Which two-phase pressure gradient correlation can be used for any pipe inclination and flow direction?

• A. Lockhart-Martinelli
• B. Hagedorn and Brown
• C. Zuber and Findlay
• D. Beggs and Brill

Answer: (D)

Predicting two-phase pressure drop in pipes requires a correlation that handles how the gas and liquid share the cross-section (phase slip) and how pipe orientation affects the flow regime and holdup. Beggs and Brill is best here because it was designed to cover a wide range of pipe orientations and flow directions. It uses a flow-regime map together with holdup and slip calculations, plus a two-phase friction multiplier that adapts to the geometry and the specific regime (slug, annular, churn, etc.). This framework naturally includes horizontal, vertical, and inclined pipes and accounts for hydrostatic effects that vary with angle, making it applicable across different directions. The other correlations were developed with more limited orientation or regime applicability, so they don’t offer the same universal applicability as Beggs and Brill.