STUDY OF THE NOZZLE DIAMETER INFLUENCE IN THE FLUID DYNAMICS OF A CYLINDRICAL HYDROCYCLONE SEPARATOR

This work presents a numerical study on the flow inside a gas-liquid cylindrical hydrocyclone separator. This equipment operates with a free-surface liquid film flow, which is a combination of a centrifugal and a gravitational movement originated by a tangential nozzle. Fully developed flow results taken at the outlet of the separator depend on two dimensionless numbers, the film Reynolds number and the Froude number. However, numerical results indicate that the dynamics of the flow in regions close to the inlet of the device depend also on the ratio between the nozzle diameter and the chamber diameter. This paper will be focused on investigating this new dimensionless number using both CFD and a mechanistic model. Software ANSYS-CFX was employed in the CFD analysis to simulate a wide range of operating conditions regarding the three dimensionless numbers mentioned. The results of the simulations provided basis for the development of a compact mechanistic model for calculating velocity components, film thickness and other variables. This model was derived by analyzing the motion of a fluid element and then by including additional terms that represent the sudden expansion of the flow at the inlet of the cylindrical chamber. Then, the terms included and some model coefficients were calibrated using the numerical results. The outcomes of this work can be used to predict the flow dynamics in a hydrocyclone, which is a fundamental step for more complex evaluations such as estimating the separation efficiency and developing new constructive concepts for the equipment.