Micro flow field design

Leo, H.L., He, Z.M., Ellis, J., and Yoganathan, A., Micro flow fields in the hinge region of CarboMedics bileaflet mechanical valve design. / Jhorac Cardiovasc Surg, 2002.124 p. 561-74. 

Also a simulation of the flow field in the methanol-reforming reactor of Figure 2.21 by means of the finite-volume method shows that recirculation zones are formed in the flow distribution chamber (see Figure 2.22). One of the goals of the work focused on the development of a micro reformer was to design the flow manifold in such a way that the volume flows in the different reaction channels are approximately the same [113]. In spite of the recirculation zones found, for the chosen design a flow variation of about 2% between different channels was predicted from the CFD simulations. In the application under study a washcoat cata-... 

Figure 1.114 Schematic of the cyclone mixer design (left) and streamline indicating the rotational flow field in the cyclone micro mixer [109] (by courtesy of Kluwer Academic Publishers).

Behavior of the fluids in the microfabricated channels are different from those in the millimeter scale channels. Miniaturization of micro flow devices opens a new research field, microfluidics which represents the behavior of the fluid in the micro channel [8]. Since the Reynolds number in the micro channel is usually below 200, the flow is laminar and special design concepts are necessary for the fluidic elements of mixers, reaction coils etc. in the pTAS. Some components of flow switches and fluid filters were developed using laminar flow behavior. 

Figure 7-13. Characteristic of PEM micro fuel cells. Design 1 meander anodic flow filed, design 2 parallel rib flow field...

Muller et al (IMTEK) used micro-machined metal foils to form the flow fields of their -FC [54]. Using Gore MEA, they were able to form very thin, high power density stacks. They demonstrated both uncompressed and compressed FC designs. The uncompressed... 

In general, future micro fuel cell design should forego heavy bolts and thick BPs in order to miniaturize the system. The other components, such as the GDL and MEA, are negligible in volume and weight As a result, the material selection for the BPs becomes very important. Thin sheets that are stiff enough to achieve uniform low-contact resistance between MEA, flow field and current collector are needed. The bolts for the stack compression can be replaced by, for example, clamps, straps, or coiling techniques [9]. 

Figure 5.5 Four designs of flow fields for micro DMFCs.

The Tamao-Kumada-Corriu reaction has also been carried out with supported catalytic systems. One interesting recent example has been the use of a multichannel microreactor to perform this reaction [169], The glass micro reactor was designed so as to increase the catalytic surface area and ensure a uniform distribution of the velocity/temperature field. The sol-gel procedure was used to immobilize the nickel catalyst to the channel walls. The Tamao-Kumada-Corriu reaction was conducted using bromobenzene and phenylmagnesium bromide, and was also carried out in the batch configuration for comparison, and it was observed that the reaction in-flow was four orders of magnitude more rapid than that performed under batch conditions and there was a threefold increase in the yield of the biaryl compound. 

Fluid flow is important not only in almost all engineering fields but also in micro- and nanofluidic chips. Flow measurements are required to increase our understanding of the physicochemical mechanisms of processes, improve the designs of the devices, and enhance the corresponding function of the devices. The measurement of the flow velocity is important in fluid mechanics. There are many conventional... 

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