Two-stage Water Desalination Equipment CFD Simulation

Description

Description

Water desalination or distillation is a widely used mechanism for purifying water by removing impurities such as salts, minerals, and other contaminants. This process involves heating water to its boiling point, which causes the water to vaporize and leave the impurities behind.

The water vapor is then condensed into a liquid, resulting in pure water. Distillation is a highly effective method for removing impurities from water, as it can remove the smallest contaminants that other methods may not eliminate.

Distillation/desalination can be performed using various equipment, ranging from simple pot stills to more complex industrial-scale distillation systems. The process has numerous applications, including producing drinking water, pharmaceuticals, and industrial chemicals.

Two-stage Water Desalination Equipment Methodology

The VOF multiphase model was used in this project to simulate the surface evaporation occurring inside the desalination system. A user-defined function (UDF) was hooked to the Fluent source code to model the mass transfer through surface evaporation, as this mechanism is not included in the base code.

The device’s bottom surface increases the bulk temperature of water to around 353 K, resulting in increased molecular energy of water, which helps with the surface evaporation process occurring faster. The vaporized water will then hit cool sloped surfaces where it will condense into water liquid and be directed to the system outlet.

Furthermore, a realizable k-epsilon model is used to solve turbulent fluid equations. This model provides higher accuracy when simulating internal flows. The energy equation is also enabled due to the fact that we have heat transfer in this model. The present study is performed in transient format and 3D. Moreover, gravity is enabled to capture the upward motion of vapor due to its lesser density than water liquid.

The geometry of the present project is designed in Design Modeler and meshed in ANSYS Meshing software. The mesh type is unstructured, and the element number equals 1,936,581.

Conclusion

As observed in the obtained results and contours, stratified pressure distribution inside the system trays is clearly shown. This is due to the hydrostatic pressure of the water column inside the trays.

Also, as observed in the temperature contour, the bottom surface has an increased temperature which causes the water liquid’s molecular motion path to increase. This increase in molecular motion will lead to the increased kinetic energy of water molecules, which would, in turn, cause the surface evaporation process to occur faster.

Moreover, the amount of the generated vapor can be obtained by viewing the mass transfer rate contour. The exact amount of the vaporized water will distill after it touches the cool sloped plates. Therefore, the amount of vaporized water within the trays equals the amount of distilled water leaving the system through outlet boundaries.