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This paper investigates the natural convection inside a partially layered porous cavity with a heated wavy solid wall; the geometry is encountered in compact heat exchangers. Alumina nanoparticles are included in the water to enhance the heat exchange process. The incidental entropy generation is also studied to evaluate the thermodynamic irreversibility. The nanofluid flow is taken as laminar and incompressible while the advection inertia effect in the porous layer is taken into account by adopting the Darcy–Forchheimer model. The problem is explained in the dimensionless form of the governing equations and solved by the finite element method. The Darcy number (Da), porosity of the porous layer (ε ), number of undulations (N), and the nanoparticles volume fraction (ϕ ) are varied to assess the heat transfer and the incidental entropy generation. It is found that the waviness of the solid wall augments the average Nusselt number and minimizes the generation of entropy. The results show for some circumstances that the Nusselt number is augmented by 43.8% when N is raised from 0 (flat solid wall) to 4. It is also found that the porosity of the porous layer is a more crucial parameter than its permeability, where a 37.4% enhancement in the Nusselt number is achieved when the porosity is raised from 0.2 to 0.8. [ABSTRACT FROM AUTHOR]

The main focus of the present research work is to elaborate the Reiner–Philippoff fluid flow over a stretching sheet along with thermal radiation effect. A Darcy–Forchheimer medium was imposed and a linear stretching surface was used to generate the flow. Application of appropriate transformation yields nonlinear ordinary differential equation through nonlinear Navier–Stokes equations and solved by Runge–Kutta–Fehlberg shooting technique. Importance of influential variables such as velocity and temperature was elaborated graphically. It is envisaging that the boost up values of γ declines the both velocity and temperature profiles. [ABSTRACT FROM AUTHOR]

This manuscript brings out with an enhancement of the freshwater productivity from the active inclined solar panel basin solar still (AISPBSS). The research was conducted on the AISPBSS by the diversified mass flow rate of water (mf). The maximum freshwater yield obtained at mf at 1.8, 3.2 and 4.7 kg/h is 7.5, 6.5 and 5.4 kg, respectively. The daily average thermal and exergy efficiency of the AISPBSS at mf at 1.8, 3.2 and 4.7 kg/h is 43.71, 38.27 and 29.62% and 8.39, 6.94 and 5.08%, respectively. The daily average PV panel power production of 47.71, 49.84 and 53.83 watts, electrical efficiency of 7.2, 7.6 and 8.1%, thermal efficiency of 17.3, 18.3 and 19.7%, exergy efficiency of 18.32, 20.23 and 22.39%, the overall thermal efficiency of 61.39, 57.44 and 51.37% and the overall exergy efficiency of 26.52, 27.14 and 27.40% are obtained from the system under mf at 1.8, 3.2 and 4.7 kg/h, respectively. When mf increases, there are decreases in the AISPBSS distillate yield, thermal, exergy and the overall thermal efficiency and increases in the PV panel power production and electrical, thermal, exergy and the overall exergy efficiency. Further, energy return term and carbon credit attained for the AISPBSS have been calculated. It was found that payback period of 20, 18.7 and 17.5 years and carbon credit earned of 21, 25 and 30 $ are obtained at mf at 1.8, 3.2 and 4.7 kg/h, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the problem of steady forced convection heat transfer and fluid flow characteristics of a hybrid nanofluid flowing through an isothermally heated horizontal tube considering various nanoparticle shapes has been investigated numerically. The three dimensionless cylindrical coordinate equations are discretized using the finite volume method and solved via a FORTRAN program. A numerical parametric investigation is carried out for a tube filled with regular water, (TiO2/water) nanofluid and (Ag–TiO2/water) hybrid nanofluid. Four different types of nanoparticle shapes are considered in this study, spherical, cylindrical, platelets and blades, with different volume fractions ranging from 0 to 8% using water as a base liquid. The influence of nanoparticle shape, nanoparticle concentration and Reynolds number on the local Nusselt number and the friction factor is essentially examined. The results showed that the friction factor of both nanofluid and hybrid nanofluid flow was increased as the nanoparticle volume fraction increased for all kinds of nanoparticle shapes, whereas it decreased as the Reynolds number increased. Nusselt number increased with increase in the nanoparticle concentration and Reynolds number. The highest heat transfer rate was acquired for the maximum nanoparticle volume concentration by using blade nanoparticle shape followed by platelet shape, cylindrical shape and lastly the sphere shape. It was found that the maximum values of the friction factor were registered for platelet-shape nanoparticles. [ABSTRACT FROM AUTHOR]

