scholarly journals Numerical Study of Mixed Convection of the Nanofluids in Two-Sided Lid-Driven Square Cavity with a Pair of Triangular Heating Cylinders

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Zoubair Boulahia ◽  
Abderrahim Wakif ◽  
Rachid Sehaqui
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Numerical Study ◽  
Simple Algorithm ◽  
Design Parameters ◽  
Rate Variation ◽  
Square Cavity

A numerical study is carried out concerning mixed convection of the nanofluid in two-sided lid-driven square cavity with a pair of triangular heat sources. The upper and bottom moving walls are thermally insulated while the left and right walls are cooled at constant temperature. Two-dimensional Navier-Stokes and energy equations are solved using the finite volume discretization method with SIMPLE algorithm. The method used is validated against previous works. Two cases were considered depending on the direction of moving walls. Effects of various design parameters such as Richardson number(0.1≤Ri≤100), nanoparticle volume fraction(0≤φ≤0.05), and size(25 nm≤dp≤145 nm)and type(Cu,Al2O3,TiO2)of nanoparticles on the heat transfer rate are investigated. The results of this investigation illustrate that, by reducing the diameter of the nanoparticles andRi, the heat transfer rate increases. Moreover, it is found that by changing horizontal direction of the moving walls the heat transfer rate variation is negligible.

Numerical analysis of mixed convection of different nanofluids in concentric annulus

2019 ◽  
Vol 29 (4) ◽  
pp. 1506-1525 ◽  
Author(s):  
Ahad Abedini ◽  
Saeed Emadoddin ◽  
Taher Armaghani
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Flow Pattern ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Simple Algorithm ◽  
Content Type ◽  
Volume Method

Purpose This study aims to investigate the numerical analysis of mixed convection within the horizontal annulus in the presence of water-based fluid with nanoparticles of aluminum oxide, copper, silver and titanium oxide. Numerical solution is performed using a finite-volume method based on the SIMPLE algorithm, and the discretization of the equations is generally of the second order. Inner and outer cylinders have a constant temperature, and the inner cylinder temperature is higher than the outer one. The two cylinders can be rotated in both directions at a constant angular velocity. The effect of parameters such as Rayleigh, Richardson, Reynolds and the volume fraction of nanoparticles on heat transfer and flow pattern are investigated. The results show that the heat transfer rate increases with the increase of the Rayleigh number, as well as by increasing the volume fraction of the nanoparticles, the heat transfer rate increases, and this increase is about 8.25 per cent for 5 per cent volumetric fraction. Rotation of the cylinders reduces the overall heat transfer. Different directions of rotation have a great influence on the flow pattern and isotherms, and ultimately on heat transfer. The addition of nanoparticles does not have much effect on the flow pattern and isotherms, but it is quantitatively effective. The extracted results are in good agreement with previous works. Design/methodology/approach Studying mixed convection heat transfer in the horizontal annulus in the presence of a water-based fluid with aluminum oxide, copper, silver and titanium oxide nanoparticles is carried out quantitatively using a finite-volume method based on the SIMPLE algorithm. Findings Increasing the Rayleigh number increases the Nusselt number. Increasing the Richardson number increases heat transfer. Adding nanoparticles does not have much effect on the flow pattern but is effective quantitatively on heat transfer parameters. The addition of nanoparticles sometimes increases the heat transfer rate by about 8.25 per cent. In constant Rayleigh numbers, increasing the Reynolds number reduces heat transfer. The Rayleigh and Reynolds numbers greatly affect the isotherms and streamlines. In addition to the thermal conductivity of nanoparticles, the thermo-physical properties of nanoparticles has great effect in the formation of isotherms and streamlines and ultimately heat transfer. Originality/value Studying the effect of different direction of rotation on the isotherms and streamlines, as well as the comparison of different nanoparticles on mixed convection heat transfer in annulus.

scholarly journals Improved Energy Efficiency of Mixed Convection Heating Process in Eccentric Annulus

2021 ◽  
Vol 13 (8) ◽  
pp. 168781402110391
Author(s):  
Ben Abdelmlek Khaoula ◽  
Ben Nejma Fayçal
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Rayleigh Number ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Rotation Speed ◽  
Numerical Study ◽  
Heating Process ◽  
Eccentric Annulus

