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1 – 10 of over 2000The purpose of this paper is to numerically investigate steady, laminar natural and mixed convection heat transfer in a two-dimensional cavity by using a finite volume method with…
Abstract
Purpose
The purpose of this paper is to numerically investigate steady, laminar natural and mixed convection heat transfer in a two-dimensional cavity by using a finite volume method with a fourth-order approximation of convective terms, with and without the presence of nanoparticles. Highly accurate benchmark results are also provided.
Design/methodology/approach
A finite volume method on a non-uniform staggered grid is used for the solution of two-dimensional momentum and energy conservation equations. Diffusion terms, in the momentum and energy equations, are approximated using second-order central differences, whereas a non-uniform four-point fourth-order interpolation (FPFOI) scheme is developed for the convective terms. Coupled mass and momentum conservation equations are solved iteratively using a semi-implicit method for pressure-linked equation method.
Findings
For the case of natural convection problem at high-Rayleigh numbers, grid density must be sufficiently high in order to obtain grid-independent results and capture reality of the physics. Heat transfer enhancement for natural convection is observed up to a certain value of the nanoparticle volume fraction. After that value, heat transfer deterioration is found with increasing nanoparticle volume fraction.
Originality/value
Developed a non-uniform FPFOI scheme. Highly accurate benchmark results for the heat transfer of Al2O3-water nanofluid in a cavity are provided.
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Sayed Mahdi Naghavi and Ghanbar Ali Sheikhzadeh
The purpose of this study is the identification of the best method to apply the body force in the lattice Boltzmann method (LBM). In the simulation of mixed convection, especially…
Abstract
Purpose
The purpose of this study is the identification of the best method to apply the body force in the lattice Boltzmann method (LBM). In the simulation of mixed convection, especially for large Richardson number flows in a square cavity.
Design/methodology/approach
First, three methods for applying the body force were compared to each other in the LBM. Then, an LBM-based code was written in the FORTRAN language using these three methods. Next, that code was used to simulate natural/mixed convection in a two-dimensional cavity to evaluate the methods for applying the body force. Finally, the optimum way for applying the body force was used for the simulation of free convection heat transfer in a concentric annulus with Rayleigh number in a range of 1,000 to 50,000, and mixed convection heat transfer in a concentric annulus with Rayleigh number in a range of 10,000 to 50,000 and Reynolds number in a range of 100 to 400.
Findings
Mixed convection heat transfer was simulated in a two-dimensional cavity with Richardson number in a range of 0.0001 to 100. The results which were obtained in low Richardson number flows have shown good adaptation to the available data. However, the results of large Richardson number flows, for example, Ri = 100, have shown a significant difference to the available data. Investigations revealed that this difference was due to the method of applying the body force. Therefore, the choice of the best way to apply the body force was investigated. Finally, for the large Richardson number flows, the best method to apply the body force has been identified among the several techniques.
Originality/value
To the authors’ knowledge, the effects of methods for applying the body force were not investigated in the cavities mixed convection, even though there are numerous investigations conducted on mixed convection with the LBM. In this study, the effects of techniques to apply the body force were investigated in large Richardson number flows. Finally, the best method to apply the body force is distinguished between several techniques for the large Richardson number mixed convection flows.
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The purpose of this paper is to propose an efficient/robust numerical algorithm for solving the two‐dimensional laminar mixed‐convection in a lid‐driven cavity using the mixed…
Abstract
Purpose
The purpose of this paper is to propose an efficient/robust numerical algorithm for solving the two‐dimensional laminar mixed‐convection in a lid‐driven cavity using the mixed finite element (FE) technique.
Design/methodology/approach
A numerical algorithm was based on the so‐called consistent splitting scheme, which improved the numerical accuracy of the primitive variables. In order to obtain a stable solution, two choices of mixed FEs, the Taylor‐Hood and Crouzeix‐Raviart types, were used. Two mesh layouts were considered; uniform and non‐uniform.
Findings
To verify that the proposed scheme had a second‐order accuracy, some numerical results are presented and compared with the known solution. The answer was confirmative. Numerically accurate solutions were obtained for a fixed Prandtl number, Pr=0.71, for a range of the Reynolds number, Re from 100 to 3,000, and for a range of the Richardson number, Ri from 0.001 to 100. The results from these calculations, using the mixed FE consistent splitting scheme, agreed with the existing ones.
Research limitations/implications
Further extensions of this work could include the influence of various choices of Reynolds numbers, Prandtl numbers and Richardson numbers, and the effect of aspect ratio.
Originality/value
The present work was the first to apply a mixed FE in association with the consistent splitting scheme to the mixed convection problem.
