension of liquid system. However, the continuous phase flow rate and mass transfer direction have a weaker impact. Furthermore, it is observed that the behavior of hold-up in the horizontal and vertical sections of the used column is distinctive in some case. Such that any factor which reduces the dispersed drop size, leads to an increase in hold-up in the vertical section of the column and a decrease in hold-up in the horizontal section of the column. Finally, new correlation is proposed to accurately predict the dispersed phase hold-up. Good agreement between predictions and experiments was found for all operating conditions, chemical systems and mass transfer direction that were investigated.

Cattaneo-Christov heat flux theory and thermal enhancement in hybrid nano Oldroyd-B rheological fluid in the presence of mass transfer

This article develops a system of partial differential equations (PDEs) for thermal enhancement in Oldroyd-B rheological fluid (OBF) using Cattaneo-Christov heat flux theory for simultaneous transport of heat energy and species in the presence of nanostructures (Cu,Al2O3). System of PDE characterizing thermal heat, momentum, and conservations relaxation times are modeled via conservation of momentum, energy, and species. This system of nonlinear PDEs is solved by the finite element method (FEM). Convergence and grid-independent solutions are derived which are further used for numerical simulations against parametric analysis. An increase in momentum relaxation time causes a significant declination in wall shear stress. However, the opposite trend for wall heat transfer rate and mass flux versus momentum relaxation time is noted. The impact of Prandtl number on wall heat transfer rate is similar to the impact of Schmidt number on wall mass flux.

Molecular dynamics simulation of thermal diffusion processes in non-isothermal flow of the medium

The article presents a brief information on the discovery and experimental study of a new thermoelectrokinetic effect consisting in the formation of thermoelectrokinetic EMF in viscous conductive media in the presence of mass transfer (particles) and the action of a temperature gradient. On the basis of the molecular dynamics method, a mathematical model is developed and a numerical simulation of the non-isothermal flow of the Lennard-Jones fluid under the conditions of thermoelectrokinetic effect formation is carried out. As a result of the simulation the microscopic regularities of its formation are established.

A new iterative least square Chebyshev wavelet Galerkin FEM applied to dual phase lag model on microwave drying of foods

In this paper, we developed a dual-phase-lag (DPL) model of heat and mass transfer in presence of a source term for microwave drying foods of different geometrical configuration like slab, cylinder or sphere under the most generalized boundary conditions. The particular cases of present model are the diffusion model, Luikov model, Weng-Chang model and Andarwa-Tabrizi model. The proposed model is the most generalized boundary value problem of a coupled system of two hyperbolic second order partial differential equations. Stability analysis of present model is provided. A new iterative least square Chebyshev wavelet Galerkin finite element method provided for solution. The discretization in space and then application of Chebyshev wavelet Galerkin method converts our problem into a coupled system of two most generalized Sylvester equations. The iterative least square method provide solution of coupled system of Sylvester equations. Convergence and stability analysis of present method is discussed in detail. In a particular case of DPL model, the solution obtained by present method is compared with exact solution (Laplace transform technique) and are approximately same. Effect of relaxation time, Fourier number, phase change coefficient, thermo-gradient coefficient, heat generation, radius of the food and diffusion coefficient on heat and mass transfer are discussed in detail. This generalized model and its solution play important role in the study of microwave food drying.

Chemical Reaction Effect on MHD Flow of Casson Fluid with Porous Stretching Sheet

In this analysis, the magnetohydrodynamic flow of a Casson fluid over a permeable stretching sheet in the presence of mass transfer is studied. Using similarity transformations, the governing equations are converted to ordinary differential equations and then solved through MATHEMATICA. The skin friction coefficient and local Sherwood number are analyzed through numerical values for various parameters of interest. The velocity and concentration profiles are illustrated for several pertinent flow parameters. We observed that the Casson parameter and Hartman number have similar effects on the velocity in a qualitative sense. We further analyzed that the concentration profile decreases rapidly in comparison to the fluid velocity when we increased the values of the suction parameter.

