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AbstractThe utilization of molten salts in heat transfer applications, specifically within shell-and-tube heat exchangers, has garnered significant attention for its potential in sustainable energy solutions. this study employs advanced machine learning algorithms, including decision tree regressor, support vector regressor, extreme gradient boosting, and random forest, to not only predict the heat transfer behavior of molten salts but also unravel the complex mechanisms underlying this process. Achieving a remarkable accuracy score of 0.985, the Support Vector Regressor leads the predictive models, closely followed by random forest (0.982), Decision Tree Regressor (0.974), and Extreme Gradient Boosting (0.965). The incorporation of Shapley Additive exPlanations values accentuates the Reynolds number’s pivotal role, elucidating a robust correlation with the Nusselt value. These insights transcend mere prediction, offering a profound understanding that can significantly impact the design and optimization of molten salt heat exchangers. The applications of molten salts extend across various sectors, including concentrated solar energy and thermal storage, solidifying their position as a versatile and effective solution in the pursuit of sustainable and efficient energy systems. [ABSTRACT FROM AUTHOR]

AbstractThis study underscores the critical role of heat transfer modeling in the design and optimization of heat exchangers, recognizing the challenges posed by traditional numerical methods. To address the need for more efficient alternatives, machine learning emerges as a promising solution, leveraging its capacity to unravel intricate relationships in heat transfer processes. The research focuses on forced convection heat transfer involving nanoparticles (specifically TiO2, Al2O3, and Cu) dispersed in water, employing the Lagrangian–Eulerian approach under turbulent flow conditions with a constant surface heat flux. Machine-learning techniques, namely extreme gradient boosting, support vector regression, and tree regression are employed to predict heat transfer outcomes based on collected data. The achieved results exhibit promising accuracy levels, with eXtreme gradient boosting, support vector regression, and tree regression algorithm models demonstrating impressive accuracies of 91%, 91%, and 94%, respectively. The mean absolute errors for these machine-learning models were recorded as 1.07, 7.24, and 3.74. This research serves as a demonstration of the potential of machine-learning methodologies in modeling complex physical systems, as evidenced by their efficiency in capturing the behavior of nanofluids under various conditions. The obtained accuracy and low mean absolute error values indicate the robustness of these machine-learning models in predicting heat transfer results. The implications of these findings are substantial for the field of heat exchanger design and optimization. The study suggests that machine-learning techniques offer a more efficient and cost-effective approach compared to traditional numerical simulations. By leveraging the capabilities of these models, there is potential for enhanced accuracy and efficiency in the design and optimization processes of heat exchangers, contributing to advancements in thermal engineering. [ABSTRACT FROM AUTHOR]

AbstractThis study presents a new model for effective thermal management of a channel with elastic sinusoidal obstacles and pulsating multiple nano-jet impingements. The channel was cooled by alumina Al2O3 in various forms (platelets, blades, cylinders, and bricks) and water as a basic fluid. A hybrid nanofluid (multi-wall carbon nanotube-Fe3O4) was also used. The governing equations were solved using the finite volume method. Results were recorded for Reynolds numbers (Re = 350), Strouhal numbers (St = 0.01–1), pulse amplitude (A = 0.25–1), and the number of slots (Nj = 1–13). The results showed that the cooling efficiency was improved by using pulsating flow by 24.383%. It was also noted that using sinusoidal elastic obstacles improved the heat transfer rate by 8.344%. In addition, the number of slots affected the heat transfer rate, increasing it to 259.983%. The results obtained from this study demonstrate the effectiveness of the proposed design, which incorporates elastic sinusoidal obstacles and pulsating multiple nano-jet impingements, in significantly improving thermal management performance and reliability. These advancements hold great importance in various industrial and consumer applications. [ABSTRACT FROM AUTHOR]

An attempt is made to improve the overall performances of channel heat exchangers. The techniques of baffles and nanofluids are combined to enhance the dynamic and thermal behaviors within the channel exchanger. Baffles under various attack angles are used as vortex generators. In addition, oil/multiwalled carbon nanotubes (MWCNT) is used as a working fluid. Both inclinations in the upstream and downstream directions were considered, referenced as Case A (UIB) and Case B (BIB), respectively. While the channel equipped with vertical baffles is referenced as Case C. The proposed models with combined techniques allowed a considerable enhancement in the overall efficiency. The comparison between the three cases revealed that the most significant value of thermal enhancement factor (TEF) of 5.634 was reached with vertical baffles (Case C) at the highest value of Reynolds number. When using inclined baffles, the 75° upstream attack angle (Case A) allowed the highest TEF of 4.814, compared with Case B. [ABSTRACT FROM AUTHOR]

