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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]

Transformer oil is used to maintain the core and winding of the transformer. The main tasks of transformer oil as an industrial oil are insulation and cooling of a transformer. In the current study, the thermophysical and thermal properties of transformer oil nanofluid with volume percentages of 0.017% and 0.56% have been experimentally investigated which improves the performance of the base fluid due to the high thermal conductivity coefficient of carbon nanotubes compared to transformer oil. Ultrasonic baths and chemically functionalizing techniques were utilized in a two-step process to create nanofluids, which were stabilized by these techniques. In a double-tube carbon steel heat exchanger, the nanofluids were employed, and the thermal characteristics of the base fluid and nanofluids were evaluated. The findings indicated that the effective thermal conductivity improves with increasing temperature and CNT concentration, reaching its maximum value at a temperature of 45 °C in a volume fraction of 0.56. Observations showed that the heat transfer coefficient rose with rising Reynolds number and volume percentage, whereas the friction factor reduced when the hot fluid flowed at an intake temperature of 80 °C compared to the nanofluid in the outer tube. The flow rates for the nanofluids were calculated to be 0.2, 0.3, 0.4 lit/s, and 0.18 lit/s for the hot fluid, respectively. As a general conclusion, carbon nanotubes have a very high potential to improve the thermal performance of transformer oils, which is a serious challenge. [ABSTRACT FROM AUTHOR]

This article discusses a mathematical model for the electrokinetic and Darcy's resistance of Williamson fluid in an electroosmotic pumping environment. The zeta potential at walls aids in peristaltic movement, and porous dissipation is incorporated into this modulation by the Williamson fluid's material parameters. Through the use of Debye-Huckel approximations, long wavelengths, and low Reynolds numbers, the model equations are simplified. Mathematica software is used to produce analytical and numerical results, and plots and analyses are done using the included parameters on physical quantities of interest. This study has various practical applications, such as modifying belt resistance in laboratory drainage testing and improving pipeline design. It could also potentially aid in the development of blood filtration and purification techniques and optimize drug delivery systems that utilize fluids. It is observed that the modified Darcy's law is more accurate for porosity effects in electroosmotic peristaltic channels and results in higher shear stress at the channel wall compared to Darcy's law. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid computational fluid dynamics technique is proposed to study turbulent flow and conjugate heat transfer patterns. A typical shaped room with a radiant heating panel is considered. The mesoscopic lattice Boltzmann method coupled with the finite difference solution of macroscopic energy equation is used to compute the thermal and flow fields. To describe the radiant flux distribution along the solid–fluid interfaces, the Lambert law is implemented. An in-house code written in MatLab is validated against direct numerical simulation data obtained for a Rayleigh number up to 1011. A computational study is conducted when varying the Rayleigh number, heat flux density, radiant panel length, physical properties of the enclosure and external heat transfer coefficients with constant walls thickness and the ambient temperature. It is found that the air temperature is decreased in the room as the Rayleigh number is raised. The panel length is found to drastically affect the thermal field. However, the flow structure is altered insignificantly. The stagnant zone of air is formed at the bottom corners with low values of heat fluxes. [ABSTRACT FROM AUTHOR]

This paper examines the capability of hybrid lattice Boltzmann method to simulate developed turbulent buoyancy-driven flows in closed rectangular cavities. The two-relaxation time mesoscopic lattice Boltzmann method is used as a fluid dynamics solver, whereas the thermal behavior is described in terms of the macroscopic energy equation. Numerical simulation is performed for air-filled square and tall cavities in a range of the Rayleigh number 10 9 ≤ R a ≤ 10 11 . An in-house numerical code is developed in this study and successfully validated against up-to-date numerical and experimental data of other researches. It is found that the proposed hybrid approach accurately predicts the location of thermal plumes at the isothermal walls despite an insignificant error in the heat transfer rate with the R a ≥ 3 · 10 10 . [ABSTRACT FROM AUTHOR]

The objectives of this study are (i) to find exact analytical solutions to the unsteady hybrid nanofluid flow and heat transfer due to a moving infinite flat plate, and (ii) to investigate the impacts of different hybrid nanofluids (Cu‐Al2O3/water, CuO‐Al2O3/water, and Ag‐Al2O3/water) on the unsteady flow and heat transfer characteristics with MHD and variable temperature. The Laplace transform technique is employed to find the exact analytical solutions of the partial differential equations with appropriate boundary conditions governing the problem considered. The results computed for engineering quantities, namely skin friction coefficient and Nusselt number and velocity and temperature profiles by the Laplace transform technique are analyzed using graphs and tables. It has been found that there is a significant increase in the heat transfer rate for hybrid nanofluids than for nanofluids and we observed a higher heat transfer rate for Cu‐Al2O3/water and a lower heat transfer rate for Ag‐Al2O3/water than for the others. The novelty of this study is finding an exact analytical solution to the problem of hybrid nanofluid flow due to moving vertical plate where the effects of magnetic field and variable plate temperature conditions are considered. The obtained results can be used in various engineering applications, including geothermal reservoirs, packed‐bed storage tanks, packed‐bed catalytic reactors, thermal insulation, grain storage, porous solids drying, and petroleum resource gas production. Furthermore, the findings can be used to validate numerical solutions for more complex transient hybrid nanofluid flow and convective heat transfer problems. [ABSTRACT FROM AUTHOR]

