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Owing to enhanced performance, the hybrid nanofluids are finding increasingly varied applications in areas such as energy systems, extrusion operations, industrial activities, and chemical processes. The aim of current model is to explore thermal behavior of Casson hybrid nanofluid flow when subjected to a magnetic force. Two types of carbon nanotubes, the single‐walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs), dispersed in blood were investigated. The study addressed the problem based on time‐dependent thermal conductivity and considering an external heat source. It is important to understand how heat transfer occurs in nanofluids with variable thermal conductivity because it is a significant feature in many thermodynamic systems where nanofluids play important roles. To formulate the set of dimensionless governing equations, similarity variables are employed. The numerical shooting method, known for its high precision, is applied to solve these equations. The accuracy of the solutions is verified by comparison with results from previous studies, and the impact of various parameters is examined. It is noticed that velocity profile declined due to unsteady parameter for both types of CNTs (SWCNTs‐MWCNTs). An increase in the nanoparticles' volume fraction results in elevated temperatures. [ABSTRACT FROM AUTHOR]

The current study presents a time dependent couple stress nanofluid flow across a bidirectional periodically stretched surface under magnetic effects. The effects of nonuniform heat source and variable thermal conductivity on the convective heat transfer are analyzed. The effect of the chemical reaction, nonlinear mixed convection, and activation energy are also considered. Adequate dimensional quantities are utilized to entertained the problem in simplified from. Then, a series of solutions are obtained via homotopic analysis method. Tables and graphs are organized to evaluates the physical dynamic of problem. The archived observations convey that the nonlinear convective parameters cause a rise in horizontal velocity component. It is determined that flow intensity and skin friction have an increasing behavior with most of the governing parameters. Current investigation emphasized that the temperature increases by imposing variable thermal conductivity. The concentration values become higher by increasing the activation energy but decrease with the reaction rate. [ABSTRACT FROM AUTHOR]

This study numerically investigates the two-dimensional natural convection in a square enclosure with an isothermal diamond elliptic array at Rayleigh numbers of 104 ≤ Ra ≤ 107. Three cases are considered, i.e., case 1 where two pairs of circular heating bodies are used inside the cavity, one is placed on the vertical centerline (VC) of the cavity and the other on the horizontal centerline (HC), case 2 where one pair of horizontal elliptic heating bodies is placed on the VC of the cavity and the other on the HC and case 3 where the horizontal elliptic heating bodies are replaced by vertical elliptic heating bodies. Numerical simulation was carried out based on the mesoscopic approach (LBM). The effects of the horizontally and vertically heated arrays were investigated. We demonstrate that, only when the Rayleigh number increases to Ra = 107, the numerical solutions reach an unsteady state for all cases. The transition of the flow regime from the unsteady state to the steady state depends on the variation in the ratio of the elliptical cylinder. [ABSTRACT FROM AUTHOR]

With effective thermal performances and stability, the nanomaterials are intended to be the focus of investigators due to applications in energy systems, thermal extrusions, pharmaceutical processes, diagnoses and therapies, domestic refrigerators, bio-medical technologies, nuclear processes, antibacterial activities, etc. This research addresses thermal transport in stagnation point flow of nanofluid over a curved surface with nonlinear radiative effects and chemical reaction effects. Basic mass and momentum conservation laws are used to model the flow problem, whereas Cattaneo–Christov theories are used in thermal diffusion relations to model the heat and concentration equations. The similarity variables transformed the governing partial differential equations and the resulting equations are numerically simulated by the fourth-order finite difference scheme. The effective change in velocity, heat transfer rate, and mass fluctuation are reported due to effective values of parameters. It is noted that velocity, temperature, and concentration are affected by the curvature of the surface. [ABSTRACT FROM AUTHOR]

The recent progress in nanotechnology developed more stable nanofluid models with ultra-high thermal performances. The immersion of hybrid nanoparticles in the base fluid presents novel applications in the thermal transport processes, solar energy, engineering devices, and heating systems. This continuation identified the thermal outcomes of the hybrid nanofluid model with the water base fluid. The thermal investigation is encountered by utilizing the copper oxide (CuO), silver (Ag), and titanium dioxide (TiO2) nanoparticles. The thermal selection of these three types of nanoparticles is associated with impressive characteristics and stability. To attain the more progressive thermal aspects, thermal radiation consequences are also focused. The inclined infinite configuration is assumed where these nanoparticles and base fluid are specified. The comparative results for the hybrid nanofluid and modified hybrid models are pronounced. The fractional model of dimensionless partial differential leading equations is formulated by following the recent definitions of fractional derivatives, namely, Atangana–Baleanu and Caputo–Fabrizio fractional derivatives. The semi-analytical simulations are performed via the Laplace technique for nanoparticles temperature and velocity inspection. The significances of the fractional parameter and volume fraction are observed for the velocity profile. [ABSTRACT FROM AUTHOR]

In this study, confined slot nano-jet impingement cooling of a hot moving surface is investigated under the combined utilization multiple rotating cylinders and magnetic field. Both convective heat transfer and entropy generation analysis are conducted using a finite element method. Parametric variation of the rotational Reynolds number (Rew between −500 and 500), velocity ratio (VR between 0 and 0.25), Hartmann number (Ha between 0 and 20) and the horizontal location of cylinders (Mx between −8 and 8) are considered. Rotation of the cylinders generally resulted in the degradation of cooling performance while increasing the wall velocity, and the horizontal location of the cylinder was found to positively contribute to this. Heat transfer rate reductions of 20% and 12.5% are obtained using rotations at the highest Rew for the case of stationary (VR = 0) and moving wall (VR = 0.25). When magnetic field at the highest strength is imposed in the rotating cylinder case, the cooling performance is increased by about 18.6%, while it is reduced by about 28% for the non-rotating cylinder case. The hot wall movement contributes, by about 14%, to the overall cooling performance enhancement. Away from the inlet location of the rotating cylinders, thermal performance improvement of 12% is obtained. The entropy generation rises with higher hot wall velocity and higher horizontal distances of the rotating cylinders, while it is reduced with a higher magnetic field for non-rotating cylinders. The best configurations in terms of cooling performance provide 8.7% and 34.2% enhancements for non-rotating and rotating cylinders compared with the reference case of (Rew, VR, Ha, Mx) = (0, 0, 0, 0), while entropy generation becomes 1% and 15% higher. [ABSTRACT FROM AUTHOR]

