Separation efficiency analysis of multiphase flow inside hydrocyclone using CFD / Mohamad Mazwan Mahat, Hazran Husain and Nor Safwan Mohmad

Separation phenomena inside the hydrocyclone often encounter issues related to misplaced particles at the outlet since there is a large variation of particle density. This research presents a computational numerical study of multiphase flow inside hydrocyclone to analyse the relationship between separation efficiency of particles and the diameter of the cylindrical section to complete the separation process which greatly affect the overall performance of hydrocyclone. The performance of hydrocyclone will be evaluated using CFD to simulate multiphase flow inside the hydrocyclone. In this study, the Reynolds Stress Model (RSM) is used in the model to simulate the swirling turbulent flow of gas and liquid, and the Volume of Fluid (VoF) Multiphase Model is used to simulate the interface between the liquid and the air core. The Discrete Element method (DEM) model simulation of particle flow then makes use of the results to track the solid particle motion. Pressure and velocity play important roles in the separation of particles. A centrifugal force that separates particles according to their mass is produced when the hydrocyclone's input is subjected to higher pressure. The hydrocyclone rotates and produces a spiral flow pattern as the fluid's velocity increases as it goes towards the centre of the device. Higher diameter of the cylindrical section, provide higher tangential velocity of particles and their centrifugal forces, resulting in great collection efficiency. In this paper, it has been demonstrated numerically that the performance of hydrocyclone is significantly influenced by different diameters of the cylindrical sections. Increasing the diameter of the cylindrical section increased the separation efficiency from 34.4% to 44.3% for particle size of 5 μm. Based on the pressure, velocity and streamlines distribution profiles obtained, the results revealed that the tangential velocity contributes largely to the centrifugal forces, resulting in greater collection at the outlet. The increase in diameter increases the residence time of particles inside the hydrocyclone, causing a more frequent swirl rotation of the particles; thus, increasing the clarity of particle separation and enhances the separation efficiency.