Local Thermal Non-equilibrium Condition Research Articles

Prediction of flow and heat transfer through a microtube filled with bidisperse porous medium under local thermal nonequilibrium condition

AbstractIn this paper, the thermal and hydrodynamic solutions of a microtube filled with bidisperse porous medium (BDPM) under the local thermal nonequilibrium (LTNE) condition are presented. Considering the LTNE condition, the energy equations have been numerically solved. The rarefaction effects are considered for Knudsen numbers ranging from 0 to 0.1; therefore, first‐order boundary condition is applied on the wall. The temperature distribution of each phase is examined with respect to the involved parameters in the BDPM system. For the first time, the Nusselt number ratio (NRDP) is introduced to study the influence of Darcy number on the Nusselt number more precisely. Also, the effect of different thermophysical parameters on the Nusselt number is studied. The advantage of BDPM system over monodisperse porous medium (MDPM) structure is examined through the heat transfer performance parameter. The findings exhibit a good agreement with the literature. Also, the LTNE condition produces more realistic results in comparison to local thermal equilibrium assumption. On the whole, although implementing the BDPM enhances the heat transfer rate compared with the MDPM, it does not improve the thermal hydrodynamic performance significantly.

UNCERTAINTY QUANTIFICATION FOR NATURAL CONVECTION IN RANDOM POROUS MEDIA WITH INTRUSIVE POLYNOMIAL CHAOS EXPANSION

The paper presents a framework for the construction of a stochastic projection method for the natural convection in random porous media under the local thermal nonequilibrium conditions. In this approach, the input stochastic field (porosity) is represented by the Karhunen−Loeve expansion and the output fields (e.g., velocity, pressure, fluid phase temperature, and solid phase temperature) are expressed by the polynomial chaos expansion. Using the spectral decomposition, the stochastic problem in random porous media is reformulated to a set of deterministic problems to be solved for each polynomial chaos. A stochastic projection method is implemented to obtain the chaos coefficients in the corresponding deterministic governing equations and the statistics of the numerical solution is obtained. The prediction results are compared against results obtained using a Monte Carlo method. Excellent agreement between these results indicates the efficiency and accuracy of the proposed method.

Multiple-relaxation-time lattice Boltzmann model for convection heat transfer in porous media under local thermal non-equilibrium condition

In this work, a thermal multiple-relaxation-time (MRT) lattice Boltzmann (LB) model is proposed for simulating convection heat transfer in porous media under local thermal non-equilibrium (LTNE) condition. In the present model, the thermal non-equilibrium effects are incorporated into the model by adding source terms into the temperature-based MRT-LB equations. The discrete effects of the source terms are eliminated, and the temperatures of the fluid and solid phases are obtained through algebraic operations. Moreover, the error term which exists in the macroscopic temperature equation of the fluid phase is eliminated via a way that is consistent with the philosophy of the LB method. Numerical simulations show that thermal non-equilibrium natural convection problems can be well simulated.

Two-Phase Microscopic Heat Transfer Model for Three-Dimensional Stagnation Boundary-Layer Flow in a Porous Medium

Abstract This work examines the steady three-dimensional forced convective thermal boundary-layer flow of laminar and incompressible fluid in a porous medium. In this analysis, it is assumed that the solid phase and the fluid phase, which is immersed in a porous medium are subjected to local thermal nonequilibrium (LTNE) conditions, which essentially leads to one thermal boundary-layer equation for each phase. Suitable similarity transformations are introduced to reduce the boundary-layer equations into system of nonlinear ordinary differential equations, which are analyzed numerically using an implicit finite difference-based Keller-box method. The numerical results are further confirmed by the asymptotic solution of the same system for large three-dimensionality parameter, and the corresponding results agree well. Our results show that the thickness of boundary layer is always thinner for all permeability parameters tested when compared to the nonporous case. Also, it is noticed that the temperature of solid phase is found to be higher than the corresponding fluid phase for any set of parameters. There is a visible temperature difference in the two phases when the microscopic interphase rate is quite large. The physical hydrodynamics to these parameters is studied in some detail.

