Brinkman-Forchheimer flow of SWCNT and MWCNT magneto-nanoliquids in a microchannel with multiple slips and Joule heating aspects

2018 ◽  
Vol 14 (4) ◽  
pp. 769-786 ◽  
Author(s):  
Shashikumar N.S. ◽  
Gireesha B.J. ◽  
B. Mahanthesh ◽  
Prasannakumara B.C.
Keyword(s):  
Carbon Nanotubes ◽  
Nusselt Number ◽  
Joule Heating ◽  
Microchannel Flow ◽  
Governing Equations ◽  
Content Type ◽  
Swcnts And Mwcnts ◽  
Walled Carbon Nanotubes ◽  
Multiple Slips ◽  
Forchheimer Flow

Purpose The microfluidics has a wide range of applications, such as micro heat exchanger, micropumps, micromixers, cooling systems for microelectronic devices, fuel cells and microturbines. However, the enhancement of thermal energy is one of the challenges in these applications. Therefore, the purpose of this paper is to enhance heat transfer in a microchannel flow by utilizing carbon nanotubes (CNTs). MHD Brinkman-Forchheimer flow in a planar microchannel with multiple slips is considered. Aspects of viscous and Joule heating are also deployed. The consequences are presented in two different carbon nanofluids. Design/methodology/approach The governing equations are modeled with the help of conservation equations of flow and energy under the steady-state situation. The governing equations are non-dimensionalized through dimensionless variables. The dimensionless expressions are treated via Runge-Kutta-Fehlberg-based shooting scheme. Pertinent results of velocity, skin friction coefficient, temperature and Nusselt number for assorted values of physical parameters are comprehensively discussed. Also, a closed-form solution is obtained for momentum equation for a particular case. Numerical results agree perfectly with the analytical results. Findings It is established that multiple slip effect is favorable for velocity and temperature fields. The velocity field of multi-walled carbon nanotubes (MWCNTs) nanofluid is lower than single-walled carbon nanotubes (SWCNTs)-nanofluid, while thermal field, Nusselt number and drag force are higher in the case of MWCNT-nanofluid than SWCNT-nanofluid. The impact of nanotubes (SWCNTs and MWCNTs) is constructive for thermal boundary layer growth. Practical implications This study may provide useful information to improve the thermal management of microelectromechanical systems. Originality/value The effects of CNTs in microchannel flow by utilizing viscous dissipation and Joule heating are first time investigated. The results for SWCNTs and MWCNTs have been compared.

A comparative study of wall jet flow containing carbon nanotubes with convective heat transfer and MHD

2017 ◽  
Vol 34 (3) ◽  
pp. 739-753 ◽  
Author(s):  
Syed Zulfiqar Ali Zaidi ◽  
Syed Tauseef Mohyud-din ◽  
Bandar Bin-Mohsen
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Nusselt Number ◽  
Biot Number ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Skin Friction Coefficient ◽  
Wall Jet ◽  
Content Type ◽  
Walled Carbon Nanotubes

Purpose The purpose of this study is to conduct a comparative investigation for incompressible electrically conducting nanofluid fluid through wall jet. Single-walled carbon nanotubes (SWCNTs) and multiple-walled carbon nanotubes (MWCNTs) are considered as the nanoparticles. To record the effect of Lorentz forces, a magnetic field is applied normally with the assumption that the induced magnetic field is negligible. Design/methodology/approach Boundary layer approximation is used to convert governing equations into ordinary differential equations along with appropriate boundary conditions. To obtain the results, used homotopy analysis method (HAM) has been used as an analytical technique and to validate the obtained results a famous numerical Runge–Kutta–Fehlberg method is also exploited. It has been observed that the results obtained through both of the methods are in excellent agreement with exact solution. Findings The Hartmann number is used as controlling parameter for velocity and temperature profile. That can be recorded as its extended values help to normalize the velocity, whereas it controls the rapid increase in temperature. The temperature profile is boosted by increasing the value of the Biot number, a physical parameter. Similarly, it also increases for an increased percentage of volume fraction of particles (SWCNTs/MWCNTs). The Hartmann number plays an important role in decreasing local skin friction coefficient. The influence of the Biot number and volume fraction of nanoparticles caused similar increasing effects on the local Nusselt number. Nanoparticles of the form SWCNT provide better heat transfer as compared to MWCNTs. Influence of the Biot number and volume fraction of nanoparticles caused similar increasing effects on the local Nusselt number. Nanoparticles of the form SWCNT provide better heat transfer as compared to MWCNTs. Originality/value To gain insight into the problem, the effects of various emerging parameters and physical quantities such as Biot number, Nusselt number and skin friction coefficient, have been explored.

