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Posted by Bob D. on March 26, 2004 at 13:00:14:
In Reply to: steam flow calcualtion posted by Phil La Mori on March 25, 2004 at 14:15:12:
Previously covered in this forum. See:
http://www.boilerroom.com/wwwboard/messages2/4513.shtml
I'll also reproduce it below.
After that, think seriously about installing a mass flow meter that inherently pressure compensates. - Bob
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Posted by gburns on August 23, 2003 at 04:00:27:
In Reply to: Pressure Reduction Definition posted by Hard times on August 22, 2003 at 10:35:15:
Ideally you need temperature and pressure compensation to your flow. Your flow meter is calibrated only for one condition, however, when the pressure drops (if steam output is saturated) both the temperature as well as the specific volume of the steam changes. The typical flow measurement is the meter constant times the sqareroot of the transmitter differential pressure measurement.
Steam flow = K * sqareroot(dp)
K = Flow constant
dp = transmitter differential pressure
What you need to do is compensate the differential pressure signal for pressure and temperature (Note: Pressure and temperature must be in absolute terms):
Steam flow = K * sqareroot(dp * P2/P1 * T1/T2)
P2 = Current pressure (PsiA P+14.7)
P1 = Calibration pressure (PsiA P+14.7)
T1 = Calibration Temperature (Deg Rankine T+460)
T2 = Current temperature (Deg Rankine T+460)
Example:
At 70 psig and 316 DegF uncompensated flow is 8,344.4 lbs/hr. Compensated flow would be:
Comp. Flow = 8,344.4 * sqareroot((84.7/124.7)*(804/776)) = 7000 lb/hr
Note: Current flow 8,344.4 = K * Sqrt(dp)
Hope this helps.