In this article, the effects of angle of inclination on heat transfer by mixed convection have been analyzed numerically in a square cavity packed with a CuO nanofluid. Cavity boundaries are constructed by having sinusoidal varying temperature on sidewalls, inactive horizontal walls, and the hot passing plate at the center of the cavity. The transport equations for fluid and heat are solved using the finite‐volume method with SIMPLE algorithm. The Richardson number (Ri) varying from 0.01 to 100, inclination angle (γ) from 0° to 90°, wall speed ratios (λ) from 0 to 3 and volume fraction of nanoparticles (φ) from 0.0 to 0.1 are given and represented in the form of flow fields, temperature fields, and mean heat transfer graphs. It is detected that the principal flow constraints have a substantial impact on the flow lines and thermal lines. Specifically, the structures of cavity inclination, existence of copper nanoparticles, and the hot wall in motion at the midpoint of the cavity are established to enrich the overall rate of heat transfer. Correspondingly, in the present study, the Vajjha and Das model is taken into account for the effective thermal conductivity and viscosity of the nanofluid; application of this model is beneficial for the industries working in a high‐temperature environment. [ABSTRACT FROM AUTHOR]

In the present study, it is explored theoretically Hall and ion slip effects on the unsteady magnetohydrodynamic (MHD) rotating flow of a viscous, incompressible electrically conducting, and optically thick radiating Jeffreys fluid over an impulsively, moving vertical plate embedded in a saturated porous medium, when the temperature of the plate has a provisionally ramped profile. The exact solutions of the governing equations for the flow domain are attained by making use of the Laplace transform method. The specified analytical solutions are also acquired for some limiting cases. The research phrases of engineering curiosity for skin friction and Nusselt number are originated for both ramped wall temperature and the isothermal plate. Sherwood number is also obtained. The numerical results of velocity, temperature, and concentration distributions are exhibited graphically whereas skin friction, Nusselt number, and also Sherwood number are mentioned in a table form. It is observed that on either cases of ramped wall temperature and isothermal plate, the resultant velocity enhances with an increase in Hall and ion slip parameters. Reversal behavior is observed with an increase in magnetic field parameter, Jeffreys fluid parameter and Prandtl number. Thermal and concentration buoyancy forces and thermal radiation tend to accelerate the resultant velocity throughout the boundary layer region. The temperature reduces with an increase in Prandtl number and reverse effect is observed with an increase in thermal radiation parameter. Mass diffusion tends to enhance to species concentration. The rotation and Jeffreys fluid parameters tend to enhance both stress components. Nusselt number enables to lessen with growing in thermal radiation parameter and is magnified on escalating in time. The Sherwood number is improved with increasing in Schmidt number at the plate and it is refused on increasing in time. [ABSTRACT FROM AUTHOR]

Riga plate is known to create a crossing electric and magnetic field to generate a wall-parallel Lorentz force. The significance of Casson nanofluid flow past a Riga plate is observed in the sphere of engineering, such as polymer extrusion, food manufacturing, plastic films, oil reserves and geothermal manufacturing. Researchers are interested in this model because of its potential use in biological rheological models. As Casson nanofluid flows are of great interest, this study aims to investigate the three-dimensional magnetohydrodynamics (MHD) flow with heat and mass transport of Casson nanofluid over a flat Riga plate. As a novelty, this study also includes the effectiveness of wall velocity slip, activation energy, nonlinear radiation, and temperature and space-dependent heat source/sink. Suitable similarity transformations have been employed to generate the dimensionless ordinary differential equations (ODEs) from the partial differential equations (PDEs) regulating the fluid flow problem. The transformed nonlinear boundary value problem is then solved numerically using the in-built routine "bvp4c" in MATLAB. The visual demonstrations are provided for the effects of various significant physical factors on the flow, heat and mass distributions. On the other hand, wall shear stress and rates of heat and mass transport at the surface are measured and displayed numerically in tabular form. The findings indicate that the fluid velocity in both directions slows as the velocity slip parameter increases. However, the velocity profile is escalated with the boost of modified Hartmann number. An increase in heat source parameters leads to decrease the heat transmission rate at the wall. The higher values of the radiation parameter result in a better wall heat transmission rate. Further, the rate of mass transport drops when the activation energy parameter is hiked. [ABSTRACT FROM AUTHOR]

