Shape effect of nanoparticles on MHD nanofluid flow over a stretching sheet in the presence of heat source/sink with entropy generation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hamza Berrehal ◽  
G. Sowmya ◽  
Oluwole Daniel Makinde
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Heat Transfer Enhancement ◽  
Ag Nanoparticles ◽  
Stretching Sheet ◽  
Volume Fraction ◽  
Transfer Enhancement ◽  
Shooting Technique ◽  
Content Type ◽  
Source Sink

Purpose In heat transfer, fluids and nanoparticles can provide new innovative technologies with potential to adapt the heat transfer fluid’s thermal properties through control over particle size, shape and others. This paper aims to examine the effects of spherical and non-spherical (cylinder, disk, platelets, etc.) shapes of silver (Ag) nanoparticles on heat transfer enhancement and inherent irreversibility in hydromagnetic water base nanoliquid flow over a convectively heated stretching sheet with heat generation/absorption. Design/methodology/approach Applying suitable similarity constraints, the model partial differential equations are transformed into a set of nonlinear ordinary differential equations. Solutions are obtained analytically via optimal homotopy asymptotic method (OHAM) and numerically via shooting technique coupled with the Runge-Kutta-Fehlberg (RK-F) method. Findings The impact of Ag nanoparticle’s shape along with other germane factors, such as Biot number, magnetic field, solid volume fraction and heat source/sink on velocity and thermal profiles, Nusselt number, skin friction coefficient, heat transfer enhancement, rate of entropy generation and irreversibility ratio, are scrutinized via graphical simulations and discussed. This study revealed that cylindrical shape Ag nanoparticles generate high entropy and fluid friction irreversibility, whereas disk shape Ag nanoparticles exhibit high transfer enhancement rate. Moreover, a boost in magnetic field intensity, volume-fraction parameter and Biot number enhances the thermal boundary layer thickness. Originality/value The main objective of this work is to examine the different Ag nanoparticles shape effects on the heat transfer enhancement and inherent irreversibility owing to hydromagnetic nanoliquid flow past a convectively heated stretching sheet with heat source/sink, which has not been yet studied. It is hope that this study will bridge the gap in the present literature and serve as impetus to scholars, engineers and industries for more exploration in this direction. The intrinsic nonlinearity of the model equations precludes its exact solution; hence, OHAM and shooting technique coupled with the RK-F method have been used to numerically tackle the problem. Pertinent results are discussed quantitatively and displayed graphically and in tabular form.

Study of the boundary layer heat transfer of nanofluids over a stretching sheet: Passive control of nanoparticles at the surface

2015 ◽  
Vol 93 (7) ◽  
pp. 725-733 ◽  
Author(s):  
M. Ghalambaz ◽  
E. Izadpanahi ◽  
A. Noghrehabadi ◽  
A. Chamkha
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Heat Transfer Enhancement ◽  
Base Fluid ◽  
Stretching Sheet ◽  
Volume Fraction ◽  
Enhancement Ratio ◽  
Transfer Enhancement

The boundary layer heat and mass transfer of nanofluids over an isothermal stretching sheet is analyzed using a drift-flux model. The relative slip velocity between the nanoparticles and the base fluid is taken into account. The nanoparticles’ volume fractions at the surface of the sheet are considered to be adjusted passively. The thermal conductivity and the dynamic viscosity of the nanofluid are considered as functions of the local volume fraction of the nanoparticles. A non-dimensional parameter, heat transfer enhancement ratio, is introduced, which shows the alteration of the thermal convective coefficient of the nanofluid compared to the base fluid. The governing partial differential equations are reduced into a set of nonlinear ordinary differential equations using appropriate similarity transformations and then solved numerically using the fourth-order Runge–Kutta and Newton–Raphson methods along with the shooting technique. The effects of six non-dimensional parameters, namely, the Prandtl number of the base fluid Prbf, Lewis number Le, Brownian motion parameter Nb, thermophoresis parameter Nt, variable thermal conductivity parameter Nc and the variable viscosity parameter Nv, on the velocity, temperature, and concentration profiles as well as the reduced Nusselt number and the enhancement ratio are investigated. Finally, case studies for Al2O3 and Cu nanoparticles dispersed in water are performed. It is found that increases in the ambient values of the nanoparticles volume fraction cause decreases in both the dimensionless shear stress f″(0) and the reduced Nusselt number Nur. Furthermore, an augmentation of the ambient value of the volume fraction of nanoparticles results in an increase the heat transfer enhancement ratio hnf/hbf. Therefore, using nanoparticles produces heat transfer enhancement from the sheet.

