where is the effluent volumetric flow rate. In other words, N is the amount
of material exiting the reactor that has spent an amount of time between t and
t t in the reactor. If we now divide by the total amount of material that was
injected into the reactor, N0 , we obtain
(13-2)
which represents the fraction of material that has a residence time in the reac-
tor between time t and t t.
For pulse injection we define
E(t) -
(13-3)
so that
-
E(t) t (13-4)
The quantity E(t) is called the residence-time distribution function. It is the
function that describes in a quantitative manner how much time different fluid
elements have spent in the reactor. The quantity E(t)dt is the fraction of fluid
exiting the reactor that has spent between time t and t + dt inside the reactor.