Numerical simulation for Darcy-Forchheimer flow of carbon nanotubes due to convectively heated nonlinear curved stretching surface

2019 ◽  
Vol 29 (9) ◽  
pp. 3290-3304 ◽  
Author(s):  
Muhammad Ijaz Khan ◽  
Khursheed Muhammad ◽  
Tasawar Hayat ◽  
Shahid Farooq ◽  
Ahmed Alsaedi
Keyword(s):  
Carbon Nanotubes ◽  
Volume Fraction ◽  
Continuous Phase ◽  
Curved Surface ◽  
Content Type ◽  
Porosity Parameter ◽  
Forchheimer Number ◽  
Forchheimer Flow ◽  
Walled Cnts ◽  
Behavior Index

Purpose This paper aims to discuss the salient aspects of the Darcy–Forchheimer flow of viscous liquid in carbon nanotubes (CNTs). CNTs are considered as nanofluid, and water is taken as the continuous phase liquid. The flow features are discussed via curved surface. Water is taken as the base liquid. Flow is generated via nonlinear stretching. Energy expression is modeled subject to heat generation/absorption. Furthermore, convective conditions are considered at the boundary. The Xue model is used in the mathematical modeling which describes the features of nanomaterials. Both types of CNTs are considered, i.e. single-walled CNTs and multi-walled CNTs. Design/methodology/approach Appropriate transformations are used to convert the flow expressions into dimensionless differential equations. The bvp4c method is used for solution development. Findings Velocity enhances via higher estimations of nanoparticles volume fraction while decays for higher Forchheimer number, curvature parameter, behavior index and porosity parameter. Furthermore, thermal field is an increasing function of nanoparticle volume fraction, behavior index, Forchheimer number and porosity parameter. Originality/value Here, the authors have discussed two-dimensional CNTs-based nanomaterial Darcy–Forchheimer flow of viscous fluid over a curved surface. The authors believe that all the outcomes and numerical techniques are original and have not been published elsewhere.

Free convection in a square porous cavity filled with a nanofluid using thermal non equilibrium and Buongiorno models

2016 ◽  
Vol 26 (3/4) ◽  
pp. 671-693 ◽  
Author(s):  
Ioan Pop ◽  
Mohammad Ghalambaz ◽  
Mikhail Sheremet
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Brownian Motion ◽  
Base Fluid ◽  
Average Nusselt Number ◽  
Solid Phase ◽  
Porous Matrix ◽  
Governing Equations ◽  
Content Type ◽  
Brownian Motion And Thermophoresis

Purpose – The purpose of this paper is to theoretically analysis the steady-state natural convection flow and heat transfer of nanofluids in a square enclosure filled with a porous medium saturated with a nanofluid considering local thermal non-equilibrium (LTNE) effects. Different local temperatures for the solid phase of the nanoparticles, the solid phase of porous matrix and the liquid phase of the base fluid are taken into account. Design/methodology/approach – The Buongiorno’s model, incorporating the Brownian motion and thermophoresis effects, is utilized to take into account the migration of nanoparticles. Using appropriate non-dimensional variables, the governing equations are transformed into the non-dimensional form, and the finite element method is utilized to solve the governing equations. Findings – The results show that the increase of buoyancy ratio parameter (Nr) decreases the magnitude of average Nusselt number. The increase of the nanoparticles-fluid interface heat transfer parameter (Nhp) increases the average Nusselt number for nanoparticles and decreases the average Nusselt number for the base fluid. The nanofluid and porous matrix with large values of modified thermal capacity ratios (γ p and γ s ) are of interest for heat transfer applications. Originality/value – The three phases of nanoparticles, base fluid and the porous matrix are in the LTNE. The effect of mass transfer of nanoparticles due to the Brownian motion and thermophoresis effects are also taken into account.

