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Research Papers

A Porous Media Approach for Bifurcating Flow and Mass Transfer in a Human Lung

[+] Author and Article Information
Fujio Kuwahara, Yoshihiko Sano

Department of Mechanical Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561, Japan

Jianjun Liu

Department of Civil Engineering, Wuhan Polytechnic University, Hubei, Wuhan 430023, China

Akira Nakayama

Department of Mechanical Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561, Japan; Department of Civil Engineering, Wuhan Polytechnic University, Hubei, Wuhan 430023, China

J. Heat Transfer 131(10), 101013 (Jul 31, 2009) (5 pages) doi:10.1115/1.3180699 History: Received September 29, 2008; Revised March 26, 2009; Published July 31, 2009

A porous media approach was proposed to investigate the characteristics of the bifurcating airflow and mass transfer within a lung. The theory of porous media was introduced in order to deal with a large number of bifurcations and a vast scale difference resulting from bifurcations. Upon introducing a two-medium treatment for the air convection and the diffusion in its surrounding wall tissue, the oxygen mass transfer between the inhaling air and the tissue was considered along with the effects of the blood perfusion on the mass transfer within the tissue. The overall mass transfer resistance between the inlet of the trachea and the blood in the capillaries was obtained on the basis of the porous media approach. The analysis reveals that there exists the optimal number of the bifurcation levels, namely, 23, that yields the minimum overall mass transfer resistance for the mass transport from the external air to the red blood cells. The finding is consistent with Bejan’s constructal law, namely, that for a flow system to persist in time, it must evolve in such a way that it provides easier access to its currents.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Fluid tree in the respiratory system

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Figure 2

One-dimensional mass transfer model

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Figure 3

Airway and its surrounding tissue

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Figure 4

Overall mass transfer resistance as a function of the number of bifurcations

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