This manuscript aims to analyze the passive inclined solar panel basin (PISPB) still at diversified flow rate of water (mf). The freshwater collected from the solar still for different mf at 4.68, 7.56 and 10.08 kg h−1 is 3.7, 2.7 and 1.6 kg, respectively. Results showed that at higher flow condition, the still energy and exergy efficiency decreases and it is estimated as 36.06, 25.56 and 16.95% and 2.97, 1.91 and 1.01%, respectively, for flow rates of 4.68, 7.56 and 10.08 kg h−1. Results revealed that electrical, thermal and exergy efficiency of photovoltaic panel increases under higher flow condition and it is found as 8.05, 8.81 and 9.44%, 11.43, 20.8 and 22.17 and 19.38, 20.58 and 21.16% for mass flow rates of (mf) 4.68, 7.56 and 10.08 kg h−1, respectively. When the mf increases, there is a decrease in the PISPB still distilled water production rate, thermal and exergy efficiency, and there is an increase in power production, electrical, thermal and exergy efficiency through the photovoltaic panel. [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 article explores the influence of thermal radiation on the flow and heat transfer of single-walled carbon nanotubes over both a convergent and divergent channel. Flow is induced due to a Darcy–Forchheimer medium. Further, the heat transfer mechanism is analyzed in the presence of a thermal radiation process. Guided by some appropriate similarity transformations, the fundamental PDEs are converted into a self-similar system of coupled non-linear ODEs. The findings are obtained with the help of the Runge–Kutta-45-based shooting method. The roles of the Reynolds number, porosity parameter, inertia coefficient parameter, Prandtl number and radiation parameter are presented graphically. Results are displayed and show that the rate of heat transfer is higher in a divergent channel as compared to a convergent channel. [ABSTRACT FROM AUTHOR]

The conjugate natural convection of a new type of hybrid nanofluid (Ag–MgO/water hybrid nanofluid) inside a square cavity is addressed. A thick layer of conductive solid is considered over the hot wall. The governing partial differential equations (PDEs) representing the physical model of the natural convection of the hybrid nanofluid along with the boundary conditions are reported. The thermophysical properties of the nanofluid are directly calculated using experimental data. The governing PDEs are transformed into a dimensionless form and solved by the finite element method. The effect of the variation of key parameters, such as the volume fraction of nanoparticles, Rayleigh number, and the ratio between the thermal conductivity of the wall and the thermal conductivity of the hybrid nanofluid (Rk), is studied. Furthermore, the effects of the key parameters are investigated on the temperature distribution, local Nusselt number, and average Nusselt number. The results of this study show that the heat transfer rate increases by adding hybrid nanoparticles for a conduction-dominant regime (low Rayleigh number). The heat transfer rate is an increasing function of both the Rayleigh number and the thermal conductivity ratio (Rk). In the case of a convective-dominant flow (high Rayleigh number flow) and an excellent thermally conductive wall, the local Nusselt number at the surface of the conjugate wall decreases substantially by moving from the bottom of the cavity toward the top. [ABSTRACT FROM AUTHOR]

In this work, the double-diffusive natural convection was studied in an open-ended cavity with the help of the lattice Boltzmann method. In this study, the driven force is developed by a change in the temperature gradient and concentration gradient on the left side of the cavity, which is the closed end. The temperature and concentration are maintained high at this end. The study is carried out for various parameters such as Rayleigh number (Ra) ranging from 103 to 106, aspect ratio (Ar) of 0.5, 1 and 2 and constant Prandtl number (Pr) of 0.7 and Lewis number (Le) of 2. The results are concentrated on for different buoyancy ratios (N = − 1, 0, 1) also. The results obtained are validated with existing literature results. The results show that when N value is negative, two buoyancy forces oppose each other and also the influence of concentration buoyancy force on fluid flow behavior gets dominant, and for aspect ratios 1 and 2, this effect was suppressed when Ra is increased but for the shallow cavity increasing in Ra helps the concentration force to become more dominant. [ABSTRACT FROM AUTHOR]