Unsteady heat and mass transfer magnetohydrodynamic (MHD) nanofluid flow over a stretching sheet with heat source–sink using quasi-linearization technique

2015 ◽  
Vol 93 (12) ◽  
pp. 1477-1485 ◽  
Author(s):  
R. Ahmad ◽  
Waqar A. Khan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Differential Equations ◽  
Heat Source ◽  
Stretching Sheet ◽  
Volume Fraction ◽  
Numerical Technique ◽  
Stretching Surface ◽  
Nanofluid Flow ◽  
Source Sink

The current study deals with two-dimensional unsteady incompressible MHD water-based nanofluid flow over a convectively heated stretching sheet by considering Buongiorno’s model. A uniform magnetic field is applied in the direction normal to the stretching sheet. It is assumed that the lower surface of the sheet is heated by convection by a nanofluid at temperature Tf, which generates the heat transfer coefficient, hf. Uniform temperature and nanofluid volume fraction are assumed at the sheet’s surface and the flux of the nanoparticle is taken to be zero. The assumption of zero nanoparticle flux at the sheet’s surface makes the model physically more realistic. The effects of the uniform heat source–sink are included in the energy equation. With the help of similarity transformations, the partial differential equations of momentum, energy, and nanoparticle concentration are reduced to a system of nonlinear ordinary differential equations along with the transformed boundary conditions. The derived equations are solved with the help of the quasi-qinearization technique. The model is solved by considering the realistic values for the Lewis number, thermophoresis, and Brownian motion parameters. The objective of the current study is (i) to provide an efficient numerical technique for solving the boundary layer flow model and (ii) introduction of zero nanoparticle flux on the convectively heated stretching surface. The current study also focuses on the physical relevance and accurate trends of the boundary layer profiles, which are adequate in the laminar boundary layer theory. The dependence of the nanoparticle volume fraction and other pertinent parameters on the dimensionless velocity, temperature, shear stress, and heat transfer rates over the stretching surface are presented in the form of profiles.

Effect of adding nanoparticle on squeezing flow and heat transfer improvement using KKL model

2017 ◽  
Vol 27 (7) ◽  
pp. 1535-1553 ◽  
Author(s):  
M. Sheikholeslami ◽  
D.D. Ganji
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Nusselt Number ◽  
Heat Transfer Enhancement ◽  
Volume Fraction ◽  
Nanoparticle Volume Fraction ◽  
Transfer Enhancement ◽  
Content Type ◽  
Flow And Heat Transfer ◽  
Squeeze Number

Purpose Nanofluid flow which is squeezed between parallel plates is studied using differential transformation method (DTM). The fluid in the enclosure is water containing different types of nanoparticles: Al2O3 and CuO. The effective thermal conductivity and viscosity of nanofluid are calculated by Koo–Kleinstreuer–Li (KKL) correlation. The comparison between the results from DTM and numerical method are in well agreement which proofs the capability of this method for solving such problems. Effects of the squeeze number and nanofluid volume fraction on flow and heat transfer are examined. Results indicate that Nusselt number augment with increase of the nanoparticle volume fraction. Also, it can be found that heat transfer enhancement of CuO is higher than Al2O3. Design/methodology/approach The problem of nanofluid flow which is squeezed between parallel plates is investigated analytically using DTM. The fluid in the enclosure is water containing different types of nanoparticles: Al2O3 and CuO. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL correlation. In this model, effect of Brownian motion on the effective thermal conductivity is considered. The comparison between the results from DTM and numerical method are in well agreement which proves the capability of this method for solving such problems. The effect of the squeeze number and the nanofluid volume fraction on flow and heat transfer is investigated. The results show that Nusselt number increase with increase of the nanoparticle volume fraction. Also, it can be found that heat transfer enhancement of CuO is higher than Al2O3. Findings The effect of the squeeze number and the nanofluid volume fraction on flow and heat transfer is investigated. The results show that Nusselt number increase with increase of the nanoparticle volume fraction. Also, it can be found that heat transfer enhancement of CuO is higher than Al2O3. Originality/value This paper is original.

Thermophoresis and Brownian effects on natural convection of nanofluids in a square enclosure with two pairs of heat source/sink

2015 ◽  
Vol 25 (5) ◽  
pp. 1030-1046 ◽  
Author(s):  
Aminreza Noghrehabadi ◽  
Amin Samimi Behbahan ◽  
I. Pop
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Heat Source ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Numerical Results ◽  
Content Type ◽  
Source Sink

Purpose – The purpose of this paper is to study natural convection heat transfer and fluid flow in a square cavity filled with CuO-water nanofluid. Design/methodology/approach – The entire length of the bottom wall of the cavity is covered by two pairs of heat source-sink, whereas the other walls are insulated. The governing equations of fluid flow are discretized using a finite volume method with a collocated grid arrangement. The coupling between velocity and pressure is solved using the SIMPLEC and the Rhie and Chow interpolation is used to avoid the checker-board solutions for the pressure. Findings – The numerical results are reported for the effect of Rayleigh number, solid volume fraction and both presence and absence of thermophoresis and Brownian motion effects. The numerical results show an improvement in heat transfer rate for the whole range of Rayleigh numbers when Brownian and thermophoresis effects are considered. Furthermore, an increase in the Rayleigh number and nanoparticle volume fraction in both cases – when Brownian and thermophoresis effects are neglected or considered – has an excellent influence on heat transfer of nanofluids. Originality/value – The area of nanofluids is very original.

