Double-diffusive Natural Convection Research Articles

Enhanced Efficiency of MHD-Driven Double-Diffusive Natural Convection in Ternary Hybrid Nanofluid-Filled Quadrantal Enclosure: A Numerical Study

The study investigates the performance of fluid flow, thermal, and mass transport within a cavity, highlighting its application in various engineering sectors like nuclear reactors and solar collectors. Currently, the focus is on enhancing heat and mass transfer through the use of ternary hybrid nanofluid. Motivated by this, our research delves into the efficiency of double-diffusive natural convective (DDNC) flow, heat, and mass transfer of a ternary hybrid nanosuspension (a mixture of Cu-CuO-Al2O3 in water) in a quadrantal enclosure. The enclosure’s lower wall is set to high temperatures and concentrations (Th and Ch), while the vertical wall is kept at lower levels (Tc and Cc). The curved wall is thermally insulated, with no temperature or concentration gradients. We utilize the finite element method, a distinguished numerical approach, to solve the dimensionless partial differential equations governing the system. Our analysis examines the effects of nanoparticle volume fraction, Rayleigh number, Hartmann number, and Lewis number on flow and thermal patterns, assessed through Nusselt and Sherwood numbers using streamlines, isotherms, isoconcentration, and other appropriate representations. The results show that ternary hybrid nanofluid outperforms both nanofluid and hybrid nanofluid, exhibiting a more substantial enhancement in heat transfer efficiency with increasing volume concentration of nanoparticles.

Influence of location of twin-adiabatic blocks on magnetohydrodynamics-based double-diffusive convection and entropy generation for a liquid metal

This research deals with a rectangular cavity encompassing two adiabatic rectangular and impermeable obstacles at various positions. This study serves as a platform to explore the interplay between diverse flow-governing parameters, such as the buoyancy ratio (N = −1, 0, and +1), Hartmann number (Ha = 0, 50, and 100), Lewis number (Le = 1, 5, and 10), Rayleigh number (Ra = 103 and 104), and geometric arrangements of twin-blocks (C1, C2, and C3) to help in developing insights into such complex transport phenomenon driven under the influence of buoyancy and concentration. The arrangements are chosen such that C1 and C3 represent the off-center position of the first obstacle, while C2 represents the in-line position with the second obstacle. The influence of liquid sodium–potassium alloy (Pr = 0.054) on fluid flow, heat, and mass transfer, and entropy generation characteristics due to double-diffusive natural convection in the twin obstacle-filled rectangular enclosure are observed using the lattice Boltzmann method. The results reveal that the maximum amount of heat and mass transfer occurs at the C2 position, making it the most efficient for heat and mass transfer among all. In contrast, the C2 configuration is a thermodynamically inefficient arrangement as entropy generation is maximum, while the C3 configuration is obtained to be more efficient thermodynamically. Furthermore, the results reveal that the average total entropy generation is directly related to the Lewis number, while it has an inverse relation with the Hartmann number.

Expression of Concern: Lattice-Boltzmann numerical simulation of double-diffusive natural convection and entropy generation in an n-shaped partially heated storage tank

Expression of Concern: Lattice-Boltzmann numerical simulation of double-diffusive natural convection and entropy generation in an n-shaped partially heated storage tank

Investigating double-diffusive natural convection in a sloped dual-layered homogenous porous-fluid square cavity

This article investigates natural convection with double-diffusive properties numerically in a vertical bi-layered square enclosure. The cavity has two parts: one part is an isotropic and homogeneous porous along the wall, and an adjacent part is an aqueous fluid. Adiabatic, impermeable horizontal walls and constant and uniform temperatures and concentrations on other walls are maintained. To solve the governing equations, the finite element method (FEM) employed and predicted results shows the impact of typical elements of convection on double diffusion, namely the porosity thickness, cavity rotation angle, and thermal conductivity ratio. Different Darcy and Rayleigh numbers effects on heat transfer conditions were investigated, and the Nusselt number in the border of two layers was obtained. The expected results, presented as temperature field (isothermal lines) and velocity behavior in X and Y directions, show the different effects of the aforementioned parameters on double diffusion convective heat transfer. Also results show that with the increase in the thickness of the porous layer, the Nusselt number decreases, but at a thickness higher than 0.8, we will see an increase in the Nusselt number. Increasing the thermal conductivity ratio in values less than one leads to a decrease in the average Nusselt number, and by increasing that parameter from 1 to 10, the Nusselt values increase. A higher rotational angle of the cavity reduces the thermosolutal convective heat transfer, and increasing the Rayleigh and Darcy numbers, increases Nusselt. These results confirm that the findings obtained from the Finite Element Method (FEM), which is the main idea of this research, are in good agreement with previous studies that have been done with other numerical methods.

