scholarly journals Effects of a Rotating Cone on the Mixed Convection in a Double Lid-Driven 3D Porous Trapezoidal Nanofluid Filled Cavity under the Impact of Magnetic Field

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 449 ◽  
Author(s):  
Ali J. Chamkha ◽  
Fatih Selimefendigil ◽  
Hakan F. Oztop
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Aspect Ratio ◽  
Mixed Convection ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Rotational Velocity ◽  
Rotating Cone ◽  
The Impact

Effects of a rotating cone in 3D mixed convection of CNT-water nanofluid in a double lid-driven porous trapezoidal cavity is numerically studied considering magnetic field effects. The numerical simulations are performed by using the finite element method. Impacts of Richardson number (between 0.05 and 50), angular rotational velocity of the cone (between −300 and 300), Hartmann number (between 0 and 50), Darcy number (between 10 − 4 and 5 × 10 − 2 ), aspect ratio of the cone (between 0.25 and 2.5), horizontal location of the cone (between 0.35 H and 0.65 H) and solid particle volume fraction (between 0 and 0.004) on the convective heat transfer performance was studied. It was observed that the average Nusselt number rises with higher Richardson numbers for stationary cone while the effect is reverse for when the cone is rotating in clockwise direction at the highest supped. Higher discrepancies between the average Nusselt number is obtained for 2D cylinder and 3D cylinder configuration which is 28.5% at the highest rotational speed. Even though there are very slight variations between the average Nu values for 3D cylinder and 3D cone case, there are significant variations in the local variation of the average Nusselt number. Higher enhancements in the average Nusselt number are achieved with CNT particles even though the magnetic field reduced the convection and the value is 84.3% at the highest strength of magnetic field. Increasing the permeability resulted in higher local and average heat transfer rates for the 3D porous cavity. In this study, the aspect ratio of the cone was found to be an excellent tool for heat transfer enhancement while 95% enhancements in the average Nusselt number were obtained. The horizontal location of the cone was found to have slight effects on the Nusselt number variations.

Effects of Variable Viscosity and Thermal Conductivity of CuO-Water Nanofluid on Heat Transfer Enhancement in Natural Convection: Mathematical Model and Simulation

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Eiyad Abu-Nada
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Nusselt Number ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Variable Viscosity ◽  
Cylinder Surface ◽  
Transfer Enhancement

Heat transfer enhancement in horizontal annuli using variable thermal conductivity and variable viscosity of CuO-water nanofluid is investigated numerically. The base case of simulation used thermal conductivity and viscosity data that consider temperature property dependence and nanoparticle size. It was observed that for Ra≥104, the average Nusselt number was deteriorated by increasing the volume fraction of nanoparticles. However, for Ra=103, the average Nusselt number enhancement depends on aspect ratio of the annulus as well as volume fraction of nanoparticles. Also, for Ra=103, the average Nusselt number was less sensitive to volume fraction of nanoparticles at high aspect ratio and the average Nusselt number increased by increasing the volume fraction of nanoaprticles for aspect ratios ≤0.4. For Ra≥104, the Nusselt number was deteriorated everywhere around the cylinder surface especially at high aspect ratio. However, this reduction is only restricted to certain regions around the cylinder surface for Ra=103. For Ra≥104, the Maxwell–Garnett and the Chon et al. conductivity models demonstrated similar results. But, there was a deviation in the prediction at Ra=103 and this deviation becomes more significant at high volume fraction of nanoparticles. The Nguyen et al. data and the Brinkman model give completely different predictions for Ra≥104, where the difference in prediction of the Nusselt number reached 50%. However, this difference was less than 10% at Ra=103.

scholarly journals Numerical study of heat transfer enhancement in the entrance region for low-pressure gaseous laminar pipe flows using Al2O3–air nanofluid

2018 ◽  
Vol 10 (7) ◽  
pp. 168781401878441 ◽  
Author(s):  
Wael Al-Kouz ◽  
Rafat Al-Waked ◽  
Ma’en Sari ◽  
Wahib Owhaib ◽  
Anas Atieh
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Aspect Ratio ◽  
Knudsen Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Low Pressure ◽  
Entrance Region ◽  
Physical Parameters ◽  
Nanoparticles Volume Fraction