The bioconvective flow of a Jeffrey fluid conveying tiny particles under the effect of an oscillating stretched bidirectional surface is considered in this paper. The effects of thermal radiation and a porous medium are also investigated. The Cattaneo–Christov diffusion theories are used to analyze the heat and mass transfer phenomena. The activation energy effects are included in the concentration equation. The solved dimensionless equations system is established, based on non-dimensional variables. The analytical findings are evaluated using the homotopic analysis technique. The convergence of solutions is ensured. The results are validated by already available published findings and a good concordance is encountered. The fundamental physical aspect of flow parameters is graphically evaluated. The main results reveal that the velocity is reduced by increasing the permeability of the porous medium. An increase in the temperature occurs when the viscosity of the fluid is varied. The obtained results can be useful in thermal systems, energy production, heat transfer devices, solar systems, biofuels, fertilizers, etc. [ABSTRACT FROM AUTHOR]

A numerical investigation of a phase change material (PCM) energy storage tank working with carbon nanotube (CNT)–water nanofluid is performed. The study was conducted under actual climatic conditions of the Ha'il region (Saudi Arabia). Two configurations related to the absence or presence of conductive baffles are studied. The tank is filled by encapsulated paraffin wax as the PCM, and CNT–water nanofluid flows through the capsules. The main goal is to increase the temperature of the PCM to 70 °C in order to store the thermal energy, which can then be used during the night and cloudy weather. Numerical computations are made using the finite element method (FEM) based on actual measured weather conditions. Climate conditions were collected from a weather station located on the roof of the engineering college's building at the University of Ha'il. The collected data served as input to the numerical model, and the simulations were performed for three months (December, March, and July). The solid CNT volume fraction range was (0 ≤ ϕ ≤ 0.05) and the nanofluid volume flow rate ranged was (0.5 L/min ≤ V ≤ 3 L/min). For both considered cases (with and without baffles), it was found that the use of CNT–nanofluid led to a reduction in the charging time and enhanced its performance. An increase in the volumetric flow rate was found to accelerate the melting process. The best performances of the storage tank occurred during July due to the highest solar irradiation. Furthermore, it was found that the use of baffles had no beneficial effects on the melting process. [ABSTRACT FROM AUTHOR]

In this work, double rotating active cylinders and slot nanojet impingement are considered for the cooling system of a conductive panel. Colder surface temperatures of the cylinders are used, while different rotational speeds are assigned for each of the cylinders. The impacts of cylinder rotational speeds, size and distance between them on the cooling performance are evaluated. The rotational effects and size of the cylinders are found to be very effective on the overall thermal performance. At the highest rotational speeds of the cylinders, the average Nusselt number (Nu) rises by about 30.8%, while the panel temperature drops by about 5.84 ° C. When increasing the cylinder sizes, temperature drops become 7 ° C, while they are only 1.75 ° C when varying the distance between the cylinders. Subcooling and nanofluid utilization contributes positively to the cooling performance, while 1.25 ° C and 10 ° C temperature drops are found by varying the subcooled temperature and solid volume fraction. An artificial neural network is used for the estimation of maximum and average panel temperatures when double cylinder parameters are used as the input. [ABSTRACT FROM AUTHOR]

Cost-effective, lightweight design alternatives for the thermal management of heat transfer equipment are required. In this study, porous plate and perforated-porous plates are used for nanoliquid convection control in a flexible-walled vented cavity system under uniform magnetic field effects. The finite element technique is employed with the arbitrary Lagrangian–Eulerian (ALE) method. The numerical study is performed for different values of Reynolds number ( 200 ≤ Re ≤ 1000 ), Hartmann number ( 0 ≤ Ha ≤ 50 ), Cauchy number ( 10 − 8 ≤ Ca ≤ 10 − 4 ) and Darcy number ( 10 − 6 ≤ Da ≤ 0.1 ). At Re = 600, the average Nusselt number (Nu) is 6.3% higher by using a perforated porous plate in a cavity when compared to a cavity without a plate, and it is 11.2% lower at Re = 1000. At the highest magnetic field strength, increment amounts of Nu are in the range of 25.4–29.6% by considering the usage of plates. An elastic inclined wall provides higher Nu, while thermal performance improvements in the range of 3.6–6% are achieved when varying the elastic modulus of the wall. When using a perforated porous plate and increasing its permeability, 22.8% increments of average Nu are obtained. A vented cavity without a plate and elastic wall provides the highest thermal performance in the absence of a magnetic field, while using a porous plate with an elastic wall results in higher Nu when a magnetic field is used. [ABSTRACT FROM AUTHOR]

