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 _1800_05.htmhttp:// 6_1800_05.htm 3.

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

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 1.

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 Fill Tank Measure Level No Action Full Low

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

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

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

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

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

Materials 1.3V DC motor 2.Two AA batteries (each 1.5 V) mL clear water bottle 4.AA Battery holder 5.Electrical wire 6.Electrical wire clips m of ¼”clear, flexible tubing 8.Straws 9.Wooden skewers 10.Plastic core bard 11.High density Styrofoam 12.Two magnets with centre holes 13.Glue 14.Reed switch 15.Small plastic dish 16.Multimeter

Calculations

Energy Input Power input (W in ) = AV where: A = current (A) V = voltage across load (V) A V

Energy Output Power output (W out ) = Q  gh where: Q = vol flow rate (m 3 /s) g = acc. Gravity (m/s 2 ) h = height between pump inlet and outlet (m)  = fluid density (kg/m 3 ) * 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.) h Q Fluid input (  )

Efficiency Overall pump efficiency = W out /W in Pump efficiency is always less than 1 Source of energy lost: –Electrical resistance –Friction (fluid viscosity, piping, motor) –Impeller (inherent pump efficiency) A V h Q Fluid in (  )

Customize the Project

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

Questions?