Diffusion-thermo Effects Research Articles

Radiation Absorption and Diffusion Thermo Effects on Unsteady MHD Kuvshinski Fluid Flow Past an Inclined Porous Plate in the Presence of Thermal Radiation and Chemical Reaction

The aim of the present paper is to investigate investigated the Radiation absorption and diffusion thermo on unsteady magneto hydrodynamic Kuvshinski fluid flow past an infinite vertical permeable moving plate in Presence of thermal radiation, heat absorption and homogenous chemical reaction, subjected to variable suction. The plate is assumed to be embedded in a uniform porous medium and Moves with a constant velocity in the flow direction in the presence of a transverse magnetic Field. The equations governing the flow are transformed into a system of nonlinear ordinary differential equations by using perturbation technique. Graphical results for the velocity distribution, temperature distribution and concentration distribution based on the numerical solutions are presented and discussed. Also discuss the effects of various parameters on the skin-friction coefficient and the rate of heat transfer in the form of Nusselt number and rate of mass transfer in the form of Sherwood number at the surface. Velocity and temperature distribution is observed to increase with an increase in Radiation absorption and Dufour parameter, whereas diminishes with enhances of Magnetic field, heat absorption coefficient, radiation parameter and chemical reaction parameter in respective velocity, temperature and concentration distributions.

Soret-Dufour Effects on Heat and Mass Transfer of Newtonian Fluid Flow over the Inclined Sheet and Magnetic Field

Newtonian fluid is ideal for lubrication purposes because the viscosity of this fluid remains as a function of the shear. Besides, the heat and mass transfer are an important study area in fluid dynamics due to its vast applications in industrial processes. The heat-mass transfer can be defined as the Soret and Dufour effect, which implemented in many industrial applications such as in chemical engineering and geosciences field. In addition, the fluid flow over an extending/compressing sheet has significant industrial applications such as the cooling of continuous strips, glass fibre production, the extrusion of plastic sheets from a die, etc. As a response, this study aims to investigate the impacts of Soret and Dufour parameters on the Newtonian fluid flow over an inclined stretching/shrinking sheet. The methodology of this mathematical model are stated as follow: 1) the transformation of partial differential equations (PDEs) to the ordinary differential equations (ODEs), and 2) The ODEs are solved using bvp4c solver in MATLAB software. The bvp4c solver is a MATLAB program directory that solves general form and multi-point boundary layer problems. The main sections of bvp4c are: 1) The solution of the ODEs, 2) The related boundary conditions that can produce the expected results, and 3) An initial guess to run the bvp4c solver. As a result, the numerical and graphical results show that the Soret effect increases the concentration profile whereas decreases the temperature profile. The vice versa occurrence is true for Dufour effect. The convective mass transfer caused by a temperature gradient is known as thermal-diffusion (Soret) effect. The convective heat transfer produced by concentration differences is known as diffusion-thermo (Dufour) effect. However, since the process of heat and mass transfers are related to each other, the Soret and Dufour effects are able to influence both of this process simultaneously. In conclusion, the convective heat transfer is enhanced by increasing Soret and Dufour number while the convective mass transfer is declined by increasing the two numbers.

Dynamics of a nonlinear laminated beam with thermodiffusion effects

A laminated beam system with thermodiffusion effects is considered. The main result is the long‐time dynamics of the system. By showing the system is gradient and asymptotic smoothness, the existence of a global attractor is obtained, which is characterized as unstable manifold of the set of stationary solutions. The quasi‐stability of the system and the finite fractal dimension of the global attractor are established by a stabilizability inequality. The continuity of global attractors regarding the parameter in a residual dense set is finally proved.

Effect of Magnetic field on Unsteady Mixed convection Micropolar Nanofluid flow in the Presence of Non-Uniform Heat Source/Sink.

