Consider a second-order reaction (2A → B) with a reaction rate, . This reaction takes place in a plug flow reactor or a reactor with recycle. The recycle ratio is the volume of fluid returned to the reactor entrance divided by the volume leaving the system. The ratio of the volume of the recycle reactor to the volume of the plug flow reactor, , is plotted versus the dimensionless exit concentration , where and are the concentration of the species A at the inlet and outlet, respectively.