Two-dimensional numerical simulations are performed to investigate the problem of thermocapillary, and buoyancy driven convection. A hybrid MWCTN-Fe 3 O 4 -thermal oil nanofluid was used in an enclosed cavity equipped with a hot obstacle. The entire set of equations associated with the convective heat transfer phenomena in a hybrid nanofluid layer with a free surface are solved numerically using the blocked-off region method of Patankar. A parametric study varying the position, the size of the obstacle, the Marangoni number, the Rayleigh number, the volume fraction of the nanofluid has been performed. The results concern the flow profile, the temperature profile and the evolution of the Nusselt number under different conditions. It was shown that an enhancement of the convective heat transfer of more than 170% can be achieved on the cold wall just by switching the position of the obstacle from the bottom to the top. [ABSTRACT FROM AUTHOR]

Combined effects of using inclined partition and magnetic field on the cooling performance of double slot jet impingement are analyzed with finite element method. Two different shear thinning nanofluids are used while experimental data is available for the rheological properties. Different values of of Reynolds number (Re between 100 and 1000), velocity ratio (VR, between 0.2 and 1), opening ratio (OR, between 0.05 and 0.95), magnetic field strength (Ha, between 0 and 30) and inclination of partition (Ω , between 0 and 40) are used. It is observed that varying VR of the jets, size/inclination of the partition, magnetic field strength and nanfluid type, can be used to control the local and average convective heat transfer and cooling performance features effectively. The average Nusselt number (Nu) rises with higher VR while at the highest VR the amount of increments are 23.5 % and 28.5 % with first (NF1) and second (NF2) nanofluid (NF). When magnetic field is imposed, effects of OR becomes important with NF1 at the lowest strength of magnetic field. Average Nu reduces with higher magnetic field strength for NF1 while 14.4 % reduction for the highest strength at OR = 0.95 is achieved. However, for NF2 the trend is opposite and 18.8 % increment is obtained. Variations in the average Nu becomes 7.6 % and 1.8 % for NF1 and NF2 when inclination of the partition is changed. The cooling performance is estimated by using a feed-forward network modeling approach in terms of average Nu for NF1 and NF2 by using 25 neuron in the hidden layer. [ABSTRACT FROM AUTHOR]

In this work, a new finite element (FE) EDM model was established to estimate the material removal rate (MRR) and thermal stresses in the AISI 316L and AISI D2 steels. Numerical simulation of EDM process was performed using dynamic coupled thermo-mechanical analysis considering plane-strain assumption. Different thermal loading conditions were tested during numerical simulation of the discharge phase while altering heat input size function. Time-dependent plasma channel radius forms with and without discharge current effect have been investigated for each material. The appropriate discharge radius function was identified for each grade of steel based on the comparison of numerically predicted MRR-discharge current diagrams with experiments from previously published work. It was found that the heat input size functions that take into account the effect of discharge current are the most suitable for the prediction of the MRR. Moreover, thermal stresses were predicted via a cooling analysis. The confrontation between experiment and the computed thermal stress profiles for the AISI 316L in the same erosion regime was deemed satisfactory. [ABSTRACT FROM AUTHOR]

The present paper focuses on a review recalling the main contributions of studies that involve nanofluids on automotive industry. The novelty of the paper consists on the concise synthesis presented, that highlights new tested nanofluids in several applications in automotive. The review includes critics on the efficiency, the impact on material and the environmental issues when nanofluids are used as fuel. Three main sections are presented, which deploy the use of nanofluids as coolant in a car radiator, addition in the fuel or engine oil and finally the last section reviews the assessment of the wear effects of nanofluids on materials used in a car coolant system and in the car engine. The current review emphasized some major findings and critics: (1) The contradictory conclusions denoted about the effect of volume concentration on pumping power loss and the Nusselt number in a car radiator system. (2) Remarkable discrepancies in the determination of the optimal nanoparticles volume concentration and the precise heat transfer enhancement. (3) The viscosity of a nanolubricant needs a deep analysis to determine the optimal value that ensures the best lubricant film between components in a car engine. (4) Some mechanical problems should be analyzed when using nanofluids in fuel. [ABSTRACT FROM AUTHOR]

In this paper a numerical investigation on the double diffusive natural convection in a finned solar still is performed using the finite volume method. The 3D vector potential-vorticity formalism is used to eliminate the gradient pressure terms and due to the complex shape of the cavity the blocked-off-region method is adopted. After getting the dimensionless governing equations, they are written in a generalised form then discretised. The effects of the buoyancy ratio, conductivity ratio and Rayleigh number of the flow structure, temperature field and heat and mass transfer are studied. The results show that the increase of conductivity ratio and Rayleigh number leads to an enhancement of the heat and mass transfer. [ABSTRACT FROM AUTHOR]

This study deals with the influence of a wavy interface separating two layers filled with power law fluid and porous media, respectively. The governing equations are solved using the Finite Element Method (FEM) and the numerical model is validated by comparing with experimental findings. The parameters governing the studied configuration are varied as: Rayleigh number (103 ≤ Ra ≤ 106), power law index (0.6 ≤ n ≤ 1.4), Darcy number (10−2 ≤ Da ≤ 10−6), buoyancy ratio (0.1 ≤ N ≤ 10) and Lewis number (1 ≤ Le ≤ 10). It is inferred that the temperature gradient increases by augmenting the Rayleigh number, as the flow is observed from the vertical to horizontal direction in both layers. Constant enhancement in the heat and mass transfer is also observed by enriching the buoyancy effect. Moreover, the average Nusselt and Sherwood numbers decline by increasing the width of the porous layer. [ABSTRACT FROM AUTHOR]

