No abstract

No abstract

Interfacial s t r e s s e s are calculated from new measurements of liquid height a n d p r e s s u r e d r o p for fully d e v e l o p e d horizontal stratified flow. T h e s e are related to w a v e properties. An improved d e s i g n m e t h o d is s u g g e s t e d . IntroductionFor low gas and liquid flows in a horizontal pipe, a stratified regime exists whereby the liquid moves along the bottom of the pipe and the gas concurrently above it. The most widely used method for predicting frictional pressure drop and liquid height (holdup) for this system is the analysis of Taitel and Dukler ( 1 976) that uses separate force balances for the gas and for the liquid.This approach, however, has limitations because of the assumption that drag at the interface, 7,, is the same as for a flat surface and because the Blasius equation is used to calculate the drag of the wall on the liquid, T~~. Experiments were therefore performed to determine 7, and 7wL. These were conducted with horizontal pipelines having diameters of 2.52 and 9.53 cm and with liquid viscosities of 1 to 80 cp (mPa -s).In a previous paper (Andritsos and Hanratty, 1986) we defined two types of interfacial waves:I . Regular two-dimensional waves 2. Large-amplitude irregular waves associated with a KelvinHelmholtz instability. The large-amplitude waves can cause large increases in 7,. A goal of this paper is to use this information to interpret measurements of 7,.The Taitel-Dukler method is found to do a good job in predicting the liquid height and the frictional pressure drop. However, considerable improvement is possible if the influence of waves on T , is taken into account. Improvements obtained by using a better relation for T~~ than the Blasius equation are not so large.It is found that the interfacial friction factor, J , increases linearly with gas velocity at gas velocities larger than needed to initiate waves, and that the proportionality constant is insensitive to pipe diameter. The effects of liquid viscosity and liquid flow rate are found to be of secondary importance over the range of liquid viscosities studied, and can be taken into account by assuming that f; is a function of the ratio of the height of the liquid to the pipe diameter, h / D . This influence of flow proper- Nikolaos Andritsos and T. J. Hanratty University of IllinoisUrbana, IL 6 180 1 ties onf; can be related to wave properties by assuming that the difference ofJ from the value for a smooth surface,f,, is related to the ratio of the wave amplitude to the wavelength. These results are used to suggest improved design relations for the frictional pressure drop and holdup. Background Literature

No abstract