Free convection of a hybrid nanofluid past a vertical plate embedded in a porous medium with anisotropic permeability

2019 ◽  
Vol 30 (8) ◽  
pp. 4083-4101 ◽  
Author(s):  
Aneela Bibi ◽  
Hang Xu ◽  
Qiang Sun ◽  
Ioan Pop ◽  
Qingkai Zhao
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Stability Analysis ◽  
Flat Surface ◽  
Saturated Porous Medium ◽  
Heat Energy ◽  
Hybrid Nanofluid ◽  
Anisotropic Permeability ◽  
Content Type ◽  
Hybrid Nanofluids

Purpose This study aims to carry out an analysis for flow and heat transfer of a new hybrid nanofluid over a vertical flat surface embedded in a saturated porous medium with anisotropic permeability at high Rayleigh number. Here the hybrid nanofluid is considered as the working fluid, with different kinds of small particles in nanoscale being suspended. Design/methodology/approach The generalized homogenous model is introduced to describe the behaviors of hybrid nanofluid. Within the framework of the boundary layer approximations, the governing equations embodying the conservation equations of total mass, momentum and thermal energy are reduced to a set of fully coupled ordinary differential equations via relevant scaling transformations. A flow stability analysis is performed to examine the behavior of convective heat energy. Accurate solutions are obtained by means of a very efficient homotopy-based package BVPh 2.0. Findings Results show that the linear correlations of physical quantities among the base fluid and its suspended nanoparticles are adequate to give accurate results for simulation of behaviors of hybrid nanofluids. Heat enhancement can be also fulfilled by hybrid nanofluids. A flow stability analysis suggests the heat-related power index m > −1/3 for satisfying the increasing behavior of convective heat energy. Originality/value Free convection of a hybrid nanofluid near a vertical flat surface embedded in a saturated porous medium with anisotropic permeability is investigated for the first time. The simplified hybrid nanofluid model is proposed for describing nanofluid behaviors. The results of this proposed approach agree well with those given by the traditional hybrid nanofluid model and experiment. It is expected that, by using different combinations of various kinds of nanoparticles, the new generation of heat transfer fluids can be fabricated, which possess similar thermal-physical properties as regular nanofluids but with lower cost.

scholarly journals Free convection heat transfer of MgO-MWCNTs/EG hybrid nanofluid in a porous complex shaped cavity with MHD and thermal radiation effects

2019 ◽  
Vol 29 (11) ◽  
pp. 4349-4376 ◽  
Author(s):  
Mohammad Ghalambaz ◽  
Mahmoud Sabour ◽  
Ioan Pop ◽  
Dongsheng Wen
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Porous Medium ◽  
Complex Shape ◽  
Convection Heat Transfer ◽  
Hybrid Nanofluid ◽  
Convection Heat ◽  
Governing Equations ◽  
Content Type ◽  
Hybrid Nanofluids

Purpose The present study aims to address the flow and heat transfer of MgO-MWCNTs/EG hybrid nanofluid in a complex shape enclosure filled with a porous medium. The enclosure is subject to a uniform inclined magnetic field and radiation effects. The effect of the presence of a variable magnetic field on the natural convection heat transfer of hybrid nanofluids in a complex shape cavity is studied for the first time. The geometry of the cavity is an annular space with an isothermal wavy outer cold wall. Two types of the porous medium, glass ball and aluminum metal foam, are adopted for the porous space. The governing equations for mass, momentum and heat transfer of the hybrid nanofluid are introduced and transformed into non-dimensional form. The actual available thermal conductivity and dynamic viscosity data for the hybrid nanofluid are directly used for thermophysical properties of the hybrid nanofluid. Design/methodology/approach The governing equations for mass, momentum and heat transfer of hybrid nanofluid are introduced and transformed into non-dimensional form. The thermal conductivity and dynamic viscosity of the nanofluid are directly used from the experimental results available in the literature. The finite element method is used to solve the governing equations. Grid check procedure and validations were performed. Findings The effect of Hartmann number, Rayleigh number, Darcy number, the shape of the cavity and the type of porous medium on the thermal performance of the cavity are studied. The outcomes show that using the composite nanoparticles boosts the convective heat transfer. However, the rise of the volume fraction of nanoparticles would reduce the overall enhancement. Considering a convective dominant regime of natural convection flow with Rayleigh number of 107, the maximum enhancement ratio (Nusselt number ratio compared to the pure fluid) for the case of glass ball is about 1.17 and for the case of aluminum metal foam is about 1.15 when the volume fraction of hybrid nanoparticles is minimum as 0.2 per cent. Originality/value The effect of the presence of a variable magnetic field on the natural convection heat transfer of a new type of hybrid nanofluids, MgO-MWCNTs/EG, in a complex shape cavity is studied for the first time. The results of this paper are new and original with many practical applications of hybrid nanofluids in the modern industry.

