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CBE 491 /433

15 Oct 12 Model of Stirred Tank Heater. CBE 491 /433. Goal: set up models to simulate and see effect of tuning parameters 1 st principles (Chaps 3 – 6); transfer functions (just looked at this a bit) process simulators ( AspenPlus Dynamics; CBE 450/550 class).

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CBE 491 /433

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  1. 15 Oct 12 Model of Stirred Tank Heater CBE 491 /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 491 / 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)

  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 491 / 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 !!

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