Finding flow rate exiting blow tube
Finding flow rate exiting blow tube
(OP)
Hi guys,
For the past weeks i have been trying to come up with a decent setup to calculate the volume flow going through a blow head. I am dealing with air at pressure from 30psi – 60psi, have a 488 gallon air tank, air regulator, and 3 gauges upstream (one on regulator) Here is what I have tried so far.
1. placed the 488 gallon tank to a certain psi (30-60psi) and see measure the drop after a minute with data for every 10 seconds. The problem here is that the pressure drops fast and my equation shows higher losses in 30seconds than in 1 minute. The equation used is [(Volume * DP)/(Time * P(atm,14.7psi))]. I got this equation from the Dept. of Energy website while doing some compressor leakage surveys so I am not sure if it is valid in this case.
2. I tired to get the downstream pressure by strapping the blow tube to a hose with a small connector T pipe and gage but I wasn't getting any readings. After reading and talking with some folks I figured that the reason I wasn't getting reading is because air follows the path of least resistance so I attached a second tube of the inner diameter as the hose and connector attached to blow tube. I got pressure readings but not sure if this accurate.
3. My next idea is to pretty much reverse trial 1 by pushing a known pressure through the blow head and strapping the tank to the end of the blow tube and seeing how much air pressure the tank has after 1 minute. Then by using the equation in trial 1 I should be able to get a CFM
I have been reading up on orifices within the website and just brought the recommended book by Crane. My questions to you all are:
1. Is trial 1 equation valid?
2. Is any of the trials valid (trial 1,2 3)?
3. Should I just look into orifice setups for accurate data?
My end goal is to get a method that is accurate to measure the CFM at different psi for these blowheads.
I linked a picture of setup 2 and the blowtube.
http://i30.tinypic.com/bg4j79.jpg
http://i30.tinypic.com/nxroyg.jpg
Any help, thought suggestions, will be appreciated. If the idea is crappy let me know as well I have tough skin.





RE: Finding flow rate exiting blow tube
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RE: Finding flow rate exiting blow tube
Thanks for the reply, I believe the equation you are talking about is on page 42 (VCP(a)/P1-P2). When you rearrange that formula to solve for C you get the same equation i am using stated in trial 1. I guess for the information i need i have to try my trial 3 to get the amount of air used and a certain PSI and then use the equation. Atleast i know i am not going in the wrong direction.