Mixed convection and stability analysis of stagnation-point boundary layer flow and heat transfer of hybrid nanofluids over a vertical plate

2019 ◽  
Vol 30 (7) ◽  
pp. 3737-3754 ◽  
Author(s):  
Mohammad Ghalambaz ◽  
Natalia C. Roşca ◽  
Alin V. Roşca ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Stability Analysis ◽  
Mixed Convection ◽  
Boundary Layer Flow ◽  
Hybrid Nanofluid ◽  
Content Type ◽  
Flow And Heat Transfer ◽  
Hybrid Nanofluids ◽  
Layer Flow

Purpose This study aims to study the mixed convection flow and heat transfer of Al2O3-Cu/water hybrid nanofluid over a vertical plate. Governing equations for conservation of mass, momentum and energy for the hybrid nanofluid over a vertical flat plate are introduced. Design/methodology/approach The similarity transformation approach is used to transform the set of partial differential equations into a set of non-dimensional ordinary differential equations. Finite-deference with collocation method is used to integrate the governing equations for the velocity and temperature profiles. Findings The results show that dual solutions exist for the case of opposing flow over the plate. Linear stability analysis was performed to identify a stable solution. The stability analysis shows that the lower branch of the solution is always unstable, while the upper branch of the solution is always stable. The results of boundary layer analysis are reported for the various volume fractions of composite nanoparticles and mixed convection parameter. The outcomes show that the composition of nanoparticles can notably influence the boundary layer flow and heat transfer profiles. It is also found that the trend of the variation of surface skin friction and heat transfer for each of the dual solution branches can be different. The critical values of the mixed convection parameter, λ, where the dual solution branches joint together, are also under the influence of the composition of hybrid nanoparticles. For instance, assuming a total volume fraction of 5 per cent for the mixture of Al2O3 and Cu nanoparticles, the critical value of mixing parameter of λ changes from −3.1940 to −3.2561 by changing the composition of nanofluids from Al2O3 (5 per cent) + Cu (0%) to Al2O3 (2.5%) + Cu (2.5 per cent). Originality/value The mixed convection stability analysis and heat transfer study of hybrid nanofluids for a stagnation-point boundary layer flow are addressed for the first time. The introduced hybrid nanofluid model and similarity solution are new and of interest in both mathematical and physical points of view.

Darcy-Forchheimer porous medium effect on rotating hybrid nanofluid on a linear shrinking/stretching sheet

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Liaquat Ali Lund ◽  
Zurni Omar ◽  
Ilyas Khan
Keyword(s):  
Porous Medium ◽  
Stability Analysis ◽  
Differential Equations ◽  
Three Dimensional ◽  
Spherical Particles ◽  
Medium Effect ◽  
Hybrid Nanofluid ◽  
Three Dimensional Flow ◽  
Content Type ◽  
Dimensional Flow

Purpose The purpose of this study is to find the multiple branches of the three-dimensional flow of Cu-Al2 O3/water rotating hybrid nanofluid perfusing a porous medium over the stretching/shrinking surface. The extended model of Darcy due to Forchheimer and Brinkman has been considered to make the hybrid nanofluid model over the pores by considering the porosity and permeability effects. Design/methodology/approach The Tiwari and Das model with the thermophysical properties of spherical particles for efficient dynamic viscosity of the nanoparticle is used. The linear similarity transformations are applied to convert the partial differential equations into ordinary differential equations (ODEs). The system of governing ODEs is solved by using the three-stage Lobatto IIIa scheme in MATLAB for evolving parameters. Findings The system of governing ODEs produces dual branches. A unique stable branch is identified with help of stability analysis. The reduced heat transfer rate has been shown to increase with the reduced ϕ2 in both branches. Further, results revealed that the presence of multiple branches depends on the ranges of porosity, suction and stretching/shrinking parameters for the particular value of the rotating parameter. Originality/value Dual branches of the three-dimensional flow of Cu-Al2 O3/water rotating hybrid nanofluid have been found. Therefore, stability analysis of the branches is also conducted to know which branch is appropriate for the practical applications. To the best of the authors’ knowledge, this research is novel and there is no previously published work relevant to the present study.

