Scale microchannel

Four elements of microchannel scale-up models will be described pressure-drop design, heat-transfer design, reactor design, and mechanical and manufacturing designs. 

Fig. 2.9 A POM images of 8CB in PEI coated (Aa) rectangular microchannel, (Ab) V-shaped microchannel, and (Ac) trapezoidal microchannel (scale bar 50 mm) [48]. Schematic illustrations of 8CB textures in three types of microchannels in (Aa-Ac) [48]. The yellow rods represent each 8CB molecules. Reproduced with permission [48]. Copyright 2011, Royal Society of Chemistry. B Optical (first column) and POM images (second and third columns) of LC droplet according to the aspect ratio of confined PDMS in smectic-A phase (Ba), nematic phase (Bb) and isotropic phase (Be) [49]. Reproduced with permission [49]. Copyright 2012, American Physical Society...

Fhght times are extremely short (microseconds) for all of the ions, and therefore the scanning of the total mass spectrum from m/z 1 to about m/z 2000-3000 appears to be instantaneous on a human time scale. The arrival of ions at the finishing point is determined by a time-to-digital (TDC) microchannel plate collector (detector). 

Celata GP, Cumo M, Marcom V, McPhail SJ, Zummo Z (2005) Micro-tube heat transfer scaling effects an experimental validation. In Proceedings of ECI International Conference on Heat Transfer and Fluid Flow in Microchannels, Caste/Vecchio PascoU, Italy, 25-30 September 2005... 

Background on Medium-to Large-Scale Processes in Microchannels... 

Scale-up of microchannel reactors is based on using the optimal channel dimensions rather than seeking the smallest or the largest microchannel. In some cases, the channels may range from 100 pm in hydrauhc diameter to a few millimeters. The classification of a rigorous size range to designate a reactor as microchannel is not necessary. 

Technology developers for medium- to large-scale microchannel technology are listed in Table 11.1. 

Figure 11.1 Scale-up versus numbering up for microchannels. All critical channel dimensions remain constant in a microchannel system independent of the overall process capacity.

The scale-up challenges for microchannel reactors are addressed through integrated mathematical models to describe all elements of the physics. Integrated... 

Numbering up microchannels to large-scale capacity reactors is driven by a rigorous understanding of pressure drop in every parallel circuit Passive flow distribution permits sufficient flow to each channel. No serious evaluation of microvalves or actuators has been undertaken for high-capacity systems with thousands to tens... 

For most medium- and large-scale micromanifold structures, where one passage feeds multiple parallel channels, flow traverses through turbulent and transition flows in the micromanifold region. This fluid in turbulent to transition flow also turns in the micromanifold region as it drops flow into parallel microchannels, which are primarily in the laminar flow regime. 

Heat transfer in laminar single-phase, two-stream microchannels has been well described in the literature [33, 39-41]. The challenge for medium- to large-scale processes is an added complexity if more than two fluids are required and also the micromanifold region. 

Multiple fluid streams in medium- to large-scale processes become important for many oxidation reactions. MicroChannel operation allows safe operation in the explosive regions [42, 43], but this advantage ceases as the dimensions become... 

As described above, microchannel reactor scale-up requires integrated models, which include the reaction chemistry with heat transfer, pressure drop, flow distribution, and manufacturing tolerances. The culmination of scale-up models is their successful demonstration. 

Figure 11.19 Manufacturing scale-up device with submanifolds for passive flow distribution to feed thousands of parallel microchannels. Flow is mapped using ranges to show variations from a normalized value.

Medium- to large-scale microchannel processes offer tremendous economically promising advantages in the chemical and energy process industries, and many such demonstrations are underway. Moving from one charuiel to tens of thousands... 

Tonkovich, A.L., Kuhlmann, D., Rogers, A. et al. (2005) MicroChannel Technology Scale-up to Commercial Capacity. Chemical Engineering Research and Design, 83(A6), 634—639. 

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