TPF-14 Pressure Drop and Void Fraction for Vertical Upflow in Large Diameter Pipes

S. Talapatra
2016; rev 06/2016

Liquid holdup correlations from open literature, HTRI, and Honeywell’s UniSim® Design PIPE module are summarized and compared against data for adiabatic vertical upflows. The HTRI database includes (a) pressure drop measurements for steam and saturated hydrocarbons in the outlet piping of a thermosiphon reboiler and (b) pressure drop measurements and flow visualization for air-water flow inside a transparent flow loop. Unlike other studies, this report focuses on large diameter pipes with developing flow effects because correlations applicable only to the fully developed section of the piping are generally unsuitable for the process industry. For two-phase flows with high density ratios, comparison of data and correlations reveals that the pipe section with developing flow has a higher liquid holdup and thus a higher pressure drop per unit length than the fully developed section. This observation can be attributed to liquid-vapor separation. Our analysis shows that the UniSim Design Liquid Slip model predicts adiabatic vertical upflow pressure drop best.