Blower Flow rate measurement
Blower Flow rate measurement
(OP)
Hi All!
Can anyone help us in finding out what would be the best possible location of a pitot tube for the flow measurement in a blower?
Currently, we are locating it at the discharge line, but we have seen some arrangements showing it at the suction of the blower. Is there any significant difference??
Thx,
ChemE2912
Can anyone help us in finding out what would be the best possible location of a pitot tube for the flow measurement in a blower?
Currently, we are locating it at the discharge line, but we have seen some arrangements showing it at the suction of the blower. Is there any significant difference??
Thx,
ChemE2912
RE: Blower Flow rate measurement
Maybe it's better to ask this question on the measurement & control instrumentation group.
> There's no principal difference to measure in the suction or in the discharge.
1) Keep in mind to measure not to close to bends or other obstacles, because turbulence will spoil your measurement then.
2) Then what exactly do you want to measure? Volumeflow (m3/sec) or massflow (kg/sec). For massflow you need to measure pressure and temperature as well since the density of gasses change with pressure and temperature.
3) At what point are you going to measure? In the centre of the channel the flow will be higher then near the wall.
There are good Pitot systems around who take say 5 measurements across the whole channel and take the average.
See for example Endress + Hauser: Deltatop / Deltaset.
http://www.endress.com/
These are complete systems with flow computer, where all temperature and pressure caculations are done to covert to massflow.
Hope this helps,
MVD
RE: Blower Flow rate measurement
V=sqrt(2GH),Where H is the FT of air column. H is obtained by multiplying the Press by density of manameter fluid and dividing Press by Density of air for the corresponding press where pitot is inserted.
RE: Blower Flow rate measurement
Averaging Pitot tubes are prefered to pitot tube (as MVD points out). Annubar is the name used by Rosemount.
Discharge lines typically have less diameter and often has the advantage of more choice in selecting the location. Another advantage is that pressure drop in discharge is less of a loss (operationally cheaper) than in the suction (dP/P). DPs in suction of blower, for pitot tube, are probably very small (draft range or less) which can be problematic.
dont forget to mount dp instrument above the taps with no utubes, condensed and trapped h2o will create alot of problems.
only observed pitot tubes in cheme lab, never in industry.
RE: Blower Flow rate measurement
drop your e-mail adress and I'll sent you two nice spreadsheets on air flow mass balance across an air blower.
Cheers,
MVD
RE: Blower Flow rate measurement
MVD, My email address is abaumeister@member.aiche.org
Regards,
ChemE2912
RE: Blower Flow rate measurement
see further: Thread378-47551
Good luck,
MVD