The aim of the current study is to investigate the natural convection heat transfer in a square enclosure with a wavy circular heater under magnetic field and nanoparticles. The governing equations that are expressed in dimensionless form are solved by means of control volume finite element method employing a validated FORTRAN code. The dimensionless controlling parameters of the present investigation are shape factor of nanoparticles (m), Hartmann number (Ha), Rayleigh number (Ra), and nanoparticle volume fraction (ϕ). In this study, the amplitude A and number of undulations N are fixed at a constant value of 0.2 and 8, respectively. The obtained results portray that in the presence of waves on the inner wall of the annulus, the heat transfer rate is an ascending function of Rayleigh number, nanoparticle volume fraction and less obvious function of their shape factor, while it is a descending function of the Hartmann number. [ABSTRACT FROM AUTHOR]

A numerical study is carried out on mixed convection and entropy generation of Al2O3/water nanofluid due to a rotating cylinder inside a square cavity. The numerical computations are performed taking the non-homogenous model of Buongiorno into consideration. The inner moving rotating circular cylinder is maintained at a constant hot temperature Th and the other left and right vertical walls of the cavity are maintained at a constant cold temperature Tc. The bottom and top horizontal walls are maintained as adiabatic. The Galerkin weighted residual method is implemented to numerically solve the governing equations. The Rayleigh number (104 ≤ Ra ≤ 107), angular rotational velocity (0 ≤Ω≤ 600) nanoparticles loading (0 ≤ ϕ ≤ 0.04) and the dimensionless radius of rotating cylinder (0.1 ≤ R ≤ 0.4) are the governing parameters of this study. Numerical results for the streamlines, isotherms, isentropic lines, nanoparticle loading, local and average Nusselt number and Bejan number are obtained and presented graphically. A detailed discussion of the results is performed to highlight the physics of the problem. [ABSTRACT FROM AUTHOR]

Nowadays, various types of engine oils are widely used in lubricating and cooling internal combustion engines. In this study, the behavior of MWCNTs–SiO2 (30–70)/10W40 hybrid nanofluid as part of a new generation of engine oil is investigated experimentally. A mixture of SiO2, with 20–30 nm particle diameter, and MWCNT, with 3–5 nm inner and 5–15 nm outer nanoparticle diameter was dispersed into a base fluid of 10W40 engine oil. Then, the viscosity of the product was measured at nanofluid concentrations and temperatures, respectively, ranging from 0.05 to 1% and 5 to 55 °C, for different values of shear rate. Also, a sensitivity analysis to the solid volume fraction was performed at different temperatures. The results show that the behavior of the samples is well fitted with the pseudo-plastic Ostwald de Waele non-Newtonian model. The viscosity of the produced hybrid nano-lubricant is found to be 35% greater than that of pure engine oil. Because of the significant deviation between the measured viscosity and the values predicted by existing classical viscosity models, a new regression model is obtained. The R2 and adj. R2 for the model are computed as 0.988 and 0.977, respectively, signifying strong predictability with ± 3% margin of deviation. [ABSTRACT FROM AUTHOR]

The study ahead deals with the natural convection of MWCN–Fe3O4/water magnetic hybrid nanofluid flowing in a porous medium. The flow domain is affected by an inclined magnetic field influencing the dynamic viscosity. The dependency of the flow and heat transfer characteristics on Rayleigh number, Ra = 103–106; Hartman number, Ha = 0–50; inclination angle of the magnetic field, ϕ = 0°–180°; magnetic number, δ0 = 0–2.0; porosity, ε = 0.1–0.9; Darcy number, Da = 10−7–10−1;and volume fraction of the composite nanoparticles, φ = 0, 0.1 and 0.3% is studied numerically. At low Rayleigh number Ra = 104, dispersing the nanocomposite particles increases the average Nusselt number Nuavg, while that decreases the Nuavg when Ra = 105 and 106. The dependency of viscosity on the magnetic field decreases the Nuavg at 0° < ϕ < 135°, which is due to an increase in overall viscosity of the nanofluid. After that (ϕ ≥ 135°), the average Nusselt number is greatly enhanced by increasing ϕ from 135° up to 180°. There is no meaningful change in average Nusselt number of the hybrid nanofluid by increasing the inclination angle of magnetic field in the absence of magnetic field-dependent viscosity (δ0 = 0). [ABSTRACT FROM AUTHOR]