This paper deals with a numerical study of mixed convection heat transfer in horizontal eccentric annulus. The inner cylinder is supposed hot and rotating, however the outer one is kept cold and motionless. The numerical problem was solved using COMSOL Multiphysics® which is based on finite element method. The resolution of the partial differential equations was conducted through an implicit scheme with the use of the damped Newton’s method. The present numerical analysis concerns the effect of eccentricity, rotation speed and Rayleigh number on the flow patterns, heat transfer rate, and energy efficiency of the process. It was found that the heat transfer rate increases with the increase of Rayleigh number. In addition, the heat transfer rate drops with the increase of rotation speed. Finally, we have demonstrated that maximum energy efficiency is achieved not only with higher Rayleigh number but also it is maximum with small eccentricity.

scholarly journals 3D Magneto-Buoyancy-Thermocapillary Convection of CNT-Water Nanofluid in the Presence of a Magnetic Field

Processes ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 258 ◽  
Author(s):  
Lioua Kolsi ◽  
Salem Algarni ◽  
Hussein A. Mohammed ◽  
Walid Hassen ◽  
Emtinene Lajnef ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Flow Structure ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Numerical Study ◽  
Flow Stabilization ◽  
Magnetic Field Magnitude ◽  
The Magnetic Field

A numerical study is performed to investigate the effects of adding Carbon Nano Tube (CNT) and applying a magnetic field in two directions (vertical and horizontal) on the 3D-thermo-capillary natural convection. The cavity is differentially heated with a free upper surface. Governing equations are solved using the finite volume method. Results are presented in term of flow structure, temperature field and rate of heat transfer. In fact, results revealed that the flow structure and heat transfer rate are considerably affected by the magnitude and the direction of the magnetic field, the presence of thermocapillary forces and by increasing nanoparticles volume fraction. In opposition, the increase of the magnetic field magnitude leads to the control the flow causing flow stabilization by merging vortexes and reducing heat transfer rate.

scholarly journals Role of Rotating Cylinder toward Mixed Convection inside a Wavy Heated Cavity via Two-Phase Nanofluid Concept

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1138 ◽  
Author(s):  
Ammar I. Alsabery ◽  
Mohammad Ghalambaz ◽  
Taher Armaghani ◽  
Ali Chamkha ◽  
Ishak Hashim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Rotating Cylinder ◽  
Alumina Nanoparticles ◽  
Optimum Number ◽  
Two Phase ◽  
Rotation Direction

The mixed convection two-phase flow and heat transfer of nanofluids were addressed within a wavy wall enclosure containing a solid rotating cylinder. The annulus area between the cylinder and the enclosure was filled with water-alumina nanofluid. Buongiorno’s model was applied to assess the local distribution of nanoparticles in the host fluid. The governing equations for the mass conservation of nanofluid, nanoparticles, and energy conservation in the nanofluid and the rotating cylinder were carried out and converted to a non-dimensional pattern. The finite element technique was utilized for solving the equations numerically. The influence of the undulations, Richardson number, the volume fraction of nanoparticles, rotation direction, and the size of the rotating cylinder were examined on the streamlines, heat transfer rate, and the distribution of nanoparticles. The Brownian motion and thermophoresis forces induced a notable distribution of nanoparticles in the enclosure. The best heat transfer rate was observed for 3% volume fraction of alumina nanoparticles. The optimum number of undulations for the best heat transfer rate depends on the rotation direction of the cylinder. In the case of counterclockwise rotation of the cylinder, a single undulation leads to the best heat transfer rate for nanoparticles volume fraction about 3%. The increase of undulations number traps more nanoparticles near the wavy surface.

scholarly journals Premium jet cooling with two ribs over flat plate utilizing nanofluid mixed convection

2017 ◽  
Vol 21 (2) ◽  
pp. 963-976 ◽  
Author(s):  
Wael El-Maghlany ◽  
Mohamed Teamah ◽  
A.E. Kabeel ◽  
Ahmed Hanafy
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Mixed Convection ◽  
Flat Plate ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Richardson Number ◽  
Volume Fraction ◽  
Solid Volume Fraction