The gaseous low-pressure nanofluid flow of a steady-state two-dimensional laminar forced convection heat transfer in the entrance region of pipes is numerically investigated. Such flows are of interest for many engineering applications like the nuclear reactor and electronic equipment cooling, heat exchangers, and many others. Physical parameters considered in this study are Reynolds number ( Re), Prandtl number ( Pr), nanosolid particles volume fraction [Formula: see text], Knudsen number ( Kn), and the aspect ratio ( AR). These parameters ranges are as follows: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]. The outcome of this study shows that by increasing Kn, velocity slip and temperature jump at the solid boundaries increase. In addition, heat transfer is enhanced by dispersing Al2O3 nanoparticles in the base low-pressure gaseous flow. Results show that there is no effect of the nanoparticles volume fraction with values below 0.03 on the average Nusselt number. The average Nusselt number increases [Formula: see text] as the value of the nanoparticles volume fraction exceeds 0.03. For instance, at Re = 1000, results show that when dispersing Al2O3 nanosolid particles with volume fractions of 0.3 and 0.5; there is an enhancement in the average Nusselt number of 30.35% and 136.74%, respectively, when compared to the case of dispersing Al2O3 nanosolid particles of 0.03 volume fraction.. Moreover, it is concluded that the average Nusselt number [Formula: see text] depends directly on Reynolds ( Re), Prandtl ( Pr) numbers, and the nanoparticles volume fraction [Formula: see text] and inversely on Knudsen number ( Kn) and the aspect ratio ( AR) for the investigated range of parameters considered in this study. Finally, a correlation of Nusselt number among all the investigated parameters in this study is proposed as [Formula: see text].

Laminar Mixed Convection of Non-Newtonian Nanofluids Flowing Vertically Upward Across a Confined Circular Cylinder

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Abhipsit Kumar Singh ◽  
Nanda Kishore
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Circular Cylinder ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Numerical Results ◽  
Total Drag ◽  
Drag Coefficients

Numerical results on laminar mixed convective heat transfer phenomenon between a confined circular cylinder and shear-thinning type nanofluids are presented. The cylinder is placed horizontally in a confined channel through which nanofluids flow vertically upward. The effect of buoyancy is same as the direction of the flow. Because of existence of mixed convection, governing continuity, momentum, and energy equations are simultaneously solved within the limitations of Boussinesq approximation. The ranges of parameters considered are: volume fraction of nanoparticles, ϕ = 0.005–0.045; Reynolds number, Re = 1–40; Richardson number, Ri = 0–40; and confinement ratio of circular cylinder, λ = 0.0625–0.5. Finally, the effects of these parameters on the streamlines, isotherm contours, individual and total drag coefficients, and local and average Nusselt numbers are thoroughly delineated. The individual and total drag coefficients decrease with the increasing both ϕ and Re; and/or with the decreasing both Ri and λ. The rate of heat transfer increases with the increasing Re, ϕ, Ri, and λ; however, at Re = 30–40, when ϕ > 0.005 and Ri < 2, the average Nusselt number decreases with the increasing Richardson number. Finally, correlations for the total drag coefficient and average Nusselt number are proposed as functions of pertinent dimensionless parameters on the basis of present numerical results.

scholarly journals Mixed convection inside nanofluid filled rectangular enclosures with moving bottom wall

2011 ◽  
Vol 15 (3) ◽  
pp. 889-903 ◽  
Author(s):  
Mostafa Mahmoodi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Flow And Heat Transfer ◽  
Simpler Algorithm ◽  
Horizontal Wall

The mixed convection fluid flow and heat transfer in lid-driven rectangular enclosures filled with the Al2O3-water nanofluid is investigated numerically. The left and the right vertical walls as well as the top horizontal wall of the enclosure are maintained at a constant cold temperature Tc. The bottom horizontal wall of the enclosure, which moves from left to right, is kept at a constant hot temperature Th, with Th>Tc. The governing equations written in terms of the primitive variables are solved using the finite volume method and the SIMPLER algorithm. Using the developed code, a parametric study is performed and the effects of the Richardson number, the aspect ratio of the enclosure and the volume fraction of the nanoparticles on the fluid flow and heat transfer inside the enclosure are investigated. The results show that at low Richardson numbers, a primary counterclockwise vortex is formed inside the enclosure. More over it is found that for the range of the Richardson number considered, 10-1-101, the average Nusselt number of the hot wall, increases with increasing the volume fraction of the nanoparticles. Also it is observed that the average Nusselt number of the hot wall of tall enclosures is more that to that of the shallow enclosures.

scholarly journals Pulsating Flow of CNT–Water Nanofluid Mixed Convection in a Vented Trapezoidal Cavity with an Inner Conductive T-Shaped Object and Magnetic Field Effects

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 848 ◽  
Author(s):  
Ali J. Chamkha ◽  
Fatih Selimefendigil ◽  
Hakan F. Oztop
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Steady Flow ◽  
Average Nusselt Number ◽  
Pulsating Flow ◽  
Cavity Wall ◽  
Magnetic Field Effects ◽  
Field Effects

