Repeat Example CDE9-1 using a proportional-integral controller instead of only an integral controller.

Solution

We note that while the output temperature returns to 138°F, the temperature oscillates over a 20°F range, which may be unacceptable in many situations. To overcome this we will add proportional to integral control. The equations here to be added to those in Table CDE9-1.1 to represent the PI controller are

(CDE9-3.1)



(CDE9-3.2)

with the exception of the perturbation variable and the variable being controlled.

(Note that all equations are the same as before.)

We will set the k_C 8.5 and_I =_av = 0.165 hr. We see that the output outlet temperature does not oscillate as much as with just an integral controller. Try different controllers (differential, proportional, integral) and combinations thereof, along with different parameter values to study the behavior of CSTRs which have upsets to their system (Figures CDE9-3.1 and CDE9-3.2).