: The idea of the current investigation is to study the two-dimensional unsteady mixed convection MHD flow of a micro-polar nanofluid with non-uniform heat source/sink. Effects of radiation, reaction, thermo-diffusion, and viscous dissipation are considerednanoparticles are suspended in water base fluid. The governing non-linear system of PDEs is transformed into a system of ODEs using the similarity transformation and HAM is employed for obtaining solutions. Effects of different physical parameter on momentum, microrotation, energy, and concentration profiles are discussed through graphs. From graphical results, it is concluded that the unsteady parameter and magnetic parameter tend to improve the motion of the fluid. It is also seen that microrotation is raised in the shrinking sheet and reduced in the stretching sheet with the increase in the unsteady parameter. The mass transfer process improved with thermal diffusion parameter while delayed with chemical reaction.

Radiation Absorption and Diffusion Thermo Effects on Unsteady MHD Casson Fluid Flow Past a Moving Inclined Plate Embedded in Porous Medium in the Presence of Chemical Reaction and Thermal Radiation

The aim of the present paper is to investigate the effects of Radiation absorption and diffusion thermo on unsteady magnetohydrodynamic Casson fluid flow past an inclined permeable moving plate in Presence of thermal radiation, heat absorption and homogenous chemical reaction. The plate is assumed to be embedded in a uniform porous medium and Moves with a constant velocity in the flow direction in the presence of a transverse magnetic Field. The equations governing the flow are transformed into a system of nonlinear ordinary differential equations by using perturbation technique. Graphical results for the velocity distribution, temperature distribution and concentration distribution based on the numerical solutions are presented and discussed. Also discuss the effects of various parameters on the skin-friction coefficient and the rate of heat transfer in the form of Nusselt number and rate of mass transfer in the form of Sherwood number at the surface. Velocity and temperature distribution is observed to increase with an increase in radiation absorption and Dufour parameter, whereas diminishes with enhances of Magnetic field, heat absorption coefficient, radiation parameter and chemical reaction parameter in respective velocity, temperature and concentration distributions.

Effects of Activation Energy Diffusion Thermo and Nonlinear Thermal Radiation on Mixed Convection Casson Fluid Flow Through a Vertical Cone with Porous Media in the Presence of Brownian Motion and Thermophoresis

In this paper, analyze the impact of Activation energy, Diffusion thermo and nonlinear thermal radiation of mixed convection casson fluid flow through a vertical cone with porous material in the presence of Brownian and thermophoresis has been studied. Numerical techniques, namely Runge–Kutta integration and the shooting method, were applied to obtain solutions to similarity-transformed equations governing continuity, momentum, energy and concentration. The study examined the distributions of flow velocity, temperature and concentration under the interactive effects of the fluid. The results revealed that the activation energy of the Arrhenius equation plays an important role in fluid transport mechanisms within a chemically reactive system involving the Soret effect for a low-Schmidt-number fluid. When the activation energy parameter E was greater within the range 0 < E < 5, the wall shear stress was stronger, heat transfer rate increased, and mass transfer rate decreased.

Analytical Solution of Diffusion Thermo Effect on MHD Second Grade Fluid Flow with Heat Generation and Chemical Reaction through an Accelerated Vertical Plate

Abstract: The objective of this model is to examine the Dufour effect on unsteady free convection second-grade fluid flow past an accelerated moving plate subjected to the magnetic field through a porous medium. The thermal radiation and chemical reactions are also taken into account. The constitutive governing equations of the model with all levied initial and boundary conditions are written in non-dimensional form. The non-dimensional equations that govern the flow model are transformed into a time-fractional model using the Caputo, Caputo–Fabrizio, and Atangana–Baleanu time-fractional derivatives. The Laplace transform technique is applied to the differential equations of the flow model to obtain the exact solution for concentration, temperature, and velocity fields. The expression for the Sherwood number, the Nusselt number, and skin friction are also derived analytically. The effects of diffusion-thermo, chemical reactions, second-grade parameterfractional parameter (γ), porosity, magnetic parameter, heat absorption/generation, and thermal radiation on velocity profiles are studied through various figures. It is observed that the velocity profiles for Caputo–Fabrizio fractional derivatives are higher as compared to Caputo and Atangana–Baleanu fractional derivatives. It is also seen that for the value of fractional parameter γ→1, the velocity profiles obtained via Caputo, Caputo–Fabrizo, and Atangana–Baleanu derivatives are identical. Keywords: Second-grade fluid, Free convection, Chemical reaction, Diffusion thermo, Heat generation, Caputo, Caputo–Fabrizio, Atangana–Baleanu fractional derivative.