The thermal radiation and convective condition principles were working on specific functions like gas turbines, electrical fuel, renewable energy, projectiles, nuclear power plants, aerospace engineering, and thermal transportation. Considering the aforementioned functions, the present analysis inspected the stagnation point hybrid nanofluids movement over the rotating sphere on the behavior of viscous dissipation and thermal radiation. Silver and Ferrous nanoparticles including the host fluid water were held into affected the flow. The presence of convective boundary conditions is incorporated within the system. Applying appropriate correspondence factors, nonlinear governing equations were transformed with ordinary differential equations. This finite element method is applied to find the mathematical solutions to the boundary conditions and simplified equations. These outcomes convey to temperature was decreased about accelerated factor, although primary velocity was found into increased. The heat transfer was magnified by thermal Biot number, and that rate of development was greater about hybrid nanosuspension. The heat transport method was reduced by the Eckert number; also that reduction rate was similarly dull on hybrid. [ABSTRACT FROM AUTHOR]

The problem of natural convection in an eccentric annulus between two horizontal cylinders filled with Cu–Al2O3/water hybrid nanofluids is investigated numerically in this paper. The inner cylinder wall is heated at a uniform temperature whereas the outer wall is kept isothermally cooled. The basic equations that govern the problem are formulated in the bipolar coordinates and written in terms of the vorticity-stream function equations using the dimensionless form for the bidimensional, laminar, and incompressible flow under steady-state conditions. The dimensionless equations are discretized using the finite-volume method and solved by a FORTRAN program. A numerical parametric study is performed for an annulus filled with regular water, Al2O3/water nanofluid, and Cu–Al2O3/water hybrid nanofluid for various volume fractions of nanoparticles and hybrid nanoparticles (0 ≤ ϕ ≤0.12) and Rayleigh numbers (103 ≤ Ra ≤ 106). It is found that employing a Cu–Al2O3/water hybrid nanofluid provides a better thermal and dynamic performance compared with the similar Al2O3/water nanofluid. [ABSTRACT FROM PUBLISHER]

Abstract The interfacial nanolayer is a tinny coating of liquid molecules convened around the immersed solid nanoparticles in the base liquid which plays a vital role to control the flow and improve the thermophysical properties of the fluid. Features are more prominent for hybrid nanomaterials. Hence, the present analysis deals with the concomitant effects of an interfacial nanolayer of nanomaterials MWCNT and Ag during a viscous Darcy Forchheimer flow over a moving needle. Thermal radiation, Joule heating, and viscous dissipations concerning the Cattaneo-Christov thermosolutal flux have been introduced. An appropriate transition is applied to rationalize the substantially paired and nonlinear governing equations. Equations after similarity transformation are processed by the finite element method. The impression of different governing parameters on the governing systems in conjunction with entropy and Bejan number is displayed through graphs and tables. Graphs are drawn with an evaluation of general and hybrid nanofluids and different nanolayer thicknesses of nanoparticles. A similarity feature concerns existing literature with good promise. The thermal impact is more significant with the occurrence of Cattaneo-Christov heat flux and is further supported by thermal radiation and the Brinkman number. It has been found that Brinkman numbers boost the rate of heat transfer. Entropy generation is nonlinearly raised with advanced outcomes of radiation parameters, Brinkman number, and Reynolds number, while Bejan number shows the opposite behavior with respect to those parameters. The nanolayer thickness of the nanoparticles restricted the irreversibility phenomena of the system, and the same feature is supported by the Bejan number. [ABSTRACT FROM AUTHOR]

