Continuous flow systems. Distribution of residence times (Reprinted from Chem Engng Sci, vol 2, pg 1-13, 1953)

When a fluid flows through a vessel at a constant rate, either ''piston-flow'' or perfect mixing is usually assumed. In practice, many systems do not conform to either of these assumptions, so that calculations based on them may be inaccurate. It is explained how distribution-functions for residence-times can be defined and measured for actual systems. Open and packed tubes are discussed as systems about which predictions can be made. The use of the distribution-functions is illustrated by showing how they can be used to calculate the efficiencies of reactors and blenders. It is shown how models may be used to predict the distribution of residence-times in large systems.