The present flow problem analyzes the impact of radiative heat and mass transfer with inclined magnetic field on thermal exchange and entropy production of two immiscible nature of electrically conducting couple stress fluid in a static porous saturated conduit. In this model, the lower and upper porous regions of the rectangular channel are occupied by two different types of couple stress fluids. The static horizontal parallel plates of the porous duct are completely isothermal and the flow of immiscible fluid through the porous duct develops because of a constant pressure gradient at the entry zone of the duct. The Brinkman model is utilized in the modeling of fluid flow through porous saturated domain and Rosseland's approximation is utilized to compute the radiative thermal exchange effect on nonmiscible couple stress fluid. In this work, authors have analyzed the effect of various thermo-physical parameters such as the Hartmann number (Ha), permeability parameter (Da), Schmidt number (Sc), Soret number (Sr) and couple stress parameter ( s i , i = 1 , 2) on the entropy generation characteristics, Bejan number distribution, thermal behavior, concentration distribution and flow characteristics of immiscible couple stress fluid which passes through the porous channel. The parameters Ha, Da, s i , Sc, Sr correspond to magnetic field effect, permeability of porous media, couple stress, mass diffusion and thermal diffusion, respectively. The most significant findings of this research work are as follows: • In a porous saturated channel, the immiscible couple stress fluid velocity, entropy production number and thermal profile get enhanced on increasing the couple stress parameter. • On increasing the Hartmann number and decreasing the permeability of porous region, the thermal properties and entropy production number both decrease. • The couple stress fluid's concentration field and Bejan number distribution get decreased on enhancing Soret number Sr and Schmidt number Sc. • The entropy generation near the wall of the channel rapidly increases on increasing the Schmidt number and Soret number. The emerging finding of this research work exhibits excellent agreement with previously published work. This research work can be utilized in food processing, petroleum products and chemical process. [ABSTRACT FROM AUTHOR]

The principal aim of this investigation is to examine the gold and magnesium oxide hybrid nanoparticles in different physical capacities on the water-based hybrid nanofluid and elaborate on an erratic squeezing flow among both infinite plates. Melting effect and thermal radiation depict heat transfer features. Production of the Bejan number and entropy is upward. The explains the governing equations, and the standard transformation is supplied. The numerical solutions are carried out using an efficient finite element method. To analyze difference between heat transfer and its implication in industrial zone, the Nusselt number was arranged in a horizontal pattern. The results showed that a thicker thermal boundary layer increased the Eckert number and the volume fraction of gold nanoparticles. Anyhow, the heat transfer rate by Au–MgO/water was necessarily greater than the Au–water. The obtained results are excellent and vigorously oppose those that are applicable to the literature by the attached position. It was established for hybrid nanofluids to display higher entropy generation rates. The outcomes of this analysis were the consequence of the appraisal of the impact on few required form parameters in heat transfer and consequently on the expansion for industrial use. [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]

In the current study, magnetohydrodynamics mixed convective flow of Ag–MgO/water hybrid nanofluid in a triangular shaped partitioned cavity involving a porous layer is numerically investigated by using the finite element method. In the numerical simulation, various effects of pertinent parameters such as Richardson number (between 0.01 and 100), Hartmann number (between 0 and 60), magnetic field inclination angle (between 0 and 90), Darcy number (between 10 - 4 and 5 × 10 - 2 ), location of the vertex of triangular porous region (between 0.2 and 0.8 H) and hybrid nanoparticle solid volume fraction ( ϕ 1 between 0 and 0.01, ϕ 2 between 0 and 0.01) on the fluid flow and convective heat transfer features are examined. It was observed that a large vortex is established below the main vortex near the upper wall for the lowest value Ri number. At the highest magnetic field strength, multi-recirculation flow pattern is seen in the right bottom corner. The average heat transfer enhances with higher values of permeability of the porous medium, magnetic field inclination angle, distance of the porous layer vertex from the hot wall and solid nanoparticle volume fraction of each particles in the hybrid nanofluid. The impact is reverse for higher values of Richardson number and Hartmann number. In the current work, significant changes in the average Nusselt number are obtained by varying the location of the porous medium. The triangular shaped porous compound can be used as an excellent tool for convective heat transfer control. [ABSTRACT FROM AUTHOR]

This paper aims to understand the characteristics of heat transfer and flow by natural convection of Al2O3–Cu/water-based hybrid nanofluid-filled square domain containing various configurations of a corrugated conducting solid under a horizontal magnetic field. The basic equations in their non-dimensional form are numerically solved using the finite volume discretization technique. The Corcione correlations are utilized to estimate the overall heat conductivity and overall viscosity of the hybrid nanoliquid when the nanoparticle's Brownian motion is taken into account. The dependency of different governing factors of the investigation, namely volume fraction of the combined nanoparticles, Rayleigh and Hartmann numbers, undulation number, undulation amplitude and the fluid/solid heat conductivity ratio, on thermohydrodynamic characteristics are delineated. Results stated that the maximum heat transmission rate was obtained for weak values of Hartmann, undulation number, undulation amplitude and high values of Rayleigh and nanoparticles volumic fraction. In addition, the fluid/solid heat conductivity ratio parameter was found to boost the heat transfer at weak Rayleigh while reducing it at high Rayleigh. [ABSTRACT FROM AUTHOR]

