The essence of reactor design is the combination of chemical kinetics with transport phenomena. The chemical kineticist, who can be a chemical engineer but by tradition is a physical chemist, is concerned with the interactions between molecules (and sometimes within molecules) in well-defined systems. By well-defined, we mean that all variables that affect the reaction can be controlled at uniform and measurable values. Chemical kinetic studies are usually conducted in small equipment where mixing and heat transfer are excellent and where the goal of having well-defined variables is realistic. Occasionally, the ideal conditions can be retained upon scaleup. Slow reactions in batch reactors or CSTRs are examples. More likely, scaleup to industrial conditions will involve fast reactions in large equipment where mixing and heat transfer limitations may emerge. Transport equations must be combined with the kinetic equations, and this is the realm of the chemical reaction engineer.

Chapter 8 combined transport with kinetics in the purest and most fundamental way. The flow fields were deterministic, time-invariant, and calculable. The reactor design equations were applied to simple geometries, such as circular tubes, and were based on intrinsic properties of the fluid, such as molecular diffusivity and viscosity. Such reactors do exist, particularly in polymerizations as discussed in Chapter 13, but they are less typical of industrial practice than the more complex reactors considered in this chapter.

The models of Chapter 9 contain at least one empirical parameter. This parameter is used to account for complex flow fields that are not deterministic,...