Numerical Investigation of Double-Diffusive Convection in an Irregular Porous Cavity Subjected to Inclined Magnetic Field Using Finite Element Method

Purpose—This study aims to perform an in-depth analysis of double-diffusive natural convection (DDNC) in an irregularly shaped porous cavity. We investigate the convective heat transfer process induced by the lower wall treated as a heat source while the side walls of the enclosure are maintained at a lower temperature and concentration, and the remaining wall is adiabatic. Various factors, such as the Rayleigh number, Darcy effects, Hartmann number, Lewis number and effects of magnetic inclination are evaluated for their influence on flow dynamics and heat distribution. Design/methodology/approach—After validating the results, the FEM (finite element method) is used to simulate the flow pattern, temperature variations, and concentration by solving the nonlinear partial differential equations with the modified Rayleigh number (104 ≤ Ra ≤ 107), Darcy number (10−4 ≤ Da ≤ 10−1), Lewis number (0.1≤Le≤10), and Hartmann number 0≤Ha≤40 as the dimensionless operating parameters. Findings—The finding shows that the patterns of convection and the shape of the isotherms within porous enclosures are notably affected by the angle of the applied magnetic field. This study enhances our understanding of how double-diffusive natural convection (DDNC) operates in these enclosures, which helps improve heating and cooling technologies in various engineering fields. Research limitations/implications—Numerical and experimental extensions of the present study make it possible to investigate differences in thermal performance as a result of various curvatures, orientations, boundary conditions, and the use of three-dimensional analysis and other working fluids. Practical implications—The geometry configurations used in this study have wide-ranging applications in engineering fields, such as in heat exchangers, crystallization, microelectronics, energy storage, mixing, food processing, and biomedical systems. Originality/value—This study shows how an inclined magnetic field affects double-diffusive natural convection (DDNC) within a porous system featuring an irregularly shaped cavity, considering various multiphysical conditions.

Computational study of double diffusive MHD natural convection flow of non-Newtonian fluid between concentric cylinders

This study investigated double diffusion natural convection of Casson fluids in an asymmetrical cavity under a constant magnetic field. The intricacies of flow and heat/mass transfer were explored computationally using the finite element method. With applications in fields such as geology, oceanography, metallurgy, and astrophysics, it investigates the impact of key parameters like the Rayleigh number, Casson parameter, buoyancy ratio, Hartmann number, and Darcy number on entropy generation, fluid velocity, and temperature/concentration gradients. The findings illustrate that increasing the Rayleigh number enhances convection and entropy, while a higher Casson parameter leads to reduced mixing due to the fluid's more solid-like behavior. Enhancing the buoyancy ratio improves heat and mass transfer, and a greater Darcy number boosts convection efficiency. Additionally, a higher Hartmann number reduces fluid friction but increases mass diffusion and magnetic disorder, subtly improving thermodynamic efficiency. This research offers valuable insights for optimizing heat transfer and energy efficiency in high-temperature industrial processes, contributing to advancements in sustainability and energy utilization.

Enhancing thermal performance: A numerical study of MHD double diffusive natural convection in a hybrid nanofluid-filled quadrantal enclosure

Enhancing thermal performance: A numerical study of MHD double diffusive natural convection in a hybrid nanofluid-filled quadrantal enclosure

Enhancing the convective heat transfer in vertical and horizontal rectangular enclosures using nanofluids: The crucial role of aspect ratio

