Mixing patterns in water plugs during water/ionic liquid segmented flow in microchannels

Flows of two immiscible liquids are encountered in a diverse range of processes and equipments In particular in the petroleum industry, where mixtures of oil and water are transported in pipes over long distances Accurate prediction of oil-water flow characteristics, such as flow pattern, water holdup and pressure gradient is important in many engineering applications However, despite of their importance, liquid-liquid flows have not been explored to the same extent as gas-liquid flows In fact, gas-liquid systems represent a very particular extreme of two-fluid systems characterized by low-density ratio and low viscosity ratio In liquid-liquid systems the density difference between the phases is relatively low However, the viscosity ratio encountered extends over a range of many orders of magnitude Table 11 summarizes experimental studies reported in the literature on horizontal oil-water pipe flows, while studies on inclined and vertical systems are summarized in Table 12 and 13 (The tables can be found at the end of the end of this article before the bibliography) These tables reflect the wide range of physical properties encountered Moreover, oils and oil-water emulsions may show a Newtonian or non-Newtonian rheological behavior Therefore, the various concepts and results related to gas-liquid two-phase flows cannot be readily applied to liquid-liquid systems

Liquid-Liquid Two-Phase Flow Systems

The phase distribution of water-oil flows was studied experimentally from a separated flow without mixer to a oil in water or water in oil dispersed in horizontal tubes Under most conditions the pattern was oil continuous in water dispersed or water continuous in oil dispersed flow continuously and there is entrainment in the form of drops of phase into the other The investigations were carried out through the cross-sectional phase distribution in the flow of mixtures of water and kerosene such as EXXSOL-D80 in a horizontal 254 mm bore stainless steel section The phase fraction distribution was determined using a traversing beam gamma densitometer, with the beam being traversed in three directions (0 0 , 45 0 and 90 0 of the vertical line passing through the axis of the tube) Measurements were made at three positions spaced along the 97 m test section length (10 m, 585 m and 772 m along the horizontal tube) The measurements were done in the Two-phase Oil Water Experimental Rig (TOWER) facility This facility allows the two fluids to be fed to the test section before they are separated and returned once more to the test line The flow developed naturally from an initial stratified flow in which the oil and water were introduced separately at the top and the bottom of the test section respectively It was found that the liquids were fully inter-dispersed by the end of the test section The results were also used to define the flow patterns in water-oil liquid-liquid flow system The phase fraction distribution was shown to be homogeneously mixed near to the outlet of the test section

https://jafmonline.net/JournalArchive/download?file_ID=15223

Water local volume fraction on oil in water dispersion

En este trabajo se evalua la precision de 76 modelos homogeneos de gradiente de presion para determinar el gradiente de presion experimental reportado en una base de 2415 datos de flujos bifasico gas-liquido en tuberias horizontales. Estos modelos se formularon a partir de 4 ecuaciones de densidad de mezcla combinadas con 19 ecuaciones de viscosidad de mezcla. Al estudiar el efecto de la viscosidad y de la densidad de mezcla en el gradiente de presion, utilizando el modelo homogeneo, se observa que el mejor modelo obtuvo un error absoluto promedio de 25.7%, mientras que el peor modelo obtuvo un error cercano al 2000%. Los resultados obtenidos indican que la precision del modelo homogeneo de gradiente de presion de flujo bifasico gas-liquido, depende significativamente de la adecuada seleccion de las ecuaciones de viscosidad y de densidad de mezcla.

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J.G. Knudsen

Papers

Two-phase liquid--liquid flow in pipes