scholarly journals Heat generating porous matrix effects on Brownian motion of nanofluid

2019 ◽  
Vol 29 (5) ◽  
pp. 1724-1740
Author(s):  
Aydin Zehforoosh ◽  
Siamak Hossainpour ◽  
Mohammad Mehdi Rashidi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Rayleigh Number ◽  
Porous Material ◽  
Volume Fraction ◽  
Matrix Effects ◽  
Internal Heat ◽  
Porous Matrix ◽  
Content Type ◽  
The Impact

Purpose The purpose of this study is to indicate the effect of mounting heat generating porous matrix in a close cavity on the Brownian term of CuO-water nanofluid and its impact on improving the Nusselt number. Design/methodology/approach Because of the presence of heat source in porous matrix, couple of energy equations is solved for porous matrix and nanofluid separately. Thermal conductivity and viscosity of nanofluid were assumed to be consisting of a static component and a Brownian component that were functions of volume fraction of the nanofluid and temperature. To explain the effect of the Brownian term on the flow and heat fields, different parameters such as heat conduction ratio, interstitial heat transfer coefficient, Rayleigh number, concentration of nanoparticles and porous material porosity were investigated and compared to those of the non-Brownian solution. Findings The Brownian term caused the cooling of porous matrix because of rising thermal conductivity. Mounting the porous material into cavity changes the temperature distribution and increases Brownian term effect and heat transfer functionality of the nanofluid. Besides, the effect of the Brownian term was seen to be greatest at low Rayleigh number, low-porosity and small thermal conductivity of the porous matrix. It is noteworthy that because of decrement of thermal conduction in high porosities, the impact of Brownian term drops severely making it possible to obtain reliable results even in the case of neglecting Brownian term in these porosities. Originality/value The effect of mounting the porous matrix with internal heat generation was investigated on the improvement of variable properties of nanofluid.

scholarly journals Numerical study of heat transfer in 90° bend tube by AI2O3 nano fluids using fluid injection

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hadi Mahdizadeh ◽  
Nor Mariah Adam
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Volume Fraction ◽  
Fluid Injection ◽  
Content Type ◽  
Nano Fluid ◽  
The Impact

Purpose This paper aims to investigate increasing heat transfer in bend tube 90° by fluid injection using nano fluid flow that was performed by expending varying Reynolds number. This paper studies the increased heat transfer in the bent tube that used some parameters to examine the effects of volume fraction, nanoparticle diameter, fluid injection, Reynolds number on heat transfer and flow in a bend pipe. Design/methodology/approach Designing curved tubes increases the thermal conductivity amount between fluid and wall. It is used the finite volume method and simple algorithms to solve the conservation equations of mass, momentum and energy. The results showed that the nanoparticles used in bent tube transfusion increase the heat transfer performance by increasing the volume fraction; it has a direct impact on enhancing the heat transfer coefficient. Findings Heat transfer coefficient enhanced 1.5% when volume fraction increased from 2 % to 6%, the. It is due to the impact of nanoparticles on the thermal conductivity of the fluid. The fluid is injected into the boundary layer flow due to jamming that enhances heat transfer. Curved lines used create a centrifugal force due to the bending and lack of development that increase the heat transfer. Originality/value This study has investigated the effect of injection of water into a 90° bend before and after the bend. Specific objectives are to analyze effect of injection on heat transfer of bend tube and pressure drop, evaluate best performance of mixing injection and bend in different positions and analyze effect of nano fluid volume fraction on injection.

Entropy generation analysis of nanoliquid flow through microchannel considering heat source and different shapes of nanoparticle

2019 ◽  
Vol 30 (3) ◽  
pp. 1457-1477 ◽  
Author(s):  
B.J. Gireesha ◽  
S. Sindhu
Keyword(s):  
Thermal Conductivity ◽  
Heat Source ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Internal Heat ◽  
Bejan Number ◽  
Molybdenum Disulphide ◽  
Content Type ◽  
Different Shapes ◽  
The Impact

Purpose This paper aims to focus on the steady state flow of nanoliquid through microchannel with the aid of internal heat source and different shapes of nanoparticle. The influence of MoS2 and TiO2 particles of nano size on flow and thermal fields is examined. The governing equations are modelled and then solved numerically. The obtained physical model is nondimensionalized using dimensionless quantities. The nondimensional equations are treated with numerical scheme. The outcome of the current work is presented graphically. Diverse substantial quantities such as entropy generation, Bejan number and Nusselt number for distinct parameters are depicted through graphs. The result established that nanoparticle of blade shape acquires larger thermal conductivity. Entropy analysis is carried out to explore the impact of various parameters such as nanoparticle volume fraction, magnetic parameter, radiation parameter and heat source parameter. Design/methodology/approach The resultant boundary value problem is converted into initial value problem using shooting scheme. Then the flow model is resolved using Runge-Kutta-Fehlberg-Fourth-Fifth order technique. Findings It is emphasized that entropy generation for the fluid satisfies N(ζ)(TiO2−water) > N(ζ)(MoS2−water). In addition to this, it is emphasized that N(ζ)sphere > N(ζ)brick > N(ζ)cylinder > N(ζ)platelet > N(ζ)blade. Also, it is obtained that blade-shaped nanoparticle has higher thermal conductivity for both MoS2 and TiO2. Originality/value Shape effects on Molybdenum disulphide and TiO2 nanoparticle in a microchannel with heat source is examined. The analysis of entropy shows that N(ζ)(TiO2−water) > N(ζ)(MoS2−water).

