The model is a mixing tube into which acid and alkali are injected through side holes. The reaction to be modeled is:

Equation 1.

The tube is modeled as an axisymmetric section.

The reaction between acid and alkali is represented as a single step irreversible liquid-phase reaction

Equation 2.

Reagent (dilute sulphuric acid) is injected through a ring of holes near the start of the tube. As it flows along the tube it reacts with Reagent (dilute sodium hydroxide) which is injected through a further two rings of holes downstream. The product, , remains in solution.

The composition and pH of the mixture within the tube are principal quantities of interest to be predicted by the model.

The flow is assumed to be fully turbulent and turbulence is assumed to have a significant effect on the process. The process is also exothermic.