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Technical Brief

Effect of Magnetic Field on Natural Convection and Entropy Generation in Al2O3/Water Nanofluid-Filled Enclosure With Twin Protruding Heat Sources

[+] Author and Article Information
Prasanth Anand Kumar Lam

Fluid Mechanics Laboratory,
Department of Applied Mechanics,
Indian Institute of Technology Madras,
Chennai 600036, India
e-mail: prasanth62@gmail.com

K. Arul Prakash

Fluid Mechanics Laboratory,
Department of Applied Mechanics,
Indian Institute of Technology Madras,
Chennai 600036, India
e-mail: arulk@iitm.ac.in

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received November 4, 2015; final manuscript received November 16, 2016; published online February 28, 2017. Assoc. Editor: Ranganathan Kumar.

J. Thermal Sci. Eng. Appl 9(2), 024502 (Feb 28, 2017) (12 pages) Paper No: TSEA-15-1313; doi: 10.1115/1.4035810 History: Received November 04, 2015; Revised November 16, 2016

Abstract

In this paper, the effect of magnetic field on natural convection of Al2O3/water nanofluid in an enclosure containing twin protruding heat sources placed on top and bottom walls arranged in-line and staggered manner is presented. For this purpose, coupled equations governing fluid flow and heat transfer are solved in Cartesian framework using streamline upwind/Petrov–Galerkin (SUPG) finite element method. Numerical computations are performed to predict the fluid flow, heat transfer, and entropy generation for a wide range of Hartmann number (0.0 $≤$ Ha $≤$ 100.0), Rayleigh number ($103≤Ra≤106$), and nanoparticle volume fraction ($0.0≤ϕ≤0.1$). The simulated results indicate that, for both in-line and staggered arrangement, the entropy generation due to heat transfer is significant along isothermal surfaces, whereas entropy generation due to fluid friction is higher at no-slip walls and along the regions of contact between adjacent recirculation cells. For both in-line and staggered arrangement, increase in global total entropy generation and average Nusselt number along top and bottom heat sources is obtained with decreasing Ha and increasing Ra. Furthermore, for both in-line and staggered arrangement, variation in global total entropy generation and average Nusselt number along top and bottom heat sources with increasing nanoparticle volume fraction, depend on both Ha and Ra.

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Figures

Fig. 1

Computational domain with boundary conditions (solid line: in-line arrangement, dashed line: staggered arrangement)

Fig. 2

Comparison of (a) streamlines, (b) isotherms, (c) v-velocity along vertical midplane, (d) temperature along vertical midplane, (e) local Nusselt number, and (f) average Nusselt number along hot vertical wall for a square enclosure with Al2O3/water nanofluid with Ghasemi et al. [13]

Fig. 3

Effect of Ha on (a) streamlines and (b) isotherms during natural convection of Al2O3/water nanofluid filled enclosure with built in heat sources on top and bottom walls placed in (i) in-line and (ii) staggered arrangement

Fig. 4

Effect of Ha on entropy generation contours due to (a) heat transfer irreversibility (Sθ) and (b) fluid friction irreversibility (Sψ) during natural convection of Al2O3/water nanofluid-filled enclosure with built-in heat sources placed in (i) in-line and (ii) staggered arrangement

Fig. 5

Effect of Ha on local Nusselt number distribution along the periphery of the heat sources at Ra = 105 and ϕ  = 0.03 in Al2O3/water nanofluid filled enclosure with built-in heat sources placed in (i) in-line and (ii) staggered arrangement

Fig. 6

Variation of surface-averaged Nusselt number ratio for: (a) bottom heat source (NuB¯*) and (b) top heat source (NuT¯*) and global entropy generation ratio due to (c) heat transfer (Sθ¯*) and (d) fluid friction (Sψ¯*) with Hartmann number and Rayleigh number at ϕ  = 0.0 in Al2O3/water nanofluid-filled enclosure with built in heat sources placed both in (i) in-line and (ii) staggered arrangement

Fig. 7

Variation of surface-averaged Nusselt number ratio with nanoparticle volume fraction and Hartmann number at different values of Rayleigh number (Ra = 104, 105 and 106) for both (a) bottom heat source (NuB¯**) and (b) top heat source (NuT¯**) in Al2O3/water nanofluid-filled enclosure with built in heat sources placed both in (i) in-line and (ii) staggered arrangement

Fig. 8

Variation of global entropy generation ratio for (a) heat transfer (Sθ¯**) and (b) fluid friction (Sψ¯**) with nanoparticle volume fraction and Hartmann number at different values of Rayleigh number (Ra = 104, 105, and 106) in Al2O3/water nanofluid-filled enclosure with built in heat sources placed both in (i) in-line and (ii) staggered arrangement

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