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. On represente les contenants reels, ou le mode d'ecoulement differe appreciablement de l'ecoulement frontal, a l'aide de modeles formes de zones communicantes (zone morte, zone agitee, ecoulement frontal, etc.) et comportant differents modes d'ecoulement a travers et autour de ces regions (derivation, recirculation, ecoulement eroise). L'auteur considere, dans ce travail, quelques-uns des problemes associes au choix et a l'adaptation de tels modeles, ou modeles composes, pour representer l'ecoulement dans les contenants reels. La technique de la reponse a une demande quelconque constitue un outil utile dans ce cas et la methode de selection consiste a ajuster les courbes de reponse pour le modele et pour le contenant actuel. On presente quelques-uns des modeles composes les plus simples de měme que les courbes de reponse caracteristiques qui y correspondent.