This study aims to optimize the orifice diameter to reduce pressure hunting in the pilot valves of positioners used in nuclear power plant control systems. Computational Fluid Dynamics (CFD) analysis using ANSYS CFX was conducted to create 3D models with varying orifice diameters (1 mm, 1.5 mm, 2 mm, 2.5 mm, and 3 mm). To enhance the accuracy of the analysis, boundary layer meshing techniques (Inflation) were applied, and the SST k-ω turbulence model was employed. The analysis of pressure variation and pressure hunting over time revealed that larger orifice diameters resulted in reduced pressure hunting, with a 3 mm orifice diameter achieving 0% pressure hunting. Additionally, it was observed that larger orifice radii slightly increased the average outlet pressure. Based on the findings, a 3 mm orifice diameter is recommended to effectively mitigate pressure hunting in pilot valves, contributing to improved system stability in nuclear power plants. Future studies will explore the design of slanted orifices to further analyze fluid flow characteristics.

Abstract
1. 서 론
2. 유동해석
    2.1 Analysis model
    2.2 Analysis setting
    2.3 Results
3. 결 론
References

• 곽효서(Assistant professor, Mechanical Engineering Major, Dong-Eui University) | Hyo-seo Kwak Corresponding author