Numerical investigation of two-phase flow in a horizontal porous evaporator with localised heating using non-Darcian flow and two equations model

In this article, a new mathematical model, based on the modified enthalpy formulation of Two-Phase Mixture Model (TPMM), is developed by considering non-Darcy flow and Local Thermal Non-Equilibrium (LTNE) conditions to describe numerically the two-dimensional problems of the complete evaporation process inside an asymmetrically heated porous evaporator. The governing equations have been discretised using Finite Volume Method (FVM) on a fixed non-staggered grid layout. The in-house code has been validated against experimental data and the results show good agreement between them. Three different models have been employed for the partitioning of the wall heat flux. Only the effect of the heat flux has been analysed, while all other parameters and properties have been kept fixed during the present investigation. The numerical simulations indicated that the locally high heat flux significantly influences the working fluid flow performances, and lead to extend the superheated vapour region towards the exit of the evaporator. The results also show that the two-phase zone significantly expanded in the axial direction and does not occupy a large portion inside the channel due to the energy transport through the two-phase region is significantly higher in the flow direction as compared to the transverse direction, caused by the decrease in the effective diffusion coefficient in this region and higher axial velocity. Numerical analysis reveal that the different models for the partitioning of the wall heat flux have almost no influence on the overall predictions, except in the vicinity of the wall. The results clearly demonstrate that the numerical simulations with the modified h-formulation by considering non-Darcy law and LTNE model are indispensable for the problem of complete evaporation process, particularly under the high both heat flux and inlet velocity conditions.

Hydraulic and thermal performances of metal foam and pin fin hybrid heat sink

In this study, a metal foam and pin fin hybrid heat sink (MFPFH heat sink) is proposed for thermal management of high powered electronic devices. Thermo-hydraulic performance of MFPFH heat sink is numerically investigated under local thermal non-equilibrium condition, and compared with metal foam (MF) heat sink and traditional pin fin (PF) heat sink. Influences of MF morphological parameters on flow and heat transfer of MFPFH heat sink are analyzed, and the thermal performance ratio is evaluated. Thermal contact resistance between PFs and MF is introduced to explain its effects on the thermal performance of MFPFH heat sink for its practical application. Results indicate that significant heat transfer enhancement is achieved by using the MFPFH heat sink, due to the enhanced heat conduction and the improved heat convection by the common contribution of MF and PFs. Heat transfer characteristics of MFPFH heat sink are more sensitive to foam porosity, and pressure drop to pore size. By simultaneously considering the heat transfer enhancement and flow resistance increase, the thermal performance ratio of MFPFH heat sink is 1.6 times higher than the traditional PF heat sink. When thermal contact resistance is 10−3 m2·K/W, the degradation of average Nusselt number is approximately 36%.

A model of local thermal non-equilibrium during infiltration

A realistic temperature estimation is crucial for many earth-science applications, ranging from hydro-thermal systems to plant physiology. The most common approach to calculate the temperature in multi-phase systems assumes immediate local thermal equilibrium (LTE) between the phases. However, local thermal equilibrium between the phases is not applicable in various scenarios like during the infiltration of rain or melt water in frozen soil, limiting the applicability of the approach and inhibiting the implementation of separate initial and boundary conditions for non-equilibrium situations. In local thermal non-equilibrium (LTNE) models, phase temperatures are described separately to the cost of additional differential equations and an explicitly formulated heat transfer between the phases. Especially a cumbersome parameterization of the explicit heat transfer restricts the use of the LTNE models in multi-phase conditions so far. In this work, we derive a general local thermal non-equilibrium model for dynamic, partly saturated porous media. Heat transfer between the phases is described explicitly using well-known semi-empirical parameterization accounting for velocity changes of the mobile phases. The change in volume fraction introduces an additional term in the heat equation, causing a coupling with the hydraulic model. We validate our model with a numerical simulation of historic experimental data from soil infiltration experiments of warm and cold water into drained soil, posing a perfect example of local thermal non-equilibrium conditions between the phases. Experimentally obtained mixture temperatures are reproduced within experimental accuracy. We further show the benefits of our model by applying it to rainwater infiltration into cold soil. Besides a consistent formulation of initial and boundary conditions, the derived model allows physically based conclusions about the thermal state of the separate phases.

