Browsing by Author "Chang, Wen-Jeng"

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Airside performance of fin-and-tube heat exchangers in dehumidifying conditions - Data with larger diameter
(2010-03-01)
Liu, Young-Chang
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Wongwises, Somchai
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Chang, Wen-Jeng
;
Wang, Chi-Chuan
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機械工程學系
This study presents the airside performance of the fin-and-tube heat exchangers having plain fin geometry with a larger diameter tube (D(c) = 15.88 mm) under dehumidifying condition. A total of nine samples of heat exchangers subject to change of the number of tube row and fin pitch are made and tested. It is found that the effect of fin pitch on the sensible j factor is, in general, diminished with the rise of tube row. However, there is a unique characteristic of fin pitch at a shallow tube row, the heat transfer performance is first increased at a wider pitch but a further increase of fin pitch lead to a falloff of heat transfer performance due to interactions amid flow development and bypass flow. The influence of tube row on the airside performance is rather small for both heat transfer and frictional characteristics at a fin pitch of 2.1 mm and when the Reynolds number is less than 4000. A slight deviation of this effect is encountered when fin pitch is increased to 2.54 mm or 3.1 mm due to condensate adhered phenomena. (C) 2009 Elsevier Ltd. All rights reserved.
Effect of inclination on the convective boiling performance of a microchannel heat sink using HFE-7100
(2012-01-01)
Wang, Chi-Chuan
;
Chang, Wen-Jeng
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Dai, Chia-Hsing
;
Lin, Yur-Tsai
;
Yang, Kai-Shing
The effect of inclination on the convective boiling heat transfer characteristics of the dielectric fluid HFE-7100 within a multiport microchannel heat sink having a hydraulic diameter of 825 pm is studied. The inclinations spans from -90 degrees (vertical downward) to 90 degrees (vertical upward), and a flow visualization is also conducted in this study. It is found that the heat transfer coefficient for the vertical upward and horizontal is comparable, and the heat transfer coefficient for 45 degrees upward considerably exceeds other configurations. On the other hand, the enhancement of heat transfer coefficient under inclined arrangement is reduced with the rise of mass flux. The results also indicate that downward arrangements always impair the heat transfer performance, and more than 50% deterioration of heat transfer coefficient is encountered for G = 100 kg m(-2) s(-1) relative to that of 45 degrees arrangement. The flow visualization confirms that the heat transfer augmentation for upward inclination is due to the rise of slug velocity. (C) 2011 Elsevier Inc. All rights reserved.