Natural convection heat transfer augmentation in a partially heated and partially cooled square cavity utilizing nanofluids

2009 ◽  
Vol 19 (3/4) ◽  
pp. 411-431 ◽  
Author(s):  
Manab Kumar Das ◽  
Pravin Shridhar Ohal
Keyword(s):  
Heat Transfer ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Heat Transfer ◽  
Square Cavity ◽  
Content Type ◽  
Heat Transfer Augmentation ◽  
Special Cases ◽  
Simplec Algorithm ◽  
Finite Volume Approach

PurposeThe purpose of this paper is to investigate the behaviour of nanofluids numerically inside a partially heated and partially cooled square cavity to gain insight into heat transfer and flow processes induced by a nanofluid.Design/methodology/approachA model is developed to analyze the behaviour of nanofluids taking into account the solid volume fraction χ. The transport equations are solved numerically with finite volume approach using SIMPLEC algorithm.FindingsComparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. Five different relative positions of the active zones are considered.While circulation depend strongly on the total exit length. Governing parameters were 103 < Gr < 107 but due to space constraints the results for 104 < Gr <107 are presented. It is found that both the Grashof number and solid volume fraction χ affect the fluid flow and heat transfer in the cavity. CopperWater nanofluid is used with Pr = 6.2 and solid volume fraction is varied as 0, 4, 8, 12, 16 and 20 per cent. Detailed results are presented for flow pattern and heat transfer curves.Originality/valueThe present study focusses on the analysis of several parameters on the heat transfer characteristics of nanofluids within the enclosure.

Lattice Boltzmann simulation of free convection in nanofluid filled cavity with partially active walls – entropy generation and heatline visualization

2018 ◽  
Vol 28 (10) ◽  
pp. 2254-2283 ◽  
Author(s):  
Alireza Rahimi ◽  
Abbas Kasaeipoor ◽  
Emad Hasani Malekshah ◽  
Lioua Kolsi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Entropy Generation ◽  
Lattice Boltzmann ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Heat Transfer ◽  
Content Type ◽  
Lattice Boltzmann Simulation

Purpose This paper aims to perform the lattice Boltzmann simulation of natural convection heat transfer in cavities included with active hot and cold walls at the side walls and internal hot and cold obstacles. Design/methodology/approach The cavity is filled with double wall carbon nanotubes (DWCNTs)-water nanofluid. Different approaches such as local and total entropy generation, local and average Nusselt number and heatline visualization are used to analyze the natural convection heat transfer. The cavity is filled with DWCNTs-water nanofluid and the thermal conductivity and dynamic viscosity are measured experimentally at different solid volume fractions of 0.01 per cent, 0.02 per cent, 0.05 per cent, 0.1 per cent, 0.2 per cent and 0.5 per cent and at a temperature range of 300 to 340 (K). Findings Two sets of correlations for these parameters based on temperature and solid volume fraction are developed and used in the numerical simulations. The influences of different governing parameters such as Rayleigh number, solid volume fraction and different arrangements of active walls on the fluid flow, heat transfer and entropy generation are presented, comprehensively. It is found that the different arrangements of active walls have pronounced influence on the flow structure and heat transfer performance. Furthermore, the Nusselt number has direct relationship with Rayleigh number and solid volume fraction. On the other hand, the total entropy generation has direct and reverse relationship with Rayleigh number and solid volume fraction, respectively. Originality/value The originality of this work is to analyze the two-dimensional natural convection using lattice Boltzmann method and different approaches such as entropy generation and heatline visualization.

Effect of hot obstacle position on natural convection heat transfer of MWCNTs-water nanofluid in U-shaped enclosure using lattice Boltzmann method

2019 ◽  
Vol 29 (1) ◽  
pp. 223-250 ◽  
Author(s):  
Yuan Ma ◽  
Rasul Mohebbi ◽  
Mohammad Mehdi Rashidi ◽  
Zhigang Yang
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Content Type ◽  
Boltzmann Method