Simulation of heat transfer in a closed-cell porous media under local thermal non-equilibrium condition

Purpose The purpose of this study is to validate whether the local thermal equilibrium for unsteady state is an appropriate assumption for the porous media with closed pores. It also compares the transient temperatures between the pore scale and volume averaged approaches to prove that the volume averaged method is an appropriate technique for the heat transfer in closed-cell porous media. The interfacial heat transfer coefficient for the closed-cell porous media is also discussed in details. Design/methodology/approach The governing equations for the pore scale and continuum domains are given. They are solved numerically for the pore scale and volume-averaged domains. The results are compared and discussion was done. The performed discussions and explanations are supported with figure and graphics. Findings A local thermal non-equilibrium exits for the closed-cell porous media in which voids are filled with water during the unsteady heat transfer process. Local thermal non-equilibrium condition exists in the cells under high temperature gradient and it disappears when the heat transfer process becomes steady-state. Although a local thermal equilibrium exists in the porous media in which the voids are filled with air, a finite value for heat transfer coefficient is found. The thermal diffusivity of air and solid phase are close to each other and hence a local thermal equilibrium exists. Research limitations/implications The study is done only for the closed-cell porous media and for Rayleigh number till 105. Two common working fluids as water and air are considered. Practical implications There are many applications of porous media with closed pores particularly in the industry, such as the closed-cell metal foam or the closed cells in porous materials such as foods and plastic-based insulation material. The obtained results are important for transient heat transfer in closed-cell porous materials. Social implications The obtained results are important from the transient application of heat transfer in the closed-cell material existing in nature and industry. Originality/value The authors’ literature survey shows that it is the first time the closed-cell porous media is discussed from local thermal non-equilibrium point of view and it is proved that the local thermal non-equilibrium can exist in the closed-cell porous media. Hence, two equations as solid and fluid equations should be used for unsteady heat transfer in a closed-cell porous medium.

Analysis of local thermal non-equilibrium condition for unsteady heat transfer in porous media with closed cells: Sparrow number

The local thermal non-equilibrium condition for a porous medium with closed cells under unsteady state heat transfer is analyzed. Although the fluid circulates in the closed pores due to the buoyancy effect, the volume averaged velocity for a closed pore is zero causing excluding of the continuity and momentum equations from the volume averaged governing equations. The volume averaged governing equations are non-dimensionalized by using the equilibrium thermal diffusivity and Sparrow number appears in the dimensionless governing equations automatically. The Sparrow number is interpreted as the equilibrium conduction thermal resistance to the convection thermal resistance for the entire domain. For the high values of Sparrow number (such as 1000), the convection heat transfer resistance is considerably smaller than the heat conduction resistance resulting in high possibility of the local thermal equilibrium. Dimensionless governing equations show that four dimensionless parameters as porosity, Sparrow number, solid (or fluid) dimensionless thermal capacitance and thermal conductivity play important roles on the prediction of the local thermal non-equilibrium state in a closed cell porous medium. A chart for the prediction of local thermal non-equilibrium is presented for Sparrow number of 1, 50, 100 and 500. Furthermore, a pore scale study for a closed cell porous medium with working fluids as water and air is performed. A good agreement between the pore scale and volume averaged results is observed. The obtained pore scale results support the results of the volume averaged parametric study and also the suggested chart for the prediction of local thermal non-equilibrium state.

Analysis of variable porosity, thermal dispersion, and local thermal non-equilibrium on two-phase flow inside porous media

This work involves the numerical simulations of two-phase flow inside porous media and the associated phase change processes in order to investigate the effects of thermal dispersion and variable porosity near the wall boundary. The modified enthalpy formulation has been employed. The mathematical model for the conservation of energy is based on the assumption of Local Thermal Non-Equilibrium (LTNE) condition. The relevant parameters such as free stream porosity, pore diameter, thermal conductivity of the solid phase, heat flux and Reynolds number have been used to analyse the significance of the above mentioned effects. The governing equations have been discretised using the Finite Volume Method (FVM). The developed two-dimensional code has been validated against experimental data, which definitely display that there is a good agreement between them. The numerical results indicated that considering the effects of thermal dispersion and variable porosity is significant, particularly near the heated wall. It is also observed that those two effects become more pronounced for the large values of pore diameter, free stream porosity and Reynolds number. The effect of variations in the free stream porosity, Reynolds number and the pore diameter becomes substantial near the wall when thermal dispersion and variable porosity effects are included, whereas the effect of variations in the heat flux and thermal conductivity of the solid phase have minor influence on the temperature distribution near the heated wall. It is evident that adding the effect of variable porosity and thermal dispersion have significant impact on the initiation and termination of phase change process, especially in the superheated vapour region as compared to the results that obtained by excluding those two effects. In general, it has been found that the present model provides a lower maximum fluid temperature near the wall as compared to that obtained by excluding those effects. Therefore, excluding these effects may lead to inaccurate predictions of two-phase flow with phase change process inside porous media. Most importantly, the thermal dispersion in the transverse direction plays an important role in the dispersion phenomenon inside porous media owing to the thermal boundary layer growth is more dependent on the transverse diffusion as compared to the axial diffusion.