This study extensively examines double-diffusive natural convection of a water nanofluid containing Al2O3 nanoparticles in both horizontal and vertical rectangular enclosures subjected to uniform thermal and solutal fluxes along the horizontal direction. The key contribution of this research is to emphasize the significance of aspect ratio as a critical factor for enhancing heat transfer. Neglecting this factor could have substantial implications for the advancement and practical application of nanotechnology in heat transfer. The study also examines the impact of other relevant parameters namely nanoparticle concentration, thermal Rayleigh number, and three distinct models to calculate effective viscosity and thermal conductivity. A comparison among these models highlights a notable disparity between models based on experimental data (model II and III) and that based on theoretical assumptions (model I). It was revealed that the thermal Rayleigh number manifests a notable impact on both heat and mass transfers, especially for horizontal enclosures, and an augmentation in the aspect ratio improves the convective heat and mass transfers. However, for lower Rayleigh numbers, the aspect ratio effect diminishes. The incorporation of nanoparticles might deteriorate up to 21% or enhance up to 12% heat transfer according to the dominant transfer mode, we obtain the enhancement in conduction and deterioration in convection. Model I gives higher Nusselt and Sherwood numbers, followed by models II and III, but model I showed a peculiar behavior compared to models II and III. A critical aspect ratio is identified which defines the regions where nanofluid enhances heat transfer compared with clear water.

Numerical analysis of double-diffusive natural convective flow of Ostwald-de Waele fluid in an irregular enclosure with a circular obstacle

PurposeThe current study aims to enhance the double diffusive natural convection in an Ostwald-de Waele fluid filled in a hexagonal enclosures using non-uniform magnetic field embedded with circular obstacle. The upper wall has maximum temperature Th∗ and concentration (Ch∗) whereas the lower wall is kept at minimum temperature Tc∗ and concentration Cc∗. The parameters that play a significant role in the heat and mass transfer are evaluated, including Hartmann number, power law index, Rayleigh number and buoyancy ratio. Design/Methodology/approachIn two-dimensions, the governing formulation is written as a set of balancing equations for velocities, pressures, energies and concentrations. The nonlinear governing PDEs are solved using numerical approach based on Finite Element Method (FEM). The discretization is performed using the stable finite element pair ℘2/℘1. Code validation and results are ensured by conducting a grid convergence and comparison test respectively. FindingsThe influence of flow on velocity, isotherms and iso-concentration field is examined by analyzing a broad variety of variables such as power-law index 0.7≤n≤1.2, Hartmann number 0≤Ha≤50, Rayleigh number 104≤Ra≤106, inclination angle 0°≤γ≤90° and buoyancy ratio -2≤N≤2. The findings are displayed graphically, including the flow, temperature and concentration fields. Heat and mass transfer rates are maximum for shear thinning fluids while for shear thickening fluids it reduces, whereas it is maximum for concentration dominated assistant flow and minimum for concentration dominant counter flow. ApplicationThe novel aspects of the research include its thorough examination of solar thermal power conversion and its inventive energy deficiency devices and a wide range of electrical design applications.

Second law and thermal analyses of non-Newtonian nanofluid double-diffusive natural convection within a two-hot-baffles-equipped C-shaped domain impacted by magnetic field

PurposeThe entropy and thermal behavior analyses of non-Newtonian nanofluid double-diffusive natural convection inside complex domains may captivate a bunch of scholars’ attention because of the potential utilizations that they possess in modern industries, for example, heat exchangers, solar energy collectors and cooling of electronic apparatuses. This study aims to investigate the second law and thermal behavior of non-Newtonian double-diffusive natural convection (DDNC) of Al2O3-H2O nanofluid within a C-shaped cavity emplacing two hot baffles and impacted by a magnetic field.Design/methodology/approachFor the governing equations of the complicated and practical system with all considered parameters to be solved via a formidable numerical approach, the finite element method acts as an approach to achieving the desired solution. This method allows us to gain a detailed solution to the studied geometry.FindingsThis investigation has been executed for the considered parameters of range, such as power-law index, baffle length, Lewis number, buoyancy ratio, Hartmann number and Rayleigh number. The main results reveal that isothermal and concentration lines are significantly more distorted, indicating intensified concentration and temperature distributions because of the growth of baffle length (L). Nuave decreases by 8.4% and 0.8% while it enhances by 49.86% and 33.87%, respectively, because of growth in the L from 0.1 to 0.2 and 0.2 to 0.3.Originality/valueSuch a comprehensive study on the second law and thermal behavior of DDNC of Al2O3-H2O nanofluid within a C-shaped cavity emplacing two hot baffles and impacted by magnetic field has not yet been carried out.

