Cv and mass flow rate
Cv and mass flow rate
(OP)
Hello everyone.
I fill the data sheet for a choke valve. I know the fluid (gas) and the pressures of inlet and outlet. I have to give CV values required and the mass flow rate.
For example:
p1 = 234 barg,
p2 = 1 barg,
temperature = 20 ° C,
Density @ T1, p1 = 202 kg/m3,
molecular weight = 23KJ/Kmol,
Cp / Cv = 2.31
compressibility = 0.59
How should I proceed?
Thanks
I fill the data sheet for a choke valve. I know the fluid (gas) and the pressures of inlet and outlet. I have to give CV values required and the mass flow rate.
For example:
p1 = 234 barg,
p2 = 1 barg,
temperature = 20 ° C,
Density @ T1, p1 = 202 kg/m3,
molecular weight = 23KJ/Kmol,
Cp / Cv = 2.31
compressibility = 0.59
How should I proceed?
Thanks





RE: Cv and mass flow rate
....well, you could of course use a sensible link, as the one below:
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... but then you would find you lack the most essential of necessary information: the required mass flow per time unit.
This can not be calculated, but has to be determined from other facts.
The pressure drop you give is so large that it is possible you have to use more than one valve in series - I have not looked into this.
If this is a pressure relief valve/situation a single step is possible, perhaps by rupture disc as an alternative.
RE: Cv and mass flow rate
therefore without knowing the mass flow not I continue? not I do assumptions and then verify? For example, I think, take the exit Mach numbers less than a certain value.
RE: Cv and mass flow rate
Trying again: this is a practical case. The throtteling is for some real purpose. Ask the user or pipe engineer: what is the real output needed at this throtteling point: maximum, minimum and average over time.
RE: Cv and mass flow rate
The most fundamental Cv equation: Cv=Q Sqrt(SG/Delta-P)
Q would be flowrate
SG=specific gravity (water=1)
Delta-P= inlet pressure - outlet pressure, PSI.
This equation does not apply to your choke, but it still gives you the idea.