scholarly journals Effects of Microwave Absorption on Long and Short Single-Walled Carbon Nanotubes at 10-6 Torr

2015 ◽  
Vol 14 (05n06) ◽  
pp. 1550025 ◽  
Author(s):  
S. Ferguson ◽  
P. Bhatnagar ◽  
I. Wright ◽  
G. Sestric ◽  
S. Williams
Keyword(s):  
Carbon Nanotubes ◽  
Microwave Absorption ◽  
Joule Heating ◽  
Infrared Radiation ◽  
Single Walled Carbon Nanotubes ◽  
Blackbody Radiation ◽  
Structural Modifications ◽  
Nanotube Defects ◽  
Double Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Carbon nanotubes have been observed to emit ultraviolet, visible and infrared radiation when exposed to microwaves. We have performed experiments in which both short (0.5 μm–2 μm) and long (5 μm–30 μm) single and double-walled carbon nanotubes were exposed to 2.46 GHz microwaves at a pressure of ~ 10-6 Torr. Structural modifications of the carbon nanotubes due to microwave absorption have been studied using the Raman spectroscopy G-band and D-band intensities, which suggest that microwave irradiation at relatively low pressure results in an increase in nanotube defects, especially in the case of the long nanotubes. Furthermore, a comparison of the spectra of the radiation emitted from the nanotubes suggests that the longer nanotubes emitted radiation of much greater intensity than the shorter nanotubes. Based on the results of the experiments and results described in previous reports, the ultraviolet, visible and infrared radiation emitted as the result of microwave absorption by carbon nanotubes seems to be primarily blackbody radiation emitted due to Joule heating. However, the presence of several broad photopeaks in the spectra of the emitted radiation (which do not seem to be related to gases absorbed by the nanotubes or the presence of catalyst particles) suggest that emissions are not the result of Joule heating alone.

scholarly journals Buckling analysis of a non-concentric double-walled carbon nanotube

2020 ◽  
Vol 231 (12) ◽  
pp. 5007-5020 ◽  
Author(s):  
Mohammad Malikan ◽  
Victor A. Eremeyev ◽  
Hamid M. Sedighi
Keyword(s):  
Carbon Nanotubes ◽  
Theoretical Study ◽  
Static Stability ◽  
Governing Equations ◽  
Stability Threshold ◽  
Lennard Jones ◽  
The Stability ◽  
Double Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
Nonlocal Approach

Abstract On the basis of a theoretical study, this research incorporates an eccentricity into a system of compressed double-walled carbon nanotubes (DWCNTs). In order to formulate the stability equations, a kinematic displacement with reference to the classical beam hypothesis is utilized. Furthermore, the influence of nanoscale size is taken into account with regard to the nonlocal approach of strain gradient, and the van der Waals interaction for both inner and outer tubes is also considered based on the Lennard–Jones model. Galerkin decomposition is employed to numerically deal with the governing equations. It is evidently demonstrated that the geometrical eccentricity remarkably affects the stability threshold and its impact is to increase the static stability of DWCNTs.

Numerical investigation of nonlinear vibration analysis for triple-walled carbon nanotubes conveying viscous fluid

2019 ◽  
Vol 30 (4) ◽  
pp. 1689-1723 ◽  
Author(s):  
Bijan Mohamadi ◽  
S. Ali Eftekhari ◽  
Davood Toghraie
Keyword(s):  
Carbon Nanotubes ◽  
Aspect Ratio ◽  
Viscous Fluid ◽  
Boundary Conditions ◽  
Nonlinear Vibration ◽  
Vibration Analysis ◽  
Couple Stress ◽  
Characteristic Length ◽  
Content Type ◽  
Walled Carbon Nanotubes

