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International Heat Transfer Conference 15

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

Enhancement of Heat Transfer Performance by Using Sawtooth Fin Structure in the Multiport Microchannel Flat Tube

DOI: 10.1615/IHTC15.hte.008904
pages 4253-4263

Ji Zhang
Beijing University of Technology

Yanhua Diao
Beijing University of Technology

Yaohua Zhao
Institute of Engineering Thermophysics Chinese Academy of Sciences, Beijing 100080, China; Department of Mechanical Engineering Kyushu Institute of Technology, Kitakyushu, 804-8550 Japan

Yanni Zhang
Beijing University of Technology


KEY WORDS: Heat transfer enhancement, Convection, Transition, Multiport microchannel flat tube, Sawtooth fin structure

Abstract

In this study, the flow and heat transfer characteristics of two multiport microchannel flat tubes (MMFT) which have same boundary dimensions 26 mm × 2.5 mm, but different internal structures were studied. Moreover, the enhancement of heat transfer was compared with the increase of friction factor to assess comprehensively the tube applicability for heat exchanger. For the tube with fin structure, the height of fin is 279 ?m, and the ratio of fin height to hydraulic diameter is 15%. The experiment used water as working fluid is performed with Reynolds number ranging from 140 to 5900. The results show that the experimental data of friction factor and Nusselt number for smooth tube are in reasonable agreement with the conventional correlations. And the laminar-turbulent transition occurs at Re=1700, an accepted value for macrochannel. Meanwhile, laminar-turbulent transition of tube with fin structure occurs at Re=1100, earlier to the value for macrochannels. Compared with smooth tube, the significant heat transfer enhancement by using fin structure tube was obtained, while the friction factor values are also lager than that of smooth tube. The maximum heat transfer enhancement is 481% at Re=5182 with penalty of friction factor increase of 140%. A performance evaluation criterion (PEC) based on same pumping power consumption for tubes with and without fin structure was defined and calculated to evaluate the practical use. The maximum value of PEC is about 4.2, which is a good value compared with that of other researches.

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