Two-phase horizontal flow regimes are based on the Baker Chart for vapor-liquid non-flashing flow through circular ducts (pipe). It is further assumed that the line pressure drop is less than 10% of the absolute pressure to support the use of a single vapor density and flow regime for the entire line. Violation of this assumption requires the line to be broken into a number of segments which individually have pressure drops less than 10% of the segment absolute pressure.
Each flow regime has an individual pressure drop correlation. The pressure drops for stratified, plug, slug, and annular flow regimes are based on correlations by Baker. The wave flow regime pressure drop is based on the Huntington correlation. The dispersed flow regime is based on the Lockhart-Martinelli correlation for turbulent flow in both phases.
Mandhane, Gregory and Aziz present a brief discussion of the difficulties of discontinuities arising from composite pressure drop methods as used here and in their paper. A brief quotation from that work will suffice to highlight the difficulties.
"A serious potential problem associated with the use of any composite design procedure is related to discontinuities that may occur at flow-regime transition boundaries. These arise from using different methods of correlations in adjacent increments of the pipeline where flow conditions are only marginally different."
Flow Regimes and Pressure Drop
Copyrighted 2000, 2003