• Study of a novel geothermal-based clean combined cooling, heating, and power system. • Using Aspen HYSYS for simulation and comprehensive 4E analysis. • The energy and exergy efficiencies are found at 61.81 % and 72.52 %. • Total unit cost of exergy and levelized cost of energy are 5.13 $/GJ and 0.511 $/kWh. • Power production and exergy efficiency increases with geo-fluid expansion pressure. In recent years, geothermal energy has received significant attention as it provides a sustainable and renewable energy resource for various applications. The primary objective of this study is to manage the relative irreversibility and enhance productivity through efficient utilization of geothermal energy. The present paper establishes a high-efficiency and environmentally sustainable heat integration model in a novel configuration to be a geothermal energy source having the ability to produce power, heat, and cooling. The proposed framework consists of a Kalina cycle, two organic Rankine cycles, an ammonia Rankine cycle, a single-flash power unit, and a combined cooling and power unit. The simulation of the proposed system is implemented within the Aspen HYSYS software, with an examination of its feasibility across energy, exergy, economic, and environmental considerations. The research findings indicate that the system can generate 23250.8 kW of power, 582.1 kg/s of hot water, and 2.812 kg/s of chilled water. Therefore, the total exergy destruction rate is 14104 kW, with the Kalina cycle accounting for the majority share at 40.47 % Moreover, the energy and energy efficiencies of the suggested structure are 61.81 % and 72.52 %, respectively. The environmental analysis indicates that the entire process lacks carbon dioxide emissions. Furthermore, the economic analysis reveals that the total unit exergy cost and levelized cost of energy are determined to be 5.13 $/GJ and 0.511 $/kWh, respectively. Also, the proposed system exhibits a favorable net present value of approximately 32.16 M$. Hence, the project demonstrates profitability. [ABSTRACT FROM AUTHOR]

This study aims to investigate numerically the Rayleigh–Bénard Convection using an in-house Fortran 90 code based on the lattice Boltzmann method. The bottom wall is equipped with two hot circular/elliptical sources and the right wall is open. The non-linear coupled differential governing equations are formulated using the lattice Boltzmann equation associated with the Boussinesq approximation. The simulations are conducted for (103 ≤ Ra ≤ 106) and Pr = 0.7 (corresponding to air). The code verification showed a good reliability of the present mesoscopic numerical approach. Several configurations related to the size and shape of the heaters were studied. It was found that elliptically shaped heat sources provide higher heat transfer rates compared to circular sources. [ABSTRACT FROM AUTHOR]

This study presents 2-D simulations of a flow-through a sudden expansion/contraction micro-channel with the existence of obstacles. The bottom wall is maintained at constant flux, while the other walls are adiabatic. Rectangular adiabatic obstacles are mounted before the expansion region on the upper and lower wall of the channel used. The finite element method was used to discretize the equations that govern the physical model. Results indicate the apparition of a separate vortex, situated in the corner after the sudden expansion of the micro-channel for low Reynolds numbers. For higher values and expansion ratios, the vortex separation length increases. The obtained results show that the obstacles have a considerable effect on the dynamics of the flow and enhancement of heat transfer. [ABSTRACT FROM AUTHOR]

The electro-thermo-convection in a square cavity with incorporated hot solid body is numerically investigated. The finite volume method associated with Patankar's "blocked-off-regions" technique is applied. A potential difference is applied between the hot obstacle and the horizontal walls in order to eliminate the so-called dead zone created at the bottom of the cavity. The flow movement is induced not only by thermal buoyancy forces but also by the electric Coulomb force. Calculations are made for several injection levels (1 ≤ C ≤ 10), various obstacle shape factors (1 ≤ l/w ≤ 9), different number of electric Rayleigh (0 ≤ T ≤ 800), multiple thermal Rayleigh numbers (2000 ≤ Ra≤ 30,000) and 03 obstacle positions. The results show that according to the intensity of the applied electrical forces, two types of regimes are identified: a thermally dominated regime characterized by a low heat exchange at the bottom of the obstacle and conversely an electrically dominated regime with an excellent heat exchange over the entire cavity. It has been demonstrated that it is possible to improve the heat transfer up to: 43% by changing the shape factor of the obstacle; 82% by varying the injection level and 532% by applying electrical forces. [ABSTRACT FROM AUTHOR]

Having information about the impact of some parameters on the microstructure of parts manufactured by the laser powder bed fusion process is considered among the serious challenges to be achieved. In this regard, a wide range of scan speed and laser power values were chosen to predict how much these parameters affect the microstructure such as grain orientations, shapes, and sizes. These represent the basic factors to monitor the mechanical properties of printed parts. A two-dimensional microstructure model based on the cellular automata (CA) was adopted to track the grain structure features of 316L stainless steel. The microstructure in XY and XZ planes including the grain orientation and the grain size are debated with details in our outcomes. The results clearly show that the microstructure is significantly influenced by modifying the process parameters. The higher the scan speed, the finer the grain size, and vice versa for the laser power, which improves the mechanical properties. Increasing the scan speed leads to an enhanced grain orientation towards the building direction. Result predictions are approved by experimental investigations. [ABSTRACT FROM AUTHOR]

Abstract Modeling and simulation of nanofluid flows is crucial for applications ranging from the cooling of electronic devices to solar water heating systems, particularly when compared to the high expense of experimental studies. Accurate simulation of a thermal-fluid system requires a deep understanding of the underlying physical phenomena occurring in the system. In the case of a complex nanofluid-based system, suitable simplifying approximations must be chosen to strike a balance between the nano-scale and macro-scale phenomena. Based on these choices, the computational approach – or set of approaches – to solve the mathematical model can be identified, implemented and validated. In Part I of this review (Mahian et al., 2019), we presented the details of various approaches that are used for modeling nanofluid flows, which can be classified into single-phase and two-phase approaches. Now, in Part II, the main computational methods for solving the transport equations associated with nanofluid flow are briefly summarized, including the finite difference, finite volume, finite element, lattice Boltzmann methods, and Lagrangian methods (such as dissipative particle dynamics and molecular dynamics). Next, the latest studies on 3D simulation of nanofluid flow in various regimes and configurations are reviewed. The numerical studies in the literature mostly focus on various forms of heat exchangers, such as solar collectors (flat plate and parabolic solar collectors), microchannels, car radiators, and blast furnace stave coolers along with a few other important nanofluid flow applications. Attention is given to the difference between 2D and 3D simulations, the effect of using different computational approaches on the flow and thermal performance predictions, and the influence of the selected physical model on the computational results. Finally, the knowledge gaps in this field are discussed in detail, along with some suggestions for the next steps in this field. The present review, prepared in two parts, is intended to be a comprehensive reference for researchers and practitioners interested in nanofluids and in the many applications of nanofluid flows. [ABSTRACT FROM AUTHOR]