Purpose This paper aims to numerically investigate the natural convection heat transfer of multi-wall carbon nanotubes (MWCNTs)-water nanofluid in U-shaped enclosure equipped with a hot obstacle by using the lattice Boltzmann method. Design/methodology/approach The combination of the three topics (U-shaped enclosure, different positions of the hot obstacle and MWCNTs-water nanofluid) is innovative in the present study. In total, 15 different positions of the hot obstacle have been arranged, and the effects of pertinent parameters such as Rayleigh numbers, the solid volume fraction of the MWCNTs nanoparticles on the flow field, temperature distribution and the rate of heat transfer inside the enclosure are also investigated. Findings It is found that the average Nusselt number increased by raising the Rayleigh number, and so did the nanoparticle solid volume fraction regardless the position of the hot obstacle. Moreover, enclosures where the hot obstacle is located at the bottom region proved to provide a better rate of heat transfer at high Rayleigh number (106). It is concluded that at a low Ra number (103-105), the higher heat transfer rate and Nu number will be obtained when the hot obstacle is located in the left or right channel. Originality/value In the literature, no trace of studying the natural convection of nanofluids in U-shaped enclosures with heating obstacles was found. Also, MWCNTs were less used as nanoparticles. As the natural convection of nanofluids in thermal engineering applications would expand the existing knowledge, the current researchers conducted a numerical study of the natural convection of Maxwell nanofluid with MWCNTs in U-shaped enclosure equipped with a hot obstacle by using lattice Boltzmann method.

scholarly journals Numerical Analysis of Nanofluids in Differentially Heated Enclosure Undergoing Orthogonal Rotation

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
H. Saleh ◽  
I. Hashim
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Heat Transfer ◽  
Staggered Grid ◽  
Governing Equations ◽  
Nanoparticles Concentration ◽  
Quantity Of Heat ◽  
Velocity Pressure

Natural convection heat transfer in a rotating, differentially heated enclosure is studied numerically in this paper. The rotating enclosure is filled with water-Ag, water-Cu, water-Al2O3, or water-TiO2nanofluids. The governing equations are in velocity, pressure, and temperature formulation and solved using the staggered grid arrangement together with MAC method. The governing parameters considered are the solid volume fraction,0.0 ≤ ϕ ≤ 0.05, and the rotational speeds,3.5≤ Ω ≤ 17.5 rpm, and the centrifugal force is smaller than the Coriolis force and both forces were kept below the buoyancy force. It is found that the angular locations of the local maximums heat transfer were sensitive to rotational speeds and nanoparticles concentration. The global quantity of heat transfer rate increases about 1.5%, 1.1%, 0.8%, and 0.6% by increasing 1%ϕof the nanoparticles Ag, Cu, Al2O3, and TiO2, respectively, for the considered rotational speeds.

Influence of Cu-Water and CNT-Water Nanofluid on Natural Convection Heat Transfer in a Triangular Solar Collector

2020 ◽  
Author(s):  
Didarul Ahasan Redwan ◽  
Md. Habibur Rahman ◽  
Hasib Ahmed Prince ◽  
Emdadul Haque Chowdhury ◽  
M. Ruhul Amin
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Solar Collector ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat

Abstract A numerical study on natural convection heat transfer in a right triangular solar collector filled with CNT-water and Cuwater nanofluids has been conducted. The inclined wall and the bottom wall of the cavity are maintained at a relatively lower temperature (Tc), and higher temperature (Th), respectively, whereas the vertical wall, is kept adiabatic. The governing non-dimensional partial differential equations are solved by using the Galerkin weighted residual finite element method. The Rayleigh number (Ra) and the solid volume-fraction of nanoparticles (ϕ) are varied in the range of 103 ≤ Ra ≤ 106, and 0 ≤ ϕ ≤ 0.1, respectively, to carry out the parametric simulations within the laminar region. Corresponding thermal and flow fields are presented via isotherms and streamlines. Variations of average Nusselt number as a function of Rayleigh number have been examined for different solid volume-fraction of nanoparticles. It has been found that the natural convection heat transfer becomes stronger with the increment of solid volume fraction and Rayleigh number, but the strength of circulation reduces with increasing nanoparticles’ concentration at low Ra. Conduction mode dominates for lower Ra up to a certain limit of 104. It is also observed that when the solid volume fraction is increased from 0 to 0.1 for a particular Rayleigh number, the average Nusselt number is increased to a great extent, but surprisingly, the rate of increment is more pronounced at lower Ra. Moreover, it is seen that Cu-water nanofluid offers slightly better performance compared to CNT-water but the difference is very little, especially at lower Ra.

