If you are referring to Napier's formula that is frequently used to estimated the steam flow from a system at a pressure Pgage through an orifice to atmosphere, this would interest me too.
quote begin(By Henry Manczyk, CPE, CEM Manczyk Energy Consulting):
Steam loss through an orifice can be estimated using a variant of the Napier
formula:
Steam Flow (lb/hr) = 24.24 x Pa x D²
where: Pa = Pgage + Patmospheric
Pa = Absolute Pressure, psia
Pgage = Gage Pressure, psig
Patmospheric = Atmospheric Pressure, psi = 14.696 psi
D = Diameter of Orifice, in.
quote end.
It is quite astonishing that the formula uses the absolute pressure. This would mean that if a system had a relative pressure of Pgage=0, then it would still leak steam with a flow rate of 24.24 x 14.696 x D² lb/hr to atmospheric pressure?!? It seems very strange to me that the absolute and not the relative pressure enters this formula. This formula and a corresponding table are stated by various steam trap manufacturers and vendors for steam trap monitoring and it is always used to estimate the steam leakage to atmosphere.
I would really appreciate any reference to the origine of this formula or any further comments.
Thanks
JF