In the present paper, natural convection in an annulus between two confocal elliptic cylinders filled with a Cu-Al2O3/water hybrid nanofluid is investigated numerically. The inner cylinder is heated at a constant surface temperature while the outer wall is isothermally cooled. The basic equations are formulated in elliptic coordinates and developed in terms of the vorticity-stream function formulation using the dimensionless form for 2D, laminar and incompressible flow under steady-state condition. The governing equations are discretized using the finite volume method and solved by an in-house FORTRAN code. Numerical simulations are performed for various volume fractions of nanoparticles (0 ≤ ϕ ≤ 0.12) and Rayleigh numbers (103 ≤ Ra ≤ 3 × 105). The eccentricity of the inner and outer ellipses and the angle of orientation are fixed ate1 = 0.9,e2 = 0.6 andγ = 0° respectively. It is found that employing a Cu-Al2O3/water hybrid nanofluid is more efficient in heat transfer rate compared to the similar Al2O3/water nanofluid. [ABSTRACT FROM AUTHOR]

In this work, the effect of a variable spatial magnetic field on ferro-nanofluid flow and heat transfer in a double-sided lid-driven enclosure with a sinusoidal hot wall is investigated. The working fluid is a mixture of iron oxide (Fe3O4) nanoparticles and water and is referred to as a ferro-nanofluid. The control volume-based finite element method (CVFEM) is used to solve the governing equations in the stream function–vorticity formulation. In deriving the governing equations for this investigation, the effect of both ferro-hydrodynamics and magneto-hydrodynamics is taken into account. The numerical calculations are performed for different governing parameters namely; the Reynolds number, nanoparticle volume fraction, magnetic number (arising from Ferrohydrodynamics (FHD) consideration), and the Hartmann number (arising from Magnetohydrodynamics (MHD) consideration). The results show that an enhancement in heat transfer has a direct relationship with the Reynolds number and the Hartmann number, but it has an inverse relationship with the magnetic number. Also, it can be concluded that the Nusselt number increases with the increase of the nanoparticle volume fraction, magnetic number, and the Reynolds number while the opposite trend is observed for the Hartmann number. [ABSTRACT FROM AUTHOR]

Natural convection heat transfer of a nanofluid in the presence of an electric field is investigated. The control volume finite element method (CVFEM) is utilized to simulate this problem. A Fe3O4–ethylene glycol nanofluid is used as the working fluid. The effect of the electric field on nanofluid viscosity is taken into account. Numerical investigation is conducted for several values of Rayleigh number, nanoparticle volume fraction, and the voltage supplied. The numerical results show that the voltage used can change the flow shape. The Coulomb force causes the isotherms to become denser near the bottom wall. Heat transfer rises with increase in the voltage supplied and Rayleigh number. The effect of electric field on heat transfer is more pronounced at low Rayleigh numbers due to the predomination of the conduction mechanism. [ABSTRACT FROM AUTHOR]

In this study, mixed convection in a cavity that has a fluid and superposed porous medium with an adiabatic rotating cylinder is numerically investigated. The bottom horizontal wall is heated and the top horizontal wall is cooled while the remaining walls are assumed to be adiabatic. An adiabatic rotating cylinder is inserted inside the cavity. The governing equations are solved by the Galerkin weighted residual finite element method. The effects of Rayleigh number (between 103and 106), angular rotational speed of the cylinder (between 0 and 6,000), Darcy number (between 10−5and 10−2), cylinder sizes (betweenR = 0.1 andR = 0.3) and three different vertical locations of the cylinder on the fluid flow and heat transfers characteristics are numerically investigated. It is observed that the cylinder size has a profound effect on the local and averaged heat transfer. The local and averaged heat transfers generally increase and the convection is more effective in the upper half of the cavity as the Rayleigh number and Darcy number enhance. The averaged heat transfers increases with the cylinder size untilRa = 105. The averaged heat transfer increases almost linearly with the angular rotational velocity of the cylinder and the increase rate becomes higher as the cylinder size increases. The local and averaged heat transfers enhances/deteriorate as the cylinder approaches the upper/lower wall of the cavity. [ABSTRACT FROM AUTHOR]

Mixed convection heat transfer and fluid flow fields inside a lid-driven trapezoidal cavity were studied numerically. The cavity horizontal walls were thermally insulated while the inclined side walls were maintained isothermally at different temperatures. Forced convection was induced by moving the hotter right inclined side wall. The problem is formulated using the stream function–vorticity procedure. Together with the established boundary conditions on the right moving wall, the problem is solved by the finite difference method. The Richardson number Ri (0.01–10) and inclination angle of the side walls Φ (66–80°) were considered as pertinent parameters and investigated in two lid-driven cases: aiding and opposing directions. The results show that the behavior of Nusselt number is different from Richardson number depending on the direction of the lid. The inclination angle of the side walls was found to have a significant effect on Nusselt number when Ri was relatively low (≤1); otherwise, a negligible effect of Φ on Nusselt number was recorded. [ABSTRACT FROM PUBLISHER]

