Numerical investigation of the MHD forced convection and entropy generation in a straight duct with sinusoidal walls containing water–Al<sub>2</sub>O<sub>3</sub> nanofluid

Mayeli, Peyman; Hesami, Hanieh; Moghaddam, Mohammad Hassan Dolatkhah Faraji

doi:10.1080/10407782.2017.1346998

Cited by 25 publications

(19 citation statements)

References 29 publications

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“…Based on equation ( 5) and according to the considered range of , the corresponding Froude number range is 0 ≤ ≤ 0.6/ . The governing equations are solved using a control-volume finite element solver [11][12][13][14][15][16][17][18] with a second-order temporal accuracy. A mesh resolution study is performed and it is found that a mesh size of × = 121 2 makes the problem independent of mesh size for both approximations in considered range of the and .…”

Section: Resultsmentioning

confidence: 99%

Studying the natural convection problem in a square cavity by a new vorticity-stream-function approach

Mayeli¹,

Tsai²,

Sheard³

2020

Australasian Fluid Mechanics Conference (AFMC)

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In this study, a benchmark natural convection problem is studied under a Gay-Lussac type approximation incorporating centrifugal effects in the context of a new vorticity-streamfunction approach. This approximation differs from the classic Boussinesq approximation in that density variations are considered in the advection term as well as the gravity term in the momentum equations. Such a treatment invokes Froude number as a non-Boussinesq parameter deviating results from the classic Boussinesq approximation. Numerical simulations of the natural convection in square cavity are performed up to = 10 6 and = 0.3 at = 0.71 via proposed formulation and results are compared against the conventional Boussinesq approximation in terms of the average and local Nusselt number and entropy generation. Comparing results indicate that, up to = 10 5 , mentioned approaches are showing almost identical performance, but as the Rayleigh number exceeds 10 5 , formed thermal boundary layer under Gay-Lussac type approximation is slightly thicker compared to the Boussinesq approximation accompanied by a stronger velocity gradient.

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Section: Resultsmentioning

confidence: 99%

Studying the natural convection problem in a square cavity by a new vorticity-stream-function approach

Mayeli¹,

Tsai²,

Sheard³

2020

Australasian Fluid Mechanics Conference (AFMC)

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“…They found that for higher values of Pr , total entropy generation for a wavy channel is smaller than the plane channel. The entropy generation for Al 2 O 3 -water nanofluid MHD flow through the sinusoidal wavy channel, as well as wavy ribbed channel in the laminar regime as analyzed by Mayeli et al (2017Mayeli et al ( , 2018 and found that the increase in volume fraction and Ha enhances the total entropy generation.…”

Section: Hff 314mentioning

confidence: 99%

“…They found that for smaller values of pressure gradient, the increase in f and Ha increases the average Nusselt number. Mayeli et al (2017) investigated the effects of magnetic field on the heat transfer for Al 2 O 3 -water nanofluid flow in a wavy channel in the laminar regime and found 41% increase in average Nusselt number when Hartman number increases from 0 to 40 for f = 4%, Reynolds number (Re) = 250 and dimensionless amplitude = 0.2. Mayeli et al (2018) investigated the heat transfer characteristics for the flow of Al 2 O 3 -water nanofluid through a ribbed-wavy channel under the effect of the magnetic field in the laminar regime.…”

Section: Introductionmentioning

confidence: 99%

“…Any heat transfer process occurring in thermal systems always associates with the energy losses commonly expressed in terms of entropy generation (Mayeli et al, 2017;Mayeli et al, 2018). Efforts have been made by the researchers to analyze the entropy generation associated with the heat transfer process and thereby designing efficient thermal systems.…”

Section: Introductionmentioning

confidence: 99%

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Thermo-hydraulic and entropy generation analysis for magnetohydrodynamic pressure driven flow of nanofluid through an asymmetric wavy channel

