scholarly journals Free convection from a corrugated heated cylinder with nanofluids in a porous enclosure

2020 ◽  
Vol 12 (8) ◽  
pp. 168781402095221 ◽  
Author(s):  
Abeer Alhashash
Keyword(s):  
Heat Transfer ◽  
The Finite Element Method ◽  
Governing Equations ◽  
Corrugated Surface ◽  
Heated Cylinder ◽  
Smooth Cylinder ◽  
Current Article ◽  
Water Base ◽  
Porous Enclosure ◽  
Better Than

Natural convection between a cold square porous enclosure and a hot corrugated cylinder is studied numerically in the current article. The enclosure is filled with a water-base nanofluids suspending metal nanoparticles and the porous layer is modelled applying the Brinkman-Forchheimer law. The finite element method has been utilised to solve the governing equations. Analysis in this studies are: the amplitude of corrugated surface, the number of corrugated surface and the concentration are considered. It is found that the heat transfer of the corrugated cylinder might be slightly better than the heat transfer of the smooth cylinder under specific circumstances, but in general, the heat transfer is reduced by applying the corrugated surface. The heat transfer enhances up to [Formula: see text] by increasing nanoparticle concentration. The heat transfer rate does not increase linearly by increasing the concentration, but it is proportional to the square root of the concentration.

scholarly journals Natural convection induced by undulated surfaces in a porous enclosure filled with nanoliquid

2019 ◽  
Vol 11 (9) ◽  
pp. 168781401987528 ◽  
Author(s):  
Abeer Alhashash ◽  
Habibis Saleh
Keyword(s):  
Heat Transfer ◽  
Convective Flow ◽  
Darcy Law ◽  
Nanoparticle Concentration ◽  
Governing Equations ◽  
Transfer Rates ◽  
Number Formula ◽  
Water Base ◽  
Porous Enclosure ◽  
Effect Of Surface

Effect of surface undulation on convective flow in a porous enclosure is investigated in this present article. The porous enclosure is filled with a water-base nanoliquid containing Cu solid nanoparticles, and the porous layer is modeled using the Darcy law. The governing equations are solved numerically using the built-in finite element method of COMSOL. The investigation was carried out for several parameters: the nanoparticle concentration, [Formula: see text]; the amplitude of undulations, [Formula: see text]; the number of undulations, [Formula: see text]; and the Rayleigh number, [Formula: see text]. It is concluded that the strength of the nanoliquid circulation increases with increasing the amplitude or number undulations. It is found that the heat transfer rates were sensitive to the variation of undulation property, convection intensity, and nanoparticle concentration.

scholarly journals Transient free convection in an inclined square porous cavity filled with a nanofluid using LTNE and Buongiorno’s models

2018 ◽  
Vol 240 ◽  
pp. 03014
Author(s):  
Mikhail Sheremet ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Inclination Angle ◽  
Equilibrium Temperature ◽  
Brownian Diffusion ◽  
Governing Equations ◽  
Nanofluid Flow ◽  
Porous Cavity ◽  
Flow And Heat Transfer ◽  
The Finite Difference Method ◽  
Porous Enclosure

The combined effect of Brownian diffusion, thermophoresis and cavity inclination angle on natural convective heat transfer in an inclined porous enclosure has been studied numerically. Fluid containing nanoparticles of low concentration circulates inside the cavity under the effect of the buoyancy force. Governing equations with corresponding boundary conditions formulated using the non-dimensional stream function and vorticity variables have been solved by the finite difference method. An influence of the cavity inclination angle, Darcy and Nield numbers on nanofluid flow and heat transfer has been investigated. It has been found that high Nield numbers illustrate more equilibrium temperature distribution inside the porous cavity.

scholarly journals Convection Heat Transfer of MgO-Ag /Water Magneto-Hybrid Nanoliquid Flow into a Special Porous Enclosure

2020 ◽  
Vol 2 (2) ◽  
pp. 84-95
Author(s):  
Fateh Mebarek Oudina ◽  
◽  
Fares Redouane ◽  
Choudhari Rajashekhar ◽  
◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Computational Study ◽  
Convection Heat Transfer ◽  
Darcy Number ◽  
Governing Equations ◽  
Galerkin Finite Element ◽  
Element Technique ◽  
The Magnetic Field ◽  
Porous Enclosure

This work explores numerically a computational study of free convection in a grooved porous enclosure filled with water-based hybrid-nanoliquid in the presence of an external magnetic field. To solve the governing equations of the problem, the Galerkin finite element technique is utilized. For a several governing parameters such as Rayleigh number (102≤Ra ≤106), magnetic field parameter (0≤Ha≤100), Darcy number (10-2≤ Da ≤10-4) the results are obtained and discussed via streamlines, isotherms and average Nusselt number. The magnetic field has a good regulating effect for the fluid flow and the heat transfer in porous media