In this study, a numerical simulation of the thermal performance of two ribs mounted over a horizontal flat plate and cooled by Cu-water nanofluid is performed. The plate is heated and maintained at a constant temperature and cooled by mixed convection of laminar flow at a relatively low temperature. The top wall is considered as an adiabatic condition. The effects of related parameters such as Richardson number (0.01 ? Ri ? 10), the solid volume fraction (0.01 ? ? ? 0.06), the distance ratio between the two ribs (d/W = 5, 10, and 15), and the rib height ratio (b/W = 1, 2, and 3) on the ribs thermal performance are studied. The numerical simulation results indicate that the heat transfer rate is significantly affected by the distance and the rib height. The heat transfer rate is improved by increasing the nanoparticles volume fraction. The influence of the solid volume fraction with the increase of heat transfer is more noticeable for lower values of the Richardson number. The numerical results are summarized in the effect of pertinent parameters on the average Nusselt number with the assistance of both streamlines and isothermal ones. Throughout the study, the Grashof and Prandtl numbers, for pure water are kept constant at 103 and 6.2, respectively. The numerical work was displayed out using, an in-house computational fluid dynamic code written in FORTRAN, which discretizes non-dimensional forms of the governing equations using the finite volume method and solves the resulting system of equations using Gauss-Seidal method utilizing a tri diagonal matrix algorithm.

scholarly journals Numerical Study of Entropy Generation due to Coupled Laminar and Turbulent Mixed Convection and Thermal Radiation in an Enclosure Filled with a Semitransparent Medium

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
M. Goodarzi ◽  
M. R. Safaei ◽  
Hakan F. Oztop ◽  
A. Karimipour ◽  
E. Sadeghinezhad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Turbulent Flow ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Numerical Study ◽  
Radiation Heat Transfer ◽  
Radiation Heat ◽  
Semitransparent Medium

The effect of radiation on laminar and turbulent mixed convection heat transfer of a semitransparent medium in a square enclosure was studied numerically using the Finite Volume Method. A structured mesh and the SIMPLE algorithm were utilized to model the governing equations. Turbulence and radiation were modeled with the RNGk-εmodel and Discrete Ordinates (DO) model, respectively. For Richardson numbers ranging from 0.1 to 10, simulations were performed for Rayleigh numbers in laminar flow (104) and turbulent flow (108). The model predictions were validated against previous numerical studies and good agreement was observed. The simulated results indicate that for laminar and turbulent motion states, computing the radiation heat transfer significantly enhanced the Nusselt number (Nu) as well as the heat transfer coefficient. Higher Richardson numbers did not noticeably affect the average Nusselt number and corresponding heat transfer rate. Besides, as expected, the heat transfer rate for the turbulent flow regime surpassed that in the laminar regime. The simulations additionally demonstrated that for a constant Richardson number, computing the radiation heat transfer majorly affected the heat transfer structure in the enclosure; however, its impact on the fluid flow structure was negligible.

scholarly journals Numerical Simulation of the Cooling of Heated Electronic Blocks in Horizontal Channel by Mixed Convection of Nanofluids

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Mustapha Ait Hssain ◽  
Rachid Mir ◽  
Youness El Hammami
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Numerical Study ◽  
Solid Volume Fraction ◽  
Simple Algorithm ◽  
Separation Distance ◽  
Horizontal Channel ◽  
Laminar Mixed Convection ◽  
Finite Volume Approach

The present work is devoted to the numerical study of steady and laminar mixed convection of nanofluid (water nanoparticles) in a horizontal channel provided with sources of heat at constant temperature, which simulate hot electronic components. The transport equations for continuity, momentum, and energy are solved with finite volume approach using the SIMPLE algorithm. The effective thermal conductivity and the dynamic viscosity of the nanofluid are calculated using, respectively, the Maxwell-Garnett and Brinkman model. The influence of the volume fraction of the nanoparticles 0%≤φ≤10%, Reynolds numbers 5≤Re≤75, the distance between the blocks 0≤d/H≤3, and the types of nanoparticles added (TiO2, Al2O3, CuO, Ag, Cu, and MgO) were investigated and discussed. It emerges from this simulation that the heat transfer increases with the increase in the volume fraction of the nanoparticles and the Reynolds number and decreases with the augmentation of separation distance between heated sources. Moreover, the study shows that the heat transfer is improved by 20% at a solid volume fraction of 10% of Cu nanoparticles.