Abstract It has been more than two decades since the discovery of nanofluids-mixtures of common liquids and solid nanoparticles less than 100 nm in size. As a type of colloidal suspension, nanofluids are typically employed as heat transfer fluids due to their favorable thermal and fluid properties. There have been numerous numerical studies of nanofluids in recent years (more than 1000 in both 2016 and 2017, based on Scopus statistics). Due to the small size and large numbers of nanoparticles that interact with the surrounding fluid in nanofluid flows, it has been a major challenge to capture both the macro-scale and the nano-scale effects of these systems without incurring extraordinarily high computational costs. To help understand the state of the art in modeling nanofluids and to discuss the challenges that remain in this field, the present article reviews the latest developments in modeling of nanofluid flows and heat transfer with an emphasis on 3D simulations. In part I, a brief overview of nanofluids (fabrication, applications, and their achievable thermo-physical properties) will be presented first. Next, various forces that exist in particulate flows such as drag, lift (Magnus and Saffman), Brownian, thermophoretic, van der Waals, and electrostatic double layer forces and their significance in nanofluid flows are discussed. Afterwards, the main models used to calculate the thermophysical properties of nanofluids are reviewed. This will be followed with the description of the main physical models presented for nanofluid flows and heat transfer, from single-phase to Eulerian and Lagrangian two-phase models. In part II, various computational fluid dynamics (CFD) techniques will be presented. Next, the latest studies on 3D simulation of nanofluid flow in various regimes and configurations are reviewed. The present review is expected to be helpful for researchers working on numerical simulation of nanofluids and also for scholars who work on experimental aspects of nanofluids to understand the underlying physical phenomena occurring during their experiments. [ABSTRACT FROM AUTHOR]

In this paper, the effect electric field on the flow induced by the combined buoyancy and thermocapillary forces is carried out. Calculations are performed for a strong unipolar injection (C = 10) and different values of Marangoni number (−10000 ≤ Ma ≤ 10000), thermal Rayleigh number (5000 ≤ Ra ≤ 50,000) and electric Rayleigh number (0 ≤ T ≤ 800). The Prandtl number (Pr) and the mobility parameter (M) are fixed at 116.6 and 49, respectively. These values correspond to the Silicone oil used as working liquid several practical applications. The full set of coupled equations: Navier–Stokes, Electro-hydrodynamic (EHD) and heat transfer equations are directly solved using stream function-vorticity formalism. Obtained results show that the electric forces can control the thermocapillary instabilities. According to the intensity and the direction of the applied electric forces, it is demonstrated that these instabilities can be accentuated, attenuated, or even completely eliminated. [ABSTRACT FROM AUTHOR]

Abstract The kinetics of antigen–antibody binding reaction, in the electrokinetically controlled microfluidic heterogeneous immunoassays, have been numerically simulated and discussed. The aim of this study is to demonstrate how to model phenomena defined in different 2D and 3D dimensions in a fully coupled manner using COMSOL Multiphysics. Moreover, we explain how to examine a convection-diffusion phenomenon present in a 2D domain (respectively 3D) coupled to diffusion-reaction phenomenon which is occurring only on a 1D boundary of this same area (respectively 2D). In our developed model, microfluidic networks for surface immunoassays were used. Antibodies, immobilized on one wall of a microchannel, absorb the employed analytes. The reaction rates in the modification area function of the reactants' concentration in the phase that transports the chemicals. Nevertheless, for surface reactions it is necessary to highlight the surface concentrations of the active sites and surface adsorbed species. The obtained results show that the increase of the concentration can reduce the growth of the diffusion boundary layer and raise the biosensor performance. Finally, the 2D simulations are described as crucial in predicting more accurate results. Highlights • Kineticks of antigen-antibody reaction in microfluidic heterogeneous immunossays. • The finite element method is used to solve the governing equations. • 2D and 3D geometries were considered. • The effect of diverse parameters is investigated. [ABSTRACT FROM AUTHOR]

A computational study has been performed to investigate the effects of partially active magnetic field on natural convection heat transfer in CNT-nanofluid filled and three-dimensional differentially heated closed space. Two cases are considered to see this effect as magnetic field is applied to upper half (Case I) and lower half (Case II) while remaining walls are insulated. The finite volume method is used to solve governing equations and results are obtained for different governing parameters as Hartmann number (0 ≤ Ha ≤ 100), nanoparticle volume fraction (0 ≤ φ ≤ 0.05) and height of the active zone (0 ≤ L B  ≤ 1). It is found that location of magnetic field plays an important role even at the same Hartmann number. Thus, it can be a good parameter to control heat and fluid flow inside the closed space. [ABSTRACT FROM AUTHOR]