The natural-convection thermal performance of a dielectric liquid in a cubical module triggered by a varying rectangular heat generation source is numerically examined. The rectangular generating source is connected to the center of one vertical wall of the cubical module, which is constructed either vertically or horizontally. Two vertical walls neighboring the source-mounted wall are kept cold, and the remaining walls are insulated from the environment. The isotherms and the velocity contours are computed for a wide range of the Rayleigh number as well as the generating-source aspect ratio and the thermal conductivity ratio, demonstrating the variations of the thermal and stream structures inside the module. It is established that the thermal performance is more significant and is an increasing function of the heat generating-source aspect ratio and the Rayleigh number for the two altered alignments of the generating source. According to the practical demands of the thermal management of electronic devices, the heat transfer rate can be magnified or diminished by choosing the proper parameters such as thermal conductivity ratio, Rayleigh number, the aspect ratio and orientation of the generating source. [ABSTRACT FROM AUTHOR]

Mixed convective heat transfer of Cu–water nanofluid in a porous cavity with non-uniform temperature profiles on vertical sidewalls in the presence of thermal radiation and magnetic field is examined numerically. The vertical sidewalls are heated sinusoidally. Thermally insulated walls are considered at the remaining sides of the cavity. The magnetic field is applied parallel to the horizontal walls uniformly. The SIMPLE algorithm based on finite volume approach is applied to solve the governing equations. The numerical outcomes are discussed in the wide range of the parameters, Richardson number, phase deviation, amplitude ratio, Darcy number, Hartmann number, the thermal radiation, and the solid volume fraction. It is found that the average Nusselt number is decreased in value with the raise in the either Hartmann number or Richardson number in the presence of thermal radiation. The average heat transfer rate is enhanced with an augment in the solid volume fraction, and this enhancement is more effective in the presence of thermal radiation than that of in the absence of thermal radiation. The highest heat transfer rate is obtained for φ = 0 in the forced convection regime, whereas it is maximum at φ = 3 π / 4 in the mixed and free convection regimes. [ABSTRACT FROM AUTHOR]

The objective of the present study is to peruse the natural convection in the cavity containing inclined elliptical heater under shape factor of nanoparticles and magnetic field. The control volume-based finite element method is used for solving conservation equations. Numerical results show very good grid independency and very good compromise with other works. The result shows the heat transfer grows via mounting nanofluid volume fraction. The increment of Ra number also leads the heat transfer to ascend. Heat transfer of nanofluid with three different shapes of nanoparticles is studied, and results show the platelet nanoparticle is better than the other ones. The influence of magnetic field on heat transfer is also investigated and discussed. The obtained outcomes represent that at a certain Rayleigh number, the average Nusselt number descends with the ascendant of Hartmann number. Finally, the new correlation is reported for calculating the Nu number in these geometries. [ABSTRACT FROM AUTHOR]

The paper presents the mixed convection heat transfer and entropy generation of a nanofluid containing carbon nanotubes, flowing in a 3D rectangular channel, subjected to opposed buoyant forces. The governing equations, including the continuity, momentum and energy equations, have been numerically solved using the finite volume technique. The results, including the contours of the axial velocity and temperature, have been presented for different values of the opposed buoyancy parameter (− 300 < Ω < − 100). The outcomes show that with an increase in the opposed buoyancy parameter, the nanofluid velocity near the channel wall drastically reduces and, therefore, causes a reduction in the Nusselt number. In addition, due to the occurrence of backflow phenomenon, an increment of the opposed buoyancy parameter enhances the total entropy generation along the channel. In brief, the friction-induced entropy generation is negligible compared with the entropy generation due to heat transfer. Finally, by increasing the value of the opposed buoyancy parameter, the ratio of the heat transfer rate to irreversibility decreases within the system. [ABSTRACT FROM AUTHOR]