scholarly journals Effect of Straight, Inclined and Curved Fins on Natural Convection and Entropy Generation of a Nanofluid in a Square Cavity Influenced by a Magnetic Field

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1339
Author(s):  
Yacine Khetib ◽  
Ahmad Aziz Alahmadi ◽  
Ali Alzaed ◽  
Hamidreza Azimy ◽  
Mohsen Sharifpur ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Entropy Generation ◽  
Transfer Rate ◽  
Simple Algorithm ◽  
Square Cavity ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Volume Method

In this paper, the free convective heat transfer of nanofluids in a square cavity is simulated using a numerical method. The angle of the cavity could be changed in the horizontal axis from 0 to 90 degrees. The cavity is exposed under a constant magnetic field. Two opposite walls of the cavity are cold and warm, and the rest of the walls are insulated. On the hot wall, there are two fins with the same wall temperature. The equations were discretized by the finite volume method (FVM) and then solved using the SIMPLE algorithm. Three different fin configurations (straight, inclined and curved) were studied in terms of heat transfer rate and generation of entropy. According to the simulation results, the heat transfer rate was improved by tilting the fins toward the top or bottom of the cavity. At Ra = 105 and Ha = 20, the maximum heat transfer rate was achieved at a cavity inclination of 90° and 45°, respectively, for straight and curved fins. In the horizontal cavity, heat transfer rate could be improved up to 6.4% by tilting the fins and up to 4.9% by warping them. Increasing the Hartmann number from 0 to 40 reduced the Nusselt number and entropy generation by 37.9% and 33.8%, respectively.

scholarly journals Free Convection of Ag/H2O Nanofluid in Square Cavity with Different Position and Orientation of Egg Shaped Cylinder

2021 ◽  
Vol 53 (4) ◽  
pp. 210409
Author(s):  
Atheer Saad Hashim
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Orientation Angle ◽  
Numerical Results ◽  
Vertical Position ◽  
Square Cavity

A numerical simulation was conducted to study the free convection of Ag/H2O nanofluid between a square cavity with cold walls and an egg shaped cylinder with a hot wall. Utilizing the egg equation, dimensionless governing equations were solved using the Galerkin Finite Element Method (GFEM). In this work, several parameters were studied, i.e. Rayleigh number (103 ≤ Ra ≤ 106), volume fraction (0 ≤ φ ≤ 0.05), position (-0.2 ≤ Y ≤ 0.2), and orientation angle (-90° ≤ γ ≤ 90°). The numerical results are presented as streamline contours, isotherm contours, and local and average Nusselt numbers. Moreover, the results were used to analyze the fluids’ structure, temperature distribution, and heat transfer rate. The numerical results confirmed that the stream intensity value increased with an increase of the Rayleigh number as well as the movement of the cylinder towards the bottom wall for all values of the orientation angle. Variation of the vertical position of the cylinder inside the cavity had a noticeable effect on , which increased by 50% at γ = -90°, and by 58% at γ = -45°. However, at Y = -0.2,  increased by 58% at γ = -45° and decreased by 7% at γ = -90°. The highest heat transfer rate was obtained at high Rayleigh number (Ra = 106), volume fraction (φ = 0.05), negative position (Y = -0.2), and the highest positive orientation angle (γ = 90°).

Magnetohydrodynamic Mixed Convection of a Cu-Water Nanofluid in a Vertical Channel

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
A. Raisi ◽  
S. M. Aminossadati ◽  
B. Ghasemi
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Heat Transfer ◽  
Vertical Channel ◽  
Mixed Convection Heat Transfer

This technical brief numerically examines the mixed convection heat transfer of a Cu-water nanofluid in a parallel-plate vertical channel that is influenced by a magnetic field. An upward flow of Cu-water nanofluid enters the channel at a relatively low temperature and a uniform velocity. It is found that the magnetic field has dissimilar effects on the heat transfer rate at different Richardson numbers. The increase of solid volume fraction results in an increase of the heat transfer rate especially at low Richardson numbers.

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