Convective heat transmission inside a porous trapezoidal enclosure occupied by nanofluids: local thermal nonequilibrium conditions for a porous medium

Convective heat transmission inside a porous trapezoidal enclosure occupied by nanofluids: local thermal nonequilibrium conditions for a porous medium

Analytical solutions of fluid flow and heat transfer in a partial porous channel with stress jump and continuity interface conditions using LTNE model

Forced convection heat transfer is analytically performed in a channel partially filled with porous media located at two inner walls under local thermal non-equilibrium (LTNE) condition. A constant heat flux is imposed at the channel walls. The Brinkman extended Darcy model is applied in the porous region and the stress jump and continuity conditions are employed at the interface. Exact solutions are obtained for velocity, pressure drop, the fluid and solid temperatures and Nusselt number. The effects of pertinent parameters on the fluid flow and heat transfer are conducted. Furthermore, the solution for the Nusselt number is compared to that by applying the local thermal equilibrium (LTE) assumption and the validity of the LTE is examined. It is shown that by applying LTNE model for different solid to fluid effective thermal conductivity ratios (K) and Biot numbers (Bi), the variations of Nusselt number with hollow ratio include three types of curves, which are: a maximized Nusselt number occurs at a small optimum hollow ratio, Nusselt number monotonically decreases by increasing hollow ratio and a minimized Nusselt number occurs at a small hollow ratio, respectively. For high K, a small critical value of S at which the Nusselt number reaches to LTE Nusselt number occurs and it lowers with the increase of Bi number and the decrease of Darcy number; while for low K, the LTNE Nu number versus hollow ratio is almost the same with LTE Nu number and therefore the LTE is valid. The stress jump at the interface is found to have negligible effect on the Nusselt number and the pressure drop, except in a high Darcy number with a low stress jump coefficient where the calculation of pressure drop need to account for the stress jump effect at the interface and the Nusselt numbers for both LTE and LTNE models slightly differs from the case of stress continuity interface condition.

MHD natural convection of a micropolar nanofluid flowing inside a radiative porous medium under LTNE condition with an elliptical heat source

The present study deals with MHD (Magnetohydrodynamic) natural convection associated to a micropolar nanofluid flowing in a radiative porous medium. An elliptical heat source is placed in the porous medium. The Darcy model and local thermal non-equilibrium condition are acceptable to simulate the porous medium. KKL model is employed to simulate the nanofluid flow. This model associates the viscosity and thermal conductivity with the temperature and considers the effects of Brownian motions on these two thermos-physical properties. The Galerkin finite element approach is utilized to dissolve the equations. The impacts of governing key parameters are investigated on the streamlines, isotherms of fluid and solid phases, and isolines of micro-rotation as well as the rates of heat transfer. The range of these parameters are Darcy-Rayleigh number Ra = 10–1000, Hartman number Ha = 0–50, nanoparticles volume fraction φ = 0–0.04, interface heat transfer coefficient H = 1–1000, porosity ε = 0.1–0.9, modified thermal conductivity ratio Kr = 0.1–10, vortex viscosity parameter Δ = 0–2 and radiation parameter Rd = 0–2. The results illustrate that the strength of the particles' micro-rotations slightly increases when Rd grows. The increment of porosity increases and decreases the strength of the flow and micro-rotations of the particles, respectively. In addition, an increase in Δ, Ha and ε enhance the total Nusselt number, while a reverse trend can be observed for H, Rd, Kr and Ra.

