Microstructured heat-exchanger

FIGURE 1 Photograph (left) and schematic illustration (right) of a microstructured heat exchanger or reactor (Forschungszentrum Karlsruhe [25]). Channel dimensions length, L — 14 mm, width, b = 100 pm, height, e — 78 pm. (Adapted with permission from Elsevier.)... 

If fast pre-heating is required, larger heats are released, or if quenching of the hot reaction fluid is needed (or for any other more demanding heat-transfer task), cross- or counter-flow microstructured heat exchangers may be the appropriate solution (Fig. 6.11). They typically have a stacked plate-type design, similar to conventional analogues. 

Fig. 6.13 Example of a heavy-pilot microstructured heat exchanger integrated 5 kW i reactor-heat exchanger system for selective oxidation to achieve gas purification of H2-rich reformer gas for fuel cells. (Source IMM.)...

On the basis of the experimental results, the authors predicted a reactor performance for MBE production of up to 12000kgm h depending on pressure and temperature even at moderate temperature differences in the microstructured heat exchanger. This corresponds to a PI of two orders of magnitude compared to a standard batch slurry reactor with a typical specific productivity of 125 kgm h ... 

Besides microstructured heat exchanger/reactors constructed in the form of plates as shown in Figure 5.1, shell and tube micro heat exchangers are available. An example is shown in Figure 5.6. The heat transfer within the reactor tubes can be estimated with the asymptotic Nu or with Equation 5.12 for short channels. The outer heat transfer coefficient depends on the flow regime, the arrangement of the tubes, and the presence of baffles [8, 13]. For small-scale systems, capillaries submerged in constant temperature baths are commonly used. In this case, the main heat transfer resistance is mostly located at the outer side of the reactor. 

Figure15.2 (a) Photograph and (b) schematic representation ofa microstructured heat exchanger/reactor (Forschungszentrum Karlsruhe [1]). Channel length L= 14 mm, width W= 100 tm, height H= 78 Xm.

Figure 2.18 Counterflow design microstructured heat exchanger made by microstereolithography.

M. Wichert, R. Zapf, V. Hessel, H. Lowe, Fuel processing in integrated microstructured heat-exchanger reactors. f Power Sources 2007, 171 (1), 198-204. 

Different configurations are used for the screening of catalyst activity in MSRs. As stressed before, the easiest way to incorporate a catalyst is by filling the micro-channels directly with catalyst powder. This allows the use of optimized powder catalysts while still taking the benefit of good heat transfer by coupling it to a microstructured heat exchanger [51]. 

Kolb, G., Schiirer, )., Tiemann, D., Wichert, M., Zapf, R., Hessel, V., and Lowe, H. (2007) Fuel processing in integrated microstructured heat-exchanger reactors. J. Power Sources,... 

The process flow sheet of the microreactor plant is shown in Figure 9.33 [133,134]. Toluene is heated to 40 ° C using a microstructured heat exchanger while, at the same time, liquid sulfur trioxide is vaporized by heating to 60 °C. Nitrogen is added to the sulfur trioxide gas in a micromixer for dilution. This stream is then passed into a... 

Figure 2.2 Schematic illustration of a microstructured heat exchanger/reactor. (Adapted from Ref [4] with permission from Elsevier.)...

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