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强化传热期刊
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ISSN 打印: 1065-5131
ISSN 在线: 1026-5511

强化传热期刊

DOI: 10.1615/JEnhHeatTransf.v11.i4.160
pages 379-390

Numerical Simulation on Heat Transfer Enhancement in Twisted-Tape-Inserted Tubes

Yuki Kazuhisa
Tohoku University
Hashizume Hidetoshi
Dept. of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Aramaki-Aoba 01, Aoba-ku, Sendai, 980-8579, Japan
Toda Saburo
Dept. of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Aramaki-Aoba 01, Aoba-ku, Sendai, 980-8579, Japan
Sato Chikahiro
Tepco Systems, Shinbashi 6-19-15, Minato-ku, Tokyo, 105-0004, Japan

ABSTRACT

To clarify the mechanism of heat transfer enhancement in swirl tubes, especially the effect of secondary flow generated in a pipe cross-section on temperature field mixing, numerical simulation of swirl flow under the laminar condition including a mixed convection region is performed. As the result of the simulation, the generation and development processes of secondary flow are visualized clearly, and it is clarified that these transitional processes depend on a twist ratio of swirl-tape γ and Reynolds (Re) number. Furthermore, these behaviors of secondary flow also greatly contribute to the heat removal performance, and the Nusselt (Nu) number becomes higher, especially if the secondary flow has some instability such as that found in the transition from one to two vortices. Numerical data on the heat transfer performance as well as the flow patterns show good agreement with conventional experimental results. On the other hand, it is shown that the transition process of secondary flow under a high heat flux condition is strongly affected by gravity effect, and its flow pattern and the local Nu number change periodically in a streamwise direction. By summarizing all the numerical data, a new prediction formula for the Nusselt number is constructed in wide Re, Prandtl (Pr), Grashof (Gr), and γ ranges, and it is shown that this formula almost corresponds to the conventional experimental results.


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