Models chemical reactors

Bakker, R. A., Micromixing in chemical reactors models, experiments and simulations , Ph.D. 

Only direct numerical simulation (DNS) resolves all scales (Moin and Mahesh 1998). However, DNS is com-putationally intractable for chemical reactor modeling. 

In general, liquid-phase reactions (Sc > 1) and fast chemistry are beyond the range of DNS. The treatment of inhomogeneous flows (e.g., a chemical reactor) adds further restrictions. Thus, although DNS is a valuable tool for studying fundamentals,4 it is not a useful tool for chemical-reactor modeling. Nonetheless, much can be learned about scalar transport in turbulent flows from DNS. For example, valuable information about the effect of molecular diffusion on the joint scalar PDF can be easily extracted from a DNS simulation and used to validate the micromixing closures needed in other scalar transport models. 

The IEM model is a simple example of an age-based model. Other more complicated models that use the residence time distribution have also been developed by chemical-reaction engineers. For example, two models based on the mixing of fluid particles with different ages are shown in Fig. 5.15. Nevertheless, because it is impossible to map the age of a fluid particle onto a physical location in a general flow, age-based models cannot be used to predict the spatial distribution of the concentration fields inside a chemical reactor. Model validation is thus performed by comparing the predicted outlet concentrations with experimental data. 

In the present paper we study common features of the responses of chemical reactor models to periodic forcing, and we consider accurate methods that can be used in this task. In particular, we describe an algorithm for the numerical computation and stability analysis of invariant tori. We shall consider phenomena that appear in a broad class of forced systems and illustrate them through several chemical reactor models, with emphasis on the forcing of spontaneously oscillating systems. 

Chemical reactor models invariably start from the two-phase theory (12). The interstitial flow is assumed to be in good and continuous contact with solids whilst some by-passing occurs in the bubble phase. There is, however, very little axial or radial mixing of the gas. There may be some exchange between the two phases and Figure 4 depicts this kind of model. 

Chemical reactor modeling will be considered first, followed by kinetic modeling, and then the integration of various elements of chemical reaction engineering into a more useful whole. The status of each area will be briefly reviewed. Then current and future frontiers will be discussed, emphasizing those that provide the most challenge and the greatest potential impact. 

Shinnar, R. Chemical Reactor Modeling—The Desirable and the Achievable, ACS Symposium Series, 72, 1-36 (1978). 

Shirmar, R. Chemical Reactor Modeling for the Purposes of Controller Design," Chem. 

Chemical reaction models play a major role in chemical engineering as tools for process analysis, design, and discovery. This chapter provides an introduction to structures of chemical reaction models and to ways of formulating and investigating them. Each notation in this chapter is defined when introduced. Chapter 3 gives a complementary introduction to chemical reactor models, including their physical and chemical aspects. 

H.A. Jakobsen, Chemical Reactor Modeling, doi 10.1007/978-3-540-68622-4 l, Springer-Verlag Berlin Heidelberg 2008... 

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