Description

Mist Eliminators are specifically engineered to extract impurities from process air emissions that evolve in the form of mist droplets. These impurities may consist of oil mist, machine coolant mist, chromic acid mist, sulfuric acid mist, and various other types of entrained mist.

As part of the project, a small amount of humid air (approximately 1%) is entered into a sophisticated mist eliminator device. The air and water droplets that are assumed to have a diameter of 0.0001 m, have a mass flow rate of 1.5132104 kg/s and 0.015 kg/s, respectively. The speed of air is 6.4 m/s and it drives the water particles into the domain.

Mist Eliminators work by utilizing composite mesh or vane plate surfaces to separate the mist droplets from gas streams through mechanical impingement and inertial impaction. The large surface area coupled with a small volume allows for the collection of liquid without substantially impeding the flow of gas.

These innovative devices work by collecting the droplets upon impact, without significantly slowing down the gas flow. Thanks to their compact size and large surface area, Mist Eliminators are a reliable solution for eliminating unwanted droplets in gas. So, by defining the trap boundary condition for mist eliminator plates, the flow behavior when it passes through these surfaces will be shown.

The geometry of the solution is designed in ANSYS Design Modeler. Afterward, the elements are generated in ANSYS Meshing software. The mesh file then is imported into ANSYS Fluent and the type of the elements changed to polyhedra and the final number of elements reached 2,062,734.

Methodology

The Discrete Phase Model (DPM) is used to model water-liquid particles in transient mode, while the air behavior is assumed to be steady-state. The realizable K-epsilon model is selected for turbulence characteristics of fluid flow and the effects of gravity are considered in the Z direction with a value of -9.81 m/s2.

Conclusion

The contour, vector, pathlines, and particle tracking graphical results are extracted from ANSYS Fluent software. Based on the velocity contour, it is evident that air enters the domain and rotates both above and below the inlet boundary condition. After coming into contact with the mist eliminator plates, it passes along them and exits the domain via the outlet boundary condition with a greater velocity. This behavior is more easily seen in the air pathlines view.

Finally, the animation file shows the movement of water droplets, which hit the mist eliminator plates and get trapped there.