Mixed convection of carbon-nanotube/water nanofluid in a vented cavity with an inner conductive T-shaped object was examined under pulsating flow conditions under magnetic field effects with finite element method. Effects of different parameters such as Richardson number (between 0.05 and 50), Hartmann number (between 0 and 30), cavity wall inclination (between 0 ∘ and 10 ∘ ), size (between 0.1 H and 0.4 H) and orientation (between −90 ∘ and 90 ∘ ) of the T-shaped object, and amplitude (between 0.5 and 0.9) and frequency (Strouhal number between 0.25 and 5) of pulsating flow on the convective flow features were studied. It was observed that the average Nusselt number enhanced with the rise of strength of magnetic field, solid nanoparticle volume fraction, and amplitude of the pulsation, while the effect was opposite for higher values of Ri number and cavity wall inclination angle. The presence of the T-shaped object and adjusting its size and orientation had significant impact on the main flow stream from inlet to outlet and recirculations around the T-shaped object and in the vicinity of hot wall of the cavity along with the magnetic field strength. Pulsating flow resulted in heat transfer enhancement as compared to steady flow case for all configurations. However, the amount of increment was different depending on the variation of the parameters of interest. Heat transfer enhancements were 41.85% and 20.81% when the size of the T-shaped object was increased from 0.1 H to 0.4 H. The T-shaped object can be utilized in the vented cavity as an excellent tool for convective heat transfer control. As highly conductive CNT particles were used in water, significant enhancements in the average Nusselt number between 97% and 108% were obtained both in steady flow and in pulsating flow cases when magnetic field was absent or present.

A Numerical Investigation of Laminar Mixed Convection Flow and Heat Transfer in a Lid Driven Cavity with Two Cylinders

2015 ◽  
Vol 789-790 ◽  
pp. 282-286 ◽  
Author(s):  
Khalil Khanafer ◽  
M. El Haj Assad
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Convection Flow ◽  
Mixed Convection Flow ◽  
Driven Cavity ◽  
Flow And Heat Transfer ◽  
The Impact

Mixed convection flow and heat transfer characteristics in a lid-driven cavity with two isothermally heated circular cylinders inside are studied numerically using a finite element formulation based on the Galerkin method of weighted residuals. The top lid of the cavity is moving rightwards with a constant speed. The two cylinders are maintained at an isothermal hot temperature, while the walls of the cavity are maintained at a cold temperature. Comparisons of streamlines, isotherms and average Nusselt number are presented to show the impact of the Richardson number, non-dimensional radius of the cylinder, and the location of the cylinders on the transport phenomena within the cavity. The results of this investigation show that the presence of the cylinders results in an increase in the average Nusselt number compared with a case with no cylinder. The average Nusselt number increases with an increase in the Richardson number for all non-dimensional radius of the cylinder studied in this work. It is seen that changing the boundary condition on one of the cylinders from isothermal to adiabatic has minimal effect on the average Nusselt number around the walls of the cavity.

MHD mixed convection of nanofluid in a cubic cavity with a conductive partition for various nanoparticle shapes

2019 ◽  
Vol 29 (10) ◽  
pp. 3584-3610 ◽  
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Öztop ◽  
Ali J. Chamkha
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Nanoparticle Volume Fraction ◽  
Content Type ◽  
Particle Shapes

