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[black friday]

I'm currently doing some mass balances over a series of condesnsers, V/L separators and a column. The flow readings from the RO's in place are reasonably different with up to 15% variance between the columns inputs and outputs (the outputs being higher).
I was wondering if two phase flow might be an issue as this seems to be an error greater than I usually see in the RO's on the plant. If this is an issue I was hoping whether someone could tell me if two phase flow causes an erroneously high or low reading from an RO. If anyone felt like elucidating the reasons behind this that would also be appreciated just for my enlightenment.
Thanks for your time.

[ashetty]

Hi,

Yes 2-phase or multiphase flow does have an effect on orifice measurement.The measured gas flowrates can be way off, depending on the amount of entrained liquid in the gas.We had similar problems some years ago with metering a gas well.The wells had started producing some liquids (Actually the well was completed not in a true gas reservoir but in the associated gas cap of a light oil reservoir).The well was only equipped with gas metering (senior orifice meter) and not only was there was a need to have a Multiphase Flow meter for reliable quantification of liquids produced ....but the gas flowrates being measured had errors of 15-20% as well.
Flow rate measured across an orifice is related to the differential pressure across the the plate and density of fluid being measured.P1-P2 changes when you have entrained liquid in the gas.I think there is overmeasurement of gas flow when the amount of liquid increases.Operating conditions and flow regimes also make a difference, but im not sure of the mechanisms.

Thanks.