Sieve tray pressure drop by means of CFD modeling and simulation

Abstract

Sieve trays must be designed to have and operated at acceptably low enough tray pressure drop. Both of these tasks (i.e., tray design and tray analysis) require method(s) for sieve tray pressure drop determination. So far, only empirical correlations have been used for sieve tray pressure drop estimation. However, the correlations are not based on actual mechanics of flow but are based on gross oversimplifications and empirical correlations– hence often have large errors and are not reliable. A reliable and accurate way for the pressure drop determination can be achieved by use of working computational fluid dynamics (CFD) modeling and simulation. With working CFD model provided, the CFD modeling and simulation is mechanistic and first principles based or fundamentals based. In this work, a CFD model is developed and used to model and simulate and predict sieve tray pressure drop. The model considers the three-dimensional twophase flow of gas (or vapour) and liquid in which each phase is treated as an interpenetrating continuum having separate transport equations. Interaction between the two phases occurs via interphase momentum transfer. For the CFD analysis, the commercial package CFX 17.0 of ANSYS was employed. Total and dry tray pressure drops are predicted for various combinations of gas and liquid flow rates. Predicted results are inacceptable and good agreement with experimental results. The objective of the work was developing CFD model for sieve tray pressure drop and studying and finding out the extent to which the CFD modeling and simulation can be used as a prediction and design tool and method for sieve tray pressure drop. From the results and the CFD model performance, it is concluded that the CFD model provided here is acceptably good for sieve tray pressure drop modeling and simulation and hence is acceptably good for tray design and analysis.