A computational analysis of the natural ventilation process and entropy generation in 3-D prismatic greenhouse was performed using CFD. The aim of the study is to investigate how buoyancy forces influence air-flow and temperature patterns inside the greenhouse having lower level opening in its right heated façade and also upper level opening near the roof top in the opposite cooled façade. The bottom and all other walls are assumed to be perfect thermal insulators. Rayleigh number is the main parameter which changes from 10³ to 106 and Prandtl number is fixed at Pr = 0.71. Results are reported in terms of particles trajectories, iso-surfaces of temperature, mean Nusselt number, and entropy generation. It has been found that the flow structure is sensitive to the value of Rayleigh number and that heat transfer increases with increasing this parameter. Also, it have been noticed that, using asymmetric opening positions improve the natural ventilation and facilitate the occurrence of buoyancy induced upward cross air-flow (low-level supply and upper-level extraction) inside the greenhouse. [ABSTRACT FROM AUTHOR]

Three-dimensional natural convection in an inclined solar collector equipped with partitions has been investigated numerically. The presence of partitions improves the performances of the collector by increasing the heat transfer near the absorber. A parametric study was done for various partitions length and Rayleigh numbers, while Prandtl number and inclination angle were fixed at 0.71 and 45°, respectively. Results are reported in terms of isosurfaces of temperature, isotherms, particles trajectories, velocity vector projection, average Nusselt number along the absorber plate and entropies generation contours. [ABSTRACT FROM AUTHOR]

The effect of inclination angle on three dimensional (3D) natural convection in an inclined rectangular cavity similar to a solar collector equipped with partitions has been investigated numerically. Governing equations were established using the 3D velocity vector-vorticity formalism and discretized via the finite volume method (FVM). A parametric study has been performed for various inclination angles (from 0° to 90°), different partitions length (from 0.2 to 0.8). and a range of Rayleigh numbers varied from 103 to 10s while, Prandtl number was fixed at Pr = 0.71. Results are reported in terms of iso-surfaces of temperature, isotherms, particles trajectories, vector velocity projection, average Nusselt number and the entropies generation contours and graphs. Results showed the 3D character of the flow is more pronounced for higher Rayleigh numbers and lower partition lengths. For all inclinations and partition lengths, heat transfer and entropy generation are enhanced by increasing Rayleigh number [ABSTRACT FROM AUTHOR]

Entropy generation inside an inclined cubical differentially heated cavity filled with CNT-water nanofluid is evaluated numerically using FVM based on 3D vorticity-vector potential formalism. A conductive Ahmed body is incorporated at the center of the enclosure. The effects of several parameters such as Rayleigh number (10 3 ≤ Ra ≤ 10 5 ), volumetric fraction (0 ≤ φ ≤ 0.05) of nanoparticles, angle of inclination of cavity (0° ≤ α ≤ 180°) and thermal conductivity ratio (0.01 ≤ R c ≤ 100) on entropy generation are analyzed. The results are elucidated with local and total entropy generations and Bejan number. Entropy generation increases when Raleigh number increases due to buoyancy. Entropy declines when the inclination angle is increased up to 90°, after that entropy generation surges. [ABSTRACT FROM AUTHOR]

A computational analysis has been performed in this work to solve three-dimensional magnetohydrodynamic natural convection in an open cubical enclosure filled with CNT-water nanofluid. The cavity is heated from left vertical wall and an inclined plate is attached inside the cavity with finite length. The study is solved for different governing parameters as Rayleigh number (10 3 ≤ Ra ≤ 10 5 ), nanoparticle volume fraction (0% ≤ φ ≤ 5%), Hartmann number (0 ≤ Ha ≤ 100) and inclination angle of the fin (0° ≤ θ ≤ 360°). It is observed that all of these parameters can be used as passive control element for heat and fluid flow and the maximum heat transfer is formed when θ = 180° but minimal value of average Nusselt number is changed according to nanoparticle addition into base fluid. [ABSTRACT FROM AUTHOR]

Owing to novel thermos-physical properties, various applications of nanofluids are noted in thermal systems, solar energy, extrusion framework, industrial processes, cooling system, heating devices and biomedical applications. In order to attain more thermal impact of nanofluids, various features are endorsed by researchers. However, the thermal applications of nanofluids with interaction of induced magnetic field intended less attention. The aim of this study is to report the significance of induced magnetic force for non-Newtonian nanofluid containing microorganisms. The thixotropic non-Newtonian fluid model is used to classify the distinct rheological impact. The bioconvective thermal model is presented in view of variable thermal conductivity. The problem is further entertained with thermal radiation impact and activation energy. The convective boundary conditions are used to simulate the computations. The governing system is first reduced into dimensionless models which are numerically treated with implementation of shooting technique. The physical parameters report high fluctuation in the thermal phenomenon which are carefully evaluated. [ABSTRACT FROM AUTHOR]

In this study, heat transfer, flow structure and produced entropy due to natural convection in a threedimensional cavity heated via heat sinks are investigated numerically. One wall of the cavity is heated via pinfins and opposite wall is maintend at lower temperature. Remaining bouandaries are considered as adiabatic. Finite volume method is used to solve governing equations. Three geometrical cases are tested according to number and location of the fins. Other governing parameters are Rayleigh number and fin length. Number and length of the fins were found to be the most effective parameters on both heat transfer and entropy generation. [ABSTRACT FROM AUTHOR]

In this work, the heat and mass transfers in 3D lid driven cavity is analyzed. Double-diffusive convective flow in a cubic enclosure with moving left side in −y (Case I) or +y (Case II) directions is studied numerically. The cavity is heated from left side and cooled from right and constant different concentration is imposed, while remaining surfaces are adiabatic. The FVM based on the 3D vector-potential – vorticity formalism is used as numerical method. Prandtl number and Lewis number are fixed at 10, 0.7 and 2, respectively. The study covers a wide range for Richardson number 0.1 ≤ Ri ≤ 10 and Buoyancy ratio −10 ≤ Ri ≤ 10. Results are presented by particle trajectories, isotherms, Iso-concentration and local and mean Nusselt and Sherwood numbers. [ABSTRACT FROM AUTHOR]