Purpose The purpose of this paper is to investigate nonlinear vibrations of triple-walled carbon nanotubes buried within Pasternak foundation carrying viscous fluids. Design/methodology/approach Considering the geometry of nanotubes, the governing equations were initially derived using Timoshenko and modified couple stress theories and by taking into account Von-Karman expressions. Then, by determining boundary conditions, type of fluid motion, Knudsen number and, ultimately, fluid viscosity, the principal equation was solved using differential quadrature method, and linear and nonlinear nanotube frequencies were calculated. Findings The results indicated that natural frequency is decreased as the fluid velocity and aspect ratio increase. Moreover, as the aspect ratio is increased, the results converge for simple and fixed support boundary conditions, and the ratio of nonlinear to linear frequencies approaches. Natural frequency of vibrations and critical velocity increase as Pasternak coefficient and characteristic length increase. As indicated by the results, by assuming a non-uniform velocity for the fluid and a slip boundary condition at Kn = 0.05, reductions of 10.714 and 28.714% were observed in the critical velocity, respectively. Moreover, the ratio of nonlinear to linear base frequencies decreases as the Winkler and Pasternak coefficients, maximum deflection of the first wall and characteristic length are increased in couple stress theory. Originality/value This paper is a numerical investigation of nonlinear vibration analysis for triple-walled carbon nanotubes conveying viscous fluid.

Comparative studies between the influence of single- and multi-walled carbon nanotubes addition on Gd-123 superconducting phase

2016 ◽  
Vol 30 (36) ◽  
pp. 1650418 ◽  
Author(s):  
A. I. Abou-Aly ◽  
M. Anas ◽  
Shaker Ebrahim ◽  
R. Awad ◽  
I. G. Eldeen
Keyword(s):  
Carbon Nanotubes ◽  
Electron Microscope ◽  
Phase Formation ◽  
Electrical Network ◽  
Sem And Tem ◽  
Transmission Electron ◽  
Composite Superconductor ◽  
Multi Walled Carbon Nanotubes ◽  
Swcnts And Mwcnts ◽  
Walled Carbon Nanotubes

The effect of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) addition on the phase formation and the superconducting properties of GdBa2Cu3O[Formula: see text] phase has been studied. Therefore, composite superconductor samples of type (CNTs)[Formula: see text] GdBa2Cu3O[Formula: see text], 0.0 [Formula: see text] 0.1 wt.% have been synthesized by a standard solid-state reaction technique. The samples have been characterized using X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results of XRD show an enhancement in the phase formation up to 0.06 wt.% and 0.08 wt.% for SWCNTs and MWCNTs, respectively. SEM and TEM reveal that CNTs form an electrical network resulting in well-connected superconducting grains. The electrical properties of the prepared samples have been examined by electric resistivity and I–V measurements, and their results reinforce the XRD, SEM and TEM. Consequently, both [Formula: see text] and [Formula: see text] improve as the addition percentage increases up to 0.06 wt.% and 0.08 wt.% for SWCNTs and MWCNTs, respectively.

Influence of multiple slips and chemical reaction on radiative MHD Williamson nanofluid flow in porous medium

2019 ◽  
Vol 15 (3) ◽  
pp. 630-658 ◽  
Author(s):  
Nilankush Acharya ◽  
Kalidas Das ◽  
Prabir Kumar Kundu
Keyword(s):  
Porous Medium ◽  
Nusselt Number ◽  
Chemical Reaction ◽  
Homotopy Perturbation Method ◽  
Velocity Slip ◽  
Nanofluid Flow ◽  
Content Type ◽  
Transfer Rates ◽  
Order Chemical Reaction ◽  
Multiple Slips

Purpose The purpose of this paper is to focus on the influence of multiple slips on MHD Williamson nanofluid flow embedded in porous medium towards a linearly stretching sheet that has been investigated numerically. The whole analysis has been carried out considering the presence of nth-order chemical reaction between base fluid and nanoparticles. Design/methodology/approach A similarity transformation technique has been adopted to convert non-linear governing partial differential equations into ordinary ones and then they are solved by using both the RK-4 method and Laplace transform homotopy perturbation method. The consequences of multiple slip parameters on dimensionless velocity, temperature and concentration and heat and mass transfer rates have been demonstrated using tabular and graphical outline. Findings The investigation explores that the Nusselt number reduces for escalating behaviour of velocity slip and thermal slip parameter. Fluid’s temperature rises in the presence of generative reaction parameter. Originality/value A fine conformity of the current results has been achieved after comparing with previous literature studies. Considering destructive chemical reaction, reduced Nusselt number is found to decrease, but reverse consequence has been noticed in the case of generative chemical reaction. Mass transport diminishes when the order of chemical reaction amplifies for both destructive and generative reactions.

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