1. Model of Stirred Tank Heater
14 Mar 12
Model of Stirred Tank Heater
CBE / MET 433
Goal: set up models to simulate and see effect of tuning parameters
1st principles (Chaps 3 – 6);
transfer functions (just looked at this a bit)
process simulators (AspenPlus Dynamics; CBE 450/550 class)

2. Stirred Tank Heater (w/ PI Controller)+ + + -
energy balance on tank w/o control
PI controller equation

3. Stirred Tank Heater (w/ PI Controller)
Let:

4. ODE Solver (POLYMATH; MATLAB; MATHCAD; etc)
Polymath code:
step= if (t<1) then (0) else (1)
Ti = 0 + step * 10

5. ODE Solver: POLYMATH Polymath code (stirred tank heater):
d(C) / d(t) = -1/tau*C + KT/tau*Ti + K1KT/tau*M
C(0) = 0
d(errsum) / d(t) = R – C
errsum(0) = 0
tau = 5 # min
KT = 0.5 # %TO/degC
K1KT = 0.8 # %TO/%CO
R = 0 # set point stays same
M = Kc*(R-C) + Kc/tauI*errsum
step = if (t<1) then (0) else (1)
Ti = 0 + step * 10 # step change disturbance
Kc = 1.3 # %CO/%TO
tauI = 10 # min
t(0) = 0
t(f) = 100 # min
In Class Demo / Exercise:
Polymath Demonstration
Build model in Polymath (ODE solver)
Solve; graph C vs t
Explore:
Try P-only controller
Adjust Kc and tauI to get QAD
Try different Kc/tauI sets
Can you get underdamped response?
What is response to step change in R(t); holding Ti at the SS value?

6. Model of Stirred Tank Heater
CBE / MET 433
Model of Stirred Tank Heater
Goal: set up models to simulate and see effect of tuning parameters
1st principles (Chaps 3 – 6);
transfer functions (just looked at this a bit)
process simulators (AspenPlus Dynamics; CBE 450/550 class)

7. Stirred Tank Heater (transfer function simulator)+ + + -
Transfer function simulator: Loop Pro Developer (Control Station)
In Class Demo / Exercise:
Build model in Loop Pro Developer (Custom Process)
Turn on PI Controller and set Kc and tauI
Explore:
Change load (Ti) up by 10 to 60%; observe system response
Change back to 50%; observe response
Try P-only controller
Adjust Kc and tauI to get QAD
Try different Kc/tauI settings
Can you get underdamped response?
What is response to step change in R(t) to 60%?

8. Model of Stirred Tank Heater
CBE / MET 433
Goal: set up models to simulate and see effect of tuning parameters
1st principles (Chaps 3 – 6);
transfer functions (just looked at this a bit)
process simulators (AspenPlus Dynamics; CBE 450/550 class)

9. SAVE your Polymath and Loop Pro Developer Models !!