The problem of unsteady, laminar, combined forced-free convection flow in a square cavity in the presence of internal heat generation or absorption and a magnetic field is formulated. Both the top and bottom horizontal walls of the cavity are insulated while the left and right vertical walls are kept at constant and different temperatures. The left vertical wall is moving in its own plane at a constant speed while all other walls are fixed. A uniform magnetic field is applied in the horizontal direction normal to the moving wall. A temperature-dependent heat source or sink is assumed to exist within the cavity. The governing equations and conditions are solved numerically by the finite-volume approach along with the alternating direct implicit (ADI) procedure. Two cases of thermal boundary conditions corresponding to aiding and opposing flows are considered. Comparisons with previously published work are performed and the results are found to be in excellent agreement. A parametric study is conducted and a set of representative graphical results is presented and discussed to illustrate the influence of the physical parameters on the solution. [ABSTRACT FROM AUTHOR]

The problem of unsteady, laminar double-diffusive convective flow of a binary gas mixture in a rectangular enclosure filled with a uniform porous medium is considered. A temperature-dependent heat source or sink is assumed to exist within the enclosure boundaries. Transverse cooperating gradients of heat and mass are applied on the two opposing vertical walls of the enclosure while the other two horizontal walls are adiabatic and impermeable to mass transfer. A numerical solution based on the finite-difference methodology is obtained. Representative results illustrating the effects of the inverse Darcy number, the heat generation or absorption coefficient, and the buoyancy ratio on the contour maps of the streamline, temperature, and concentration as well as the profiles of velocity, temperature, and concentration at the midsection of the enclosure are reported. In addition, results for the average Nusselt and Sherwood numbers are presented in tabulated form and discussed for various parametric conditions. [ABSTRACT FROM AUTHOR]

We formulate the problem of coupled heat and mass transfer by natural convection from a horizontal cylinder embedded in a uniform porous medium in the presence of an external magnetic field and internal heat generation or absorption effects. The cylinder surface is maintained at a constant temperature and a constant concentration and is permeable to allow for possible fluid wall suction or blowing. The resulting governing equations are nondimensionalized and transformed into a nonsimilar form and then solved numerically by an implicit, iterative, finite-difference method. Comparisons with previously published work are performed and excellent agreement is obtained. A parametric study of the physical parameters is conducted and a representative set of numerical results for the stream function, temperature, concentration profiles, and the Nusselt and Sherwood numbers is illustrated graphically to show interesting features of the solutions. [ABSTRACT FROM AUTHOR]

This work is focused on steady, laminar, coupled heat and mass transfer by natural convective boundary layer flow over a permeable isothermal truncated cone in the presence of magnetic field and radiation effects. A suitable set of dimensionless variables is used and nonsimilar equations governing the problem are obtained. The resulting equations have the property that they reduce to various special cases previously considered in the literature. An adequate implicit, tridiagonal finite difference scheme is employed for the numerical solution of the obtained equations. Various comparisons with previously published work are performed and the results are found to be in excellent agreement. Representative results for the velocity, temperature, and concentration profiles as well as the local skin-friction coefficient; local Nusselt number and the local Sherwood number illustrating the influence of the Hartmann number; the concentration to thermal buoyancy ratio; and the wall mass transfer coefficient are presented and discussed. [ABSTRACT FROM AUTHOR]

This study examines how a chemical reaction and a nonuniform heat source effect the flow of an MHD Casson nanofluid over a nonlinear stretching sheet. By incorporating viscous dissipation, the energy equation is strengthened. Brownian diffusion, thermophoresis diffusion effects are taken place. By using the necessary similarity transformations, the governing equations for the current flow are converted into a nonlinear system. The RKF technique yields a numerical solution along with a shooting technique for the condensed system. Thereafter, to better understand the physical interpretation of flow and heat transfer, the flow-controlling parameters are shown graphically and in tabular form in the current work. Based on the present study's numerical results, a fair connection is found between this analysis and previous studies. Some of the observations are velocity profile is decreased for the effects of magnetics and stretching parameter variations and Eckert number plays a great role in the increase of temperature profile. [ABSTRACT FROM AUTHOR]