In current attempt, nanoparticle Electrohydrodynamic transportation has been modeled numerically via control volume based finite element method. Mixture of Fe3O4 and Ethylene glycol is elected. Impact of radiation parameter (R d) , voltage supplied (Δ φ) , nanoparticle concentration, Permeability and Reynolds number have been displayed. Results display that permeability and thermal radiation can improve temperature gradient. [ABSTRACT FROM AUTHOR]

Bioconvection in magneto-nanoliquid embedded with gyrotactic microorganisms across an elongated sheet with velocity slip of second order is addressed. Nonlinear thermal radiation and chemical reaction aspects are retained in energy and concentration equations. Numerical simulations for the modeled problem are proposed via Runge–Kutta–Fehlberg-based shooting technique. Special attention is given to the impact of involved parameters on the profiles of motile microorganisms, nanoparticle volume fraction, temperature and velocity. Our simulations figured out that assisting flow generates more heat transfer than the opposing flow situation. The motile microorganism's boundary layer decayed for higher bioconvection Peclet and bioconvection Lewis numbers. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study provides numerical analysis of the free convection of copper-water-based nanofluid filling a triangular cavity with semicircular bottom wall. The cavity sidewalls are maintained at cold temperature, while the semicircular wall is maintained at hot temperature. The other wall segments are thermally insulated. To control the energy transport within the cavity, a uniform magnetic field is applied horizontally. The physical domain is discretized according to the control volume finite element method which has been used to solve the governing equations. The physical and geometrical aspects of the current problem are investigated by inspecting the impacts of Rayleigh number, Hartman number, aspect ratio and the volume fraction of the Cu nanoparticles. Decreasing the radius of the hot semicircle enlarges the average Nusselt number at the absence of the magnetic field. When the magnetic field is applied, this effect is conversed within Ra ≤ 104. This conversed impact does not hold up when Ra is raised to 105. The numerical results are correlated in a sophisticated correlation of the average Nusselt number with other parameters. [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]

Buongiorno model is applied to investigate nanofluid migration through a permeable duct in the presence of external forces. Influences of radiation and Joule heating on first law equation are added. Final formulas are solved via differential transform method. Roles of suction, thermophoretic, radiation and Brownian motion parameters, Schmidt number, Hartmann number, Eckert number were presented. Results show that temperature gradient improves with the enhancement of Reynolds number, suction and Radiation parameters. Nu augments with the augmentation of Hartmann and Eckert numbers, while reverse behavior is seen for skin friction coefficient. Also, it can be concluded that Nusselt number enhances with the increase in radiation parameter but it decreases with the increase in Brownian motion. [ABSTRACT FROM AUTHOR]

This paper carries on investigation to study the effects of variable magnetic field and thermal radiation on free convective flow of an electrically conducting incompressible nanofluid over an exponential stretching sheet. The model implemented in the present study significantly enriches the thermal conductivity and hence more heat transfer capability of nanofluids. The transformed governing equations have been solved numerically using fourth-order Runge-Kutta method along with shooting technique. The influence of variable magnetic field and thermal radiation associated with thermal buoyancy on the dimensionless velocity, temperature, skin friction and Nusselt number have been analyzed. The obtained numerical results in the present study are validated and found to be in excellent agreement with some previous results seen in the literature. The present study contributes to the result that augmented Hartmann number belittles the fluid flow and enhances the fluid temperature and the related thermal boundary layer thickness. [ABSTRACT FROM AUTHOR]

In this study, natural convection of CuO-water nanofluid in a square cavity with a conductive partition and a phase change material (PCM) attached to its vertical wall is numerically analyzed under the effect of an uniform inclined magnetic field by using finite element method. Effects of various pertinent parameters such as Rayleigh number (between 105 and 106), Hartmann number (between 0 and 100), magnetic inclination angle (between 0∘ and 90∘), PCM height (between 0.2H and 0.8H), PCM length (between 0.1H and 0.8H), thermal conductivity ratio (between 0.1 and 100) and solid nanoparticle volume fraction (between 0 and 0.04) on the fluid flow and thermal characteristics were numerically analyzed. It was observed that when magnetic field is imposed, more reduction in average Nusselt number for water is obtained as compared to nanofluid which is 31.81% for the nanofluid at the highest particle volume fraction. The average heat transfer augments with magnetic inclination angle, but it is less than 5%. When the height of the PCM is increased which is from 0.2H to 0.8H, local and average Nusselt number reduced which is 42.14%. However, the length of the PCM is not significant on the heat transfer enhancement. When the conductivity ratio of the PCM to the base fluid within the cavity is increased from 0.1 to 10, 29.5% of the average Nusselt number enhancement is achieved. [ABSTRACT FROM AUTHOR]