Recently, many researchers have focused on their studies on the analysis of nanofluid flows due to their participation in the enhancement of heat transfer rates in industrial processes. The ordinary fluids, such as water, mineral oils, and so on, are known for their low thermal conductivity in heat transfer processes. A significant enhancement in the thermal properties of ordinary fluid may be obtained by adding nanoparticles having a diameter of less than 100 nm or suspension of fibers. Better spreading, wetting, dispersion, and stability and with acceptable viscosity are the main advantageous properties of nanofluids on a solid surface. The nanofluids are encountered in various thermal engineering systems such as in heat exchangers, refrigeration, thermal management of fuel cells, cooling of nuclear reactors, microelectromechanical systems, and others. In particular, the thermal conversion is known as a great application of nanotechnology, and many studies have been achieved with such fluids in heat exchangers. Therefore, this paper aims to present a global insight into the different applications of nanofluids in various heat exchangers, that is, heat pipe and plate'fin heat exchangers. All research works have been summarized into three main parts: laminar, transition, and turbulent nanofluid flow regimes. [ABSTRACT FROM AUTHOR]

The steady flow of a nanofluid (mixture of titanium dioxide and water) in a rectangular channel under the influence of an inclined magnetic field is studied. The channel contains an upstream hot splitter plate in alignment with the upper and lower plates of the channel. It may be said that two incoming channel flows merge to form a single channel flow. This setup may apply to the heating chamber in which titanium dioxide can be used to enhance the thermal transfer rate. It is observed that the position of the splitter plate (that may act as an electric heater) affects the velocity and temperature of the fluid. Therefore, in order to ensure these facts, the examination of the flow behavior and the temperature distributions in the channel if the splitter is placed at different positions in the upstream have been probed. In addition, the effect of nanoparticles on the convection process has been probed. The streamlines are almost similar for a clear fluid as well as for a nanofluid (for low values of solid volume fraction of nanoparticles (i.e. φ < 0.05 )) for all values of the Reynolds number. However, the rise in the temperature is noted for the nanofluid if the concentration of nanoparticles is increased. The increase in the Reynolds number also supports the enhancement of the Nusselt number and, hence, the thermal transfer rate of the nanofluid. The Nusselt number is dominant in the vicinity of the trailing edge of the splitter because the trailing edge exhibits as a stagnation point. In addition, the maximum Nusselt number for nanofluid at moderate Reynolds number (e.g., Re = 100) is enhanced to 0.3% with respect to the clear fluid. Moreover, obtained results for this particular case are compared with the existing literature, and the results compare well. [ABSTRACT FROM AUTHOR]

This paper presents a numerical analysis on turbulent flow and forced-convection characteristics of rectangular solar air heater tube fitted with staggered, transverse, V-shape, modern obstacles on the heated walls. Air, whose Prandtl number is 0.71, is the working fluid used, and the Reynolds number considered equal to 6×103. The governing flow equations are solved using a finite volume approach and the semi-implicit pressure linked equation (SIMPLE) algorithm. With regard to the flow characteristics, the quadratic upstream interpolation for convective kinetics differencing scheme (QUICK) was applied, and a second-order upwind scheme (SOU) was used for the pressure terms. The dynamic thermo-energy behavior of the V-shaped baffles with various flow attack angles, i.e., 50°, 60°, 70°, and 80° are simulated, analyzed, and compared with those of the conventional flat rectangular baffles with attack value of 90°. In all situations, the thermal transfer rate was found to be much larger than unity; its maximum value was around 3.143 for the flow attack angle of 90° and y = H/2. [ABSTRACT FROM AUTHOR]

Improving the hydrodynamic characteristics of STHECs (Shell-and-Tube Heat Exchanger Channels) by using BVGs (Baffle-type Vortex Generators) is among the common passive methods due to their proved efficiency. In this computational investigation, the same method is used to enhance the hydrodynamic behavior of STHECs, by inserting W-shaped Baffle-type Vortex Generators. The numerical model represented by the computational FVM (Finite Volume Method) is used to simulate and analyzed the considered physical model. The fluid used is air, its thermal physical properties are constant, turbulent, incompressible, and its temperature is 300 K at the inlet section of the STHEC. The flow velocity (Uin) and atmospheric pressure (Patm) are considered as boundary conditions at the entrance (x = 0) and exit (x = L) of the channel, respectively. The results showed that the friction coefficients were related to the pressure, velocity, and Reynolds number values. High values of Re yielded an acceleration of the fluid, resulting thus in increased pressure on the solid walls and augmented friction values. [ABSTRACT FROM AUTHOR]

The main objective of this numerical investigation was to analyze the entropy generation and natural convection flow under magnetic field in a square enclosure filled with Cu–Al2O3/water hybrid nanofluid. The enclosure is equipped with a conducting hollow cylinder. The free convective flow in the enclosure is created by a horizontal temperature difference between the vertical left hot wall and the right cold wall under the Boussinesq approximation. The dimensionless equations of steady laminar natural convection flow for Newtonian and incompressible mixture are discretized using the finite volume method. The effective thermal conductivity and viscosity of the hybrid nanofluid are calculated using Corcione correlations taking into consideration the Brownian motion of nanoparticles. Numerical solutions were performed for different values of the nanoparticles volumic concentration, Hartmann number, Rayleigh number, radius ratio, and solid–fluid thermal conductivity ratio. The analyzed results show that inserting a hollow conducting cylinder plays an important role in controlling flow characteristic and heat transfer rate as well as irreversibilities within the cavity. [ABSTRACT FROM AUTHOR]