Mixed Convective Heat Transfer Past a Heated Square Porous Cylinder in a Horizontal Channel With Varying Channel Height

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Horng-Wen Wu ◽  
Ren-Hung Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Darcy Number ◽  
Convection Flow ◽  
Channel Height ◽  
Porous Cylinder ◽  
Governing Equations ◽  
Height Ratio ◽  
Heated Cylinder ◽  
Laminar Mixed Convection

The laminar mixed convection flow across the porous square cylinder with the heated cylinder bottom at the axis in the channel has been carried out numerically in this paper using a semi-implicit projection finite element method. The governing equations with the Brinkman–Forcheimer-extended Darcy model for the region of square porous cylinder were solved. The parameter studies including Grashof number, Darcy number, and channel-to-cylinder height ratio on heat transfer performance have been explored in detail. The results indicate that the heat transfer is augmented as the Darcy number and channel-to-cylinder height ratio increase. The buoyancy effect on the local Nusselt number is clearer for B/H=0.1 than for B/H=0.3 and B/H=0.5.

scholarly journals Hydrothermal and Entropy Investigation of Ag/MgO/H2O Hybrid Nanofluid Natural Convection in a Novel Shape of Porous Cavity

2021 ◽  
Vol 11 (4) ◽  
pp. 1722
Author(s):  
Nidal Abu-Libdeh ◽  
Fares Redouane ◽  
Abderrahmane Aissa ◽  
Fateh Mebarek-Oudina ◽  
Ahmad Almuhtady ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Natural Convection ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Hybrid Nanofluid ◽  
The Finite Element Method ◽  
Governing Equations ◽  
Nanofluid Flow ◽  
The Magnetic Field

In this study, a new cavity form filled under a constant magnetic field by Ag/MgO/H2O nanofluids and porous media consistent with natural convection and total entropy is examined. The nanofluid flow is considered to be laminar and incompressible, while the advection inertia effect in the porous layer is taken into account by adopting the Darcy–Forchheimer model. The problem is explained in the dimensionless form of the governing equations and solved by the finite element method. The results of the values of Darcy (Da), Hartmann (Ha) and Rayleigh (Ra) numbers, porosity (εp), and the properties of solid volume fraction (ϕ) and flow fields were studied. The findings show that with each improvement in the Ha number, the heat transfer rate becomes more limited, and thus the magnetic field can be used as an outstanding heat transfer controller.

Natural Convection Around a Heated Cylinder in a Saturated Porous Medium

1988 ◽  
Vol 110 (3) ◽  
pp. 642-648 ◽  
Author(s):  
B. Farouk ◽  
H. Shayer
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Water Distribution ◽  
Numerical Solutions ◽  
Saturated Porous Medium ◽  
Convection Heat Transfer ◽  
Governing Equations ◽  
Heated Cylinder ◽  
Finite Difference Equations

Numerical solutions are presented for the natural convection heat transfer from a heated cylinder buried in a semi-infinite liquid-saturated porous medium. The governing equations are expressed in the stream function–temperature formulation and finite difference equations are obtained by integrating the governing equations over finite cells. The heat transfer characteristics of the heated cylinder are studied as functions of the Rayleigh number and the vertical depth of the cylinder center from a permeable surface. The numerical scheme involves the use of a cylindrical network of nodes in the vicinity of the cylinder with a Cartesian mesh covering the remainder of the flow domain. The results are of use in the design of underground electrical cables, power plant steam, and water distribution lines, among others.

scholarly journals Nanofluid convection taking into account the Soret effect and its impact on heat transfer and fluid flow

2020 ◽  
Vol 330 ◽  
pp. 01021
Author(s):  
Ibtissem Mhamdi ◽  
Fakhreddine S. Oueslati ◽  
Rachid Bennacer
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Fluid Flow ◽  
Soret Effect ◽  
Comsol Multiphysics ◽  
The Finite Element Method ◽  
Nanoparticle Concentration ◽  
Governing Equations ◽  
Square Cavity ◽  
Flow And Heat Transfer

The present study is a numerical simulation of natural convection in nanofluids, within in a square cavity differentially heated, to identify the fluid flow and heat transfer by considering the Soret effect during which a temperature gradient in a binary mixture gives rise to a concentration gradient. The governing equations solved numerically using the finite element method following the use of COMSOL Multiphysics. The effects of various parameters, the Rayleigh number, the nanoparticle concentration and the type of nanofluid are analyzed. Our simulations reveal that the heterogeneity of the nanofluid, which is generated by the Soret effect, increases the heat transfer.