This work considers steady, laminar, hydromagnetic simultaneous heat and mass transfer by mixed convection flow over a permeable vertical plate immersed in a uniform porous medium for the cases of power law variations of both the wall temperature and concentration and the wall heat flux and mass flux. Appropriate transformations are employed to transform the governing differential equations to a nonsimilar form. The transformed equations are solved numerically by an accurate, implicit, iterative, finite difference method. The obtained results are validated by favorable comparisons with previously published work on special cases of the problem. A parametric study illustrating the influence of all involved parameters on the local Nusselt and Sherwood numbers is conducted. The results of this parametric study are shown graphically, and the physical aspects of the problem are discussed. [ABSTRACT FROM AUTHOR]

Analyzes the mixed convection flow along a vertical permeable plate in a porous medium of a transverse magnetic field. Derivation of continuum boundary layer equations; Process of wall heat transfer; Detection of non-uniform fluid mass transfer in the plate surface.

AbstractThis article delves into the theoretical analysis of hydromagnetic bioconvection involving a radiating and reacting Casson nanofluid containing motile microorganisms, past an exponentially stretching permeable vertical surface within a porous medium, incorporating heat and mass transfer characteristics. The model problem’s nonlinear differential equations are derived by applying relevant conservation laws and subsequently solved numerically using the homotopy analysis method (HAM). The graphical representation and quantitative discussion of the effects of emerging parameters on various aspects, including nanofluid velocity, temperature distribution, nanoparticles, gyrotactic microorganisms concentration, skin friction, Nusselt number, Sherwood number,and Motile density number are presented. The findings reveal significant influences on both heat and mass transference rates, as well as motile microorganism rates, in response to variations in bioconvection parameters. Additionally, the integration of gyrotactic microbes into nanoparticles is identified as a crucial factor for enhancing the thermal performance of devices, such as microbial fuel cells, bacteria-activated micromixers, microfluidic tools, enzyme biosensors, and chip-like bio microsystems. The bioengineering implications of these results are noteworthy, providing valuable insights for the design and optimization of relevant technologies. [ABSTRACT FROM AUTHOR]

AbstractThis research focuses on investigating the impact of magnetized nanoparticles’ heat and mass transfer process two-dimensional (2D) porous medium ternary hybrid Magnetohydrodynamics (MHD) ferrofluid flow through a two movable permeable porous surface, with a specific emphasis on the Darcy Forchheimer effect, activation energy, and chemical reaction parameters. Recently, motile microorganisms have become a significant area of interest in the study of heat and mass transfer. This study employs colored plots to analyze the optimum heat transfer over a double porous plate by altering different physical parameters. Using the shooting technique, the study provides numerical solutions to nonlinear systems of equations by transforming the partial differential equations (PDE) into ordinary differential equations (ODEs) via the dimensionless similarity transformation. Tables and graphs demonstrate how the governing parameters impact velocity, temperature, mass concentration profiles, and motile microorganisms, as well as physical quantities like skin friction coefficient, Nusselt number, Sherwood number, and motile number. Ternary hybrid ferrofluid exhibits a significantly improved heat transfer rate compared to both Ferro and hybrid ferrofluid. The convective flux of heat and mass transfer experiences a decrement with an escalation in the values of the activation energy (E) parameter. The presence of positive values for both the similarity variable (n) and Exothermic/Endothermic parameter (λ) leads to an enhancement in the flow of thermal transfer on both porous surfaces. This research will have far-reaching implications in various fields, including coolant technology in the manufacturing industry, heat dissipation in electronic modules, high-performance computing cooling facilities, the automotive sector, and space applications. [ABSTRACT FROM AUTHOR]