Multiple-Relaxation-Time Lattice Boltzmann Simulation of Soret and Dufour Effects on the Thermosolutal Natural Convection of a Nanofluid in a U-Shaped Porous Enclosure

This article reports an investigation of the Soret and Dufour effects on the double-diffusive natural convection of Al2O3-H2O nanofluids in a U-shaped porous enclosure. Numerical problems were resolved using the multiple-relaxation-time (MRT) lattice Boltzmann method (LBM). The indented part of the U-shape was cold, and the right and left walls were heated, while the bottom and upper walls were adiabatic. The experimental data-based temperature and nanoparticle size-dependent correlations for the Al2O3-water nanofluids are used here. The benchmark results thoroughly validate the graphics process unit (GPU) based in-house compute unified device architecture (CUDA) C/C++ code. Numeral simulations were performed for a variety of dimensionless variables, including the Rayleigh number, (Ra = 104,105,106), the Darcy number, (Da = 10−2,10−3,10−4), the Soret number, (Sr = 0.0,0.1,0.2), the Dufour number, (Df = 0.0,0.1,0.2), the buoyancy ratio, (−2≤Br≤2), the Lewis number, (Le = 1,3,5), the volume fraction, (0≤ϕ≤0.04), and the porosity, ϵ = (0.2−0.8), and the Prandtl number, Pr = 6.2 (water) is fixed to represent the base fluid. The numerical results are presented in terms of streamlines, isotherms, isoconcentrations, temperature, velocity, mean Nusselt number, mean Sherwood number, entropy generation, and statistical analysis using a response surface methodology (RSM). The investigation found that fluid mobility was enhanced as the Ra number and buoyancy force increased. The isoconcentrations and isotherm density close to the heated wall increased when the buoyancy force shifted from a negative magnitude to a positive one. The local Nu increased as the Rayleigh number increased but reduced as the volume fraction augmented. Furthermore, the mean Nu (Nu¯) decreased by 3.12% and 6.81% and the Sh¯ increased by 83.17% and 117.91% with rising Lewis number for (Ra=105 and Da=10−3) and (Ra=106 and Da=10−4), respectively. Finally, the Br and Sr demonstrated positive sensitivity, and the Ra and ϕ showed negative sensitivity only for higher values of ϕ based on the RSM.

Thermal analysis of transverse fluid flow in a gradient porous media with the exponentially boundary conditions

In this study, a numerical investigation was conducted on the thermal analysis of transverse fluid flow in a gradient porous medium with exponential boundary conditions. By solving a two-dimensional system of dimensionless equations using the Newton–Raphson method and Galerkin finite element technique, the authors studied the effects of cross-diffusion on double-diffusive natural convection in shells. The simulation results for isoconcentrations, isotherms, and stream functions were analyzed for different flow parameters, and it was found that the mean Dufour and Soret numbers were more susceptible to cross-diffusion impacts. The researchers also found that altering the tilt angle of the trapezoidal enclosure can significantly impact flow circulation and temperature gradient, which has important implications for thermal energy control in different technical appliances. This study provides valuable insights into the thermal behavior of fluid flow in porous media, which can aid in the development of more efficient and effective thermal systems.

Significance of a permeable semi-circular body and magnetic field on the double-diffusive traits

This study delves into the occurrence of double-diffusive natural convection while being affected by a magnetic field within a cold square enclosure, containing a heated and concentrated semi-circular body made permeable. The fusion of both flat and curved boundaries, combined with the permeable attributes, stands as the central impetus driving this inquiry. The main aim is to scrutinize the impact of buoyancy force, permeability, magnetic field strength, and angle on the double-diffusive convection taking place inside and around the permeable structure. To achieve this, a comprehensive parametric investigation is undertaken, emphasizing the importance of Darcy number (Da), buoyancy ratio (BR), Hartmann number (Ha), and magnetic field angle (γM) in relation to the flow, heat, and concentration transfer. We utilize the Lattice Boltzmann method, incorporating the Darcy-Brinkmann-Forchheimer equation as a source term, to precisely address the complex flow within the porous medium. The results will provide insights into the importance of a semi-circular body with porous characteristics in the context of thermo-solutal convection influenced by magnetic effects. These findings hold practical significance in various applications, including electronic cooling, pollutant removal, and food processing industries. The inquiry discloses that elevating the buoyancy force, permeability, and the angle of the magnetic field leads to advantageous heat and concentration characteristics. Furthermore, positioning the magnetic force in opposition to gravity reduces the restraining impact of the magnetic force on the mean Nusselt number (NuM) and the mean Sherwood number (ShM). Remarkably, instances of unsteady behaviour are predominantly noted when the BR takes on a negative value, and these phenomena’s intensity and frequency are heightened by the Da and the γM. Remarkably, there are a few irregular spikes detected in the NuM and ShM, which can be attributed to the emergence of a strong singular vortex in the upper part of the enclosure.