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Abdelraheem M. Aly, Mitsuteru Asai and Ali J. Chamkha
The purpose of this paper is to model mixed convection in a square cavity included circular cylinders motion using an incompressible smoothed particle hydrodynamics (ISPH…
Abstract
Purpose
The purpose of this paper is to model mixed convection in a square cavity included circular cylinders motion using an incompressible smoothed particle hydrodynamics (ISPH) technique.
Design/methodology/approach
The problem is solved numerically by using the ISPH method.
Findings
The SPH tool shows robust performance to simulate the rigid body motion in the mixed convective flow with heat transfer, and it may apply easily to complicated problems in 2D and 3D problem without difficulties.
Originality/value
The application of the SPH method to mixed convective flow with heat transfer and its potential application easily to complicated 3D problems is original.
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Oktay Çiçek, A. Filiz Baytaş and A. Cihat Baytaş
This study aims to numerically scrutinize the entropy generation minimization and mixed convective heat transfer of multi-walled carbon nanotubes–Fe3O4/water hybrid nanofluid flow…
Abstract
Purpose
This study aims to numerically scrutinize the entropy generation minimization and mixed convective heat transfer of multi-walled carbon nanotubes–Fe3O4/water hybrid nanofluid flow in a lid-driven square enclosure with heat generation in the presence of a porous layer on inner surfaces, considering local thermal non-equilibrium (LTNE) approach and the non-Darcy flow model.
Design/methodology/approach
The dimensionless governing equations for hybrid nanofluid and solid phases are solved by applying the finite volume method and semi-implicit method for pressure-linked equations algorithm.
Findings
The roles of the internal heat generation in the porous layer, LTNE model and nanoparticles volume fraction on mixed convection phenomenon and entropy generation are introduced for lid-driven cavity hybrid nanofluid flow. Based on the investigation of entropy generation and heat transfer, the minimum total entropy generation and average Nusselt numbers are found at 1 ≤ Ri ≤ 10 where the effect of the forced and free convection flow directions being opposite each other is very significant. When considering various nanoparticle volume fractions, it becomes evident that the minimum entropy generation occurs in the case of φ = 0.1%. The outcomes of LTNE number reveal the operating parameters in which thermal equilibrium occurs between hybrid nanofluid and solid phases.
Originality/value
The analysis of entropy generation under various shear and buoyancy forces plays a significant role in the suitable thermal design and optimization of mixed convective heat transfer applications. This research significantly contributes to the optimization of design and the advancement of innovative solutions across diverse engineering disciplines, such as packed-bed thermal energy storage and thermal insulation.
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Ismail Arroub, Ahmed Bahlaoui, Abdelghani Raji, Mohammed Hasnaoui and Mohamed Naïmi
The purpose of this paper is to investigate numerically mixed convection of Al2O3-water nanofluids flowing through a horizontal ventilated cavity heated from below by a…
Abstract
Purpose
The purpose of this paper is to investigate numerically mixed convection of Al2O3-water nanofluids flowing through a horizontal ventilated cavity heated from below by a temperature varying sinusoidally along its lower wall. The simulations focus on the effects of different key parameters, such as Reynolds number (200 ≤ Re ≤ 5,000), nanoparticles’ concentration (0 ≤ ϕ ≤ 0.1) and phase shift of the heating temperature (0 ≤ γ ≤ π), on flow and thermal patterns and heat transfer performances.
Design/methodology/approach
The Navier–Stokes equations describing the nanofluid flow were discretized using a finite difference technique. The vorticity and energy equations were solved by the alternating direction implicit method. Values of the stream function were obtained by using the point successive over-relaxation method.
Findings
The simulations were performed for two modes of imposed external flow (injection and suction). The main findings are that the dynamical and thermal fields are affected by the parameters Re, ϕ, γ and the applied ventilation mode; the addition of nanoparticles leads to an improvement of heat transfer rate and an increase of mean temperature inside the enclosure; the heat exchange performance and the better cooling are more pronounced in suction mode; the phase shift of the heating temperature may lead to periodic solutions for weaker values of Re and contributes to an increase or a decrease of heat transfer depending on the value of ϕ and the convection regime.
Originality/value
To the best of the authors’ knowledge, the problem of mixed convection of a nanofluid inside a vented cavity using the injection or suction technics and submitted to non-uniform heating conditions has not been treated so far.
