Abstract
The local dynamics of spatially developing liquid-liquid dispersed flows at low superficial velocities, ranging from 0.2 to 0.8 m s−1, are investigated. The dispersions are generated with an in-line static mixer. Detailed measurements with laser-based diagnostic tools are conducted at two axial pipe locations downstream of the mixer, namely, at 15 and 135 equivalent pipe diameters. Different flow patterns are recorded, and their development along the streamwise direction is shown to depend on the initial size and concentration of the drops as well as the mixture velocity. The drop size is accurately predicted by an empirical formula. The variations in drop concentration over the pipe cross-section along the pipe result in local changes of the physical properties of the mixture and consequently in asymmetrical velocity profiles, with the maxima of the velocity located in the drop-free region. Computational fluid dynamics simulations based on a mixture approach predict the experimental results close to the experimental uncertainties for the majority of the cases. The simulation results reveal that gravity and lift forces, as well as shear-induced diffusion are the most important mechanisms affecting the drop migration. It is found that the drops behave as suspensions of rigid spheres for the conditions investigated, despite the deformation effects, which are found experimentally to be stronger at the densely packed region.
Highlights
The flow and separation characteristics of unstable liquidliquid dispersions in pipes involve complex phenomena of fundamental theoretical interest.1 Apart from nuclear cooling systems, separators, and two-phase reactors, liquid-liquid dispersions are important for the oil and gas industry where water is often present in oil transportation pipelines, resulting either from condensation of saturated gas or directly produced from the reservoirs as they mature
Understanding the interactions between the spatial distribution of the two phases and the local flow characteristics is crucial for the design and operation of these facilities
Details of the test section can be found in the work of Voulgaropoulos and Angeli7 and Voulgaropoulos et al
Summary
The flow and separation characteristics of unstable liquidliquid dispersions in pipes involve complex phenomena of fundamental theoretical interest. Apart from nuclear cooling systems, separators, and two-phase reactors, liquid-liquid dispersions are important for the oil and gas industry where water is often present in oil transportation pipelines, resulting either from condensation of saturated gas or directly produced from the reservoirs as they mature. The flow and separation characteristics of unstable liquidliquid dispersions in pipes involve complex phenomena of fundamental theoretical interest.. Apart from nuclear cooling systems, separators, and two-phase reactors, liquid-liquid dispersions are important for the oil and gas industry where water is often present in oil transportation pipelines, resulting either from condensation of saturated gas or directly produced from the reservoirs as they mature. Dispersions often form at pieces of equipment such as choke valves or bends, and they tend to separate further downstream. There have been efforts to develop in-line separators in the pipe and avoid transporting water over long distances, especially in subsea pipelines. Understanding the interactions between the spatial distribution of the two phases and the local flow characteristics is crucial for the design and operation of these facilities
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