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Forced Convection

Effect of Uncertainties in Physical Properties on Entropy Generation Between Two Rotating Cylinders With Nanofluids

[+] Author and Article Information
Omid Mahian1

Shohel Mahmud

School of Engineering, University of Guelph, Guelph, ON, N1G 2W1, Canada

Saeed Zeinali Heris

1

Corresponding author.

J. Heat Transfer 134(10), 101704 (Aug 07, 2012) (9 pages) doi:10.1115/1.4006662 History: Received November 24, 2011; Revised April 17, 2012; Published August 07, 2012; Online August 07, 2012

Abstract

In this paper, the effects of uncertainties in physical properties on predicting entropy generation for a steady laminar flow of Al2 O3 –ethylene glycol nanofluid ($0≤φ≤6 %)$ between two concentric rotating cylinders are investigated. For this purpose, six different models by combining of three relations for thermal conductivity (Bruggeman, Hamilton–Crosser, and Yu–Choi) and two relations for dynamic viscosity (Brinkman and Maiga ) are applied. The governing equations with reasonable assumptions in cylindrical coordinates are simplified and solved to obtain analytical expressions for average entropy generation $(NS)ave$ and average Bejan number $(Be)ave$. The results show that, when the contribution of heat transfer to entropy generation for the base fluid is dominant, a critical radius ratio $(ΠC)$ can be determined at which all six models predict the reduction in entropy generation with increases of volume fraction of nanoparticles. It is also found that, when the contribution of viscous effects to entropy generation is adequately high for the base fluid ($φ=0$), all models predict the increase of entropy generation with increases of particle loading.

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Figures

Figure 6

Variation of average entropy generation for Br=1, BrΩ=35 and Π=2

Figure 5

Effects of different models on average entropy generation and Bejan number for Br=1, BrΩ=30 and Π=2

Figure 4

Effects of the models on the local entropy generation and Bejan number for Br=1, BrΩ=10 and Π=2

Figure 3

Variation of critical radius ratio with the Brinkman number for BrΩ=10

Figure 2

Effects of different models on average entropy generation and Bejan number for Br=1 and BrΩ=10

Figure 1

Geometry of the present problem

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