Bifurcation analysis of combined double-diffusive natural convection and thermal radiation under a non-uniform magnetic field in a wavy enclosure

In the current work, the bifurcation phenomenon of a double-diffusive natural convection flow is analyzed for a non-uniform magnetic field applied to a wavy enclosure in the presence of radiation, for the first time. The finite volume method has been utilized to simulate volumetric radiation. To solve the continuity, momentum, energy, and species equations, the multiple-time relaxation lattice Boltzmann technique is adopted. In addition, the immersed boundary approach has been applied to identify the complex boundaries inside the Cartesian coordinates system. The effects of specific pertinent parameters, including the optical thickness (0.1≤τ≤100), Buoyancy ratio (-5≤N≤5), Rayleigh number (104≤Ra≤105), wave amplitude (0≤λ≤0.2), and Hartmann number (0≤Ha≤50) on thermohydrodynamic characteristics of the system have been investigated. The results indicated that an increase in Hartmann number disappears the bifurcation phenomenon. In addition, it was observed that the initial condition of hot temperature and high concentration leads to instability in the flow. In the radiation case for λ>0.1, 5<τ<30, and 15≤Ha≤30, the flow appears unsteady. Bifurcation occurs in all values of wavy amplitude, and optical thickness studied. Heat and mass transfers decrease when the initial condition is cold temperature and low concentration. Also, Radiation does not affect the critical Rayleigh number.

Impact of Inclined Magnetic Field of Casson Fluid on Double Diffusive Natural Convection in a Curvilinear Enclosure

In this paper, the Casson fluid model and the inclined magnetic field are used to analyse mathematically the energy transport of double diffusive natural convection (DDNC) in a curvilinear enclosure. The Galerkin finite element method (GFEM) is used to discretize the equations. When simulating the different ranges of Rayleigh numbers (105 ≤ Ra ≤ 108) and the heated part, we adopt isotherms and streamlines to visualize the thermal and flow fields. In addition, we study the impact of the Casson parameter on the Nusselt number along the cavity wall. The results show that the lower values of Casson fluid parameter have a significant effect on the Nusselt number in the middle of the cavity. Finally, the results are verified with the existing studies, and various parameters such as streamline, isotherm, isoconcentration contour and kinetic energy are presented in the form of graphs and tabular formats.

Spatial–temporal analysis of magnetohydrodynamics flow and energy flux of power-law nanofluid in a confined domain

Energy flux analysis of power-law fluid is a novel contribution to recent developments in computational fluid dynamics. The study of the unsteady two-dimensional flow with double diffusive effect inside a complex enclosure exhibits great potential in optimizing the heat transfer rate due to the wavy nature of the side walls. The enclosure is confined with the flow circulation due to the thermal and solutal gradients acting along the left and right wavy walls. The computational time and accuracy in results are estimated and compared by implementing the finite volume method and element-free Galerkin technique. The results are obtained in terms of streamlines, isotherms, isoconcentrations, average Nusselt number, Sherwood number, and total entropy generation due to the effect of conventional parameters, namely, power-law index, Rayleigh number, buoyancy ratio parameter, thermophoresis parameter, Brownian motion parameter, and Lewis number with a fixed Prandtl number throughout the computation. The optimized double-diffusive natural convection analysis is based on entropy generation and a calculated Bejan number. The novelty of this paper lies in the implementation of a mesh-free approach, which may be useful for the further analysis of elliptical/semi-elliptical structures.

