Calculators
Two-Phase Flow Pressure Drop — Lockhart-Martinelli
Frictional pressure drop for horizontal, isothermal, non-flashing liquid-gas two-phase flow in pipes. Computes single-phase liquid and gas dP/dL via Swamee-Jain friction factors, the Martinelli parameter X, the Chisholm two-phase multiplier φL², and the total pressure drop across the line.
Method: Each phase is treated as if flowing alone in the pipe. Reynolds number Rei = 4·(Wi/3600) / (π·D·μi·0.000672) with viscosity in cP. Friction factor: laminar f = 64/Re for Re < 2000, otherwise Swamee-Jain f = 0.25 / [log10(ε/(3.7D) + 5.74/Re0.9)]². Single-phase dP/dLi = f·ρi·vsup,i² / (2·g·D) / 144 (psi/ft) with g=32.174 ft/s². Martinelli parameter X = √[(dP/dL)L / (dP/dL)G]. Each phase’s flow regime classified by Re > 2000 (turbulent T) or ≤ 2000 (viscous V). Chisholm (1967) C constant: TT=20, TV=10, VT=12, VV=5. Two-phase liquid multiplier φL² = 1 + C/X + 1/X². Two-phase pressure gradient (dP/dL)2φ = φL² · (dP/dL)L; total ΔP = (dP/dL)2φ · L. Validation: applicable to horizontal, adiabatic, non-flashing flow; X < 0.1 indicates bubble/slug regimes, X > 10 indicates mist flow. For very high gas mass fractions or vertical lines, prefer Beggs-Brill or homogeneous-flow models. References: Lockhart & Martinelli, Chem. Eng. Prog. 45, 39 (1949); Chisholm, Intl. J. Heat & Mass Transfer 10, 1767 (1967); Perry’s Chemical Engineers’ Handbook 8th Ed., Sec. 6-26; Swamee & Jain, ASCE J. Hydraulics 102, 657 (1976).
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