Critical and subcritical oil/gas/water mass flow rate experiments and predictions for chokes

A large database on critical and suberitical flow through orifice- and cage-type chokes have been obtained in the Multiphase Flow Loop (MPFL) of Norsk Hydro Oil and Gas R&D Center in Porsgrunn, Norway. This work is an extension of the studies performed in 1999 (367 data points) by Schaller et al. (2003), making a total data set of 509 data points. The downstream separator pressure and temperature were kept at 8 bara and 50 degrees C, respectively. The maximum upstream pressures were approximately 40 bara, giving a maximum pressure ratio of approximately 4. The Hydro models (Schaller et al. 2003) show a very good agreement for prediction of mass flow rate, both for critical and subcritical flow conditions, with an average error of absolute values of 6.2% and a standard deviation of 8.9%. Comparisons with the models of Sachdeva et al. (1986) and Perkins (1993) show that the performances of these models are not as good as the Hydro model. The Sachdeva model and the Perkins model both have average errors greater than 22%, with standard deviations greater than 25%. The Hydro models also seem to predict reasonably correctly the transition between subcritical and critical flow conditions.