3D optimization of baffle arrangement in a multi-phase nanofluid natural convection based on numerical simulation

2019 ◽  
Vol 30 (5) ◽  
pp. 2583-2605 ◽  
Author(s):  
Mohammad Mohsen Peiravi ◽  
Javad Alinejad ◽  
D.D. Ganji ◽  
Soroush Maddah
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Target Function ◽  
Optimal Arrangement ◽  
Content Type ◽  
Multi Phase

Purpose The purpose of this study is investigating the effect of using multi-phase nanofluids, Rayleigh number and baffle arrangement simultaneously on the heat transfer rate and Predict the optimal arrangement type of baffles in the differentiation of Rayleigh number in a 3D enclosure. Design/methodology/approach Simulations were performed on the base of the L25 Taguchi orthogonal array, and each test was conducted under different height and baffle arrangement. The multi-phase thermal lattice Boltzmann based on the D3Q19 method was used for modeling fluid flow and temperature fields. Findings Streamlines, isotherms, nanofluid volume fraction distribution and Nusselt number along the wall surface for 104 < Ra < 108 have been demonstrated. Signal-to-noise ratios have been analyzed to predict optimal conditions of maximize and minimize the heat transfer rate. The results show that by choosing the appropriate height and arrangement of the baffles, the average Nusselt number can be changed by more than 57 per cent. Originality/value The value of this paper is surveying three-dimensional and two-phase simulation for nanofluid. Also using the Taguchi method for Predicting the optimal arrangement type of baffles in a multi-part enclosure. Finally statistical analysis of the results by using of two maximum and minimum target Function heat transfer rates.

Dufour and Soret effects on Darcy-Forchheimer flow of second-grade fluid with the variable magnetic field and thermal conductivity

2020 ◽  
Vol 30 (9) ◽  
pp. 4331-4347 ◽  
Author(s):  
Ambreen A. Khan ◽  
S. Naeem ◽  
R. Ellahi ◽  
Sadiq M. Sait ◽  
K. Vafai
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
Variable Magnetic Field ◽  
Second Grade ◽  
Second Grade Fluid ◽  
Content Type ◽  
Grade Fluid ◽  
The Impact ◽  
Forchheimer Flow

Purpose This study aims to investigate the effect of two-dimensional Darcy-Forchheimer flow over second-grade fluid with linear stretching. Heat transfer through convective boundary conditions is taken into account. Design/methodology/approach Nonlinear coupled governing equations are tackled with a homotopy algorithm, while for numerical computation the computer software package BVPh 2.0 is used. The convergence analysis is also presented for the validation of analytical and numerical results. Findings Valuation for the impact of key parameters such as variable thermal conductivity, Dufour and Soret effects and variable magnetic field in an electrically conducted fluid on the velocity, concentration and temperature profiles are graphically illustrated. It is observed from the results that temperature distribution rises by Dufour number whereas concentration distribution rises by Soret number. The Forchheimer number and porosity parameter raise the skin friction coefficient. The permeable medium has a vital impact and can help in reining the rate of heat transfer. Practical implications The permeable medium has a vital impact and can help in reining the rate of heat transfer. Originality/value To the best of the authors’ knowledge, this study is reported for the first time.

Natural convection from cross blade inside a nanofluid-filled cavity using ISPH method

2020 ◽  
Vol 30 (10) ◽  
pp. 4629-4648
Author(s):  
Zehba A.S. Raizah
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Circular Cylinder ◽  
Volume Fraction ◽  
Working Fluid ◽  
Convection Flow ◽  
Physical Parameters ◽  
Cool Temperature ◽  
Content Type

Purpose The purpose of this study is to apply the incompressible smoothed particle hydrodynamics method for simulating the natural convection flow inside a cavity including cross blades or circular cylinder cylinder. Design/methodology/approach The base fluid is water and copper-water nanofluid is treated as a working fluid. The left and rights walls are maintained at a cool temperature, the horizontal cavity walls are isolated and the inner shape was heated. The physical parameters are the length of the blades L_Blade, the number of cross blades, circular cylinder radius L_R, Rayleigh number Ra and the nanoparticles volume fraction. Findings The results reveal that the lengths of the cross blade, number of the blades and radius of the circular cylinder is working as an enhancement factor for heat transfer and fluid flows inside a cavity. Adding nanoparticles augments heat transfer and reduces the fluid flow intensity inside a cavity. The best case for buoyancy-driven flow was obtained when the inner shape is the circular cylinder at a higher Rayleigh number. Originality/value This work uses a distinctive numerical method to study the natural convection heat from cross blades inside a cavity filled with nanofluid. It provides a new analysis of this issue and presented good results.

