Transcript Heat Exchanger Control Systems

Heat Exchanger Control
Systems
Some Types of Heat
Exchangers
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Sensible Heat Cooling and Heating
Change of Phase Boilers and Condensers
Partial Condensing or Partial Vaporization
Wiped Film Units for Viscous Fluids
Basic Model
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𝑄 = 𝑈𝐴Δ𝑇
Simple Heater Loop
𝑄 = 𝑆𝜆 = 𝐹𝑐𝑃 (𝑇2 − 𝑇1 )
Actual loop on P&ID
Riggs & Karim, Chemical and BioProcess Control, 2006, p. 12
Control Loop Options
• Feedback has some
lag time
• Feedforward based
on steady state
process
Perry, Chemical Engineers
Handbook, 7th Ed., p. 8-17
Alternate Methods
• Bypass Control Options
Marlin, Process Control Designing
Processes and Control Systems for
Dynamic Performance, 2000, p.784
• Combined Feedback & FeedForward
Riggs & Karim, Chemical and
Bio-Process Control, 2006 p.
401
Physical Installation
• Cascade control
http://www.spiraxsarco.com/resources/steam-engineeringtutorials/control-applications/pressure-control-applications.asp
Change of Phase HX
• Condenser on Distillation Column
http://eweb.chemeng.ed.ac.uk/courses/control/restricted/course/fourth/
course/module3-1.html
Change of Phase HX
• Partial Condenser on Distillation Column
http://eweb.chemeng.ed.ac.uk/courses/control/restricted/course/fourth/
course/module3-1.html
Change of Phase HX
• Reboiler on Distillation Column
http://eweb.chemeng.ed.ac.uk/courses/control/restricted/course/answe
rs/fourth/answer2.html
Condenser Pressure Control
Towler & Sinnott,
Chemical
Engineering
Design Principles,
Practice and
Economics of
Process Design,
2008, p. 279
Steam Boiler Control
• Steam Pressure is used to control fuel
feed rates
• Can be linked to consumer
http://www.powermag.com/issues/features/Drum-pressure-thekey-to-managing-boiler-stored-energy_300.html
Actual Boiler Control Systems
• Allow for
capacitance in
system
http://www.powermag.com
/issues/features/Drumpressure-the-key-tomanaging-boiler-storedenergy_300.html
Boiler Drum Level Control
• Can use feedback, feedforward &
combination
Riggs & Karim, Chemical and Bio-Process Control, 2006, p. 12
Partial Condenser Options
• Can control
reflux rate
William L. Luyben,
Alternative Control
Structures for Distillation
Columns with Partial
Condensers, Ind. Eng.
Chem. Res. 2004, 43,
6416-6429
Partial Condenser Options
• Can control
condenser
cooling rate
William L. Luyben,
Alternative Control
Structures for Distillation
Columns with Partial
Condensers, Ind. Eng.
Chem. Res. 2004, 43,
6416-6429
Partial Condenser Options
• Can control
reflux ratio
William L. Luyben,
Alternative Control
Structures for Distillation
Columns with Partial
Condensers, Ind. Eng.
Chem. Res. 2004, 43,
6416-6429
Wiped Film Evaporator
• Control product feed rate
http://www.artisanind.com/ps/docs/rototherm.pdf