Fluid flow and heat transfer of a stratified system during natural convection – influence of chamfered corners

2019 ◽  
Vol 29 (2) ◽  
pp. 470-486 ◽  
Author(s):  
Alireza Rahimi ◽  
Aravindhan Surendar ◽  
Aygul Z. Ibatova ◽  
Abbas Kasaeipoor ◽  
Emad Hasani Malekshah
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Immiscible Fluids ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose This paper aims to investigate the three-dimensional natural convection and entropy generation in the rectangular cuboid cavities included by chamfered triangular partition made by polypropylene. Design/methodology/approach The enclosure is filled by multi-walled carbon nanotubes (MWCNTs)-H2O nanofluid and air as two immiscible fluids. The finite volume approach is used for computation. The fluid flow and heat transfer are considered with combination of local entropy generation due to fluid friction and heat transfer. Moreover, a numerical method is developed based on three-dimensional solution of Navier–Stokes equations. Findings Effects of side ratio of triangular partitions (SR = 0.5, 1 and 2), Rayleigh number (103 < Ra < 105) and solid volume fraction (f = 0.002, 0.004 and 0.01 Vol.%) of nanofluid are investigated on both natural convection characteristic and volumetric entropy generation. The results show that the partitions can be a suitable method to control fluid flow and energy consumption, and three-dimensional solutions renders more accurate results. Originality/value The originality of this work is to study the three-dimensional natural convection and entropy generation of a stratified system.

The impacts of non-uniform magnetic field on free convection heat transfer of a magnetizable micropolar nanofluid

2019 ◽  
Vol 29 (10) ◽  
pp. 3685-3706
Author(s):  
Zafar Namazian ◽  
S.A.M. Mehryan
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Content Type ◽  
Viscosity Parameter ◽  
Micropolar Nanofluid ◽  
Free Convection Heat

Purpose The purpose of this study is to numerically study the heat transfer of free convection of a magnetizable micropolar nanofluid inside a semicircular enclosure. Design/methodology/approach The flow domain is under simultaneous influences of two non-uniform magnetic fields generated by current carrying wires. The directions of the currents are the same. Although the geometry is symmetric, it is physically asymmetric. The impacts of key parameters, including Rayleigh number Ra = 103-106, Hartman number Ha = 0-50, vortex viscosity parameter Δ = 0-4, nanoparticles volume fraction φ = 0-0.04 and magnetic number Mnf = 0-1000, on the macro- and micro-scales flows, temperature and heat transfer rate are studied. Finding The outcomes show that dispersing of the nanoparticles in the host fluid increases the strength of macro- and micro-scale flows. When Mnf = 0, the increment of the vortex viscosity parameter increases the strength of the particles micro-rotations, while this characteristic is decreased by growing Δ for Mnf ≠ 0. The increment of Δ and Ha decreases the rate of heat transfer. The increment of Ha decreases the enhancement percentage of heat transfer rate because of dispersing nanoparticles, known as En parameter. In addition, the value of Δ has no effect on En. Moreover, the average Nusselt number Nuavg and En remain constant by increasing the magnetic number Mnf for different volume fraction values. Originality/value The authors believe that all of the results, both numerical and asymptotic, are original and have not been published elsewhere yet.

Flow and heat transfer of couple stress nanofluid sandwiched between viscous fluids

2019 ◽  
Vol 29 (11) ◽  
pp. 4262-4276 ◽  
Author(s):  
C. Jawali Umavathi ◽  
Mikhail Sheremet
Keyword(s):  
Heat Transfer ◽  
Couple Stress ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Viscous Fluids ◽  
Temperature Fields ◽  
Content Type ◽  
Stress Parameter ◽  
Transfer Behavior ◽  
Velocity And Temperature Fields