Study of hall current, radiation and velocity slip on hydromagnetic physiological hemodynamic fluid with porous medium through joule heating and mass transfer in presence of chemical reaction

Study of hall current, radiation and velocity slip on hydromagnetic physiological hemodynamic fluid with porous medium through joule heating and mass transfer in presence of chemical reaction

The effect of mixed convection on the thermal field of horizontal channel flow

An experimental study was conducted to investigate the thermal field of low-speed flow of moistair in a horizontal rectangular duct, uniformly heated from below (Poiseuille–Benard flow). Averaged temperature fields were measured in vertical mid-plane using thermocouples. The buoyancy-induced secondary flow is interacting with forced Poiseuille flow which leads to complex flow behaviour with flow reversal along the top surface. Two types of bottom boundary conditions were examined: aluminium plate (only heat transfer) and water film (simultaneous heat and mass transfer) heated to the same temperature. Presence of mass transfer causes stronger transient behaviour above the bottom surface and enhancing of heat transfer, but the overall character of the thermal field remains the same as in case of heat transfer only.

Experimental investigation on the mean drop size and drop size distribution in an L-shaped pulsed sieve-plate column

ABSTRACTVertical pulsed extraction columns cannot be employed in applications with height limitations. On the other hand, the horizontal extraction columns have low throughput, which affects their applicability in industrial applications. Therefore, there is a need to design a new type of extractors for such circumstances. In this paper, an experimental study on drop sizes has been implemented in a novel L-shaped pulsed sieve-plate extraction column in the absence and presence of mass transfer. Moreover, new correlations are developed for prediction of the mean drop size and size distribution using the log-normal probability density function.

Radiation effects on stagnation point flow with melting heat transfer and second order slip

This article examines the effects of melting heat transfer and thermal radiation in stagnation point flow towards a stretching/shrinking surface. Mathematical formulation is made in the presence of mass transfer and second order slip condition. Numerical solutions to the resulting nonlinear problems are obtained by Runge-Kutta fourth fifth order method. Physical quantities like velocity, temperature, concentration, skin friction, Nusselt and Sherwood number are analyzed via sundry parameters for stretching/shrinking, first order slip, second order slip, radiation, melting, Prandtl and Schmidt. A comparative study with the previously published results in limiting sense is made.

A Single Pore Model for Displacement of Heavy Crude Oil With Carbon Dioxide

Summary The present problem analyzes displacement of heavy crude oil in a capillary by carbon dioxide (CO2) as seen in enhanced oil recovery (EOR). In immiscible displacement of viscous liquid in a tube by a gas with lower viscosity than the liquid, a gas bubble moves steadily and leaves behind a thin liquid film of thickness h∞ which is known as the Bretherton problem. With the recovery of crude oil in mind, the analysis was confined to cylindrical pores of diameter ≈1 µm, and hence disjoining pressures are included and added to the Laplace pressures. It is observed that, at small capillary numbers, the effect of disjoining pressure dominates, and at large capillary numbers, the Laplace pressure dominates. The key contribution here is the solutions to the mass-transfer problem in the form of CO2 dissolving in oil. We included the changes of the physical properties of heavy crude oil on carbonation on the basis of a real system. The thickness of thin residual oil film decreases in the presence of mass transfer, leading to an increase in oil recovery, but lowers the carbonation because of the convection in the reverse direction. The opposite is true of displacements at low capillary numbers in which the disjoining pressure dominates. The numerical solutions were obtained with ANSYS® FLUENT software for the profile shapes, capillary numbers, the thicknesses of thin oil films left behind, and the net mass-transfer rates. The capillary pressure dominates the net pressure drop that one can lower by lowering the surface tension.

Three-Dimensional Flow of Maxwell Fluid with Soret and Dufour Effects

This paper reports the heat and mass transfer effects in three-dimensional flow of a Maxwell fluid over a stretching surface with convective boundary conditions. Analysis is carried out in the presence of mass transfer with first-order chemical reactions, and with Soret and Dufour effects. Convergent series solutions to the resulting nonlinear problems were developed. It is found that the roles of Deborah and Biot parameters on the Nusselt number were opposite; however, the Sherwood number was qualitatively similar for both Biot and Deborah numbers. Also, variations of Prandtl and Biot numbers on the Nusselt and Sherwood numbers were similar.

