Mixed models to represent flow of fluids through vessels

Models consisting of interconnected regions (dead‐water, backmix, plug flow, etc.) with various modes of flow through and around these regions (bypass, recycle, cross flow) are used to represent real vessels in which flow deviates greatly from plug flow. This paper deals with some of the problems of choosing and fitting such models, called mixed models, to represent flow in real vessels. The stimulus‐response technique is a useful tool for this purpose, and matching response curves for model and real vessel then serves as the selection method. Some of the simpler mixed models and their corresponding characteristic response curves are presented.