MHD natural convection and entropy analysis of a nanofluid inside T-shaped baffled enclosure

2018 ◽  
Vol 28 (12) ◽  
pp. 2916-2941 ◽  
Author(s):  
Taher Armaghani ◽  
A. Kasaeipoor ◽  
Mohsen Izadi ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Entropy Generation ◽  
Hartmann Number ◽  
Content Type ◽  
Thermal Indexes ◽  
The Impact

Purpose The purpose of this paper is to numerically study MHD natural convection and entropy generation of Al2O3-water alumina nanofluid inside of T-shaped baffled cavity which is subjected to a magnetic field. Design/methodology/approach Effect of various geometrical, fluid and flow factors such as aspect ratio of enclosure and baffle length, Rayleigh and Hartmann number of nanofluid have been considered in detail. The hydrodynamics and thermal indexes of nanofluid have been described using streamlines, isotherms and isentropic lines. Findings It is found that by enhancing Hartmann number, symmetrical streamlines gradually lose symmetry and their values decline. It is found that by enhancing Hartmann number, symmetrical streamlines gradually lose symmetry and their values decline. The interesting finding is an increase in the impact of Hartmann number on heat transfer indexes with augmenting Rayleigh number. However, with augmenting Rayleigh number and, thus, strengthening the buoyant forces, the efficacy of Hartmann number one, an index indicating the simultaneous impact of natural heat transfer to entropy generation increases. It is clearly seen that the efficacy of nanofluid on increased Nusselt number enhances with increasing aspect ratio of the enclosure. Based on the results, the Nusselt number generally enhances with the larger baffle length in the enclosure. Finally, with larger Hartmann number and lesser Nusselt one, entropy production is reduced. Originality/value The authors believe that all the results, both numerical and asymptotic, are original and have not been published elsewhere.

Investigation of magnetohydrodynamics in Ag-TiO2/water hybrid nanofluid in a Shamse knot shaped cavity

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yuan Ma ◽  
Mohammad Mehdi Rashidi ◽  
Rasul Mohebbi ◽  
Zhigang Yang
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Side Length ◽  
Hybrid Nanofluid ◽  
Nanoparticle Volume Fraction ◽  
Heat Transfer Characteristics ◽  
Content Type

Purpose The nanofluid natural convection heat transfer in a hollow complex enclosure, which is named as Shamse knot shape, is studied numerically. This paper aims to present how the Rayleigh number, nanoparticle volume fraction, Hartmann number and hollow side length affect the fluid flow and heat transfer characteristics. Design/methodology/approach The continuity, momentum and energy equations have been solved using lattice Boltzmann method (LBM). Numerical simulation has been obtained for a wide range of Rayleigh number (103 ≤ Ra ≤ 106), nanoparticle volume fraction (0 ≤ ϕ 0.05) and Hartmann number (0 ≤ Ha ≤ 60) to analyze the fluid flow pattern and heat transfer characteristics. Moreover, the effect of hollow side length (D) on flow field and thermal performance is studied. Findings The results showed that the magnetic field has a negative effect on the thermal performance and the average Nusselt number decreases by increasing the Hartmann number. Because of the high conduction heat transfer coefficient of nanoparticles, the average Nusselt number increases by rising the nanoparticle volume fraction. The effect of adding nanoparticles on heat transfer is more effective at low nanoparticle volume fraction (0 ≤ ϕ ≤ 0.01). It was also found that at Ra = 106, when the hollow side length increases to 3, the flow pattern becomes different due to the small gap. The averaged Nu is an increasing function of D at low Ra and an opposite trend occurs at high Rayleigh number. Originality/value For the first time, the effects of magnetic field, Rayleigh number, nanoparticle volume fraction and hollow side length on natural convection heat transfer of hybrid nanofluid (Ag-TiO2/water) is investigated in a complicated cavity.