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The problem of steady, laminar, heat and mass transfer by mixed convection from a semi‐infinite, isothermal, vertical and permeable plate embedded in a uniform porous medium in…
Abstract
The problem of steady, laminar, heat and mass transfer by mixed convection from a semi‐infinite, isothermal, vertical and permeable plate embedded in a uniform porous medium in the presence of temperature‐dependent heat source or sink and magnetic field effects is considered. A mixed convection parameter for the entire range of free‐forced‐mixed convection is employed and non‐similar equations are obtained. These equations are solved numerically by an efficient implicit, iterative, finite‐difference scheme. The obtained results are checked against previously published work on special cases of the problem and are found to be in good agreement. Useful correlations for the local Nusselt number are obtained for various physical parameters. A parametric study illustrating the influence of the magnetic field, porous medium inertia effects, heat generation or absorption, concentration to thermal buoyancy ratio, and the Lewis number on the fluid velocity, temperature and concentration as well as the Nusselt and the Sherwood numbers is conducted. The obtained results are shown graphically and the physical aspects of the problem are discussed.
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Ali J. Chamkha and Jasem M. Al‐Humoud
To consider simultaneous heat and mass transfer by mixed convection for a non‐Newtonian power‐law fluid from a permeable vertical plate embedded in a fluid‐saturated porous medium…
Abstract
Purpose
To consider simultaneous heat and mass transfer by mixed convection for a non‐Newtonian power‐law fluid from a permeable vertical plate embedded in a fluid‐saturated porous medium in the presence of suction or injection and heat generation or absorption effects.
Design/methodology/approach
The problem is formulated in terms of non‐similar equations. These equations are solved numerically by an efficient implicit, iterative, finite‐difference method.
Findings
It was found that as the buoyancy ratio was increased, both the local Nusselt and Sherwood numbers increased in the whole range of free and mixed convection regime while they remained constant for the forced‐convection regime. However, they decreased and then increased forming dips as the mixed‐convection parameter was increased from the free‐convection limit to the forced‐convection limit for both Newtonian and dilatant fluid situations.
Research limitations/implications
The problem is limited to slow flow of non‐Newtonian power‐law fluids in porous media. Future research may consider inertia effects of porous media for relatively higher velocity flows.
Practical implications
A very useful source of information for researchers on the subject of non‐Newtonian fluids in porous media.
Originality/value
This paper illustrates simultaneous heat and mass transfer in porous media for power‐law fluids with heat generation or absorption effects.
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Rama Subba Reddy Gorla and Mahesh Kumari
A nonsimilar boundary layer analysis is presented for the problem of mixed convection in power‐law type non‐Newtonian fluids along a vertical wedge with variable wall temperature…
Abstract
A nonsimilar boundary layer analysis is presented for the problem of mixed convection in power‐law type non‐Newtonian fluids along a vertical wedge with variable wall temperature distribution. The mixed convection regime is divided into two regions, namely, the forced convection dominated regime and the free convection dominated regime. The two solutions are matched. Numerical results are presented for the details of the velocity and temperature fields. A discussion is provided for the effect of viscosity index on the surface heat transfer rate.
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Ammar I. Alsabery, Taher Armaghani, Ali J. Chamkha, Muhammad Adil Sadiq and Ishak Hashim
The aim of this study is to investigate the effects of two-phase nanofluid model on mixed convection in a double lid-driven square cavity in the presence of a magnetic field. The…
Abstract
Purpose
The aim of this study is to investigate the effects of two-phase nanofluid model on mixed convection in a double lid-driven square cavity in the presence of a magnetic field. The authors believe that this work is a good contribution for improving the thermal performance and the heat transfer enhancement in some engineering instruments.
Design/methodology/approach
The current work investigates the problem of mixed convection heat transfer in a double lid-driven square cavity in the presence of magnetic field. The used cavity is filled with water-Al2O3 nanofluid based on Buongiorno’s two-phase model. The bottom horizontal wall is maintained at a constant high temperature and moves to the left/right, while the top horizontal wall is maintained at a constant low temperature and moves to the right/left. The left and right vertical walls are thermally insulated. The dimensionless governing equations are solved numerically using the Galerkin weighted residual finite element method.
Findings
The obtained results show that the heat transfer rate enhances with an increment of Reynolds number or a reduction of Hartmann number. In addition, effects of thermophoresis and Brownian motion play a significant role in the growth of convection heat transfer.
Originality/value
According to above-mentioned studies and to the authors’ best knowledge, there has no study reported the MHD mixed convection heat transfer in a double lid-driven cavity using the two-phase nanofluid model. Thus, the authors of the present study believe that this work is valuable. Therefore, the aim of this comprehensive numerical study is to investigate the effects of two-phase nanofluid model on mixed convection in a double lid-driven square cavity in the presence of a magnetic field. The authors believe that this work is a good contribution for improving the thermal performance and the heat transfer enhancement in some engineering instruments.
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