Effect of a Sinusoidal Temperature Profile on Entropy Generation Due to Double-Diffusive Natural Convection in a Square Partly Porous Cavity

Abstract In this paper, entropy generation due to double-diffusive natural convection inside a partly porous enclosure under sinusoidal wall heating is numerically analyzed. The resulting dimensionless coupled partial differential equations are discretized using the finite volume method (FVM), while the pressure–velocity coupling is handled using the SIMPLE algorithm. To ensure the validity of the results obtained from the in-house FORTRAN code, a comparison is made with previous numerical and experimental works. The results of the study indicate that the dimensionless thickness of the porous layer (Δ), the thermal conductivity ratio (Rk), the angle of inclination of the cavity (α), and the buoyancy ratio (N) are critical factors in determining local distribution and global maximum value of entropy generation due to heat transfer and fluid friction. In contrast, their effect on entropy generation induced by concentration is insignificant, except for the buoyancy ratio parameter, where an enhancement of the global maximum of entropy generation is observed by increasing N. Moreover, it is found that Sψ (max) experiences a sharp decline as Δ varies from 0.2 to 0.8, resulting in a reduction of about 67% for the case with N=10 and 83% for the case with N=1. These results highlight the importance of carefully controlling system parameters to minimize energy losses and maximize system efficiency in heat transfer and fluid flow systems.

Numerical Analysis of Entropy Generation in a Double Stage Triangular Solar Still Using CNT-Nanofluid under Double-Diffusive Natural Convection

The analysis of entropy generation provides valuable information for the design and optimization of thermal systems. Solar stills are used for water desalination and purification. Using renewable energies, they provide a sustainable solution for drinking water supply in remote areas and off-grid situations. This work focuses on the 3D numerical study of entropy generation in a two-stage solar still subjected to the natural double diffusion convection phenomenon in the presence of CNT nanoparticles. The effects of Rayleigh number, buoyancy ratio, and nanofluid concentration on thermal, solutal, and viscous irreversibilities and flow structure were studied. The results show that increasing the buoyancy ratio leads to an increase in thermal and solutal entropy generation. The results of this study also show that total entropy is minimal for positive volume force ratios, N, at a nanoparticle volume fraction of around 3%, and for negative N ratios, at a volume fraction of around 4%.

Entropy optimization of MHD non-Newtonian fluid in a wavy enclosure with double diffusive natural convection

This study investigates the impact of an inclined magnetic field (MHD) on entropy generation in double diffusive natural convective flow in a wavy enclosure filled with a non-Newtonian Casson fluid. The Galerkin Finite Element Method (GFEM) is employed to numerically solve the standard formulation, utilizing quadratic polynomials for momentum interpolation and a linear interpolating function for model approximation. The discretized system is resolved using Newton’s approach and PARDISO's matrix factorization. Through simulations of varying ranges of Rayleigh numbers Casson parameter Hartmann numbers Lewis numbers and inclined angle gamma the study provides valuable insights into the behavior of double diffusive natural convection in the wavy enclosure. Isotherms, iso-concentration contours, and streamlines are analyzed to assess different input distributions, and the study presents graphical representations and tabular data on heat transfer, mass transfer rate, and entropy production.

Thermal investigation of nanofluid-filled hexagonal fillet cavity under the influence of heated and concentered cylinder

The incorporation of nanoparticles is very advantageous to address the challenges of heat transmission in numerous industrial frameworks. Double-diffusive Natural Convection (DDNC) is a key component of large-scale industrial manufacturing processes, including chemical processing, heat exchangers, and cooling systems. Understanding and optimizing DDNC can enhance process efficiency, reduce energy consumption, and improve product quality. The prime motive of current disquisition is to explicate enhancement in thermal attributes of ordinary water by adding MWCNT's saturated in hexagonal enclosure. A circular heated and concentrated cylinder is placed at the center to generate optimize thermal and concentration gradients. Additionally, magnetic field of uniform strength is applied horizontally to the domain. Problem formulation containing thermophysical relation of inducted nanoparticles are well established and solved numerically by finite element method. Outcomes of involved sundry parameters like, Rayleigh, Hartmann, Lewis numbers are displayed through snapshots. Through observation, it has been noted that the velocity field demonstrates a rising trend in the hydrodynamic case (Ha=0) in contrast to the hydromagnetic case (Ha≠0), as indicated by the stream function's magnitude. More specifically, the maximum value of 〖| |ψ|max reaches 9.8 in the absence of a magnetic field, while it decreases to 3.8 when a magnetic field is present.