Analytical solutions for contaminant transport through a GMB/CCL composite liner system considering effective porosity and thermodiffusion

This study presents analytical solutions for one-dimensional contaminant transport through a saturated double-layer composite liner system consisting of a geomembrane (GMB) and a compacted clay liner (CCL), considering the effects of CCL effective porosity, GMB defects, and thermodiffusion. The solutions provide temperature distribution at steady state and contaminant concentration distribution and total contaminant mass flux for transient-state condition. The heat transfer algorithm of the solutions accounts for advection, conduction, and thermal mechanical dispersion, while the solute transport algorithm of the solutions accounts for molecular diffusion, advection, mechanical dispersion, sorption, and thermodiffusion. The proposed solutions are validated against experimental data and verified against numerical solution. Using the proposed solutions, a series of parametric studies is conducted and the results indicate that neglecting the effect of thermodiffusion can underestimate the contaminant outflow rate at the bottom of the GMB/CCL liner by 6.9%∼130%. Depending on conditions, the effect of thermodiffusion on contaminant transport through the GMB/CCL liner decreases with increasing leachate head, increasing length of GMB wrinkle, and increasing number of GMB defects. CCL effective porosity also has a significant impact on contaminant transport through the GMB/CCL liner system, and neglecting this effect can substantially overestimate the contaminant outflow rate.

MHD 3D Mixed Upper Convective Flow of Maxwell Nanofluid Flow Past in the Presence of Diffusion Thermo and Thermophoresis Effect using Nonlinear Radiative Heat Flux

This article aims to investigate the impact of nanoparticles and magnetohydrodynamics (MHD) on the transfer of heat and mass using a three-dimensional upper-convected Maxwell (UCM) nanofluid flow across a stretched surface. A nonlinear radiative heat flow was included in formulating the equation that describes energy. The nonlinear partial differential equations of the issue are transformed into ordinary differential equations utilizing the similarity transformation. These equations are then solved using the well-known shooting approach in conjunction with the Runge-Kutta integration process of order four. To increase the dependability of our findings, make use of the MATLAB. On the velocities, temperatures, and concentrations of the particles, the graphical and numerical representations of the effects of the main parameters, such as the Dufour parameter, the Brownian motion parameter, the Prandtl number, the thermophoresis parameter, and the magnetic parameter, are presented. It has been shown that the flow velocity decreases as a function of both the linear and nonlinear thermal radiation parameters. In addition, increasing values of the Brownian motion parameter have the effect of reducing the nanoparticle concentration profile

Thermal Diffusion and Diffusion Thermo Effects on Chemically Reacting Nanofluid Flow Towards A Vertical Cone Filled by Porous Medium

Nano particles, chemical reactions, and porous media are all used in this study to look at how thermal diffusion in addition diffusion thermo work together to affect liquid that is immiscible, slurries, but instead conducts electricity flow toward a vertical cone. There is a concentration equation and an energy equation for this question. There are thermal diffusion and chemical reaction effects in both of these equations. It is done by making use of correspondence transformations make governing dynamic system with optimization algorithms of the flow into Algebraic calculations that are quasi, which then statistically solved by means of the Rung-Kutta method, there are graphs in the findings and discussion section that show how different engineering factors can affect speed, features of temperature moreover concentration. Furthermore, consequences about these factors Nu and Sh statistics for skin friction quantity also discussed and as seen in tables. By comparing present results to data that has already been published, we can see that they are very accurate. Increases with in Brownian motion attribute as well as thermal diffusion attribute significantly raise its density boundary layer. It is indeed worth noting that as solute concentration as the condensation variable is increased, the penetration depth declines. That’s for the reason that the compound genomic dispersion decreases as the temperature rises. Kr as a result, values pertaining to Dufour numeral rise, Temperature profiles are similarly rises. Expansion Enhanced Nano fluid intensity dispersion as well as expanded the Thermal diffusion attribute reverse effect in the situation of Brownian locomotion effect, can be seen. These concentration profiles are increasing with rising values of Soret number parameter.

