Flow Velocity ProfileMeasurement 5

[CARF]

Dear all,

Does anybody know of sensors (elctro magnetic flowmeters?) which are capable of measuring the Velocity Profile of the flow?

So not only the average flow, but also the flow at any position across the pipe diameter.

Many thanks,
CARF

 

[CARF]

This is what I mean:

Electromagnetic flow measurement is a widely used robust method for non-invasive flowrate measurement of electrically conducting fluids. The basic systems as used commercially consist of two coils generating a magnetic field and two electrodes for voltage measurement. By applying multiple magnetic coils and/or multiple electrodes, the principle of conventional electromagnetic flow measurement is extended yielding additional information on the flow profile. Depending on the configuration, this information can be used either for improving the accuracy of flowrate measurement or for determining the shape of the flow profile and deducing other properties of the flow like rheological behaviour. This contribution gives an overview over theory and applications of electromagnetic flowmeters with multiple coils and multiple electrodes. Particularly, the systems considered serve for flow imaging by tomographic reconstruction of the flow profile (requiring multiple coils and multiple electrodes), for accurately measuring the flowrate, almost independently of the flow profile (2 magnetic coils, multiple electrodes), and for inline viscosity measurement of non-Newtonian fluids (2 electrodes, 2 separately excited magnetic coils).

Any manufactures, practical experience?

Thanks,
CARF

 

[khan101]

What do you mean that Magnetic flowmeter is non-invasive? It is 100% invasive since the meter is an inline type. Your first question is measuring velocity profile of the flow? I am sorry but I am confused. Do you mean measuring flowrate regardless of velocity profile?

Your 2nd post gives a bit more info. I think there is a new technology which uses sonar technology to give you velocity profile and flow rate. The meter is called sonartrac and company is Cidra,

http://www.cidra.com

It is a non-invasive flow measurement technology. We have 3 or 4 meters in service and we are pleased with the data.

Visit their website and let me know if that is what you are looking for?

 

[hacksaw]

non-intrusive flow profilers do exist but are expensive

The Cidra device is classified as a correlation meter and does not offer direct information on the flow profile, as such.

 

[jmw]

Ultrasonic meters are designed to measure the flow not the flow profile.
Simple clamp on types do not account for the profile, for that you would need one of the multichord types, which are not, to my knowledge, available as clamp ons and in any case only allow the meter to measure flow accuratelt in different flow profiles.
In flow meter development i recall that a transparent pipe section was inserted to allow a laser anenometer to be used to look at the flow profile.
By the way, I would be very interested in the idea of obtaining viscosity from an electromagnetic meter.. do you have any references?


JMW

http://www.ViscoAnalyser.com

 

[m777182]

I have measured it with a small Pitot tube; I divided the cross section of a duct into small squares and measured at each x,y position with an instrument that gave me min, max and average over 60 seconds. Latter I repeated it with a small anemometer. The flow profile was really surprising. That was 20 years ago and the lesson I got was never forgotten.
m777182

 

[CARF]

Thank you all for sharing thoughts!

To explain a bit more: Some (Newtonian) fluids like beer and oil have a parabolic flow-profile, this means the flow at the core of the pipe is about 2 times the average flow. At the wall, the flow will be much lower. Other fluids ,like thick mud, have a more 'plug' flow-profile, this means the flow is the roughly the same across the whole pipe diameter (a plug). These profiles I'm interested in, because they give information about the character of the fluid (Newtonian, Power-law, Bingham).

I know some research work has been done on this (just Google for: "electromagnetic flowmeter, tomography, flow imaging, viscosity") and you will find some nice hits, i.e.:

http://www.mrt.uni-karlsruhe.de/pub_1997_31.html)

But that's from 1997, I was wondering about any practical applications 8 years later?

So m777182: please tell what did you learn!?

JMW: I know E+H can measure viscosity, but that is with an Coriolis massflowmeter. Not real visco in cP, but more a repeatable measurement in Engineering units.

Thanks all, keep posting!
C.

http://www.carf-engineering.com

 

[jmw]

Thanks for the response on viscosity.
I know of the E&H attempt with their coriolis meter but i was very disappointed that they chose to use amplitude measurement rather than bandwidth (because they wanted to retain the mass flow measuring capability).
The result is a measurement that is only around 5% FSD when less expensive and more functional devices can deliver <1% of reading.
More interesting will be to see how they progress this or if they revive their fork sensor development, though companies being what they are, if the coriolis meter doesn't suceed as a viscometer they might decide there is no market for viscometers. OK, true of many companies, one would hope for better from E&H.

JMW

http://www.ViscoAnalyser.com

 

[hacksaw]

sonics have been used for profiling complez, non-stationary flows, but not as commercial available devices.

em meter technology infers average velocity between two electrodes, is a path specific measurement, and requires a number of assumptions about the flow profile.

 

[m777182]

Hello Carf,

I wanted to make a heat and material balance and I used the thermometers that were already inserted into a in- and output pipes (600...800mm dia) of a dryer.I could not close the balance, the discrepancy among in/out was too large. Then I measured velocities(flow)and temperatures as I described and I realised that flow was very irregular, beeing in the range of -2m/s to 20m/s and T range was spread within 12C at a cross section.By -2m/s I mean that the flow at the measuring point was directed in an opposit direction. With a slight change of throat butterfly everything was changed.
The balance was not a matter of an hour...
M777182

 

[hacksaw]

m777: all the "rules" apply until you get down to details

 

[brainstorming]

Does what you are asking for apply for theoretical or application process?
If theoretical, then u should do modelling of the system by mass balance equations and using a numerical method to get the velocity profile along the length of the pipe.
if practical, It’s of interest to know such application!

Regards

 

[CARF]

Practical applied instruments of course, the theory is already known for many decades.

Regards,
C.