Browsing by Author "Chen, Yu-Feng"

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Effect of flow deflector on the flux improvement in direct contact membrane distillation
(2010-04-01)
Liu, Chu-Lien
;
Chen, Yu-Feng
;
Sheu, Wen-Junn
;
Wang, Chi-Chuan
;
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.
Surface modification of nano-porous anodic alumina membranes and its use in electroosmotic flow
(2010-03-04)
Chen, Yu-Feng
;
Hu, Yi-Hsin
;
Chou, Yen-I
;
Lai, Shih-Ming
;
Wang, Chi-Chuan
This study examines the surface-modification effects of porous anodic alumina membranes (PAAMs) on the performance of electroosmotic (EO) pumping. The modifications include using H(2)O(2)-pretreated, and followed by 3-aminopropyltriethoxysilane (APS) or 3-mercaptopropyl trimethoxysilane (MPTS) sol-gel solutions to functionalize the surface of PAAM for achieving higher surface charge density. The surface-modified membranes are analyzed by average pore size, contact angle, and FTIR measurements. The results show that APS and MPTS are successfully coated on the surface of PAAMs. The characteristics (e.g., total current, maximum pressure, and normalized flow rate) of the EO pumps with these surfacemodified PAAMs are investigated. The comparison results of total current at zero time confirmed that the surface charge density of the surface-modified PAAM has been increased. Consequently, the maximum normalized flow rate of EO pump with the APS- and MPTS-coated PAAM are higher than that with the bare PAAM in DI water but without buffer control methods. The convection current of EO flow is also investigated, and the results show that its contribution to total current is around 11% and thus cannot be ignored for EO flow with nano-size channels. (C) 2009 Elsevier B.V. All rights reserved.
Water permeation analysis on gas diffusion layers of proton exchange membrane fuel cells for Teflon-coating annotation
(2010-01-15)
Chou, Yen-I
;
Siao, Zih-Yuan
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Chen, Yu-Feng
;
Sung, Lung-Yu
;
Yang, Wen-Mei
This study presents an analysis of water permeation of a polytetrafluoroethylene (PTFE)-coated gas diffusion layer (GDL) to determine the influence of hydrophobic treatment on the GDL for diagnosis of water flooding. It is found that the behaviour of water drainage is controlled by the pore configuration instead of the hydrophobicity in GDL. Better water drainage is achieved by the action of the Teflon coating in modulating the GDL pore configuration to give both a larger average pore size and a wider distribution of pore size. The results show that water penetration through the GDL must overcome a threshold surface tension defined by the largest pore range. A 30 wt.% PTFE coating of a GDL is shown to generate a satisfactory pore configuration, explaining the improved cell polarization performance with a lower driven pressure (similar to 1.91 kPa) and a higher rate of water drainage. (C) 2009 Elsevier B. V. All rights reserved.