Gigantic and Continuous Output Power in Ionic Thermo-Electrochemical Cells by Using Electrodes with Redox Couples.

The main obstacle of ionic thermo-electrochemical cells (TECs) in continuous power supply lies in a low heat-to-electricity energy conversion efficiency because most TECs work in thermodiffusion mode in which the ions are confined in a liquid/electrolyte media. The introduction of the redox couple onto the electrode surface may overcome the obstacle by resolving the low mass transport rate of ions caused by the redox process occurring near but not on the electrode surface. Herein, the authors demonstrate enhancement of TECs by integrating the redox couple directly onto the electrode surface to maximize the mass transport efficiency. A discontinuous interfacial modification strategy is developed by using a carbon cloth/iron (II/III) phytate as the symmetric electrodes. The gelled electrolyte consisting of a polyacrylamide matrix and phytic acid is shown to promote selective ion diffusion. A synergistic combination consisting of the thermodiffusion effect and redox reactions on the electrode is established in a pre-treated layout. Such TEC affords a high output voltage of 0.4 V, an excellent instantaneous output power density (20.26 mW m-2 K-2 ) and a record-high 2 h output energy density (2451 J m-2 ) under TH = 30 °C with TC = 15 °C, with an ultrahigh Carnot-relative efficiency of 1.12%.

Simulation and interpretation of MHD peristaltic transport of dissipated third grade nanofluid flow across asymmetric channel under the influences of rheological characteristics and inclined magnetic field as well as heat and mass convection

ABSTRACT Mathematical simulation of biological fluids is of upmost significance due to its numerous medical uses. Interpreting various biological flows necessitates a thorough knowledge of the peristaltic mechanism. This paper presents a computational study for the peristaltic motion within vertical asymmetric channels filled with magnetic third grade nanofluid model under the influences of rheological characteristics. Various configurations of the outer boundaries are considered, namely, square wave, multi-sinusoidal wave, trapezoidal wave, and triangular wave. An inclined magnetic field together with nanoparticles and mass concentrations as well as viscous dissipation are considered. Influences of the Dufour and Soret numbers are examined, and the cases of biological scientific assumptions which is known as low Reynolds number and long wavelength are applied. All the computations are obtained numerically using Mathematica symbolical software (ND-Solve). The major outcomes revealed that the square wave shape gives higher pressure gradients near the inlet and outlet parts while the multi-sinusoidal wave gives periodic behaviors of dp/dx. Also, it is better to maximize the variable viscosity coefficient to enhance the rate of heat transfer while, the rate of heat transfer is diminished by the growth in the thermo-diffusion effects as well as variable thermal conductivity coefficient.

Effect of hydrogen addition on the laminar burning velocity and the flame stability of n-dodecane reacting with air at elevated pressures