AbstractThis study presents a comprehensive investigation into the intricacies of single-phase simulation concerning the behavior of fractal interfacial magnetized metallic chemical-reactive nanoparticles within fluid systems. The research focuses on unraveling the multifaceted phenomena associated with heat and mass transfer in complex nanoscale environments. To achieve this, we employ numerical techniques to address the intricate fluid flow problems that arise due to the presence of these nanoparticles. Fractal complexities are linked to critical phenomena, such as mixing and mass transport, at the turbulent/non-turbulent interface of shear layers and boundary layers. This study primarily concentrates on the phenomena of heat and mass transfer, with a focus on estimating thermal conductivity models that have significant impacts on the flow of metallic nanofluids under convective conditions. The combination of a high thermal conductivity model with a novel interfacial fractal theory reveals a substantial effect on heat and mass transfer enhancement. Furthermore, this research explores hybrid types of porous channel geometries under the combined influence of magnetohydrodynamics and chemical reaction mechanisms in the presence of metallic nanoparticles. A comprehensive numerical analysis of higher-order nonlinear differential equations is conducted, which exposes the flow field’s behavior concerning momentum, energy, and mass transfer. These insights are envisioned through single-phase simulations of nanofluids. The influence of the nanoparticles’ radius and diameter is found to play a significant role in thermal performance, with nanoparticles ranging from 1% to 8% exhibiting a notable impact on thermal conductivity. HighlightsA new mathematical relation of mass, as well as heat transfer for metallic-nanomaterial being affected by thermal conductivity (T.C.), has been established.The important role of the physical number is observed under the effect of T.C. and heat and mass transfer through orthogonal porous surfaces.An injection/suction, as well as an expansion/contraction phenomenon related to the porous surface is observed.A new mathematical relation of mass, as well as heat transfer for metallic-nanomaterial being affected by thermal conductivity (T.C.), has been established.The important role of the physical number is observed under the effect of T.C. and heat and mass transfer through orthogonal porous surfaces.An injection/suction, as well as an expansion/contraction phenomenon related to the porous surface is observed. [ABSTRACT FROM AUTHOR]

AbstractThis articles focus the dynamics of fluid conveying ternary solid particles, nano-layer, and magnetic field effects subject to porous disks. The magnetized ternary nanoparticles induced by Ferro and nano-layer are considered due to their unusual characteristics like extraordinary thermal conductivity, which are significant in advanced nanotechnology, heat exchangers, material sciences, and electronics. To avoid possible sedimentation of tiny particles, the motile microorganisms are also considered in the elaborated fluid problem. The main objective of this comprehensive study is the enhancement of heat transportation. In this study, we also investigate the physical dynamics of entropy generation, particularly emphasizing viscous dissipation related to joule heating effects. The mass transfer equation was employed to monitor the chemical interaction with diverse nanoparticles. The results of comparative and numerical validation agree well. The approach of stable and accurate numerical boundary value problem of fourth order code (bvp4c) is applied to solve the nonlinear system of ordinary differential equations. Many useful engineering results are summarized here, including the skin friction coefficient (Cf), Nusselt number (Nu), Sherwood number (Sh), and motile number (Nn). For both porous disks, several non-dimensional parameter effects are depicted graphically and tabulated. The results show that the increasing the number of nanolayer particles slows the rate of the temperature profile in both porous disks, associated with the expansion ratio, Reynolds number, and magnetic field number. Moreover, increasing the values of the density ratio number results in an increase in the flow of microorganisms profile in both porous disks. Increasing the values of the diffusivity parameters and the temperature difference enhances the flow of entropy generation. [ABSTRACT FROM AUTHOR]

Abstract In the current analysis, we delivered a computational approach to the 2D boundary layer heat and mass transfer flow of water-based nanofluids over a vertical cone saturated by porous media with heat generation/absorption, thermal radiation, chemical reactions, the Soret–Dufour number, viscous dissipation, and a magnetic field. The controlling partial differential equations are converted into devoid of dimensions form and numerically dealt with by Crank–Nicolson through an implicit finite difference approach. Specifically, the given parameters, such as volume fraction (ϕ), MHD-Magnetohydrodynamics (M), Soret/Dufour (Sr-Du), viscous dissipation (ϵ), chemical reaction (λ), thermal radiation (Rd), and heat blowing/suction (Δ), have an impact on boundary layer flow characteristics (velocity, temperature, concentration, drag coefficient, rate of heat transfer, and mass transfer rate) are thoroughly studied, and the outcomes are visually and tabulated to demonstrate the actual significance of the problem. [ABSTRACT FROM AUTHOR]

