ABSTRACT
Let us assume that we have a reactor system with the volume VR as in Figure 4.1. A volumetric flow rate V˙ passes through this volume. Consequently, at a certain point of time, we will notice one of the incoming elements, which we will follow on its journey through the reactor. In terms of its stay, the element has the age zero seconds (0 s) at the specific moment at which it emerges in the inlet of the reactor. Nevertheless, its age (ta) increases, consequently, in parallel with the “normal” clock time (tc). When this element-sooner or later-leaves the reactor, it would have reached a certain age. We refer to this time as the residence time of the element. The residence time of an element-or a volume element-is thus defined as the period that passes between the time an element enters the reactor and the time it leaves the reactor (at certain points in time). To simplify the illustrative scheme below, index r has been excluded. Thus, the residence time is denoted as t .
