Microchannels patterning

A microchannel reactor for CO preferential oxidation was developed. The reactor was consisted of microchannel patterned stainless steel plates which were coated by R11/AI2O3 catalyst. The reactor completely removed 1% CO contained in the Ha-rich reformed gas and controlled CO outlet concentration less than Ippm at 130 200°C and 50,000h. However, CH4 was produced from 180"C and CO selectivity was about 50%. For high performance of present PrOx reactor, reaction temperature should be carefully and uniformly controlled to reach high CO conversion and selectivity, and low CH4 production. It seems that the present microchaimel reactor is promising as a CO removal reactor for PEMFC systems. 

The very first flow focusing device was developed by Stone and coworkers [11] and was used for the emulsification of water in silicone oil. The geometry of this device is depicted in Figure 18.7 and was obtained after replication of a positive relief of the microchannels patterned in SU-8 photoresist. The authors named this FFD a microfluidic flow focusing device (MFFD). A few years after the development of this microsystem, Kumacheva and coworkers [12] used an MFFD (Figure 18.7, top left) made out of PDMS or polyurethane (PU) for the emulsification and polymerization of several multifunctional acrylates ethylene glycol dimethacrylate (EGDMA),... 

Besides standard designs special GDC designs have been developed for registration of charge patterns upon the electrostatic paper with thermoplastic potential layers with an input semiconductor target, with a microchannel plate at the input and so on. The GDC design provided the basis for series production of GDC with maximum dimensions (500 x 600 mm ) and a service life above 5000 hours. 

Hetsroni G, Mosyak A, Pogrebnyak E, Yarin LP (2005c) Heat transfer in micro-channels comparison of experiments with theory and numerical results. Int J Heat Mass Transfer 48 5580-5601 Hetsroni G, Mosyak A, Segal Z, Pogrebnyak E (2003b) Two-phase flow patterns in parallel microchannels. Int J Multiphase Flow 29 341-360... 

Two-phase flow in parallel micro-channels, feeding from a common manifold shows that different flow patterns occur simultaneously in different microchannels. The probability of appearance of different flow patterns should be taken into account for developing flow pattern maps. 

Galbiati L, Andreini P (1992) Elow patterns transition for vertical downward two-phase flow in capUlary tubes. Inlet mixing effects. Int Comm Heat Mass Transfer 19 791-799 Garimella S, Sobhan C (2003) Transport in microchannels - a critical review. Ann Rev Heat Transfer 13 1-50... 

Taitel Y, Bamea D, Dukler AE (1980) Modeling flow pattern transitions for steady upward gas-liquid flow in vertical tubes. AlChE J 26 345-354 Triplett KA, Ghiaasiaan SM, Adbel-Khalik SI, Sadowski DL (1999a) Gas-liquid two-phase flow in microchannels. Part 1 two-phase flow patterns. Int J Multiphase Flow 25 377-394 Triplett KA, Ghiaasiaan SM, Abdel-Khalik SI, LeMouel A, McCord BN (1999b) Gas-liquid two-phase flow in microchannels. Part 11 void fraction and pressure drop. Int J Multiphase Flow 25 395 10... 

Zhao TS, Bi QC (2001a) Co-current air-water two-phase flow patterns in vertical triangular microchannels. Int J Multiphase Flow 27 765-782... 

Hetsroni G, Mosyak A, Segal Z, Pogrebnyak E (2003) Two-phase flow pattern in parallel microchannels. Int J Multiphase Flow 29 344-360... 

We prepared microchannel reactor employing stainless steel sheet 400tan thick patterned microchannel by a wet chemical etching. The microchannel shape and dimension were decided by computer simulation of flow distribution and pressure drop of the reactants in the microchaimel sheet. Two different types of patterned plates with mirror image were prepared [5]. The plate has 21 straight microchannels which are 550/an wide, 230/an deep and 34mi long as revealed in Fig. 1(b). 

Handique K, Burke DT, Mastrangelo CH, Burns MA (2000) Nanoliter liquid metering in microchannels using hydrophobic patterns. Anal Chem 72 4100-4109... 

Aravamudhan, Rahman, and Bhansali. [70] developed a micro direct ethanol fuel cell with silicon diffusion layers. Each silicon substrate had a number of straight micropores or holes that were formed using microelec-tromechanical system (MEMS) fabrication techniques. The pores acted both as microcapillaries/wicking structures and as built-in fuel reservoirs. The capillary action of the microperforations pumps the fuel toward the reaction sites located at the CL. Again, the size and pattern of these perforations could be modified depending on the desired properties or parameters. Lee and Chuang [71] also used a silicon substrate and machined microperforations and microchannels on it in order to use it as the cathode diffusion layer and FF channel plate in a micro-PEMFC. 

Choi MC et al (2004) Ordered patterns of liquid crystal toroidal defects by microchannel confinement. Proc Natl Acad Sci USA 101(50) 17340-17344... 

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