Radiative MHD hybrid-nanofluids flow over a permeable stretching surface with heat source/sink embedded in porous medium

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Priyanka Agrawal ◽  
Praveen Kumar Dadheech ◽  
R.N. Jat ◽  
Dumitru Baleanu ◽  
Sunil Dutt Purohit
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Heat Source ◽  
Aluminum Oxide ◽  
Stretching Surface ◽  
Content Type ◽  
Similarity Transformations ◽  
Heat Transfer Efficiency ◽  
Hybrid Nanofluids ◽  
Source Sink

Purpose The purpose of this paper is to study the comparative analysis between three hybrid nanofluids flow past a permeable stretching surface in a porous medium with thermal radiation. Uniform magnetic field is applied together with heat source and sink. Three set of different hybrid nanofluids with water as a base fluid having suspension of Copper-Aluminum Oxide (Cu−Al2O3), Silver-Aluminum Oxide (Ag−Al2O3) and Copper-Silver (Cu−Ag) nanoparticles are considered. The Marangoni boundary condition is applied. Design/methodology/approach The governing model of the flow is solved by Runga–Kutta fourth-order method with shooting technique, using appropriate similarity transformations. Temperature and velocity field are explained by the figures for many flow pertinent parameters. Findings Almost same behavior is observed for all the parameters presented in this analysis for the three set of hybrid nanofluids. For increased mass transfer wall parameter ( fw) and Prandtl Number (Pr), heat transfer rate cuts down for all three sets of hybrid nanofluids, and reverse effect is seen for radiation parameter (R), and heat source/sink parameter ( δ). Practical implications The thermal conductivity of hybrid nanofluids is much larger than the conventional fluids; thus, heat transfer efficiency can be improved with these fluids and its implications can be seen in the fields of biomedical, microelectronics, thin-film stretching, lubrication, refrigeration, etc. Originality/value The current analysis is to optimize heat transfer of three different radiative hybrid nanofluids ( Cu−Al2O3/H2O, Ag−Al2O3/H2O and Cu−Ag/H2O) over stretching surface after applying heat source/sink with Marangoni convection. To the best of the authors’ knowledge, this work is new and never published before.

scholarly journals Thermal Non-Equilibrium Heat Transfer Modeling of Hybrid Nanofluids in a Structure Composed of the Layers of Solid and Porous Media and Free Nanofluids

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 541 ◽  
Author(s):  
Ali J. Chamkha ◽  
Sina Sazegar ◽  
Esmael Jamesahar ◽  
Mohammad Ghalambaz
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Conjugate Heat Transfer ◽  
Hybrid Nanofluid ◽  
Governing Equations ◽  
Flow And Heat Transfer ◽  
Clear Space ◽  
Hybrid Nanofluids ◽  
Solid Block ◽  
Non Equilibrium

The free convection heat transfer of hybrid nanofluids in a cavity space composed of a clear flow, porous medium and a solid part is addressed. The cavity is heated from the bottom and cooled from the top. The side walls are well insulated. The upper part of the cavity is a clear space with no porous or solid materials and is filled with hybrid nanofluid. The bottom part is divided into two parts of a porous space saturated with the hybrid nanofluid and a solid thermal conductive block. There are conjugate heat transfer mechanisms between the solid block and the porous medium filled with the hybrid nanofluid as well as the hybrid nanofluid in the clear space. For the porous medium model, the local thermal non-equilibrium effects are considered. The hybrid nanofluids contain copper (20 nm) and alumina nanoparticles (40 nm) hybrid nanoparticles. The governing equations for the flow and heat transfer of the hybrid nanofluid in the clear space and the porous medium are introduced. Considering the conjugate heat transfer between the solid block and the hybrid nanofluid fluid in the pores and the porous matrix, appropriate boundary conditions for heat channeling are utilized. The governing equations are transformed into non-dimensional form to generalize the model. The finite element method is employed to solve the equations. The grid check and validation procedure are performed. Subsequently streamlines, isotherms, and Nusselt number are studied as important aspects of flow and heat transfer in the cavity. The increase in the portion of the clear flow part in the cavity enhances heat transfer due to better hybrid nanofluid circulation.

