CFD study on the effect of various geometrical parameters of honeycomb type orifices on pressure drop and cavitation characteristics

Abstract

Flow zoning devices in nuclear power plants are used to achieve desired pressure drop and flow rates. Cavitation in these devices may cause erosion, flow chocking, noise, vibration, resulting in severe damage. Optimization of flow conditions, geometrical parameters, and prediction of the hydrodynamics of the flow field are necessary to avoid cavitation in these devices. In the present study, Computational Fluid Dynamics (CFD) simulations have been carried out to model flow through honeycomb shaped orifices. The effect of various geometrical parameters such as flow area, the spacing between plates, number of plates, orientation between plates (inline or offset) on pressure drop, and cavitation characteristics has been studied. The multiphase mixture model (water-liquid and water vapor), in conjunction with the Schnerr and Sauer cavitation model, is used to model the flow through orifice plates. Axial distribution profiles and contours of vapor fraction and pressure coefficient have been plotted to analyze the cavitation characteristics for different plate configurations and to get a better understanding of the flow field. Lowest pressure values are observed at the orifice throat and near plate exit. Threshold flow velocities above which flow is subjected to cavitation have been identified for different geometrical configurations. An increase in the number of plates reduces the probability of cavitation. Reduction in the flow area of the orifice plate increases the cavitation potential and pressure drop. However, an increase in plate spacing enhances the pressure recovery and reduces non-uniformities in the flow field.