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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

A Numerical and Experimental Study on Flow and Heat Transfer Characteristics of Viscoelastic Fluid in a Serpentine Channel

Kazuya Tatsumi
Department of Mechanical Engineering and Science, Graduate School of Engineering Kyoto University, Kyotodaigaku-katsura, Nishikyo-ku, Kyoto 615-8540, Japan; Advanced Research Institute of Fluid Science and Engineering, Kyoto University

Wataru Nagasaka
Kyoto University

Takuya Matsuo
Kyoto University

Kazuyoshi Nakabe
Department of Mechanical Engineering and Science, Kyoto University; Advanced Research Institute of Fluid Science and Engineering, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan

DOI: 10.1615/IHTC15.hte.009615
pages 3895-3909


KEY WORDS: Convection, Heat transfer enhancement, Viscoelastic fluid flow, serpentine channels, low Reynolds number flow

Abstract

Measurements of heat transfer coefficient and pressure loss penalty, and PIV measurements were carried out for viscoelastic fluid in a serpentine channel. Numerical simulation was carried out together to investigate the flow and heat transfer characteristics. Water solutions of polyacrylamide (PAAm) were used as viscoelastic fluids. The PIV measurements showed that in the viscoelastic fluid case, unsteady flows and longitudinal-vortex-like secondary flows were generated in the serpentine channel even under the low Reynolds number conditions smaller than 2.0. As the Re and Weissenberg number Wi increased, the magnitude of the secondary flow and the flow fluctuation increased. This led to a effective heat transfer enhancement compared with the Newtonian fluid case. Further, the influences of the fluid rheological properties on the heat transfer and pressure loss characteristics were evaluated by changing the sucrose concentration of the viscoelastic fluids. The results showed that a good correlation can be observed with the mean Nusselt number and the Wi rather than the Re. This was attributed to the fact that heat transfer enhancement was mainly due to the secondary flow generated by the normal stress differences, the magnitude of which can be represented by Wi. The computation showed that a normal stress was produced in the area particularly adjacent to the top and bottom walls, and that this would accompany the generation of a pair of vortices. Effective heat transfer was observed at the channel sidewall particularly at the inner sidewall near the inflection point of the serpentine channel.

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