Effect of interfacial mass transfer on the dispersion in segmented flow in straight capillaries

The effect of interfacial mass transfer on the extent of dispersion in liquid‐liquid segmented flow in straight capillaries is studied. In the absence of interfacial mass transfer, dispersion coefficient was seen to go through a minimum with increasing flow rates. In the presence of mass transfer, physicochemical properties of both the phases and slug lengths were seen to vary along the capillary length. The extent of dispersion was always higher in the presence of interfacial mass transfer. The predictions using axial dispersion model deviated noticeably for larger capillaries as the model does not account for varying buoyancy, dynamic contacting, and Marangoni convection. Simulations of a first‐order interfacial reaction considering varying slug lengths showed a significant change in optimum operating parameters than the conventional approach. A special case of “drop‐on‐demand” type of controlled two‐phase flow in capillaries was also studied. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4294–4308, 2015

Soret and Dufour effects in three-dimensional flow of Maxwell fluid with chemical reaction and convective condition

Purpose – The purpose of this paper is to address the heat and mass transfer effects in three-dimensional flow of Maxwell fluid over a stretching surface with convective boundary conditions. Mass transfer is considered in the presence of first order chemical reaction. Conservation laws of energy and concentration are based upon the Soret and Dufour effects. Convergent series solutions to the resulting non-linear problems are developed. Effects of Biot and Deborah numbers on the Sherwood number are decreasing. Local Nusselt reduces with an increase in Eckert numbers. It is also interesting to note further that variations of Prandtl and Biot numbers on the Nusselt number are increasing while Sherwood number decreases with an increase in Prandtl number. Design/methodology/approach – The involved partial differential systems are reduced to the ordinary differential systems using appropriate transformations. Series solutions by homotopy analysis method are constructed and analyzed. Graphical results are presented and examined in detail. Findings – It is found that roles of Deborah and Biot parameters on the Nusselt number are opposite. However, the Sherwood number is qualitative similar for both Biot and Deborah numbers. It is also interesting to note further that variations of Prandtl and Biot numbers on the Nusselt and Sherwood numbers are similar. Originality/value – The purpose of present communication is to investigate the three-dimensional flow of Maxwell fluid over a stretching surface with convective condition. Analysis has been carried out in the presence of mass transfer with first order chemical reaction and Soret and Dufour effects.

Heat and Mass Transfer Effects on MHD Natural Convective Flow Past an Infinite Vertical Porous Plate with Thermal Radiation and Hall Current

The objective of the present study is to find both the analytical and numerical solutions of the unsteady hydromagnetic natural convective radiating fluid flow of an incompressible, viscous Boussinesq's fluid past an infinite vertical plate embedded in a porous medium with heat and mass transfer in presence of hall current. The Rosseland approximation for an optically thick fluid is invoked to describe the radiative flux. Mathematical model of this mechanism has been constructed in the form of partial differential equations and are solved by an efficient finite element method as well as by Perturbation technique. A parametric study of the physical parameters is made, and a representative set of numerical results for the velocity, temperature and concentration are presented graphically as well as local shear stress and local Nusselt and Sherwood numbers are presented in tabular forms. The comparison of the analytical and numerical results is very good indicating the correctness of the present analysis and its applicability.

Similarity transformations of heat and mass transfer effects on steady MHD free convection dissipative fluid flow past an inclined porous surface with chemical reaction

This paper concerns with a steady two-dimensional flow of an electrically conducting incompressible dissipating fluid over an inclined semi-infinite porous surface with heat and mass transfer in presence of chemical reaction. The flow is permeated by a uniform transverse magnetic field. A scaling group of transformations is applied to the governing equations. The system remains invariant due to some relations among the parameters of the transformations. After finding three absolute invariants, a third-order ordinary differential equation corresponding to the momentum equation, and two second-order ordinary differential equations corresponding to energy and diffusion equations are derived. The coupled ordinary differential equations along with the boundary conditions are solved numerically. The effects of various parameters on velocity, temperature and concentration fields as well as skin-friction, Nusselt number and Sherwood number are presented graphically and in tabulated form. DOI: http://dx.doi.org/10.3329/jname.v11i2.18313

MHD boundary layer flow on heat and mass transfer over a stretching sheet with slip effect

The present paper is to investigate the effect of linear thermal stratification in stable stationary ambient fluid on steady MHD convective flow of a viscous incompressible electrically conducting fluid along a Stretching sheet in the presence of mass transfer and Magnetic effect. The governing equations of continuity, momentum, energy and species are transformed into ordinary differential equations using local similarity transformation. The resulting coupled non-linear ordinary differential equations are solved using Runge-Kutta fourth order method along with shooting technique. The velocity, temperature and concentration distributions are discussed numerically and presented through graphs. The numerical values of skin-friction coefficient, Nusselt number and Sherwood Number at the plate are derived, discussed numerically for various values of physical parameters and presented through Tables.DOI: http://dx.doi.org/10.3329/jname.v10i2.16400