Development of 200kV ultrahigh-resolution analytical electron microscope

1989 ◽  
Vol 47 ◽  
pp. 108-109
Author(s):  
T. Kaneyama ◽  
M. Naruse ◽  
Y. Ishida ◽  
M. Kersker
Keyword(s):  
Electron Microscope ◽  
Optical Constants ◽  
Materials Science ◽  
Objective Lens ◽  
The Finite Element Method ◽  
Ultrahigh Resolution ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Characteristic Features ◽  
Better Than

In the field of materials science, the importance of the ultrahigh resolution analytical electron microscope (UHRAEM) is increasing. A new UHRAEM which provides a resolution of better than 0.2 nm and allows analysis of a few nm areas has been developed. [Fig. 1 shows the external view] The followings are some characteristic features of the UHRAEM.Objective lens (OL)Two types of OL polepieces (URP for ±10' specimen tilt and ARP for ±30' tilt) have been developed. The optical constants shown in the table on the next page are figures calculated by the finite element method. However, Cs was experimentally confirmed by two methods (namely, Beam Tilt method and Krivanek method) as 0.45 ∼ 0.50 mm for URP and as 0.9 ∼ 1.0 mm for ARP, respectively. Fig. 2 shows an optical diffractogram obtained from a micrograph of amorphous carbon with URP under the Scherzer defocus condition. It demonstrates a resolution of 0.19 nm and a Cs smaller than 0.5 mm.

scholarly journals Latent Heat Phase Change Heat Transfer of a Nanoliquid with Nano–Encapsulated Phase Change Materials in a Wavy-Wall Enclosure with an Active Rotating Cylinder

2021 ◽  
Vol 13 (5) ◽  
pp. 2590
Author(s):  
S. A. M. Mehryan ◽  
Kaamran Raahemifar ◽  
Leila Sasani Gargari ◽  
Ahmad Hajjar ◽  
Mohamad El Kadri ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Wavy Wall ◽  
Governing Equations ◽  
Stefan Number ◽  
Change Material

A Nano-Encapsulated Phase-Change Material (NEPCM) suspension is made of nanoparticles containing a Phase Change Material in their core and dispersed in a fluid. These particles can contribute to thermal energy storage and heat transfer by their latent heat of phase change as moving with the host fluid. Thus, such novel nanoliquids are promising for applications in waste heat recovery and thermal energy storage systems. In the present research, the mixed convection of NEPCM suspensions was addressed in a wavy wall cavity containing a rotating solid cylinder. As the nanoparticles move with the liquid, they undergo a phase change and transfer the latent heat. The phase change of nanoparticles was considered as temperature-dependent heat capacity. The governing equations of mass, momentum, and energy conservation were presented as partial differential equations. Then, the governing equations were converted to a non-dimensional form to generalize the solution, and solved by the finite element method. The influence of control parameters such as volume concentration of nanoparticles, fusion temperature of nanoparticles, Stefan number, wall undulations number, and as well as the cylinder size, angular rotation, and thermal conductivities was addressed on the heat transfer in the enclosure. The wall undulation number induces a remarkable change in the Nusselt number. There are optimum fusion temperatures for nanoparticles, which could maximize the heat transfer rate. The increase of the latent heat of nanoparticles (a decline of Stefan number) boosts the heat transfer advantage of employing the phase change particles.

scholarly journals Free Convection Heat Transfer from Horizontal Cylinders

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 559
Author(s):  
Janusz T. Cieśliński ◽  
Slawomir Smolen ◽  
Dorota Sawicka
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Free Convection ◽  
Convection Heat Transfer ◽  
Horizontal Tube ◽  
Correlation Equations ◽  
Convection Heat ◽  
Number Range ◽  
Heated Cylinder ◽  
Free Convection Heat

The results of experimental investigation of free convection heat transfer in a rectangular container are presented. The ability of the commonly accepted correlation equations to reproduce present experimental data was tested as well. It was assumed that the examined geometry fulfils the requirement of no-interaction between heated cylinder and bounded surfaces. In order to check this assumption recently published correlation equations that jointly describe the dependence of the average Nusselt number on Rayleigh number and confinement ratios were examined. As a heat source served electrically heated horizontal tube immersed in an ambient fluid. Experiments were performed with pure ethylene glycol (EG), distilled water (W), and a mixture of EG and water at 50%/50% by volume. A set of empirical correlation equations for the prediction of Nu numbers for Rayleigh number range 3.6 × 104 < Ra < 9.2 × 105 or 3.6 × 105 < Raq < 14.8 × 106 and Pr number range 4.5 ≤ Pr ≤ 160 has been developed. The proposed correlation equations are based on two characteristic lengths, i.e., cylinder diameter and boundary layer length.

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