Compressibility effect in two-phase flow and its application to flow metering with orifice plate and convergent-divergent nozzle

The effect of solution gas on the two-phase flow behavior through an orifice plate and a convergent-divergent nozzle has been investigated with regard to the flow metering of compressible two-phase mixtures. A proper thermodynamics approach to consider more accurately the compressibility effect in an accelerated two-phase flow, in particular that through an orifice and Laval's nozzle in the presence of the solution gas, has been developed. From this approach an equation of state of mixture was derived and used in determining the orifice equation. An analysis of flow behavior has been performed and several illustrative plots were presented in order to evaluate the gas solubility effect in the flow metering with an orifice plate or a convergent-divergent nozzle. A delimitation between critical and noncritical flow has been established in terms of measured parameters and a relationship between the critical pressure and gas-liquid mass ratio was also shown.