Possible approaches to the prediction of residence time distributions

Although the experimental determination of residence time distributions is based on a black-box method, the signal shape also permits certain conclusi ons to be drawn about the internal conditions. However, if it is to provide a sole basis for elucidating process steps in a plant this method is soon overtaxed. A deeper theoretical penetration of the pertinent transport proc esses opens up the way ahead. However, since residence time distributions a re based on mass-oriented considerations, substantial advances in fluid mec hanics, where location-based considerations predominate, have not led to im proved predictive capability Yet the computer power now available offers a variety of ways of calculating residence-time distributions for a known flo w profile, thus permitting a step in the direction of better predictability of residence time distributions. This article presents utilisable methods and evaluates them with regard to their demands on time and effort and thei r predictive power. Problems arising in connection with the models are disc ussed.