Technical Briefs

Heat-Transfer Enhancement by Chaotic Advection in the Eccentric Helical Annular Flow

[+] Author and Article Information
José P. Mota, António J. Rodrigo

Requimte∕CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia,  Universidade Nova de Lisboa, 2829-516 Caparica, Portugal

Estéban Saatdjian

 LEMTA, 2 Avenue de la Forêt de Haye, BP 160, 54504 Vandœuvre Cédex, France

J. Heat Transfer 130(2), 024501 (Feb 04, 2008) (5 pages) doi:10.1115/1.2787023 History: Received July 06, 2006; Revised May 02, 2007; Published February 04, 2008

Chaotic advection in the eccentric helical annular heat exchanger is investigated as a means to enhance its thermal efficiency. Chaotic streak lines are generated by steadily rotating one boundary while the other is counter-rotated with a time-periodic angular velocity. The effects of the eccentricity ratio and modulation frequency on the heat-transfer rate are analyzed by numerically solving the 3D convection-diffusion equation for a broad range of parameter values. For the frequency range over which chaotic advection can be effectively promoted, the efficiency of the heat exchanger is enhanced over that obtained for steady boundary rotation. Other tools, such as stretching field calculations and streak-line plots, applicable for dissipative dynamical systems, are implemented. These tools qualitatively confirm the quantitative heat-transfer results obtained.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Sketch of (a) the eccentric helical annular heat exchanger and (b) its cross-sectional geometry

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Figure 2

Axial σ profile as a function of ϵ for steady boundary rotation

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Figure 3

Exit value of σ¯∞(z) as a function of NP and ϵ. Other parameters are R2∕R1=2, Ω¯1∕Ω2=−2, and NT=30.

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Figure 4

Minimum value of σ¯∞(z) at the optimal NP value as a function of ϵ. Other parameters are the same as those in Fig. 3.

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Figure 5

Logarithm of exit stretching distribution for the optimal NP value as a function of ϵ. Other parameters are the same as those in Fig. 3.

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Figure 6

Probability density function, H(logλ), at the optimal NP value for different values of ϵ. The plot is a close-up image of the low-stretching region. Other parameters are the same as those in Fig. 3.

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Figure 7

Streak lines generated for three different values of NP. The operating parameters are ϵ=0.4, R2∕R1=2, Ω¯1∕Ω2=−2, and NT=30; the NP values are, from top to bottom, 0, 16, and 64.




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