A numerical investigation on the impacts of heater length increased from left corner along with the bottom wall in a Cu-water nanofluid-filled porous cavity in the existence of MHD and thermal radiation is performed out. The bottom wall is heated with two different types of heater (both uniform and nonuniform) separately. Three various lengths of heater are considered. Constant cold upper horizontal wall moves in the positive direction. The other sidewalls and excluding the heating portion of the bottom wall are considered to be adiabatic. The system of dimensionless form of governing equations is solved by finite volume method (FVM) with appropriate boundary and initial conditions and SIMPLE algorithm has been employed for the pressure term. For both types of heating, the highest heat transfer is attained with the length of heater L H = 1 / 4 for all taken Richardson number. The effect of magnetic field is very low on heat transfer with the thermal source length L H = 1 / 2 and nonuniform heating in free convection regime. On increasing the heater length in nonuniform heating, overall heat transfer rate is decreased first and then raised. The percentage of increasing of average Nusselt number with an increase of thermal radiation parameter in nonuniform heating is higher than uniform heating. The effect of magnetic field is significant for all taken solid volume fraction in uniform heating than the nonuniform heating with heater length L H = 1 / 2. [ABSTRACT FROM AUTHOR]

In this work, a 2-D numerical investigation and a sensitivity analysis have been done on the natural convection heat transfer in a wavy surface cavity filled with a nanofluid. For this purpose, the effects of three parameters, the Rayleigh number (103 ≤Ra ≤ 105), nanoparticles volume fraction (0.00 ≤ϕ ≤ 0.04), and the shape of the nanoparticles (spherical, blade, and cylindrical), are studied. Discretization of the governing equations is performed using a finite volume method (FVM) and solved with the SIMPLE algorithm. The effective parameters analysis is processed utilizing the Response Surface Methodology (RSM). Comparison with previously published work is performed and the results are found to be in good agreement. The results showed that increasing the Rayleigh number andϕincreases the mean Nusselt number and the total entropy generation. Also, the nanofluids with spherical- and cylindrical-shaped nanoparticles have the highest and lowest Nusselt numbers and entropy generations, respectively. The sensitivity of the mean Nusselt number and entropy generation ratio to Ra andϕis found to be positive, whereas it is predicted to be negative to nanoparticles shape. [ABSTRACT FROM AUTHOR]

In this study, entropy generation of double-diffusive mixed convection is investigated inside a right-angled trapezoidal cavity with a partially heated and salted bottom wall. Similar to the approach that assigns color to streamlines, a new coloring scheme is employed to visualize heatlines and masslines in a more meaningful manner. In addition, various consequential parameters, namely the Lewis and Richardson numbers, the buoyancy ratio, the direction of lid movement, and the heat source location, have been analyzed. According to the results, as the Lewis number increases, the average Nusselt number declines, while the total entropy generation augments. Furthermore, for Le=0.1, the conduction mass transfer dominates the mass transfer field; hence, the masslines are virtually perpendicular to the isoconcentration lines. [ABSTRACT FROM AUTHOR]

The MHD phase change heat transfer of a phase change substance in the presence of a uniform magnetic field is theoretically studied in a cavity. A fixed grid method associated with the enthalpy–porosity method is utilized. The governing equations are transformed into a non-dimensional form and solved using the finite element method. The impacts of the crucial parameters such as the Hartmann number and the inclination angle on the phase change process are investigated. It is found that any increase in Hartmann number and the inclination angle of the cavity leads to a decrease in the rate of the melting process. [ABSTRACT FROM PUBLISHER]

There is growing interest in application of inclined fins to a cavity wall. As such, this paper focuses on the numerical investigation of laminar free convection flow and heat transfer in an enclosure with an inclined thin local thermal non-equilibrium porous fin and saturated by a nanofluid. The porous medium is assumed to be isotropic and homogenous, the cavity walls are assumed to be impermeable to the nanoparticles, and there is a no-slip boundary condition on the enclosure boundaries. The vertical walls are isothermal and the horizontal ones are adiabatic. Moreover, the influence of indispensable parameters regarding heat and mass transfer, such as Rayleigh number, Darcy number, Prandtl number, porosity, thermophoresis and Brownian parameters, fin length, fin position, and the fin angle on the average Nusselt number, are taken into account. Generally, it is found that the average Nusselt number is an increasing function ofRa, Pr, Da, and porosity (ε). Furthermore, increasing either fin position (Sp) or thermal conductivity ratio (η) produces corresponding decreases in average Nusselt number. Finally, heat transfer shows a different behavior for different values of fin angles and lengths. [ABSTRACT FROM AUTHOR]