In this study, mixed convection and entropy generation in a nanofluid filled triangular cavity under the influence of rotating cylinder and flexible sidewall were numerically analyzed with finite element method. The inclined sidewall was cooled while the left vertical wall is partially heated. Heat transfer rate enhances as the values of Rayleigh number, angular rotational velocity of the cylinder, elastic modulus of the flexible sidewall and solid nanoparticles volume fraction increase. Nusselt number enhances more in the counter-clockwise direction of the cylinder as compared to clockwise directional rotation and 13.55% of average heat transfer enhancement was achieved for Ω=3000 when compared to motionless cylinder. Average Nusselt number increases by about 30.50% when the elastic modulus of the flexible wall is changed from 500 to 105. The changes in the velocity profiles are significant for the lower part of the triangular enclosure with respect to changes in angular rotational velocity and elastic modulus as compared to upper part of the cavity. Adding nanoparticles increases heat transfer especially for the lower part of the cavity and 49.63% of heat transfer enhancement was achieved for the highest volume fraction when compared to base fluid. Normalized total entropy generation rates enhance for higher values of elastic modulus of the flexible wall, angular rotational speed of the circular cylinder and nanoparticle volume fractions. [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]

In this paper, the effect of a baffle on free convection heat transfer of a water-Fe3O4 nanofluid in a C-shaped enclosure in the presence of a magnetic field is investigated numerically. The enclosure is subjected to a constant magnetic field. The vertical wall on the left side is maintained at a constant hot temperature of Th, and the right one is kept at a constant cold temperature of Tc. The rest of the walls are insulated. The governing equations are discretized by the control volume method and solved simultaneously by the SIMPLE algorithm. The numerical results show very good agreement with other published works. The results indicate that by increasing the enclosure's aspect ratio, the Nusselt number is increased. It is also found that the volume fraction of nanoparticles can be raised in order to achieve increased cooling in the enclosure. By increasing the aspect ratio, the effect of the nanoparticles on the enhancement of the Nusselt number is more pronounced. Also, the maximum effect of the baffle on the heat transfer is seen at the bottom of the hot wall. Generally, increasing the baffle length produces increases in the Nusselt number. The maximum cooling level is occurred for AR = 0.7 and Bf = 0.2. [ABSTRACT FROM AUTHOR]

In this study, fluid flow and heat transfer in a vertical lid-driven CuO-water nanofluid filled square cavity with a flexible fin attached to its upper wall under the influence of an inclined magnetic field are numerically investigated. The left vertical wall of the cavity is colder than right vertical wall, and it moves in + y direction with constant speed. Horizontal walls of the cavity are insulated. The governing equations are solved with finite element method. The arbitrary Lagrangian-Eulerian method is used to describe the fluid motion within the cavity for the flexible fin in the fluid-structure interaction model. The influence of Richardson number (between 0.01 and 100), Hartmann number (between 0 and 50), inclination angle of the magnetic field (between 0 and 90%), nanoparticle volume fraction (between 0 and 0.05) and Young's modulus of flexible fin (between 250 and 5000) on the flow and heat transfer were numerically studied. It is observed that the presence of the elastic fin affects the flow field and thermal characteristics of the cavity. The local and average heat transfer enhance as the Richardson number, solid volume fraction of the nanoparticle increase whereas deteriorate as the value of the Hartmann number and inclination angle of the magnetic field increases due to the dampening of the fluid motion with Lorentz forces. The addition of the nanoparticles is more effective along the lower part of the right vertical wall where the heat transfer process is effective. The average heat transfer increases by 28.96% for solid volume fraction of 0.05% compared to base fluid when the flexible fin is attached to the upper wall. The average heat transfer deteriorates by 10.10% for cavity with and without fin at Hartmann number of 50 compared to the case without magnetic field. The average heat transfer enhances as the Young's modulus of the flexible fin decreases and the average Nusselt number increases by 13.24% for Young's modulus of 250 compared to configuration for the cavity having the Young's modulus of 5000. [ABSTRACT FROM AUTHOR]