The effects of hydrogen addition on the premixed laminar burning characteristics of n-dodecane reacting in air were experimentally investigated using the freely expanding spherical flame method. The initial operating conditions were temperature = 425 K, pressure = 1 ˗ 4 bar, equivalence ratio = 0.8–1.4, and mole fraction of H2 in n-dodecane-H2 mixture = 0–40%. Nonlinear stretch extrapolation schemes were implemented to minimize the uncertainty in the estimation of unstretched flame speed as the binary fuel mixtures of n-dodecane and H2 had non-unity Lewis numbers. All experimental operating conditions were simulated in CHEMKIN using a planar flame model with three different reaction mechanisms. The statistical uncertainty estimated for the LBV was below ±6.93%. The LBV increased by three/two times at off–stoichiometric/stoichiometric mixtures as the mole fraction of hydrogen (XH2) increased from 0 to 40% in n-dodecane. The rich mixtures of n-dodecane-air (ϕ = 1.4) were unstable to thermo-diffusive effects due to the lower mass diffusivity of n-dodecane and Le < 1, in contrast, H2 blending to the n-dodecane by keeping the other parameters being same transformed it from an unstable to a stable one. The effective Lewis number and Markstein length decreased with an increasing XH2 in n-dodecane, indicating that the mixtures were stable to thermo-diffusive effects, but with further increase in XH2, there may be a transition in flame stability. H2 addition resulted in an earlier onset of hydrodynamic instability due to a reduction in the flame thickness. In addition, sensitivity analysis was performed to identify the key reactions responsible for the enhanced reactivity associated with H2 addition. The reaction pathway and emission analysis showed a significant reduction in CO2 and CO emissions. Finally, an increase of initial pressure decreased the LBV for all investigated mixtures.

Evaluation of Thermo-diffusion and Diffusion-thermo Phenomenon on the Reactive Micropolar Fluid Motion Over an Extending Device

This articles evaluates thermo-diffusion and diffusion-thermo effects on the motion of hydromagnetic reacting micropolar fluid along an elongated surface with lateral mass flux in porous media. This kind of study includes heat and mass transport of fluids which finds regular applications in various fields of engineering and sciences like porous pipe design, groundwater hydrology, brain blood flow, etc. This body of work also presents a report on thermophoretic phenomenon together with viscous dissipation and heat source. The model equations are firstly transformed from partial derivatives to ordinary ones by the use of some similarity quantities and subsequently tacked numerically. The nonlinearity of the involving equations has compelled the use of stable Runge-Kutta-Fehlberg approach with shooting technique to provide the needed solution. To emphasize and discuss the influence of the primary governing parameters impacting on the flow fields, a variety of graphs have been sketched out and discussed qualitatively. Verification of the numerical code with existing data in literature shows an excellent agreement as checked under limiting conditions and presented in the table. It is evidently shown that the material quantity causes the fluid motion to accelerate whereas the suction term reduces the speed of fluid. Both thermo-diffusion and diffusion-thermo strengthen the heat distribution in the system while the concentration profile declines with chemical reaction.

Finite Element Error Analysis of a Viscoelastic Timoshenko Beam with Thermodiffusion Effects

In this paper, a thermomechanical problem involving a viscoelastic Timoshenko beam is analyzed from a numerical point of view. The so-called thermodiffusion effects are also included in the model. The problem is written as a linear system composed of two second-order-in-time partial differential equations for the transverse displacement and the rotational movement, and two first-order-in-time partial differential equations for the temperature and the chemical potential. The corresponding variational formulation leads to a coupled system of first-order linear variational equations written in terms of the transverse velocity, the rotation speed, the temperature and the chemical potential. The existence and uniqueness of solutions, as well as the energy decay property, are stated. Then, we focus on the numerical approximation of this weak problem by using the implicit Euler scheme to discretize the time derivatives and the classical finite element method to approximate the spatial variable. A discrete stability property and some a priori error estimates are shown, from which we can conclude the linear convergence of the approximations under suitable additional regularity conditions. Finally, some numerical simulations are performed to demonstrate the accuracy of the scheme, the behavior of the discrete energy decay and the dependence of the solution with respect to some parameters.

