Browsing by Author "Sheu, Wen-Jenn"

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Airside performance of sinusoidal wavy fin-and-tube heat exchangers subject to large-diameter tubes with round or oval configuration
(2020-01-05)
Chu, Wen-Xiao
;
Sheu, Wen-Jenn
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Hsu, Chen-Chieh
;
Wang, Chi-Chuan
;
機械工程學系
A comparative study regarding airside performance of sinusoidal wavy fin-and-tube heat exchangers (FTHXs) having round and oval tube configurations is experimentally investigated and numerically verified. The computational fluid dynamics (CFD) method is also adopted to analyze detailed local heat transfer performance. The diameter of round tube is 16.3 mm while the oval tube contains diameters of 21.0 mm (major) and 10.6 mm (minor) subject to tube rows of 2-6. Results show that the FTHXs having round configuration performs higher pressure drop when the fin pitch (F-p) is 3.0 mm, however, the oval configuration conversely shows higher pressure drop with the F-p of 1.8 mm. Meanwhile, the effect of F-p on the heat transfer performance is rather small for round configuration with the tube row of 2 and 4. When the tube row increasing to 6, the heat transfer coefficient can be improved by about 10-20% and 9.3-25.2% for FTHXs with round and oval configurations, respectively, by increasing the fin pitch from 1.8 mm to 3.0 mm. The existing experimental correlations for wavy FTHX having round configuration fail to predict the present experimental data due to different ranges of fin pitch, tube pitch and tube diameter. The overall performance of twelve tested samples are also compared using JF ratio factor.
Performance of piezoelectric fins for heat dissipation
(2015-07-01)
Sheu, Wen-Jenn
;
Chen, Guan-Jie
;
Wang, Chi-Chuan
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機械工程學系
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Department of Mechanical Engineering
In this study, a conceptual design employs the piezoelectric patch to a copper plate to form a so-called piezoelectric fin applicable for heat dissipation. A total of nine piezoelectric fins subject to various bonding and piezoelectric patch are made and tested. A piezoelectric fin array is also fabricated as a substitute of heat sink under natural convection. It is found that the tip displacement and the decay of performance of piezoelectric fin are intimately related to the bonding glues. The bonding glues with a higher Young\'s modulus lead to a larger fin tip displacement. The tip displacement increases with applied voltage and the length of piezoelectric patch and a maximum tip displacement of 10.9 mm is observed for TCE bonding under a 100 V power source. A maximum 64% heat transfer augmentation at a supplied power of 5 W is encountered for the piezoelectric fin array. The corresponding fin displacement in the fin array is suppressed owing to the resistant interactions amid adjacent piezoelectric fins. The heat transfer augmentation is moderately reduced to about 40% when the supplied power is raised to 15 W. (C) 2015 Elsevier Ltd. All rights reserved.