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Главная Архив Thermal Letter Оргкомитет Будущие конференции AIHTC
International Heat Transfer Conference 15

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

The Effect of Inner Surface Roughness and Heating on Friction Factor in Horizontal Mini-tubes

Lap Mou Tam
Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macau, China; Institute for the Development and Quality, Macau SAR, China

Hou Kuan Tam
Faculty of Science and Technology, University of Macau, Macau, China.

Afshin J. Ghajar
School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078, USA

Wa San Ng
Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau

Choi Keng Wu
Department of Electromechanical Engineering, Faculty of Science and Technology, University of Macau

DOI: 10.1615/IHTC15.nmm.008732
pages 5483-5495


Ключевые слова: Nano/Micro scale measurement and simulation, Convection, friction factor, inner surface roughness, micro-tube

Аннотация

According to the recent literature survey, it was concluded that the friction factor in mini- and micro-tubes could be predicted accurately by using macro-scale theory. However, certain issues should be further investigated. They are: (a) the effect of inner surface roughness and (b) the effect of mini- and micro-tube diameters on the start and end of the transition region. Moreover, only a few studies investigated the effect of heating on friction factor in mini- and micro-tubes, especially, in the transition region. Therefore, an experimental setup was built in this study to measure the pressure drop for the horizontal mini- and micro-tubes under the isothermal and uniform wall heat flux boundary conditions. Distilled water was used as the test fluid. Seven stainless steel minitubes (2000?m to 508?m in inner diameters) with various surface roughness values (1.94?m to 5.30?m) were used as the test section. The experimental results clearly showed the effect of heating and roughness on friction factors in the laminar, transition, and turbulent regions. For the friction factors under isothermal condition, the mini-tubes had a narrower transition range due to the roughness when compared to the macro-tubes. For the friction factor under heating condition, the laminar data and the start of transition were different from the isothermal case. Under heating condition, the narrower transition range due to the roughness was also observed in the mini-tubes. However, the effect of heating was not seen on the end of transition and in the turbulent region.

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