Purpose This paper aims to numerically examine the mixed convection of SiO2-water nanofluid flow in a three-dimensional (3D) cubic cavity with a conductive partition considering various shapes of the particles (spherical, cylindrical, blade, brick). The purpose is to analyze the effects of various pertinent parameters such as Richardson number (between 0.1 and 10), Hartmann number (between 0 and 10), solid nanoparticle volume fraction (between 0 and 0.04), particle shape (spherical, cylindrical, blade, brick) and different heights and lengths of the conductive partition on the fluid flow and heat transfer characteristics. Design/methodology/approach The numerical simulation was performed by using Galerkin-weighted residual finite element method for various values of Richardson number, Hartmann number, solid nanoparticle volume fraction, particle shape (spherical, cylindrical, blade, brick) and different heights and lengths of the conductive partition. Two models for the average Nusselt number were proposed for nanofluids with spherical and cylindrical particle by using multi-layer feed-forward neural networks. Findings It was observed that the average Nusselt number reduces for higher values of Richardson number and Hartmann number, while enhances for higher values of nanoparticle volume fraction. Among various types of particle shapes, blade ones perform the worst and cylindrical ones perform the best in terms of heat transfer enhancement, but this is not significant which is less than 3 per cent. The average Nusselt number deteriorates by about 6.53per cent for nanofluid at the highest volume fraction of spherical particle shapes, but it is 11.75per cent for the base fluid when Hartmann number is increased from 0 to 10. Conductive partition geometrical parameters (length and height) do not contribute to much to heat transfer process for the 3D cavity, except for the case when height of the partition reaches 0.8 times the height of the cubic cavity, the average Nusselt number value reduces by about 25per cent both for base fluid and for nanofluid when compared to case with cavity height which is 0.2 times the height of the cubic cavity. Originality/value Based on the literature survey, a 3D configuration for MHD mixed convection of nanofluid flow in a cavity with a conductive partition considering the effects of various particle shapes has never been studied in the literature. This study is a first attempt to use a conductive partition with nanofluid of various particle shapes to affect the fluid flow and heat transfer characteristics in a 3D cubic cavity under the influence of magnetic field. Partial or all findings of this study could be used for the design and optimization of realistic 3D thermal configurations that are encountered in practice and some of the applications were already mentioned above. In this study, thermal performance of the system was obtained in terms of average heat transfer coefficient along the hot surface, and it is modeled with multi-layer feed-forward neural networks.

scholarly journals Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

2021 ◽  
Vol 13 (9) ◽  
pp. 5086
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Ali J. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Particle Size ◽  
Aspect Ratio ◽  
Power Law ◽  
Volume Fraction ◽  
Inclined Magnetic Field ◽  
Magnetic Field Effects ◽  
Power Law Nanofluid ◽  
Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

Effect of Nanofluid on Heat Transfer Enhancement for Mixed Convection Flow Over a Corrugated Surface

2020 ◽  
Vol 45 (4) ◽  
pp. 373-383
Author(s):  
Nepal Chandra Roy ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Local Nusselt Number ◽  
Richardson Number ◽  
Thermal Boundary Layer ◽  
Volume Fraction ◽  
Convection Flow ◽  
Mixed Convection Flow

AbstractA mathematical model for mixed convection flow of a nanofluid along a vertical wavy surface has been studied. Numerical results reveal the effects of the volume fraction of nanoparticles, the axial distribution, the Richardson number, and the amplitude/wavelength ratio on the heat transfer of Al2O3-water nanofluid. By increasing the volume fraction of nanoparticles, the local Nusselt number and the thermal boundary layer increases significantly. In case of \mathrm{Ri}=1.0, the inclusion of 2 % and 5 % nanoparticles in the pure fluid augments the local Nusselt number, measured at the axial position 6.0, by 6.6 % and 16.3 % for a flat plate and by 5.9 % and 14.5 %, and 5.4 % and 13.3 % for the wavy surfaces with an amplitude/wavelength ratio of 0.1 and 0.2, respectively. However, when the Richardson number is increased, the local Nusselt number is found to increase but the thermal boundary layer decreases. For small values of the amplitude/wavelength ratio, the two harmonics pattern of the energy field cannot be detected by the local Nusselt number curve, however the isotherms clearly demonstrate this characteristic. The pressure leads to the first harmonic, and the buoyancy, diffusion, and inertia forces produce the second harmonic.

Heat transfer characteristics of nanofluids from a sinusoidal corrugated cylinder placed in a square cavity

2021 ◽  
pp. 095440622110272
Author(s):  
Salaika Parvin ◽  
Nepal Chandra Roy ◽  
Litan Kumar Saha ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Transfer Characteristics ◽  
Wide Range

A numerical study is performed to investigate nanofluids' flow field and heat transfer characteristics between the domain bounded by a square and a wavy cylinder. The left and right walls of the cavity are at constant low temperature while its other adjacent walls are insulated. The convective phenomena take place due to the higher temperature of the inner corrugated surface. Super elliptic functions are used to transform the governing equations of the classical rectangular enclosure into a system of equations valid for concentric cylinders. The resulting equations are solved iteratively with the implicit finite difference method. Parametric results are presented in terms of streamlines, isotherms, local and average Nusselt numbers for a wide range of scaled parameters such as nanoparticles concentration, Rayleigh number, and aspect ratio. Several correlations have been deduced at the inner and outer surface of the cylinders for the average Nusselt number, which gives a good agreement when compared against the numerical results. The strength of the streamlines increases significantly due to an increase in the aspect ratio of the inner cylinder and the Rayleigh number. As the concentration of nanoparticles increases, the average Nusselt number at the internal and external cylinders becomes stronger. In addition, the average Nusselt number for the entire Rayleigh number range gets enhanced when plotted against the volume fraction of the nanofluid.

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