Mehta

Pati

2020

HFF

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Purpose The purpose of this paper is to analyze the thermal, hydraulic and entropy generation characteristics for the magneto-hydrodynamic (MHD) pressure-driven flow of Al2O3-water nanofluid through an asymmetric wavy channel. Design/methodology/approach Galerkin finite element method is used to solve the governing transport equations numerically within the computational domain using the appropriate boundary conditions. The temperature and flow fields are computed by varying Reynolds number (Re), Hartmann number (Ha) and nano-particle volume fraction (ϕ) in the following range: 10 ≤ Re ≤ 500, 0 ≤ Ha ≤ 75 and 0 ≤ ϕ ≤ 5%. Findings The formation of the recirculation zones in the wavy passages, the size of it and the strength of the vortices formed can be modulated by the application of the magnetic field. The overall heat transfer rate increases with Ha for all ϕ both for a lower and higher regime of Re although the enhancement is more for lower values of Re and nanofluids as compared to base fluid and for intermediate values of Re, the effect of a magnetic field is almost insignificant. The magnetic performance factor (PFmagnetic) decreases with Ha although the rate of decrement varies with Re. The increase ϕ also enhances PFmagnetic especially at lower and higher values of Re. The addition of nano-particle enhances the entropy generation at lower values of the Re, while the opposite effect is seen for higher values of Re. Practical implications The present study has enormous practical relevance for the design of heat exchanger applied for solar collectors, process plants, textile and aerospace applications. Originality/value The combined effects on the heat transfer rate and the associated pressure drop penalty due to the applied magnetic field for the flow of nanofluid through an asymmetric wavy channel have not been reported to date. The effect of the magnetic field on the formation of recirculation zones and hot spot intensity in the asymmetric wavy channel has been examined in detail. The PFmagnetic is investigated first time for the MHD nanofluid flow through a wavy channel.

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“…Convergence criteria is considered as the maximum variation of the velocity and temperature fields over all nodes during two successive iterations less than 10 −7 . Accurate performance of the developed solver has already been validated in References 39‐46, but here it is evaluated by comparing the radial temperature profiles at three different angles including δ = 0 o , 90 o , and 180° vs dimensionless radius (

\overset{true˜}{r} = r - r_{i} / r_{o} - r_{i}

) at Ra = 5 × 10 4 for air with Pr = 0.706. Computed profiles are plotted in Figure 2 and are compared with the results of Kuhen and Goldstein 8 .…”

Section: Description Of the Problemmentioning

confidence: 99%

A centrifugal buoyancy formulation for Boussinesq‐type natural convection flows applied to the annulus cavity problem

Mayeli

Sheard

2020

Numerical Methods in Fluids

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Summary Traditionally, the Boussinesq approximation is adopted for numerical simulation of natural convection phenomena where density variations are supposed negligible except through the gravity term of the momentum equation. In this study, a recently developed formulation based on a Boussinesq approximation is presented in which the density variations are also considered in the advection terms. Extending density‐variations to the advection terms captures centrifugal effects arising from both bulk enclosure rotation and within individual vortices, and thus more accurate results are expected. In this respect, the results of the proposed formulation are compared against the conventional Boussinesq simulations and weakly compressible approximation in the concentric horizontal annulus cavity. A new relation is established which maps the magnitude of the non‐Boussinesq parameter of incompressible flow to the corresponding relative temperature difference of a compressible flow simulation which is in agreement with the maximum allowed Gay‐Lussac number to avoid unphysical density values. For comparison purposes, variations of different thermo‐fluid parameters including average and local Nusselt number, entropy generation, and skin friction up to Ra = 105 are computed. Results obtained under the proposed approximation agree with the classical Boussinesq approximation up to Ra = 103 for large non‐Boussinesq parameter corresponding to the large relative temperature difference, but at Ra = 105, computed thermo‐fluid parameters via the two approaches are not identical which justifies the inclusion of large Gay‐Lussac number for convection dominated regime in natural convection problems.

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Numerical investigation of the MHD forced convection and entropy generation in a straight duct with sinusoidal walls containing water–Al₂O₃ nanofluid

Cited by 25 publications

References 29 publications

Studying the natural convection problem in a square cavity by a new vorticity-stream-function approach

Studying the natural convection problem in a square cavity by a new vorticity-stream-function approach

Thermo-hydraulic and entropy generation analysis for magnetohydrodynamic pressure driven flow of nanofluid through an asymmetric wavy channel

A centrifugal buoyancy formulation for Boussinesq‐type natural convection flows applied to the annulus cavity problem

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Numerical investigation of the MHD forced convection and entropy generation in a straight duct with sinusoidal walls containing water–Al2O3 nanofluid

Cited by 25 publications

References 29 publications

Studying the natural convection problem in a square cavity by a new vorticity-stream-function approach

Studying the natural convection problem in a square cavity by a new vorticity-stream-function approach

Thermo-hydraulic and entropy generation analysis for magnetohydrodynamic pressure driven flow of nanofluid through an asymmetric wavy channel

A centrifugal buoyancy formulation for Boussinesq‐type natural convection flows applied to the annulus cavity problem

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Numerical investigation of the MHD forced convection and entropy generation in a straight duct with sinusoidal walls containing water–Al₂O₃ nanofluid