Investigation of the Local Thermal Nonequilibrium Conditions for a Convective Heat Transfer Flow in an Inclined Square Enclosure Filled with Cu-Water Nanofluid

In this paper, the local thermal nonequilibrium conditions between the base fluid and the nanoparticles inside an inclined square enclosure have been investigated and analyzed numerically. The effects of magnetic field intensity and the geometry inclination angle on the heat exchange between base fluid and nanoparticles are also taken into account. Two opposite walls of the enclosure are insulated, and the other two walls are kept at different temperatures. A PDE solver, Comsol Multiphysics which uses the Galerkin weighted residual finite element technique, has been employed to solve the governing nonlinear dimensionless equations. Comparisons with previously published works are performed, and excellent agreement is obtained. Numerical simulations are accomplished to calculate the dimensionless temperature profiles along lines $$X=0.05$$ and $$Y=X$$ inside the enclosure. A single-phase approach with two temperature equations is applied in this work for the first time. The results indicate that the local thermal nonequilibrium conditions are highly controlled by the Nield number and the nanoparticles volume fraction. The domains at which base fluid and nanoparticles are at local thermal equilibrium or local thermal nonequilibrium have been calculated. These findings may open a door for the researchers to choose the suitable model in analyzing the dynamics of nanofluids and will be helpful in investigating the heat transfer rate based on fluid/particle interface. It will also provide the basis for the future research on the entropy generation investigation during natural convection in order to improve the energy efficiency which may be applicable for different renewable energy systems.

Analysis of thermally developing forced convection heat transfer in a porous medium under local thermal non-equilibrium condition: A circular tube with asymmetric entrance temperature

Thermally developing forced convective heat transfer in a circular tube filled with a fluid-saturated porous medium is analytically investigated under local thermal non-equilibrium (LTNE) condition. In this study, we assume the forced convection within the porous medium obeys Darcy’s law, the tube has a constant temperature wall and possess an entrance with variable circumferential temperature distribution. Under these conditions, closed-form exact solutions of the fluid and solid phases temperatures are derived by using the method of separation of variables. The finite element (FE) analysis software COMSOL Multiphysics is employed to numerically model the studied problem. The good agreement between the presented analytical solutions and the FE solutions verifies the validity of the analytical solutions presented. Meanwhile, the consistency of the axisymmetric analytical solutions in the case of uniform entrance temperature with the existing analytical solutions in the literature confirms again the correctness and the reliability of the presented analytical solutions. Given the entrance temperature can be an arbitrary well-defined function, the presented analytical solutions are of general applicability. The subsequent parametric studies are carried out based on the presented analytical solutions. It is demonstrated that the temperature fields are non-axisymmetrical with respect to the circumferential coordinate, which is induced by the asymmetric entrance temperature. Besides, the Péclet number and the Biot number play significant roles in heat transfer. The increase of the Péclet number will result in the transition of thermally developing forced convection to the fully developed regime, while the temperature difference between the fluid and solid phases decreases with increasing the Biot number. Moreover, as a limiting case, the LTNE model degenerates to the LTE model when the Biot number approaches infinity. Our findings are of benefit to provide deep insights into the thermal behavior of forced convection in a porous circular tube with asymmetric entrance temperature under LTNE condition.

Convective heat transfer in thermally developing flow in micro-channels filled with porous media under local thermal non-equilibrium conditions

Thermally developing flow in microchannels or channels in rarefied gas filled with porous media in slip flow regime is numerically analyzed. A hydrodynamically fully developed and thermally developing flow of a dilute gas in a parallel-plate microchannel filled with porous media is carried out assuming the local thermal non-equilibrium (LTNE) condition for both the fluid and solid phases. The parallel walls are subjected to a constant heat flux.

Numerical investigation on forced convection of tubes partially filled with composite metal foams under local thermal non-equilibrium condition

In the present study, fully developed forced convection in tubes partially filled with composite metal foams (CMFs) is numerically investigated. In the CMF region, the Brinkman extended Darcy flow model and the local thermal non-equilibrium model are used to predict fluid and thermal transport. At the foam-foam interface in CMF, fluid temperature and solid energy are assumed to be continuous. At the foam-fluid interface, no-slip coupling conditions are used to couple flow and heat transfer of the foam and free regions. Governing equations are solved numerically with SIMPLE algorithm. Momentum and energy equations are discretized using the SGSD finite volume scheme for convective terms. Velocity distribution, temperature profile, the friction factor and Nusselt number in partially-filled CMF tubes are obtained. The results indicate that, porosity gradient has little effect on the friction factor at a low pore density, but the effect increases with increasing pore density. For the fixed pore density gradient, Nusselt number decreases with increasing porosity, and Nusselt number firstly increases sharply and then increases lineally with increasing Reynolds number. For the fixed material gradient, Nusselt number increases lineally with increasing Reynolds number.

