Transcript Basic centrifugal pump

Engineering and Process Control
You know more than you realize
Introduction
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Feedback control is
found everywhere
Can be natural or
anthropic
Examples:
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Electric kettle
Cruise control
Insulin levels
Image Sources
1.
http://www.stashtea.com/mocat.htm
2.
http://www.in.gr/auto/dokimes/pr_dokimes_in/Mazda_6_1800/in_Mazda_
6_1800_05.htm
3.
http://www.fda.gov/fdac/features/2002/102_diab.html
How does it work?
Controlled Variable
(temp, conc., height, speed)
Process
Actuator
Measurement
Control
(PDI)
Error
(compared to
set point)
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.
http://www.zanesville.ohiou.edu/emedia/Advertising%20archive/
Design Criteria
Measure
Level
Full
No
Action
Low
Fill
Tank
• Tank
• Constant liquid level
• Draw from a reservoir to the
hold tank
• Detect low level
• Detect full level
• Fill tank if required
Solution
Height Sensor
Fill tank
Stop/start
Float
Pump
Reed switch
+
-
Start/Stop – Reed Switch
Glass
• When a magnet comes close
to a reed switch the two
paramagnetic contacts
become magnetized and
attracted to each other (closes
the circuit)
Tube
• This allows an electrical
current to pass through
Contacts
• When the magnet is moved
away from the reed switch the
contacts demagnetize,
separate, and move to their
original position (opens the
circuit)
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
Final Schematic
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+
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Low tank
Full tank
•Primary magnet keeps
circuit closed
•Secondary magnet on float
counteracts primary magnet
•Pump operational
•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)
3. 500 mL clear water
bottle
4. AA Battery holder
5. Electrical wire
6. Electrical wire clips
7. 0.5 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
V
• Power input (Win) = AV
where:
• A = current (A)
V = voltage across load (V)
A
Energy Output
• Power output (Wout) = Qrgh
where:
Q
h
Fluid input ( r )
• 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.)
Efficiency
• Overall pump efficiency
= Wout/Win
Q
• Pump efficiency is
always less than 1
h
• Source of energy lost:
– Electrical resistance
– Friction (fluid viscosity,
piping, motor)
– Impeller (inherent pump
efficiency)
Fluid in ( r )
V
A
Customize the Project
Expandability
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Alter flexible tube diameter
Adjust size of pump
Change height of inlet and/or outlet
Use other fluids – corn syrup, (thicker than
water)
Questions?