A finite volume-based three-dimensional numerical simulation on natural convection and entropy generation in a cubical cavity filled with a nanofluid of aluminum oxide–water is presented by vorticity–vector potential formalism. The blocks are adiabatic and the vertical walls are differentially heated unidirectionally. The variables considered areRa, volumetric fraction of aluminum oxide particles, and block size. The results for fluid flow with a single-phase model are elucidated with iso-surfaces of temperature, Nusselt number, and Bejan number. The local entropy generated was due to friction surges when the volumetric fraction of nanoparticles was increased. The average Nusselt number rose with the increase in Ra and volumetric fraction of solid particles and declined with the increase in block size. [ABSTRACT FROM AUTHOR]

A three dimensional computational solution has been obtained to investigate the natural convection and entropy generation of nanofluid-filled open cavities with an adiabatic diamond shaped obstacle. In the model, the finite volume technique was used to solve the governing equations. Based on the configuration, the cavity is heated from the left vertical wall and the diamond shape was chosen as adiabatic. Effects of nanoparticle volume fraction, Rayleigh number (103ὄ Ra ὄ 106) and width of diamond shape were studied as governing parameters. It was found that the geometry of the partition is a control parameter for heat and fluid flow inside the open enclosure. [ABSTRACT FROM AUTHOR]

Laminar three dimensional flow and heat transfer in a nanofluid filled cavity with solid insert at the corners is analyzed computationaly by using finite volume method. Entropy generation is also presented from the obtained results of velocity and temperature values. In order to simulate nanofluids, an in-house numerical method was developed based on the solution of three dimensional solution of Navier–Stokes equations.Three cases are studied based on number and location of solid inserts. Effects of Rayleigh number (10 4 ≤ Ra ≤ 10 6 ), nanoparticle volume fraction (0 ≤ φ ≤ 0.15) and thermal conductivity ratio (0.01 ≤ Rc ≤ 100) are analyzed on natural convection and entropy generation. It is observed that a three dimensional solution brings a more understanding work for the study. Higher heat transfer and entropy generation are observed in the case of nanoparticle addition into base fluid. In any case, partitions can be used as a control element for heat and fluid flow and energy consumption. [ABSTRACT FROM AUTHOR]

Effects of Rayleigh number, solid volume fraction and entropy generation on the natural convection heat transfer and fluid flow inside a three-dimensional cubical enclosure filled with water-AlO nanofluid have been investigated numerically using the control volume finite difference method. The enclosure left sidewall is maintained at isothermal hot temperature, while the right one is maintained at isothermal cold temperature. The other enclosure walls are considered adiabatic. The second law of thermodynamics is applied to predict the nature of irreversibility in terms of entropy generation rate. Numerical computations are carried out for Rayleigh numbers from $${(10^{3} \leq {\rm Ra} \leq 10^{6})}$$ , solid volume fraction from $${(0\% \leq \varphi\, \leq 20\%)}$$ , while the Prandtl number of water is considered constant as (Pr = 6.2). Streamlines, isothermal lines, counters of local and total entropy generation and the variation of Bejan number, local and average Nusselt numbers are presented and discussed in detail. The results explain that the average Nusselt number increases when the solid volume fraction of nanoparticles and the Rayleigh number increase. Also, the Bejan and average Nusselt numbers have a reverse behavior to each other for the same range of Rayleigh number and solid volume fraction. In addition, the results show that the entropy generation rate due to heat transfer, friction and the total entropy generation increase as the solid volume fraction increases, while it increases highly when the Rayleigh number increases especially near the hot left sidewall. [ABSTRACT FROM AUTHOR]

Separated flow and thermal performance characteristics by combined utilization of surface corrugation, partially active magnetic field, nanoparticle loading in the base fluid and flow pulsations are analyzed numerically in a bifurcating channel by using finite element method. Size and number of vortices are affected by the variation corrugation height and wave numbers while the vortices are damped by using partially active magnetic field in different domains. When various methods are compared, by using corrugations highest heat transfer improvement is achieved followed by the flow pulsations and magnetic field. By utilization of nanofluids, thermal performance is further improved. When corrugation height is considered, enhancement up to 248.3% is obtained for wave number of 8 while variation in the average Nusselt number (Nu) becomes only 22.9% with varying wave number. The enhancement amount with pulsating flow amplitude depends upon the nanoparticle loading amount in the base fluid. At solid volume fraction of 0.02%, the average Nu increases by about 79.8% with pulsating flow at the highest amplitude as compared to steady flow case. Dynamic models with system identification are constructed for predictions of time dependent Nu variations for different pulsating amplitudes in the absence and presence of magnetic field for the bifurcating channel. The potential improvement of convective heat transfer in bifurcation channels is explored by combining different novel enhancement methods together. The results of the present analysis will be beneficial for performance improvement and optimization studies of bifurcating channel applications appeared in microelectromechanical systems, fuel cells and thermal management of diverse thermal systems. [ABSTRACT FROM AUTHOR]

