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Engineering and Process Control

Engineering and Process Control. You know more than you realize. Introduction. Feedback control is found everywhere Can be natural or anthropic Examples: Electric kettle Cruise control Insulin levels. Image Sources http://www.stashtea.com/mocat.htm

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Engineering and Process Control

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  1. Engineering and Process Control You know more than you realize

  2. Introduction • Feedback control is found everywhere • Can be natural or anthropic • Examples: • Electric kettle • Cruise control • Insulin levels • Image Sources • http://www.stashtea.com/mocat.htm • http://www.in.gr/auto/dokimes/pr_dokimes_in/Mazda_6_1800/in_Mazda_6_1800_05.htm • http://www.fda.gov/fdac/features/2002/102_diab.html

  3. How does it work? Controlled Variable (temp, conc., height, speed) Process Actuator Measurement Error (compared to set point) Control (PDI)

  4. Problem Description • To create cola, a company is continuously mixing water and syrup together • Each component comes from a hold tank • These tanks must remain full or else the production process will be interrupted • Design a control system that will maintain the liquid levels • Image Source • http://www.zanesville.ohiou.edu/emedia/Advertising%20archive/

  5. Design Criteria • Tank • Constant liquid level • Draw from a reservoir to the hold tank • Detect low level • Detect full level • Fill tank if required Measure Level Measure Level Full Low Fill Tank No Action

  6. Solution Float Pump Reed switch Height Sensor Fill tank Stop/start + -

  7. Start/Stop – Reed Switch • When a magnet comes close to a reed switch the two paramagnetic contacts become magnetized and attracted to each other (closes the circuit) • This allows an electrical current to pass through • When the magnet is moved away from the reed switch the contacts demagnetize, separate, and move to their original position (opens the circuit) Glass Tube Contacts

  8. Filling the Tank - Basic centrifugal pump • Transfer angular momentum of impeller into kinetic energy of discharged fluid • Faster impeller speed = higher discharge velocity = higher pressure • Bigger housing = larger impeller = higher volumetric flow rate Image Source http://www.yourdictionary.com/ahd/p/p0657700.html

  9. Final Schematic + + - - • Low tank • Primary magnet keeps circuit closed • Pump operational • Full tank • Secondary magnet on float counteracts primary magnet • Circuit opens • Pump deactivated

  10. Final Schematic Photo courtesy of Paul Jowlabar, Lab Manager, Department of Chemical Engineering. Reproduced with permission.

  11. Materials • 3V DC motor • Two AA batteries (each 1.5 V) • 500 mL clear water bottle • AA Battery holder • Electrical wire • Electrical wire clips • 0.5 m of ¼”clear, flexible tubing • Straws • Wooden skewers • Plastic core bard • High density Styrofoam • Two magnets with centre holes • Glue • Reed switch • Small plastic dish • Multimeter

  12. Calculations

  13. Energy Input • Power input (Win) = AV where: • A = current (A) V = voltage across load (V) V A

  14. Energy Output • Power output (Wout) = Qrgh where: • Q = vol flow rate (m3/s) g = acc. Gravity (m/s2) h = height between pump inlet and outlet (m) r = fluid density (kg/m3) * Q may also be expressed as A(dh/dt) where A is the cross section area of the tank (assuming the tank has uniform A along h.) Q h Fluid input ( r )

  15. Q h Fluid in ( r ) V A Efficiency • Overall pump efficiency = Wout/Win • Pump efficiency is always less than 1 • Source of energy lost: • Electrical resistance • Friction (fluid viscosity, piping, motor) • Impeller (inherent pump efficiency)

  16. Customize the Project

  17. Expandability • Alter flexible tube diameter • Adjust size of pump • Change height of inlet and/or outlet • Use other fluids – corn syrup, (thicker than water)

  18. Questions?

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