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A study of slip ratios for the flow of steam‐water mixtures at high void fractions
Author(s) -
Vance William H.,
Moulton R. W.
Publication year - 1965
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690110628
Subject(s) - slip ratio , slip (aerodynamics) , mechanics , vapor quality , pressure drop , chemistry , pressure gradient , thermodynamics , volumetric flow rate , materials science , heat transfer , shear stress , heat transfer coefficient , physics
A technique employing the impulse plate principle was developed whereby the ratio of the average vapor‐to‐liquid velocities (slip ratio) for flowing two‐phase mixtures could be measured accurately at high vapor volume fractions. Data were collected for steam‐water mixtures flowing adiabatically in a horizontal ½‐in. tube. Flow conditions were in the spray annular and dispersed flow regimes and covered a pressure range of 30 to 80 lb. f /sq.in.abs., flow rates of 200 to 800 lb. m /(sec.)(sq.ft.), and steam qualities of 0.02 to 0.8. The experimental slip ratios, ranging between 1 and 3.5, decreased with increasing quality and pressure and increased with increasing mass velocity and pressure gradient. A theoretical analysis in which an idealized dispersed flow model was used indicated that the observed average slip ratios were caused largely by local slip between vapor and entrained droplets and that high local slip ratios may be attained near critical flow rates due to the simultaneously occurring steep pressure gradients. The total pressure gradients, computed by adding the Martinelli‐Nelson frictional pressure drop prediction to the acceleration pressure gradients calculated by the use of an empirical correlation of the slip ratio data, deviated from the experimental values by an average of only 14%.