Industries need oil-water separators to separate oil and other hydrocarbons from water for environmental compliance and water source protection. These gravity-based separators securely release clean water by removing oil, grease, and suspended particulates from wastewater. They use coalescing plates, baffles, or other techniques to separate water in chambers or tanks. This device prevents oil pollution and preserves ecosystems in manufacturing, automotive, and petrochemical industries, where oil-water mixes are common byproducts.

In our latest study, a two-phase Oil-water Separator is simulated using ANSYS Fluent. The mechanism of separators is described above. As illustrated, coalescing plates are implemented in the separator that filters the phases.

Figure 1: two-phase oil-water separator equipped by coalescing plates

Simulation Process

The 2D computational domain requires hard work due to its details. Then, it is meshed, resulting in 90948 triangular cells. The Eulerian multiphase model solves both phases, including water and oil. The surface tension between these continuum phases plays a key role. The rest of the challenges are dedicated to setting appropriate boundary conditions. It is a transient (unsteady) study so it requires some time to be simulated.

Figure 2: 90948 triangular elements generated for two-phase oil-water separator

Post-processing

The oil velocity contour shows a complicated flow pattern inside the separator. The fastest speeds, up to 0.2 m/s, are seen at the inlet and exit areas, as well as in the small spaces between the internal plates. These structures make a serpentine path for the fluid mixture. This helps it separate by making it stay in one place longer and changing the flow pattern. The differences in speed seen near these structures show areas of possible turbulence and mixing, which can help the separation process by making oil drops stick together.

Figure 3: Velocity distribution in Two-phase Oil-water Separator

The water and oil volume fraction contours depicts that the separator design works well. There is a clear stratification, with oil (red in the third image) rising to the top and water (red in the second image) sitting at the bottom because it is denser. There is an obvious boundary between the two phases, especially in the second chamber of the separator. The plates inside seem to be very important for this separation. They probably do this by making surfaces for coalescence and still areas that make gravity separation work better. As you move from the inlet to the outlet, the volume fractions change slowly. This suggests that the phases are gradually separating along the length of the separator. The last chamber shows almost full phase separation.

Figure 4: a) Oil b) Water volume fraction in Two-phase Oil-water Separator