Surface channelling

In an od-wet rock, water resides in the larger pores, oil exists in the smaller pores or as a film on flow channel surfaces. Injected water preferentially flows through the larger pores and only slowly invades the smaller flow channels resulting in a higher produced water oil ratio and a lower oil production rate than in the water-wet case. 

For turbulent flow, Rmjpit is almost independent of velocity although it is a function of the surface roughness of the channel. Thus the resistance force is proportional to the square of the velocity. Rm/pu2 is found experimentally to be proportional to the one-third power of the relative roughness of the channel surface and may be conveniently written as ... 

Using the properties of water Li and Cheng (2004) computed from the classical kinetics of nucleation the homogeneous nucleation temperature and the critical nu-cleation radius ra. The values are 7s,b = 303.7 °C and r nt = 3.5 nm. However, the nucleation temperatures of water in heat transfer experiments in micro-channels carried out by Qu and Mudawar (2002), and Hetsroni et al. (2002b, 2003, 2005) were considerably less that the homogeneous nucleation temperature of 7s,b = 303.7 °C. The nucleation temperature of a liquid may be considerably decreased because of the following effects dissolved gas in liquid, existence of corners in a micro-channel, surface roughness. 

In order to verify that the fixed bed and the micro-channel reactor are equivalent concerning chemical conversion, an irreversible first-order reaction A —) B with kinetic constant was considered. For simplicity, the reaction was assumed to occur at the channel surface or at the surface of the catalyst pellets, respectively. Diffusive mass transfer to the surface of the catalyst pellets was described by a correlation given by Villermaux [115]. 

Figure 2.69 Structure of a porous micro channel surface (left) and schematic diagram of the flow scheme and pore arrangement (right).

Total micro-channel surface area 6.24 10- m Tube connectors inner diameter length 6 mm 40 mm... 

Catalysts can be incorporated by the various known methods. So far, sputtered platinum was used. Such films are dense so that the catalyst surface area equals the channel surface. 

Micro channel surface area 51.2 mm Typical volume flow Re number pressure drop 6 ml h0.2 1.1 bar... 

Morey et al. (25) synthesized Ti-SBA-15 with uniform tubular channels (surface area = 600-900 m2/g, pore volume = 0.6-1.3 cm3/g, average pore diameter = 6.9 nm) by direct and postsynthesis methods by using triblock copolymers, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) in... 

For example, due to the inevitable friction and impact of the channel surface to fluid flows, particularly at the bending part of the flow channels, how to reduce fluid flow rate changes or fluid pressure drop from inlet to outlet has to be considered in the fluid field design. One key part of the flow field... 

J. Homola, H. B. Lu, and S. S. Yee, "Dual-Channel Surface Plasmon Resonance Sensor with Spectral Discrimination of Sensing Channels Using a Dielectric Overlayer,"... 

The visualization study of Yang et al. further revealed the profound effects of wetting properties of gas channel walls. In a gas channel surrounded by mixed hydrophilic channel surfaces and hydro-phobic GDL surface, it was found that water conden-... 

The site-fraction constraint (Eq. 16.64) means that all the s in Eq. 16.63 are not independent. Therefore only Ks — 1 of Eq. 16.63 are solved. Solving the plug-flow problem requires satisfying the algebraic constraints represented by Eqs. 16.63 and 16.64 at every point along the channel surface. The coupled problem is posed naturally as a system of differential-algebraic equations. 

The sulphuric acid may be added to the solution before evaporation and in this case the evaporation on the water-bath should be continued until a semi-solid brown mass with a channelled surface is obtained. This is heated on the sand-bath or over a flame until the charcoal becomes detached from the walls of the dish and is then incinerated as above. 

The state of the channel surface is very important in order to obtain a good performance of the microchips. This depends on the chip material and pretreatment, mainly. Hence, prior to using the microchip, channels have to be pretreated adequately, which is needed in order to clean the channels and obtain an appropriate electroosmotic flow (EOF) [159]. It can also be useful for performing a chemical cleaning of the working electrode. 

Slentz et al. [133] described the effects of geometry (size, shape, and dimensions) on the performance of COMOSS. Vreeland and Barron [134] described the design of functional materials for genomic and proteomic analyses in NCE. The authors discussed different polymer chemistries for micro-channel surface passivation and improved DNA separation. 

From the function of a channeltron/channelplate detector it is obvious that high gains are desirable. However, ion feedback and space charge effects limit the gain with increasing charge of the electron avalanche, electron impact ionization with molecules of the residual gas or molecules desorbed under electron bombardment from the channel surface occurs more frequently. The ions produced are then accelerated towards the channel input. If such an ion hits the surface at the channel entrance, it may release an electron which again can start an avalanche of practically the same size, i.e., it causes after-pulses. 

The evaporator was fed a mixture of methanol and water and operated at a temperature of 120 °C. Prior to coating the channels with a commercial CuO/ZnO/ ai2o3 catalyst (Synetix 33-5 from ICI), an alumina sol was coated as interface to the channel surface. The catalyst was reduced in 10% hydrogen in nitrogen at 280 °C prior to exposing it to the reaction mixture. Methanol conversion increased at S/C 1.1 from 55 to 90% on increasing the reaction temperature from 200 to 260 °C at 6 Ncm3 h 1 liquid feed flow rate. 

The micro channel structure of the device is fabricated in a glass wafer by common procedures (Figure 4.14). To allow sealing of the channels, the whole surface is coated with CYTOP, a Teflon -like polymer. On the one hand it forms a bondable layer and on the other it makes the micro channel surface strongly hydrophopic. Bonding with a CYTOP-coated cover glass plate occurs under moderate pressure at 180 °C. Because sometimes the CYTOP layer peels off and disturbs the fluid flow behavior, the whole device is fabricated in polydimethylsiloxane (PDMS) [71]. 

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