In the present study, the main concern is to investigate the magnetohydrodynamic nanofluid flow subject to porous matrix and convective heating past a permeable linear stretching sheet. In addition, the influence of velocity slip, viscous dissipation, Joule heating and non-linear thermal radiation are considered. A new micro-convection model known as the Patel model is implemented for considerable enhancement of the thermal conductivity and hence, the heat transfer capability of nanofluids. Moreover, a convective heat transfer model is introduced where the bottom surface of the sheet gets heated due to a convection mechanism from a hot fluid of particular temperature. The numerical results of the transformed governing differential equations have been obtained by using fourth-order Runge-Kutta method along with shooting approach and secant method is used for better approximation. In the present analysis, base fluids such as water and Ethylene glycol and Copper, Silver and Aluminum oxide nanoparticles are considered. Results of the present investigation show that inclusion of porous matrix contributes to slow down the fluid velocity and diminution of wall shear stress (axial as well as transverse). Drag force due to magnetic field strength, velocity slip and imposed fluid suction impede the fluid motion and upsurge the heat transfer rate from the surface. In addition, rise in viscous dissipation widens the thermal boundary layer. [ABSTRACT FROM AUTHOR]

An analysis is carried out to study the coupled heat and mass transfer by mixed convection flow of a Newtonian fluid past a rotating vertical cone embedded in a porous medium in the presence of a magnetic field and chemical reaction effects. The cone surface is maintained at variable temperature and concentration. Similarity transformation is employed to transform the governing partial differential equations into a set of nonlinear ordinary differential equations, which are then solved numerically using shooting method that uses Runge-Kutta and Newton’s method. Comparisons with previously published work are performed and results are found to be in excellent agreement. Numerical Results for the velocities, temperature, concentration profiles, as well as local tangential and azimuthal skin friction coefficients, local Nusselt and Sherwood numbers are presented graphically and discussed for different values of the governing parameters to show interesting features of the solutions. This type of study finds significant applications in cooling of electric circuits, packed-bed chemical reactors, solar porous wafer absorber systems, synthesis materials and hygroscopic materials. [ABSTRACT FROM AUTHOR]

The effects of Joule-heating, chemical reaction and thermal radiation on unsteady MHD natural convection from a heated vertical porous plate in a micropolar fluid are analyzed. The partial differential equations governing the flow and heat and mass transfer have been solved numerically using an implicit finite-difference scheme. The case corresponding to vanishing of the anti-symmetric part of the stress tensor that represents weak concentrations is considered. The numerical results are validated by favorable comparisons with previously published results. A parametric study of the governing parameters, namely the magnetic field parameter, suction/injection parameter, radiation parameter, chemical reaction parameter, vortex viscosity parameter and the Eckert number on the linear velocity, angular velocity, temperature and the concentration profiles as well as the skin friction coefficient, wall couple stress coefficient, Nusselt number and the Sherwood number is conducted. A selected set of numerical results is presented graphically and discussed. [ABSTRACT FROM AUTHOR]

n analytical study of fluid flow and heat transfer in a composite channel is presented. The channel walls are maintained at different constant temperatures in such a way that the temperatures do not allow for free convection. The upper plate is considered to be moving and the lower plate is fixed. The flow is modeled using Darcy–Lapwood–Brinkman equation. The viscous and Darcy dissipation terms are included in the energy equation. By applying suitable matching and boundary conditions, an exact solution has been obtained for the velocity and temperature distributions in the two regions of the composite channel. The effects of various parameters such as the porous medium parameter, viscosity ratio, height ratio, conductivity ratio, Eckert number, and Prandtl number on the velocity and temperature fields are presented graphically and discussed. [ABSTRACT FROM AUTHOR]