This study applied the computational fluid dynamic (CFD) code, ANSYS Fluent for simulating the effect a piezoelectric fan installed inside the rectangular channel by numerical simulation method for transient flow field and investigating the influence of each parameter. To remove the disorganized form of energy from the electronic components, the reversible piezoelectric effect is employed to energize the piezoelectric fan. To observe the variation of fan characteristics and to predict the convective heat transfer coefficient, CFD code ANSYS Fluent 15.0 is used. The numerical simulation parameters included are Nusselt number, number of fins (n = 12 and 14), and counter‐shift (inward and outward‐phase), and distance between the upper portion of the fan tip to the front part of the low thermal reservoir. Numerical analysis was carried out to evaluate the effect of thermal flow fields on the heat sink and piezoelectric fan employed in a flow domain. the results showed that by varying the height from channel bottom to the center of piezoelectric fan improves the performance of the piezoelectric fan, piezoelectric fan swinging in a transient phenomena and also simultaneously influences fluid flow behavior on the heat source surface, the fan vibration at counter‐phase has a better rate of heat transfer than vibration in in‐phase. [ABSTRACT FROM AUTHOR]

• Nano-Encapsulated Phase Change Materials (NEPCMs) are suspended in a base fluid. • Free convection heat transfer of NEPCMs is addressed in a cavity. • Fusion temperature of NEPCM particles is a key factor in heat transfer enhancement. • There is an optimum range of fusion temperature leading to maximum heat transfer. • Up to 10% heat transfer enhancement was observed by using NEPCM particles. Free convective flow and heat transfer of a suspension of Nano Encapsulated Phase Change Materials (NEPCMs) in an enclosure is studied. NEPCM particles are core-shell structured with Phase Change Material (PCM) as the core. The enclosure is a square cavity with top and bottom insulated walls and differentially-heated isothermal vertical walls. The NEPCM particles circulate under natural convection inside the cavity. The PCM cores undergo phase change from solid to liquid and absorb some of the surrounding's heat in the form of latent heat in the hot region, and release the absorbed heat in the cold region by solidification. The governing equations representing the conservation of mass, flow, and heat of NEPCM suspension are introduced in the form of partial differential equations. The governing equations are transformed into non-dimensional form and solved by the finite element method. A grid check and validation test are performed to ensure the accuracy of the results. The outcomes show that the fusion temperature of NEPCM particles is the key factor affecting the heat transfer enhancement of NEPCMs in the natural convection flow. The enhancement of heat transfer is highly dependent on the non-dimensional fusion temperature, θ f , and very good performance can be achieved in the range of ¼ < θ f < ¾. Comparing to the base fluid, a relative enhancement of about 10% can be achieved by using NEPCMs at a non-dimensional fusion temperature of ¼. [ABSTRACT FROM AUTHOR]

The current study is based on the effects of microrotational dynamics, microinertial effects, and temperature changes on electroosmotic peristalsis in a tapered microchannel. This has been addressed by an analytical study of heat transfer in the setting of electroosmotic peristaltic flow involving a micropolar fluid, specifically considering a symmetrically tapered channel. The Navier–Stokes equation, the Poisson–Boltzmann equation, the energy equation, and the micropolar fluid model are all included in the mathematical model. On the flow and temperature fields, a thorough parametric analysis is carried out, investigating the impacts of numerous variables, including the micropolar parameter, Prandtl number, Brinkman number, Grashof number, thermal conductivity ratio, and channel aspect ratio. The findings show that peristalsis and electroosmosis both contribute to higher heat transfer rates. Notably, the electroosmotic parameter and Brinkman number have a substantial impact on the distribution of temperature. The micropolar parameter and Brinkman number have a significant effect on the flow and temperature fields. Furthermore, electrokinetic phenomena are crucial in controlling the axial and spin velocities of the micropolar fluid. These findings have significant ramifications for the design and optimization of microfluidic devices in engineering and biomedical applications that employ the electroosmotic peristaltic flow of micropolar fluids. [ABSTRACT FROM AUTHOR]

The present study addresses the effects of nonlinear thermal radiation and heat fall/rise on the thermal radiated viscoelastic fluid flow through spiraling disks with a homogeneous and heterogeneous chemical response. The properties of the Cattaneo-Christov heat flux model, a revised model of conventional Fourier’s law that predicts thermal relaxation properties, are examined in detail. The rotation of both the disks in the same and opposite directions is evaluated. The effect of heterogeneous-homogeneous chemical reactions is also considered in the present communication, making the study reasonably adaptable. The coupled partial differential equations, such as energy, momentum, and concentration, are transformed into ordinary differential equations by von Kármán variables. The outcomes of the present work confirm that flow behavior is reversed due to stretching action. Velocity and pressure profiles are reduced with the impact of Deborah’s number. In addition, it is noticed that increasing heterogeneous-homogeneous reaction parameters decreases the fluid concentration. Numerically computed values are compared with the predicted results using L.R. regularized L.R. and regularized S.V.R. It is observed that the regularized L.R. method outperformed the other two machine learning methods. Graphical illustrations of axial, radial, and tangential flows and concentration and temperature profiles are illustrated in graphs. [ABSTRACT FROM AUTHOR]

