Measuring Velocity in a Pipe
Measuring Velocity in a Pipe
(OP)
Hello everybody!
First, I want to thank everyone for the help that they give to these forums, I can't remember how often just browsing through threads gives me an idea or sparks a solution.
My question is this: I want to measure the velocity of air flow through a milling system. Specifically, this would be the air flow after the product has been milled and leaves the output of the mill (in most cases we will be milling wheat.) Normally, if it was just air or a similar fluid, this would be a trivial problem with an easy solution. We are aiming for ~4000 fpm velocity.
What I am worried about is how the flour will affect the measuring device. I have thought about using a hotwire anemometer like this:
http://www.amazon.com/Amprobe-TMA-20HW-Hotwire-Ane...
to gauge the velocity. This would entail installing it into a short section of piping and installing that pipe after the mill. Am I correct in thinking the flour will mess with the measuring device?
I also thought about a venturi meter, but since this is a system where we want maximum product movement, restricting the flow is an issue. Is there a way that we can install a venturi meter in parallel with the piping?
I am just trying to gather some ideas here, any help is appreciated. As usual for most requests, the cheaper the solution the better :)
Thanks!
Aaron
First, I want to thank everyone for the help that they give to these forums, I can't remember how often just browsing through threads gives me an idea or sparks a solution.
My question is this: I want to measure the velocity of air flow through a milling system. Specifically, this would be the air flow after the product has been milled and leaves the output of the mill (in most cases we will be milling wheat.) Normally, if it was just air or a similar fluid, this would be a trivial problem with an easy solution. We are aiming for ~4000 fpm velocity.
What I am worried about is how the flour will affect the measuring device. I have thought about using a hotwire anemometer like this:
http://www.amazon.com/Amprobe-TMA-20HW-Hotwire-Ane...
to gauge the velocity. This would entail installing it into a short section of piping and installing that pipe after the mill. Am I correct in thinking the flour will mess with the measuring device?
I also thought about a venturi meter, but since this is a system where we want maximum product movement, restricting the flow is an issue. Is there a way that we can install a venturi meter in parallel with the piping?
I am just trying to gather some ideas here, any help is appreciated. As usual for most requests, the cheaper the solution the better :)
Thanks!
Aaron





RE: Measuring Velocity in a Pipe
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Measuring Velocity in a Pipe
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Measuring Velocity in a Pipe
I'd be cautious about introducing anything electric or electronic.
This will probably require regular cleaning, but should give useful data:
http://www.dwyer-inst.com/Product/AirVelocity/AirV...
Mike Halloran
Pembroke Pines, FL, USA
RE: Measuring Velocity in a Pipe
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Measuring Velocity in a Pipe
Flour dust is dangerous, so as a precaution I guess it would be better to not stick anything directly into the particle stream.
zdas, do you think there will be any reduction in flow velocity in the fluid from the venturi meter that would skew the results?
RE: Measuring Velocity in a Pipe
RE: Measuring Velocity in a Pipe
I wouldn't use a pitot tube. They have to be calibrated for a specific gas and a specific pressure/temperature. It sounds like you will have considerable variability and most of the time the numbers you would get from a pitot tube would just be numbers (not much relationship to flow).
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Measuring Velocity in a Pipe
Given that, maybe a pitot tube would be an acceptable choice.
Mike Halloran
Pembroke Pines, FL, USA
RE: Measuring Velocity in a Pipe
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Measuring Velocity in a Pipe
Too bad a flywheel or flapper would not work: The energy of the blowing dust turns the wheel (or forces the flapper panel up) directly proportional to the mass of dust and speed of the dust.
then gain, if the flapper were directly over top of a 90 degree mitered joint with the exit turning down into the next pipe section, the dust would force the flapper "up" and the deflected dust and air would be blown "down" the vertical leg and away from the flapper so it would not jam up the flapper and horizontal inlet piping section ....
RE: Measuring Velocity in a Pipe
Thanks for all of the help!