Hot water is cooled in a tube-in-shell heat exchanger by cold water. The water comes from a 50 psig water header that provides water for three experiments in the laboratory. Some of the water is heated by an electrical heater before entering the heat exchanger. Each two- or three-student group performs six experiments. The temperature of the hot water leaving the heat exchanger is sensed and recorded. The control signal to the cold water valve is set from a personal computer using a data acquisition & control software package. All the test signals are generated by the computer, and data can be stored in the computer or on disks for further processing using LabView or MATLAB.
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| Identification of heat exchanger process |
Control techniques studied:
- Time-domain and frequency-domain system identification
- Open-loop and closed-loop transfer function
- Ultimate-gain and ultimate-frequency Ziegler-Nichols PI tuning
This is an experiment that demonstrates the control of a multi-input multi-output (MIMO) process. Both hot water (from a variable power electrical heater) and cold water are fed into a through their individual control valves. The flow from the tank is set by positioning a manual valve. The level in the tank is controlled by the cold water valve and the temperature in the tank by the hot water valve, using two separate controllers. The effects of interaction in this 2x2 multivariable system are explored. The instrumentation is electronic temperature, flow and level sensors and single-station micro-processor temperature and level controllers.
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| Interacting level and temperature control |
Control techniques studied:
- Mathematical Modeling
- Sensor calibration and actuator characterization
- Ultimate-gain and ultimate-frequency Ziegler-Nichols PI tuning
- MIMO feedback stabilization
This experiment is an open-loop unstable thermal process. The apparatus mimics the dynamic behavior of a feed-effluent heat exchanger and reactor system. An exothermic adiabatic tubular reactor is simulated by using a vessel with an electric heater, making the system safer and cheaper to operate while retaining the essential open-loop unstable transient behavior. This experiment and recent operating experience with it in this laboratory course are described in "A feed-effluent heat exchanger/reactor dynamic control laboratory experiment" by W.L. Luyben, in Chemical Engineering Education, Winter 2000.
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| Unstable reactor |
Control techniques studied:
- Feedback stabilization
Water is fed into a tank at a variable rate. The outflow from the tank is pumped through either a conventional control valve or one with a valve positioner. The two valves have different flow characteristics: equal percentage and linear trim. The effect of a sticking control valve is demonstrated.
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| Level control |
Control techniques studied:
- Mathematical Modeling
- Sensor calibration and actuator characterization
- Feedback stabilization
- Root-locus analysis