Browsing by Author "Sheu, Wen-Junn"

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Effect of flow deflector on the flux improvement in direct contact membrane distillation
(2010-04-01)
Liu, Chu-Lien
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Chen, Yu-Feng
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Sheu, Wen-Junn
;
Wang, Chi-Chuan
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機械工程學系
This study experimentally investigated the influence of flow deflector on the performance of direct contact membrane distillation A total of seven modules, including a smooth membrane module and six flow deflector modules were fabricated and tested Effects of the number of flow deflector, deflector height, and the placement of deflectors are examined The smooth module reveals a comparatively abrupt change of water flux when the inlet velocity is around 0.25 m s(-1), and a plateau is seen for the water flux ratio vs. the Reynolds number for modules containing flow deflectors Depending on the arrangement of flow deflectors. the maxima occur at a Reynolds number of 500 for D1 and 650 for the others. The plateau for module having more flow deflectors has shifted toward a lower Reynolds number while the pressure drop ratio does not reveal such a plateau For the same pumping power, the test results show that the water flux for smooth module are smaller than that of all flow deflector modules, and it is applicable to all temperatures. It is also found that modules with more deflectors become more and more competitive at a higher feed temperature but are less effective when the velocity is high (C) 2009 Elsevier B V. All rights reserved.
Effect of oscillatory EHD on the heat transfer performance of a flat plate
(2013-06-01)
Sheu, Wen-Junn
;
Hsiao, Jen-Jei
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Wang, Chi-Chuan
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機械工程學系
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Department of Mechanical Engineering
The present study investigates the effect of oscillatory EHD on the heat transfer performance of a flat plate. A needle type electrode with positive polarity is used to generate ionic wind with applied voltage ranging from 4 to 9.5 kV. The wave forms of the input voltage are either steady or stepped and the frequency ranges from 0.5 to 2 Hz with the separation distance between the electrode and the test plate being 5 and 15 mm, respectively. It is found that at the same applied voltage, the heat transfer performance subject to the oscillatory EHD is always inferior to that of the steady EHD for all frequencies. A parabolic dependence of the ionic current with the supplied voltage is seen under steady EHD operation. However, the ionic current vs. supplied voltage shows a rather linear dependence pertaining to the oscillatory EHD. For a smaller separation distance of 5 mm, the heat transfer performance for f = 0.5 Hz is slightly higher than that of f = 2 Hz. However, the trend is reversed when the separation distance is increased to 15 mm. (C) 2013 Elsevier Ltd. All rights reserved.