The importance of bioconvection into the application of nanoparticles has had a significant impact on fundamental technological and industrial functions in recent years. These discussions are being carried forward by the bioconvection appearance on that flow by attracting nanoparticles into additional features on thermal radiation and activation energy. The investigation had been proposed on the appealing features of the mass and thermal convective boundary constraints. The high desirable subclass on rate-type fluid, especially Williamson fluid, was used to anticipate the absolute rheological parameters. The designated partial differential system was modified along with nonlinear ordinary differential equations applying enhance being related conversion, the designated partial differential system was modified along nonlinear ordinary differential equations. The governing equations are interpreted into ordinary differential equations, and in the following, shooting process was obeyed to build up the mathematical classification on the convert dimensionless flow problem. This value of physical restraint was displayed on the table and plots tests. This noted theoretical imitation could be highly successful in improving the solar energy systems and thermal extrusion processes. The outcomes reported that the rise in Weissenberg number and Hartmann number decreased the nanoparticles velocity distribution. The progressing temperature distribution was observed to develop radiation parameter and thermal conductivity parameter. That was further noted to modify bioconvection Lewis number and Peclet number that were reduced into motile microorganism distribution effectively. [ABSTRACT FROM AUTHOR]

This Riga plate, which extends the configuration with permanent magnets and electrodes, may induce a wall-parallel Lorentz force over the magnetic field and exterior electrics, enabling efficient control of the fluid flow. In this paper, the focus is on considering the three-dimensional flow characteristics of Williamson fluid past the Riga plate in the absence of variable thermal properties. Many influential factors, such as convective boundary conditions of temperature, viscous dissipation, binary chemical reactions, and thermal radiation, are studied in their analysis. To address the study problem, dimensionless parameters are used to clarify the conductive partial differential equations. This dimensionless form was consequently determined mathematically by applying the shooting technique. The affected engineering parameters were interpreted graphically to appeal to physical interest. It was observed that the velocity distribution slows down into the viscosity parameter and stretching ratio constant. The enhanced temperature distribution was noticed in the increase in the thermal conductivity parameter. The rate of heat transport (130.56%) rises in the presence of Biot numbers. This causes significant increases in convective heat transport and heat energy. [ABSTRACT FROM AUTHOR]

A computational analysis has been conducted to investigate turbulent flow and convective thermal transfer characteristics in a twodimensional horizontal rectangular section channel with a hot lower wall-mounted diamond-shaped baffle. The calculations are based on the finite volume method, by means of Commercial Computational Fluid Dynamics software FLUENT, standard k-epsilon turbulence model with QUICK numerical scheme, and the SIMPLE discretization algorithm has been applied. The fluid flow and heat transfer characteristics, i.e., dynamic pressure coefficient, stream function, mean, axial, and transverse velocities, turbulent viscosity, temperature field, skin friction coefficients, local and average Nusselt numbers, and thermal enhancement factor are presented for flow Reynolds numbers based on the aeraulic diameter of the computational domain ranging from 12,000 to 32,000 at constant surface temperature condition along the upper and lower walls. Effect of the diamond configuration of the insulated baffle is studied numerically and the data obtained from this same baffle model are also compared with that of the simple flat rectangular baffle under similar operating conditions. Over the range under investigation, the improvements are found to be around 3.962 and 29.820 times higher than the smooth air channel with no baffle for heat thermal transfer and skin friction factor, respectively. The maximum TEF is around 1.292 at the highest Reynolds number value, Re = 32,000. [ABSTRACT FROM AUTHOR]

In this work, magneto-hydrodynamic natural convection of a nanofluid in a wavy cavity considering Brownian motion is studied numerically using the control volume finite element method. The effective viscosity and thermal conductivity of the nanofluid are defined by the correlation in which the impact of Brownian motion on the thermal conductivity is considered. The considered wavy cavity is heated from the left side and it cooled from the right side. Also, the top and bottom walls of the considered wavy cavity are assumed adiabatic. The impacts of various controlling parameters such as the Rayleigh number, wavy contraction ratio, Hartmann number and undulation number are examined on the contour maps of the streamlines and the isotherms. Further, the average and local Nusselt numbers are calculated and presented graphically and discussed. The findings narrate that the strength of the convective flow has a direct relationship with the Rayleigh number and also it has a reverse relationship with the wavy contraction ratio. [ABSTRACT FROM AUTHOR]

