The effect of the baffle length on the natural convection in an enclosure filled with different nanofluids
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The effect of the baffle length on the natural convection in an enclosure filled with different nanofluids Ahmed Kadhim Hussein1 · Mokhtar Ghodbane2 · Zafar Said3 · Rusul Salman Ward4 Received: 29 April 2020 / Accepted: 22 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract This paper presents a numerical investigation of the natural convection in an inclined rectangular enclosure with a baffle filled with Cu/water and then with A l2O3/water nanofluids using the finite difference method for tracking the thermal behavior within it versus the baffle length. The horizontal enclosure walls are assumed to be adiabatic, while the vertical ones are supposed to be a differentially heated. A thin horizontal baffle was attached to its left sidewall and is assumed to be cold. The flow and thermal fields are computed, respectively, for various values of Rayleigh number (103 ≤ Ra ≤ 105), inclination angle (0° ≤ ∅ ≤ 60°), baffle length (0.25 ≤ Lb ≤ 0.5), solid volume fraction (0.02 ≤ 𝜙 ≤ 0.06), and aspect ratio (1 ≤ AR ≤ 2). It was found that as the Rayleigh number, solid volume fraction, baffle length, and aspect ratio increase, an enhancement in the intensity of fluid flow in the enclosure was observed. In comparison, it reduces when the inclination angle increases. Moreover, it was found that the local Nusselt number (Nuc) enhances with the rise in Rayleigh number and the solid volume fraction. In contrast, it reduces with the increase in the aspect ratio and the inclination angle. Keywords Natural convection · Nanofluid · Baffle · Rayleigh number · Heat transfer rate List of symbols A Aspect ratio of the baffle AR Aspect ratio of the enclosure (H/W) Db Dimensionless baffle position db Baffle positionm dp Nanoparticle diameter/Nm g Gravitational acceleration/m s−2 H Height of enclosure/m −2 −1 h Convection heat transfer coefficient/W m ( ) K knf Keff Effective thermal conductivity ratio k f
kr Thermal conductivity ratio of the baffle Lb Dimensionless baffle length
* Ahmed Kadhim Hussein [email protected] * Zafar Said [email protected] 1
College of Engineering, Mechanical Engineering Department, University of Babylon, Babylon City, Hilla, Iraq
2
Department of Mechanical Engineering, Faculty of Technology, Saad Dahlab University of Blida 1, 09000 Blida, Algeria
3
Sustainable and Renewable Energy Engineering Department, University of Sharjah, PO Box 27272, Sharjah, UAE
4
Ministry of Electricity, Hilla, Iraq
lb Baffle length/m Np Partition number Nu Local Nusselt number ( ) 2 P Dimensionless pressure 𝜌pH𝛼2 nf f
p Pressure/Pa Pr Prandtl number qw Heat flux per unit(area/W m−2) g𝛽f H 3 (Th −Tc ) Ra Rayleigh number 𝜐2 f
rp Nanoparticles radius/Nm T Temperature/°K U Velocity component in X-direction (dimensionless) u Velocity component in X-direction (dimensionless)/m s−1 V Velocity component in Y-direction (dimensionless) v Velocity component in the Y-direction (dimensionless)/m s−1 W Width of the enclosure/m w Partition thickness/m X Non-dimensional c
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