Chapter 3 – Dimensional Analysis, Scaling, and Orders of Magnitude

Publisher Summary Dimensional analysis is a very powerful tool for the chemical engineer but should be used with care and intelligence. In its classical formulation, it has to do with the identification of the dimensionless groups that appear in the solution of every problem. For any given problem, the results provided by dimensional analysis turn out to be both useful and correct. Several examples are illustrated to demonstrate how a straightforward application of dimensional analysis and scaling may provide some very crucial insight in the solution of the problem considered. The chapter discusses two examples of approximations in the modeling of phenomena. A very common and very powerful approximation, which chemical engineers do all the time, is the quasi steady state approximation (QSSA). The QSSA is based on the general considerations—often the solution of a problem is available for steady state conditions, but it is hard to obtain for unsteady state ones.