In this paper, the researchers explore heat transfer and magneto-hydrodynamic flow of hybrid nanofluid in a rotating system among two surfaces. The upper and lower plates of the system are assumed penetrable and stretchable, respectively. The thermal radiation and Joule heating impacts are considered. A similarity technic is applied to alter governing energy and momentum equations into non-linear ordinary differential ones that contain the convenient boundary conditions and used the Duan-Rach Approach (DRA) to solve them. Influences of assorted parameters including rotation parameter, suction/blowing parameter, radiation parameter, Reynolds number, hybrid nanofluid volume fraction, and magnetic parameter on temperature and velocity profiles are examined. Also, a correlation for the Nusselt number has been developed in terms of the acting parameters of the present study. The outcomes indicate that Nusselt number acts as an ascending function of injection and radiation parameters, as well as volume fraction of nanofluid. [ABSTRACT FROM AUTHOR]

Numerical simulation of mixed convection heat transfer in a lid-driven triangular cavity filled with power law nanofluid and with an opening was performed under the effect of an inclined magnetic field. The left vertical wall of the cavity moves in + y-direction, and the bottom wall of the cavity is partially heated. Galerkin weighted residual finite element method was used to solve the governing equations. Influence of Richardson number, Hartmann number, inclination angle, opening ratio and nanoparticle volume fraction on the fluid flow and heat transfer is examined for various power law indices. It was observed that average heat transfer deteriorates as the value of Richardson number and Hartmann number enhances. At the lowest value of Richardson number, the discrepancy between the average heat transfer corresponding to different power law indices is higher. The inclination angle of the magnetic field where the minimum of the average Nusselt number is seen depends on the fluid type. Average heat transfer number is the highest for the highest value of the opening ratio. The average Nusselt number enhances with solid particle volume fraction, and there are slight variations in the reduction in the average Nusselt number when base fluid and nanofluid are considered for various power law indices. [ABSTRACT FROM AUTHOR]

• Investigating the effect of changing the position of applying magnetic field on the characteristics of non-Newtonian nanofluid flow. • Achievement of a higher the Nusselt number by increasing the phase difference of the moving speed of the semi- ellipsoidal cavity. • Controlling the effect of magnetic field by changing the type of wall heating, changing the fluid type and subjecting the flow to heat absorption or heat production. Due to the application importance of convection flows under the impact of external fields such as magnetic field for non-Newtonian nanofluids, in cases such as nuclear processes, technologies related to lubrication, production and processing of food products, the modeling of these types of currents is very important. The existing research inquires the influence of heat production/absorption on the characteristics of non-Newtonian flow and entropy formation caused by convection heat transfer. For this purpose, the phenomenon of mixed convection inside the semi-elliptical chamber containing a power-law nanofluid is presumed in such a way that the Brownian motion of nanoparticles is considered. The curved and vertical walls of the enclosure are cold and under three different types of heating, respectively. The cold wall has no speed while the chamber vertical wall has a non-uniform velocity distribution (cosine) with a phase difference. The main goal of the research is to depict the impact of changing the position of applying the magnetic field and changing the phase difference of wall movement on the fluid flow. Flow modeling was accomplished via the utilization of lattice Boltzmann method and the accuracy of the findings was affirmed by comparing previous related studies. According to the research findings, enhancing the mean Nusselt number has a direct relationship with enhancing the phase difference. In addition, by enhancing the phase difference to 180, the mean Nusselt number up to 46% more is acquired, the influence of magnetic field applying becomes more conspicuous. In addition to the fact that the enhancing in Richardson number leads to increment of in the mean Nusselt number value and flow power, the effect of varying the phase difference becomes more noticeable with the enhancing in Richardson number. Enhancing in the Hartmann number, index of power-law and decreasing in the heat production/absorption coefficient lead to decrease in the entropy value and the average Nusselt number. By changing the position of applying the magnetic field, a current with various features can be acquired. Based on the results, it was demonstrated that changing the type of wall heating along with changing the heat absorption/production coefficient are very useful strategies in controlling the system thermal characteristics. [ABSTRACT FROM AUTHOR]

The main aim of the present study is the heat transfer analysis of MHD Eyring-Powell flow over a stratified stretching sheet immersed in a porous material. Mixed convection as well as viscous dissipation effects are considered in order to observe the heat transfer analysis. To strengthen the energy equation viscous dissipation effect is incorporated in this study. Here, temperature distribution is carefully examined to assess rate of heat transmission for the present consideration. Present consideration can have many applications in various engineering fields. Later, the most appropriate similarity transformations are utilized to transform the governing partial differential equations into a nonlinear set of ordinary differential equations. Thereafter, a powerful and convergent procedure namely Runge-Kutta-Fehlberg procedure together with shooting technique is applied to obtain numerical solution for the condensed problem. Graphs are drawn for various values of flow controlling parameters to observe clear insight of the present study through velocity, temperature and concentration profiles. Numerical solutions are tabulated for comparison purpose. The main observations indicate that the temperature and velocity of the fluid decrease over a stretched sheet as the Eyring-Powell fluid material parameter increases. Moreover, mixed convection exhibits a significant impact on the present study, as the parameter value increases. correspondingly, velocity increases, but temperature shows a reverse nature. [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]