Experimental and numerical analysis on using CuO-Al2O3/water hybrid nanofluid in a U-type tubular heat exchanger

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Emine Yağız Gürbüz ◽  
Halil İbrahim Variyenli ◽  
Adnan Sözen ◽  
Ataollah Khanlari ◽  
Mert Ökten
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Thermal Performance ◽  
Single Type ◽  
Working Fluid ◽  
Hybrid Nanofluid ◽  
Tubular Heat Exchanger ◽  
Content Type ◽  
Hybrid Type ◽  
Hybrid Nanofluids

Purpose Heat exchangers (HEXs) are extensively used in many applications such as heating and cooling systems. To increase the thermal performance of HEXs, nano-sized particles could be added to the base working fluid which can improve the thermophysical properties of the fluid. In addition, further improvement in the thermal performance of nanofluids can be obtained by using two or more different nanoparticles which are known as hybrid nanofluids. This paper aims to improve the thermal efficiency of U-type tubular HEX (THEX) by using CuO-Al2O3/water hybrid nanofluid. Design/methodology/approach Numerical simulation has been used to model THEX with various configurations. Also, CuO-Al2O3/water hybrid nanofluid has been experimented in THEX in two various modes including parallel (PTHEX) and counter flow (CTHEX) regarding to the numerical findings. Hybrid nanofluids have been prepared in two particle concentrations and compared with CuO/water nanofluid at the same concentrations and also with water. Findings The numerical simulation results showed that adding fins and also using hybrid nanofluid can increase heat transfer rate in HEX. However, adding fins cannot be a good option in U-type THEX with lower diameter because it increases pressure drop notably. Experimental results of this work illustrated that using Al2O3-CuO/water hybrid nanofluid in the THEX improved thermal performance significantly. Maximum enhancement in overall heat transfer coefficient of THEX by using CuO-Al2O3/water nanofluid in 0.5% and 1% concentrations achieved as 9.5% and 12%, respectively. Originality/value The obtained findings of the study showed the positive effects of using hybrid type nanofluid in comparison with single type nanofluid. In this study, numerical and experimental analysis have been conducted to investigate the effect of using hybrid type nanofluid in U-type HEX. The obtained results exhibited successful utilization of CuO-Al2O3/water hybrid type nanofluid in HEX. Moreover, it was observed that thermal performance analysis of the nanofluids without any experiment can be done by using numerical method.

Hybrid nanofluid flow towards a stagnation point on an exponentially stretching/shrinking vertical sheet with buoyancy effects

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Iskandar Waini ◽  
Anuar Ishak ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Stability Analysis ◽  
Mixed Convection ◽  
Stagnation Point ◽  
Temporal Stability ◽  
Hybrid Nanoparticles ◽  
Hybrid Nanofluid ◽  
Nanofluid Flow ◽  
Content Type ◽  
Exponentially Stretching

Purpose This paper aims to examine the hybrid nanofluid flow towards a stagnation point on an exponentially stretching/shrinking vertical sheet with buoyancy effects. Design/methodology/approach Here, the authors consider copper (Cu) and alumina (Al2O3) as hybrid nanoparticles while water as the base fluid. The governing equations are reduced to the similarity equations using similarity transformations. The resulting equations are programmed in Matlab software through the bvp4c solver to obtain their solutions. Findings The authors found that the heat transfer rate is greater for Al2O3-Cu/water hybrid nanofluid if compared to Cu/water nanofluid. Besides, the non-uniqueness of the solutions is observed for certain physical parameters. The authors also notice that the bifurcation of the solutions occurs in the downward buoyant force and the shrinking regions. In addition, the first solution of the skin friction and heat transfer coefficients increase with the added hybrid nanoparticles and the mixed convection parameter. The temporal stability analysis shows that one of the solutions is stable as time evolves. Originality/value The present work is dealing with the problem of a mixed convection flow of a hybrid nanofluid towards a stagnation point on an exponentially stretching/shrinking vertical sheet, with the buoyancy effects is taken into consideration. The authors show that two solutions are obtained for a single value of parameter for both stretching and shrinking cases, as well as for both buoyancy aiding and opposing flows. A temporal stability analysis then shows that only one of the solutions is stable and physically reliable as time evolves.

MHD flow and heat transfer of hybrid nanofluid over a permeable moving surface in the presence of thermal radiation