FEM-CBS algorithm for convective transport of nanofluids in inclined enclosures filled with anisotropic non-Darcy porous media using LTNEM

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sameh Elsayed Ahmed
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Porous Medium ◽  
Equilibrium State ◽  
Thermal Equilibrium ◽  
Volume Fraction ◽  
Nanofluid Flow ◽  
Content Type ◽  
Thermal Fields ◽  
Nanoparticles Volume Fraction

Purpose The Galerkin finite element method (FEM) based on the characteristic-based split (CBS) scheme is applied to simulate the nanofluid flow and thermal fields inside an inclined geometry filled by a heat-generating hydrodynamically and thermally anisotropic non-Darcy porous medium using the local thermal non-equilibrium model (LTNEM). Property of the hydrodynamic anisotropy is taken in both the Forchheimer coefficient and permeability and these tools are considered as functions of inclination of the principal axes. Also, the thermal conductivity for the porous phase is assumed to be anisotropic. Design/methodology/approach The Galerkin FEM based on the CBS scheme is applied to solve the partial differential equations governing the flow and thermal fields. Findings It is noted that the net rate of the heat transfer between the nanofluid and solid phases are influenced by variations of the anisotropic properties. Also, the system is reached to the thermal equilibrium state at H > 100. Further, the maximum nanofluid temperature is reduced by 12.27% when the nanoparticles volume fraction is varied from 0% to 4%. Originality/value This paper aims to study the nanofluid flow and heat transfer characteristics inside an inclined enclosure filled with a heat-generating, hydrodynamically and thermally anisotropic porous medium using the CBS scheme. The LTNEM is considered between the nanofluid and porous phases while the local thermal equilibrium model (LTEM) between the base fluid (water) and the nanoparticles (alumina) is taken into account. The Galerkin FEM is introduced to discretize the governing system of equations. Also, examine influences of the anisotropic properties (permeability, Forchheimer terms and thermal conductivity of the porous medium), inclination angle and nanoparticles volume fraction on the net rate of the heat transfer between the nanofluid and porous phases and on the local thermal non-equilibrium state is one of the concerns of this paper.

scholarly journals Heat Transfer Analysis of MHD Water Functionalized Carbon Nanotube Flow over a Static/Moving Wedge

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Waqar A. Khan ◽  
Richard Culham ◽  
Rizwan Ul Haq
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Differential Equations ◽  
Skin Friction ◽  
Volume Fraction ◽  
Heat Transfer Analysis ◽  
Published Data ◽  
Nusselt Numbers ◽  
Moving Wedge ◽  
The Impact

The MHD flow and heat transfer from water functionalized CNTs over a static/moving wedge are studied numerically. Thermal conductivity and viscosity of both single and multiple wall carbon nanotubes (CNTs) within a base fluid (water) of similar volume are investigated to determine the impact of these properties on thermofluid performance. The governing partial differential equations are converted into nonlinear, ordinary, and coupled differential equations and are solved using an implicit finite difference method with quasi-linearization techniques. The effects of volume fraction of CNTs and magnetic and wedge parameters are investigated and presented graphically. The numerical results are compared with the published data and are found to be in good agreement. It is shown that the magnetic field reduces boundary layer thickness and increases skin friction and Nusselt numbers. Due to higher density and thermal conductivity, SWCNTs offer higher skin friction and Nusselt numbers.

Thermal performance of fully wet longitudinal porous fin with temperature-dependent thermal conductivity, surface emissivity and heat transfer coefficient

2019 ◽  
Vol 16 (4) ◽  
pp. 749-764 ◽  
Author(s):  
G. Sowmya ◽  
B.J. Gireesha ◽  
O.D. Makinde
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Surface Emissivity ◽  
Content Type ◽  
Porous Fin ◽  
Convective Parameter ◽  
The Impact ◽  
Simultaneous Variation

Purpose The purpose of this paper is to study the thermal behaviour of a fully wet porous fin of longitudinal profile. The significance of radiative and convective heat transfer has been scrutinised along with the simultaneous variation of surface emissivity, heat transfer coefficient and thermal conductivity with temperature. The emissivity of the surface and the thermal conductivity are considered as linear functions of the local temperature between fin and the ambient. Darcy’s model was considered to formulate the heat transfer equation. According to this, the porous fin permits the flow to penetrate through it and solid–fluid interaction occurs. Design/methodology/approach Runge–Kutta–Fehlberg fourth–fifth-order method has been used to solve the reduced non-dimensionalized ordinary differential equation involving highly nonlinear terms. Findings The impact of pertinent parameters, such as convective parameter, radiative parameter, conductivity parameter, emissivity parameter, wet porous parameter, etc., on the temperature profiles were elaborated mathematically with the plotted graphs. The heat transfer from the fin enhances with the rise in convective parameter. Originality/value The wet nature of the fin enhances heat transfer and in many practical applications the parameters, such as thermal conductivity, heat transfer coefficient as well as surface emissivity, vary with temperature. Hence, the main objective of the current study is to depict the significance of simultaneous variation in surface emissivity, heat transfer coefficient and thermal conductivity with respect to temperature under natural convection and radiation condition in a totally wetted longitudinal porous fin.

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