Abstract: In this work, we explore the unsteady squeezing flow and heat transfer of nanofluid between two parallel disks in which one of the disks is penetrable and the other is stretchable/shrinkable, in the presence of thermal radiation and heat source impacts, and considering the Cattaneo–Christov heat flux model instead of the more conventional Fourier's law of heat conduction. A similarity transformation is utilized to transmute the governing momentum and energy equations into nonlinear ordinary differential equations with the proper boundary conditions. The achieved nonlinear ordinary differential equations are solved by the Duan–Rach Approach (DRA). This method modifies the standard Adomian Decomposition Method by evaluating the inverse operators at the boundary conditions directly. The impacts of diverse active parameters, such as the suction/injection parameter, the solid volume fraction, the heat source parameter, the thermal relaxation parameter, and the radiation parameter on flow and heat transfer traits are examined. In addition, the value of the Nusselt number is calculated and portrayed through figures. [ABSTRACT FROM AUTHOR]

This study investigates the convective heat transfer of a hybrid nanofluid filled in a triangular cavity subjected to a constant magnetic field and heated by a constant heat flux element from below. The inclined side of the cavity is cooled isothermally while the remaining sides are thermally insulated. The finite difference method with the stream function-vorticity formulation of the governing equations has been utilized in the numerical solution. The problem is governed by several pertinent parameters namely, the size and position of the heater element, B=0.2-0.8 and D=0.3-0.7, respectively, the Rayleigh number, Ra=102-106, the Hartmann number, Ha=0-100, the volume fraction of the suspended nanoparticles, φ=0-0.2, and the heat generation parameter Q=0-6. The results show significant effect of increasing the volume fraction of the hybrid nanofluid when the natural convection is very small. Moreover, the hybrid nanofluid composed of equal quantities of Cu and Al2O3 nanoparticles dispersed in water base fluid has no significant enhancement on the mean Nusselt number compared with the regular nanofluid. [ABSTRACT FROM AUTHOR]

Nanofluids have attracted tremendous attention during the last two decades. The researchers all over the world investigate the feasibility of the nanofluids use in different phenomena and equipment. The ever-increased importance of nanofluids shows the urgent need to have a comprehensive review of nanofluids utilization in diverse areas. This paper presents a comprehensive assessment of nanofluids' applications in various microchannel geometries. All studies have been categorized into three main classes: experimental, analytical and numerical studies. Critical information has been presented in a comprehensive table in each section. Also, statistical considerations such as bibliographic analysis have been performed. The results show ever-increasing importance of nanofluids applications in microchannels. The bibliographic analysis shows the changing in the research concerns in the last decade. Almost all studies have demonstrated the preferred nanofluids thermal behavior in microchannels, compared to the base fluids. [ABSTRACT FROM AUTHOR]

The problem of unsteady conjugate natural convection and entropy generation within a semicircular porous cavity bounded by solid wall of finite thickness and conductivity has been investigated numerically. The governing partial differential equations with the corresponding initial and boundary conditions have been solved by the finite difference method using the dimensionless stream function, vorticity, and temperature formulation. Numerical results for the isolines of the stream function, temperature, and the local entropy generation due to heat transfer and fluid friction as well as the average Nusselt and Bejan numbers, and the average total entropy generation and fluid flow rate have been analyzed for different values of the Rayleigh number, Darcy number, thermal conductivity ratio, and the dimensionless time. It has been found that low values of the temperature difference reflect the entropy generation, mainly in the upper corners of the cavity, while for high Rayleigh numbers, the entropy generation occurs also along the internal solid-porous interface. A growth of the thermal conductivity ratio leads to an increase in the average Bejan number and the average entropy generation due to a reduction of the heat loss inside the heat-conducting solid wall. [ABSTRACT FROM AUTHOR]

The heat generation/absorption and thermo-diffusion on an unsteady free convective MHD flow of radiating and chemically reactive second grade fluid near an infinite vertical plate through a porous medium and taking the Hall current into account have been studied. Assume that the bounding plate has a ramped temperature with a ramped surface concentration and isothermal temperature with a ramped surface concentration. The analytical solutions for the governing equations are obtained by making use of the Laplace transforms technique. The velocity, temperature, and concentration profiles are discussed through graphs. We also found that velocity, temperature, and concentration profiles in the case of ramped temperature with ramped surface concentrations are less than those of isothermal temperature with ramped surface concentrations. Also, the expressions of the skin friction, Nusselt number, and Sherwood number are obtained and represented computationally through a tabular form. [ABSTRACT FROM AUTHOR]

The influence of a first order slip boundary condition on the diffusion of chemically reactive species in an unsteady MHD boundary-layer flow of a non-Newtonian Maxwell fluid over a vertical permeable linearly stretching or shrinking sheet is considered. The whole analysis is performed taking the first order chemical reaction and linearly varying wall concentration. Choosing appropriate similarity variables, the governing equations of the problem are transformed into a set of non-linear coupled self-similar equations, which are then solved numerically by the shooting technique. A comparison with previously published results is performed for certain cases and the results are found to be in excellent agreement. The flow features and mass transfer characteristics for different values of the governing parameters are graphically presented and discussed in detail. [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]