Exponential Stability for a Flexible Structure System with Thermodiffusion Effects and Distributed Delay

Exponential Stability for a Flexible Structure System with Thermodiffusion Effects and Distributed Delay

SORET AND DUFOUR EFFECTS IN A THREE-DIMENSIONAL MHD FLOW PAST A SEMI-INFINITE UNIFORMLY MOVING VERTICAL PLATE WITH CONSTANT HEAT FLUX

In this paper, we have considered the three-dimensional MHD flow past a semi-infinite uniformly moving porous plate with Soret and Dufour effects. The plate is subjected to a sinu-soidal suction velocity and constant heat flux. It is assumed that a uniform magnetic field is applied normal to the plate and directed into the fluid region. But the induced magnetic field is neglected in the study on the assumption that the magnetic Reynolds number is very small. The analytic solutions are obtained by adopting the method of perturbation technique. The influence of magnetic field parameter, thermal diffusion and diffusion-thermo effects on the flow, heat and mass transfer characteristics are mainly focused on the study. It is found from our study that fluid velocity increases under the influence of Soret and Dufour effects.

Modeling the boundary-layer flashback of premixed hydrogen-enriched swirling flames at high pressures

We model the boundary-layer flashback (BLF) of CH4/H2/air swirling flames via large-eddy simulations with the flame-surface-density method (LES-FSD), in particular, at high pressures. A local displacement speed model tabulating the stretched flame speed is employed to account for the thermo-diffusive effects, flame surface curvature, and heat loss in LES-FSD. The LES-FSD well captures the propagation characteristics during the BLF of swirling flames. In the LES-FSD for lean CH4/H2/air flames at 2.5 bar, the critical equivalence ratio for flashback decreases with the increasing hydrogen volume fraction, consistent with the experiments. This is due to the improved modeling of effects of the flame stretch and heat loss on the local displacement speed. We also develop a simple model to predict the BLF limits of swirling flames. The model estimates the critical bulk velocity for given reactants and swirl number, via the balance between the flame-induced pressure rise and adverse pressure for boundary-layer separation. We validate the model against 14 datasets of CH4/H2/air swirling flame experiments, with the hydrogen volume fractions in fuel from 50% to 100%. The present model well estimates the flashback limits in various operating conditions.

Exponential stability for a swelling porous-heat system with thermodiffusion effects and delay

In the present work, we consider a one-dimensional swelling porous-heat system with single time-delay in a bounded domain under Dirichlet-Neumann boundary conditions subject to thermodiffusion effects and frictional damping to control the delay term. The coupling gives new contributions to the theory associated with asymptotic behaviors of swelling porous-heat. At first, we state and prove the well-posedness of the solution of the system by the semigroup approach using Lumer-Philips theorem under suitable assumption on the weight of the delay. Then, we show that the considered dissipation in which we depended on are strong enough to guarantee an exponential decay result by using the energy method that consists to construct an appropriate Lyapunov functional based on the multiplier technique, this result is obtained without the equal-speed requirement. Our result is new and an extension of many other works in this area.

A study under the impact of Soret and Dufour effects on MHD stagnation point flow and heat transfer towards a stretching sheet

This paper signifies the consequence of the thermal diffusion (Soret) and diffusion-Thermo (Dufour) effect on MHD stagnation point flow and transportation of thermal energy near a stretching plate. However, the inclusion of thermal radiation, heat generation/absorption, and chemical reaction enriches the profiles significantly. By using similarity transformation, the set of leading equations is altered into a set of dimensionless ordinary differential equations. After that, the aim is to convert boundary layer equations into dimensionless ones so that the set of converting equations is computed by using bvp4c solver on MATLAB software. The governing nonlinear equations were resolved with Runge–Kutta fourth-order technique numerically. The significance of radiation, magnetic field, suction, Schmidt number, velocity ratio parameter, heat absorption coefficient, permeability, thermo-diffusion number, diffusion-thermo number on momentum gradient, energy gradient and concentration gradient distribution is analyzed. The parameters, diffusion-thermo number Du and thermo-diffusion number Sr have opposite behaviors on both temperature and concentration fields. Here, also, it is observed that the heat sink parameter has a noticeable influence on the fluid temperature distribution profile.