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simulations of flow and heat transfer in the Sulzer SMX static mixers. Such models can be used to evaluate newer options to efficiently carry out industrial mixing.

Catalytic converters used in the automobile industry are also a special class of tubular reactors. Many of these converters use monolith geometry in which unconverted hydrocarbons from exhaust gases are oxidized. Heat and mass transfer effects (including conjugate heat transfer and radiation) and flow mal-distribution are the crucial design issues. Detailed computational flow models can be used to understand these critical design issues and their influence on performance of the converter. Taylor (1999) developed a comprehensive CFD model to simulate heat and mass transfer in a monolithic catalytic converter. The models can be used to evaluate configurations leading to better heat transfer characteristics and therefore better converter durability at high temperatures. When catalyst does not deactivate rapidly, monolithic reactors may offer an attractive alternative to mechanically agitated slurry reactors, especially for fine chemicals (Cybulski et al., 1999). CFD-based models can make substantial contributions to enhancing selectivity and optimization of monolithic reactors.

Apart from the conventional reactor types discussed so far, there are several special reactor types such as membrane reactors, jet loop reactors, microchannel reactors, furnaces and so on. It is virtually impossible to discuss or to describe these reactor types here. The basic principles discussed in this and previous chapters, however, allow the reactor engineer to identify and to address key design issues with the help of computational flow modeling. There is a growing trend to develop multifunctional reactors and compact reactors (see for example recent articles on process intensification by Green et al., 1999 and Stankiwicz and Moulijn, 2000). For such cases, computational flow modeling will play an even more important role and will be used extensively for reactor engineering. The general approach of developing a hierarchy of modeling tools will allow reactor engineers to extend the range of computational models and to realize faster reactor development. In this book, we have discussed several examples of applying such a methodology for better reactor engineering based on tractable CFD models.

Computational flow models can also prove to be very useful for simulating a variety of reactor accessories, which may also significantly influence overall reactor performance. Reactor accessories may include distributors, instrumentation probes, safety mechanisms (vents), spargers, filters, cyclones and so on. There are several instances where minor problems such as clogging of the filter installed near the outlet nozzle, degradation (and subsequent contamination) at the relatively stagnant region near the instrument probes and so on, have caused unsatisfactory reactor performance. Computational flow models provide invaluable help to identify these problems, to identify the desired flow field and to evaluate various ways to realize the desired flow field in practice. Applications of CFD models to simulate various reactor accessories are increasing exponentially. This literature is not reviewed here explicitly, the general approach discussed in this book, however, might be used to carry out such simulations to enhance overall reactor performance.

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