A feedforward-only control system is to be designed for

QUESTION:

A feedforward-only control system is to be designed for the stirred-tank heating system shown in Fig. E15.11. Exit temperature T will be controlled by adjusting coolant flow rate, qc. The chief disturbance variable is the inlet temperature T; which can be measured on-line. Design a feedforwardonly control system based on a dynamic model of this process and the following assumptions: 1. The rate of heat transfer, Q, between the coolant and the liquid in the tank can be approximated by Q = U(1 + qc)A(T- Tc) where U, A, and the coolant temperature Tc are constant. 2. The tank is well mixed, and the physical properties of the liquid remain constant. 3. Heat losses to the ambient air can be approximated by the expression QL = ULAL(T- Ta), where Ta is the ambient temperature. 4. The control valve on the coolant line and the T; sensor/ transmitter (not shown in Fig. E15.11) exhibit linear behavior. The dynamics of both devices can be neglected, but there is a time delay e associated with the T; measurement due to the sensor location.