Flowwww Flashcards
(30 cards)
What is an ultrasonic transducer used for?
Measuring the water level to read flow
How does the ultrasonic transducer measure flow?
Sends pulse down, detects echo back. measures level as a fcn of time
Why does temp matter with ultrasonic?
Need air temp to calculate speed of sound
Advantages to ultrasonic?
non-contact, easy installation, minimal maintenance
Disadvantages to ultrasonic?
1) limitations on how high to put with the dead band 2) beam angle impacted by narrow walls, false echos 3) Wind, steam, foam, and turbulence can impact reading: steam=reflect echo, foam=absorb echo, turbulence=reduce sig strength, wind=interfere with sound wave
How does a bubbler work?
Pump pushes out a bubble, transducer measures pressure to push out 1 bubble
Advantages to a bubbler? (5)
1) good for small channels 2) not impacted by wind, steam, foam, temp, turbulence 3) No electronics in flow stream 4) Easy, cheap 5) accurate
Disadvantages to bubblers? (3)
1) restrictions or sediment can impairs line (cause a false high reading) 2) Needs higher maintenance 3) Greater power consumption
How does a submerged pressure probe work?
In flow, measures the pressure
Advantages of pressure probes? (3)
good in small channels 2) no impact from steam, wind, foam, turbulence 3) Senses pressure through silt/sand
What is a weir?
Any dam built accross open channel where water flows over
Disadvantages to submerged pressure probe? (4)
Chemistry can impact it 2) flowing debris, block channel 3) Higher maintenance 4) Temps can impact
What is a flume?
Specially made channel to accelerate flow, create relation between water level and water flow
What do you need to accruately measure open channel flow? (2 things)
A flume/weir, level sensor, and sometimes a flowmeter if cant directly read from the level sensor
Why would you put in a weir in the first place?
control the flow of water and level
What is the issue with putting level sensor right at the crest of a weir?
Drawdown effect closest to weir. False low reading. Place upstream
Difference between pipe/closed conduit flow and open channel flow?
Open channel propelled by gravity, for closed channel, pressure impacts flow
If flow is going through a closed pipe but it doesnt fill it, is that pipe flow or open channel?
Open channel
What is the most common type of flume for industrial discharge?
Parshall
Where read depth for a parshall flume?
At the converging section upstream, NOT throat and NOT diverging section
What relationship does a flume create…..
Relationship between the fluid level of flume and the flow of the water created
Where should we take the depth reading for a Parshall flume? (converging seciton, throat, diverging)?
Converging section
Where measure depth for small/medium parshall flumes?
For small and medium sized Parshall flumes, Ha is located 2/3 of the distance upstream of the beginning of the throat