Coupled effects of double porous fins and inhomogeneous magnetic field on the cooling performance of multiple nanojet impingement for a corrugated surface were numerically analyzed. Different values of magnetic field parameters (strength, inclination, and amplitude of spatially varying part) and double porous fin parameters (inclination and permeability) were used, while finite element method is used as the solution method. When parametric computational fluid dynamics (CFD) simulations were performed, there were 162.5% and 34% Nusselt number (Nu) enhancement with magnetic field for flat and wavy surfaces, respectively. The variations of average Nu became 36 % and 24 % when varying the inclination and amplitude of inhomogeneous magnetic for a flat surface, while the amounts were 43.7 % and 32 % for a corrugated one. The vortex distribution in between the jets and cooling performance was affected by the variation of double porous fin permeability and inclination. An optimization method was used for the highest cooling performance, while the optimum set of parameters was obtained at (Ha, Amp, Da, Ω) = (0.224, 0.5835, 7.59 × 10 − 4 , 0.1617). By using the double porous fins and inhomogeneous magnetic field, excellent control of the cooling performance of multiple impinging jet was obtained. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a numerical study of a double diffusive convection in a cubic cavity filled with a binary mixture. The vertical walls are given different temperatures and concentrations. The potential-vorticity formulation in three-dimensional configuration using the finite volume method is utilized in this study. The results are given for Rayleigh number Ra=105, Prandtl number Pr=10 and Lewis number Le=10, characterizing the case of aqueous solutions. The influence of the magnetic field on the structure of the three-dimensional flow, the distribution of temperature and concentration and the different characteristics of heat and mass transfer of the thermal and solutal dominated region are presented. [Copyright &y& Elsevier]

Effects of sequential velocity and variable magnetic field on the phase change during hybrid nanofluid convection through a 3D cylinder containing a phase-change material packed bed (PCM-PB) system is analyzed with the finite element method. As the heat transfer fluid, 40% ethylene glycol with hybrid TiO 2 -Al 2 O 3 nanoparticles is considered. Impacts of the sequential velocity parameter (K, between 0.5 and 1.5), geometric factor of the conic-shaped PCM-PB (M, between 0.2 and 0.9), magnetic field strength (Ha number between 0 and 50) and solid volume fraction of hybrid nanoparticles (vol.% between 0.02 % and 0.1 % ) on the phase change dynamics are explored. Effects of both constant and varying magnetic fields on the phase change process were considered. Due to the increased fluid velocity at the walls, the phase change becomes higher with higher values of the sequential velocity parameter (K). There is a 21.6% reduction in phase transition time (tF) between the smallest and highest values of K both in the absence and presence of a constant magnetic field. The value of tF is reduced with higher magnetic field strength and the amount of reduction depends upon the sequential velocity parameter. At K = 1.5, the reduction amount with the highest Ha number is 14.7%, while it is 26% at K = 0.5. When nanoparticle is loaded in the base fluid, the value of tF is further reduced. In the absence of a magnetic field, the amount of phase-transition time reduction is 6.9%, while at Ha = 50, it is 11.7%. The phase change process can be controlled with varying magnetic field parameters as well. As the wave number and amplitude of the varying magnetic field are considered, significant changes in the tF are observed. [ABSTRACT FROM AUTHOR]

The forced convection of non-Newtonian nanofluid for a backward-facing flow system was analyzed under the combined use of magnetic field and double rotating cylinders by using finite element method. The power law nanofluid type was used with different solid volume fractions of alumina at 20 nm in diameter. The effects of the Re number ( 100 ≤ Re ≤ 300 ), rotational Re number ( − 2500 ≤ Rew ≤ 3000 ), Ha number ( 0 ≤ Ha ≤ 50 ), and magnetic field inclination ( 0 ≤ γ ≤ 90 ) on the convective heat transfer and flow features were numerically assessed. The non-Newtonian fluid power law index was taken between 0.8 and 1.2 while particle volume fractions up to 4% were considered. The presence of the rotating double cylinders made the flow field complicated where multiple recirculation regions were established near the step region. The impacts of the first (closer to the step) and second cylinders on the heat transfer behavior were different depending upon the direction of rotation. As the first cylinder rotated in the clockwise direction, the enhancement in the average heat transfer of 20% was achieved while it deteriorated by approximately 2% for counter-clockwise directional rotation. However, for the second cylinder, both the rotational direction resulted in heat transfer augmentation while the amounts were 14% and 18% at the highest speeds. Large vortices on the upper and lower channel walls behind the step were suppressed with magnetic field effects. The average Nu number generally increased with the higher strengths of the magnetic field and inclination. Up to 30% increment with strength was obtained while this amount was 44% with vertical orientation. Significant impacts of power law fluid index on the local and average Nu number were seen for an index of n = 1.2 as compared to the fluid with n = 0.8 and n = 1 while an average Nu number of 2.75 times was obtained for the flow system for fluid with n = 1.2 as compared to case for fluid with the n value of 0.8. Further improvements in the local and average heat transfer were achieved with using nanoparticles while at the highest particle amount, the enhancements of the average Nu number were 34%, 36% and 36.6% for the fluid with n values of 0.8, 1 and 1.2, respectively. [ABSTRACT FROM AUTHOR]

In order to improve the performance of a solar collector in low heat transfer rate zones, a 3-D numerical study of the effects of partially moving wall sections and the use of a water nanofluid (CNT) in a tilted parallelepiped solar collector was performed. Equations governing the mixed convection phenomena occurring in the cavity are developed based on the 3-D potential-vorticity formulation and solved using the finite volume method. Two cases related to the direction of the moving surfaces are considered and compared to the base case (no driven walls). The results are presented in term of flow structures, temperature fields and local and average Nusselt numbers. The Richardson number is varied from 0.001 to 10 and the CNT volume fraction from 0 to 0.045. The results showed that for low Richardson values (less than 1), the motion direction of the moving surfaces has no significant effect on heat transfer rates and becomes effective for higher values. The highest rates of heat transfer are found for high Richardson values and CNT volume fractions, while the enhancement ratio (compared to the base case) occurs for low Richardson values. [ABSTRACT FROM AUTHOR]