Purpose The purpose of this study is a numerical analysis of steady-state heat transfer behavior of couple-stress nanofluid sandwiched between viscous fluids. It should be noted that this research deals with the development of a cooling system for the electronic devices. Design/methodology/approach Stokes model is used to define the couple-stress fluid and the single-phase nanofluid model is used to define the nanofluid transport processes. The fluids in all regions are assumed to be incompressible, immiscible and the transport properties in all the three layers are assumed to be constant. The governing coupled linear ordinary differential equations are made dimensionless by using appropriate fundamental quantities. The exact solutions obtained for the velocity and temperature fields are evaluated numerically for various model parameters. Findings The results are demonstrated using different types of nanoparticles such as copper, silver, silicon oxide (SiO2), titanium oxide (TiO2) and diamond. The investigations are carried out using copper–water nanofluid for different values of couple-stress parameter a with a range of 0 = a = 12, solid volume fraction ϕ with a range of 0.0 ≤ ϕ ≤ 0.05, Eckert number Ec with a range of 0.001 ≤ Ec ≤ 6 and Prandtl number Pr with a range of 0.001 ≤ Pr ≤ 6. It was found that the Nusselt number increases by increasing the couple stress parameter, Eckert number and Prandtl number and it decreases with a growth of the solid volume fraction parameter. It was also observed that using SiO2–water nanofluid, the optimal Nusselt number is obtained. Further, using copper, silver, diamond and TiO2, nanoparticles and water as a base fluid does not show any significant changes in the rate of heat transfer. The couple-stress parameter enhances the velocity and temperature fields whereas the solid volume fraction suppresses the flow field for both Newtonian and couple-stress fluid. Originality/value The originality of this work is to analyze the heat transfer behavior of couple-stress nanofluid sandwiched between viscous fluids. The results would benefit scientists and engineers to become familiar with the analysis of convective heat transfer and flow structures in nanofluids and the way to predict the heat transfer rate in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors, electronics, etc.

Heat transfer and entropy generation analysis of Cu-water nanofluid in a vertical channel

2018 ◽  
Vol 15 (5) ◽  
pp. 604-613
Author(s):  
Essma Belahmadi ◽  
Rachid Bessaih
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Friction Factor ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Vertical Channel ◽  
Simple Algorithm ◽  
Content Type

Purpose The purpose of this study is to analyze heat transfer and entropy generation of a Cu-water nanofluid in a vertical channel. The channel walls are maintained at a hot temperature Tw. An up flow penetrates the channel at a uniform velocity v0 and a cold temperature T0 (T0 < Tw). The effects of Reynolds number Re, Grashof number Gr and solid volume fraction ϕ on streamlines, isotherms, entropy generation, friction factor, local and mean Nusselt numbers are evaluated. Design/methodology/approach The Cu-water nanofluid is used in this study. The software Ansys-fluent 14.5, based on the finite-volume method and SIMPLE algorithm, is used to simulate the mixed convection problem with entropy generation in a vertical channel. Findings The results show that the increase of Reynolds and Grashof numbers and solid volume fraction improves heat transfer and reduces entropy generation. Correlations for the mean Nusselt number and friction factor in terms of Reynolds number and solid volume fraction are obtained. The present results are compared with those found in the literature, which reveal a very good agreement. Originality/value The originality of this work is to understand the heat transfer and entropy generation for mixed convection of a Cu-water nanofluid in a vertical channel.

Mixed convection boundary layer flow along vertical thin needles in nanofluids

2014 ◽  
Vol 24 (3) ◽  
pp. 579-594 ◽  
Author(s):  
Radu Trimbitas ◽  
Teodor Grosan ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Boundary Layer ◽  
Heat Transfer Characteristics ◽  
Content Type ◽  
Flow And Heat Transfer ◽  
Convection Boundary ◽  
Layer Flow

Purpose – The purpose of this paper is to theoretically study the problem of mixed convection boundary layer flow and heat transfer past a vertical needle with variable wall temperature using nanofluids. The similarity equations are solved numerically for copper nanoparticles in the based fluid of water to investigate the effect of the solid volume fraction parameter of the fluid and heat transfer characteristics. The skin friction coefficient, Nusselt number, and the velocity and temperature profiles and are graphically presented and discussed. Design/methodology/approach – The transformed system of ordinary differential equations was solved using the function bvp4c from Matlab. The relative tolerance was set to 1e-10. For the study of the stability the authors also used the bvp4c function in combination with chebfun package from Matlab. Findings – It is found that the solid volume fraction affects the fluid flow and heat transfer characteristics. The numerical results for a regular fluid and forced convection flow are compared with the corresponding results reported by Chen and Smith. The solutions exists up to a critical value of λ, beyond which the boundary layer separates from the surface and the solution based upon the boundary-layer approximations is not possible Originality/value – The paper describes how multiple (dual) solutions for the flow reversals are obtained. A stability analysis for this flow reversal has been also done showing that the lower solution branches are unstable, while the upper solution branches are stable.

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.

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