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nurul Amira Zainal ◽  
Roslinda Nazar ◽  
Kohilavani Naganthran ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Stability Analysis ◽  
Thermal Radiation ◽  
Mhd Flow ◽  
Heat Transfer Analysis ◽  
Problem Solver ◽  
Hybrid Nanofluid ◽  
Moving Surface ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose This paper aims to investigate the flow and heat transfer characteristics of a hybrid nanofluid (Cu-Al2O3/water) in the presence of magnetohydrodynamics and thermal radiation over a permeable moving surface. Design/methodology/approach By choosing appropriate similarity variables, the partial differential equations are transformed into a system of linear equations which are solved by using the boundary value problem solver (bvp4c) in MATLAB. The implementation of stability analysis verifies the achievable result of the first solution which is considered stable while the second solution is unstable. Findings The findings revealed that the presence of a magnetic field and suction slows down the fluid motion because of the synchronism of the magnetic and electric field occurred from the formation of the Lorentz force. Also, the enhancement of the thermal radiation parameter escalates the heat transfer rate of the current study. Originality/value The present study is addressing the problem of MHD flow and heat transfer analysis of a hybrid nanofluid towards a permeable moving surface, with the consideration of the thermal radiation effect. The authors show that in both cases of assisting and opposing flow, there exist dual solutions within a specific range of the moving parameters. A stability analysis approved that only one of the solutions are physically relevant.

Quantification of free convection within a hemispherical annulus through a porous medium saturated by water-copper nanofluid

2019 ◽  
Vol 29 (3) ◽  
pp. 1153-1166 ◽  
Author(s):  
Abderrahmane Baïri ◽  
Nagaraj Suresh ◽  
Palanisamy Gayathri ◽  
Nagarajan Nithyadevi ◽  
Purusothaman Abimanyu
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Rayleigh Number ◽  
Electronic Device ◽  
Numerical Study ◽  
Control Volume ◽  
Saturated Porous Medium ◽  
Pure Water ◽  
Thermal Design ◽  
Content Type

Purpose A porous medium saturated with a nanofluid based on pure water and copper nanoparticles is used for cooling a hemispherical electronic device contained in an annulus space. The disc of the cavity could be inclined at an angle ranging from 0 ° (horizontal disc with dome facing upwards) to 180° (horizontal disc with dome facing downwards). The important surface heat flux generated by the dome leads to high Rayleigh number values reaching 7.29 × 10^10. The purpose of this work is to examine the influence of the nanofluid saturated porous medium on the free convective heat transfer. Design/methodology/approach Heat transfer occurring between this active component and the isothermal passive cupola is quantified by means of a three-dimensional numerical study using the control volume method associated to the SIMPLE algorithm. Findings The work shows that heat transfer in the annulus space is improved by interposing a porous medium saturated with the water-copper nanofluid. Originality/value New correlation is proposed to calculate the Nusselt number for any combination of the inclination angle, the fraction volume, the Rayleigh number and the ratio between the thermal conductivities of the porous medium and the fluid. The wide ranges corresponding to these parameters allow the thermal design of this electronic equipment for various configurations.

Stagnation-point flow of an aqueous titania-copper hybrid nanofluid toward a wavy cylinder

2018 ◽  
Vol 28 (7) ◽  
pp. 1716-1735 ◽  
Author(s):  
Mohammad Yousefi ◽  
Saeed Dinarvand ◽  
Mohammad Eftekhari Yazdi ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Stagnation Point ◽  
Base Fluid ◽  
Stagnation Point Flow ◽  
Hybrid Nanofluid ◽  
Content Type ◽  
Analytic Modeling ◽  
Flow And Heat Transfer ◽  
Special Cases ◽  
Hybrid Nanofluids

Purpose The purpose of this paper is to investigate analytically the steady general three-dimensional stagnation-point flow of an aqueous titania-copper hybrid nanofluid past a circular cylinder that has a sinusoidal radius variation. Design/methodology/approach First, the analytic modeling of hybrid nanofluid is presented, and using appropriate similarity variables, the governing equations are transformed into nonlinear ordinary differential equations in the dimensionless stream function, which is solved by the well-known function bvp4c from MATLAB. Findings The current solution demonstrates good agreement with those of the previously published studies in the special cases of regular fluid and nanofluids. Graphical results are presented to investigate the influences of the titania and copper nanoparticle volume fractions and also the nodal/saddle indicative parameter on flow and heat transfer characteristics. Here, the thermal characteristics of hybrid nanofluid are found to be higher in comparison to the base fluid and fluid containing single nanoparticles. An important point to note is that the developed model can be used with great confidence to study the flow and heat transfer of hybrid nanofluids. Originality/value Analytic modeling of hybrid nanofluid is the important originality of present study. Hybrid nanofluids are potential fluids that offer better heat transfer performance and thermophysical properties than convectional heat transfer fluids (oil, water and ethylene glycol) and nanofluids with single nanoparticles. In this investigation, titania (TiO2, 50 nm), copper (Cu, 20 nm) and the hybrid of these two are separately dispersed into the water as the base fluid and analyzed.

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