scholarly journals Viscoelastic Fluid over a Stretching Sheet with Electromagnetic Effects and Nonuniform Heat Source/Sink

2010 ◽  
Vol 2010 ◽  
pp. 1-14 ◽  
Author(s):  
Kai-Long Hsiao
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Viscoelastic Fluid ◽  
Stretching Sheet ◽  
Numerical Solutions ◽  
Transfer Effects ◽  
Gauss Elimination ◽  
Heat Transfer Effects ◽  
Source Sink ◽  
Gauss Elimination Method

A magnetic hydrodynamic (MHD) of an incompressible viscoelastic fluid over a stretching sheet with electric and magnetic dissipation and nonuniform heat source/sink has been studied. The buoyant effect and the electric numberE1couple with magnetic parameterMto represent the dominance of the electric and magnetic effects, and adding the specific item of nonuniform heat source/sink is presented in governing equations which are the main contribution of this study. The similarity transformation, the finite-difference method, Newton method, and Gauss elimination method have been used to analyze the present problem. The numerical solutions of the flow velocity distributions, temperature profiles, and the important wall unknown values off''(0)andθ'(0)have been carried out. The parameter Pr,E1, orEccan increase the heat transfer effects, but the parameterMorA*may decrease the heat transfer effects.

Effect of non-uniform heat source/sink on MHD boundary layer flow and melting heat transfer of Williamson nanofluid in porous medium

2019 ◽  
Vol 15 (2) ◽  
pp. 452-472 ◽  
Author(s):  
Jayarami Reddy Konda ◽  
Madhusudhana Reddy N.P. ◽  
Ramakrishna Konijeti ◽  
Abhishek Dasore
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Heat Source ◽  
Radiation Effects ◽  
Navier Stokes ◽  
Working Fluid ◽  
Content Type ◽  
Linear Ordinary Differential Equations ◽  
Uniform Heat ◽  
Source Sink

PurposeThe purpose of this paper is to examine the influence of magnetic field on Williamson nanofluid embedded in a porous medium in the presence of non-uniform heat source/sink, chemical reaction and thermal radiation effects.Design/methodology/approachThe governing physical problem is presented using the traditional Navier–Stokes theory. Consequential system of equations is transformed into a set of non-linear ordinary differential equations by means of scaling group of transformation, which are solved using the Runge–Kutta–Fehlberg method.FindingsThe working fluid is examined for several sundry parameters graphically and in a tabular form. It is noticed that with an increase in Eckert number, there is an increase in velocity and temperature along with a decrease in shear stress and heat transfer rate.Originality/valueA good agreement of the present results has been observed by comparing with the existing literature results.

Heat transfer enhancement in microchannels using ribs and secondary flows

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Karthikeyan Paramanandam ◽  
Venkatachalapathy S. ◽  
Balamurugan Srinivasan
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Secondary Flows ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose The purpose of this paper is to study the flow and heat transfer characteristics of microchannel heatsinks with ribs, cavities and secondary channels. The influence of length and width of the ribs on heat transfer enhancement, secondary flows, flow distribution and temperature distribution are examined at different Reynolds numbers. The effectiveness of each heatsink is evaluated using the performance factor. Design/methodology/approach A three-dimensional solid-fluid conjugate heat transfer numerical model is used to study the flow and heat transfer characteristics in microchannels. One symmetrical channel is adopted for the simulation to reduce the computational cost and time. Flow inside the channels is assumed to be single-phase and laminar. The governing equations are solved using finite volume method. Findings The numerical results are analyzed in terms of average Nusselt number ratio, average base temperature, friction factor ratio, pressure variation inside the channel, temperature distribution, velocity distribution inside the channel, mass flow rate distribution inside the secondary channels and performance factor of each microchannels. Results indicate that impact of rib width is higher in enhancing the heat transfer when compared with its length but with a penalty on the pressure drop. The combined effects of secondary channels, ribs and cavities helps to lower the temperature of the microchannel heat sink and enhances the heat transfer rate. Practical implications The fabrication of microchannels are complex, but recent advancements in the additive manufacturing techniques makes the fabrication of the design considered in this numerical study feasible. Originality/value The proposed microchannel heatsink can be used in practical applications to reduce the thermal resistance, and it augments the heat transfer rate when compared with the baseline design.

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