The problem of combined heat and mass transfer by natural convection over a permeable cone embedded in a uniform porous medium in the presence of an external magnetic field and internal heat generation or absorption effects is formulated. The cone surface is maintained at either constant temperature and constant concentration or uniform heat and mass fluxes. In addition, the cone surface is assumed permeable in order to allow for possible fluid wall suction or blowing. The resulting governing equations are non-dimensionalized and transformed into a non-similar form and then solved numerically by an implicit, iterative, finite-difference method. Comparisons with previously published work are performed and excellent agreement between the results is obtained. A parametric study of the physical parameters is conducted and a representative set of numerical results for the temperature and concentration profiles as well as the local Nusselt number and the Sherwood number is illustrated graphically to show special trends of the solutions. [ABSTRACT FROM AUTHOR]

The problem of coupled heat and mass transfer by natural convection from a semi-infinite inclined flat plate in the presence of an external magnetic field and internal heat generation or absorption effects is formulated. The plate surface has a power-law variation of both wall temperature and concentration and is permeable to allow for possible fluid wall suction or blowing. The resulting governing equations are transformed using a similarity transformation and then solved numerically by an implicit, iterative, finite-difference scheme. Comparisons with previously published work are performed and good agreement is obtained. A parametric study of all involved parameters is conducted and a representative set of numerical results for the velocity and temperature profiles as well as the skin-friction parameter, average Nusselt number, and the average Sherwood number is illustrated graphically to show typical trends of the solutions. [ABSTRACT FROM AUTHOR]

This paper investigates the pressure-driven and electroosmotic flow of Bingham plastic fluid within a curved microtube in the presence of a streaming potential. Perturbation analysis is utilised to solve the governing equations and obtain approximate analytical solutions. Validation against existing literature confirms the accuracy of the approach, with highly favourable agreement observed. The electrical double-layer (EDL) distribution is analysed for various Debye lengths, perturbation parameters, curvature ratios, and zeta potentials. As curvature increases, the EDL decreases near the lower wall and increases near the upper wall. The impact of electroosmosis force, Debye lengths, perturbation parameters, curvature ratios, and ionic Peclet number on axial velocity profiles is investigated. Axial velocity increases with the electroosmotic parameter value due to a more significant axial electric force in the inner area. Additionally, velocity decreases with increasing Bingham parameter, particularly at the lower wall region, while it increases with curvature value in the upper half of the tube. Higher flow rates are observed within curved microtubes than linear ones under similar pressure gradients and cross-sectional shapes. Increasing Debye length reduces streaming potential magnitude, favouring pressure-driven flow over electroosmotic flow. Finally, the variation of electrokinetic energy conversion efficiency with curvature ratio for different Bingham parameters is analysed. Higher Bingham parameter values increase fluid viscosity, resulting in slower fluid movement, reduced streaming potential, and decreased efficiency of electrokinetic energy conversion. This study contributes to a deeper understanding of fluid dynamics within curved microtubes and offers insights into optimising energy conversion efficiency in Bingham plastic fluid systems. [ABSTRACT FROM AUTHOR]

The principal aim of this paper is to analyse the two-dimensional magnetohydrodynamic flow and heat and mass transfer phenomena of water-based nanofluid containing gyrotactic microorganisms over a vertical plate by means of heat generation or absorption. Set of nonlinear ordinary differential equations are derived from the governing partial differential equations of the two-dimensional flow of MHD nanofluid and nanoparticles by utilizing appropriate similarity transformations. The numerical results are obtained with the proposed novel spectral relaxation method. The results revealed that in the heat and mass transfer, the motile microorganism flux rates as well as the velocity profiles are decreased throughout the fluid medium with the impact of magnetic field strength. Moreover, the drag stress rate and motile microorganism profiles are increased with the enhancement of magnetic field. Even though the problem of nanofluid has been broadly investigated, limited discoveries can be found through a gyrotactic microorganisms. Indeed, this paper managed to obtain the numerical analysis is performed. Furthermore, the authors also considered the MHD phenomena, heat generation or absorption effects. Very few studies in the fluid with gyrotactic microorganisms embedded in this parameter in their problems. [ABSTRACT FROM AUTHOR]