Effect of geometrical parameters on natural convection in a porous undulant-wall enclosure saturated by a nanofluid using Buongiorno's model

The paper refers to investigate the effect of geometrical parameters on natural convection of nanofluid over a cylindrical heater located inside of a porous undulant-wall cavity using local thermal non-equilibrium (LTNE) condition. Two phase-Buongiorno's model was applied to consider the thermal and flow indexes under geometrical variations. The validity of the numerical procedure was examined by contrasting the present and the previous works. The effect of governing parameters of the cavity, including horizontal and vertical displacement of cylindrical heat source (x and y respectively), the amplitude of the lateral wave walls (λ) on streamlines, isotherms of two porous medium phases and also concentration of nanoparticles has been inquired. Overall, the results show that temperature distribution is different for the two phases in the porous medium, making it inevitable to utilize the non-equilibrium model for porous media. It is obvious that the flow is weakened as the heat source is elevated, while by the horizontal deviation of the flow toward a certain direction, it becomes stronger in the region opposite to the deviation and weakened at the deviated side. When the cylindrical heat source is located at the bottom of the cavity, the nanofluid becomes more homogeneous as a result of the agitation by strong vortices. As the corrugation amplitude of the lateral walls is increased, the nanofluid flow becomes stronger, leading to a more uniform distribution of nanoparticles around the cavity. At lower corrugation amplitudes, the average Nusselt number of the fluid is reduced as the heater is elevated. On the other hand, at higher amplitudes, the variations of the average Nusselt number of the fluid shows an increasing-decreasing trend as the cylinder is elevated.

Thermal dispersion effects on heat transfer of laminar gas flow in a microtube filled with porous medium

In this paper, dispersion effects on forced convection heat transfer in a gaseous slip flow through a microtube filled with anisotropic porous medium are investigated semi-numerically. Microtube is subjected to constant heat flux and a local thermal non-equilibrium condition is assumed. Rarefaction effects are taken into account by applying first-order velocity slip and temperature jump boundary conditions. Dispersion is proven to have a significant impact on heat transfer in rarefied gases. Temperature distributions for both solid and fluid phases are obtained. Nusselt number variation with respect to porous shape factor and Biot number is illustrated, indicating enhancement up to 10% in predicted heat transfer due to dispersion. The influence of Reynolds number on thermal dispersion is proven to be insignificant. Dispersion plays a significant role as gas becomes more rarefied. It is seen that an increase in shape factor of a porous media can improve Nu for a non-rarefied gas, but as rarefaction effects grow, this can affect heat transfer negatively. Also, effects of dispersion on heat transfer diminishes for higher values of Biot Number due to the overcoming of interstitial heat transfer to thermal dispersion effect.

A thermal non-equilibrium model for 3D double diffusive convection of power-law fluids with chemical reaction in the porous medium

The article reports a numerical study of the double-diffusive natural convection of power-law fluids in a porous cubic cavity with chemical reaction under the local thermal non-equilibrium (LTNE) state and submitted to horizontal temperature and concentration gradients. The complete governing equations, in which the generalized non-Darcy model is employed as momentum equation and a two-temperature model that represents temperature fields of the fluid and solid phases separately is used for energy equation, are solved by the compact high order finite volume method. Special attentions are given to detecting the effects of the porosity modified conductivity ratio (γ), the inter-phase heat transfer coefficient (H), the chemical reaction parameter (λ), the Dufour parameter (Du), the Soret parameter (Sr) and the Lewis number (Le) on the fluid flow as well as on rates of heat and mass transfer. Our simulations show that the heat transfer rate of solid increases, while the heat transfer rate of fluid and mass transfer rate keep constants, as the LTNE parameters (i.e., γ and H) increase. For any relatively large value of γ and H, the almost thermal equilibrium state is achieved due to the similar thermal distribution of fluid and solid phases. On the contrary, the chemical reaction parameter has significant influence on mass transfer than on heat transfer under the LTNE conditions. In addition, the heat and mass transfer enhance with the increment of the Soret and Dufour parameters. Augmentation of Lewis number enhances mass transfer but reduces heat transfer. Apart from that, our numerical tests show the flow field is influenced appreciably by the presence of the power-law index (n), Darcy number (Da) and porous thermal Rayleigh number (Ra).