An empirical investigation into enhancing natural convection heat transfer through corona wind in a needle-to-cylinder configuration

Abstract

Enhancing natural convection heat transfer in heated electrical devices, particularly those with curved geometries and limited space for cooling systems is a crucial area of research. This study experimentally evaluated the performance of a corona wind generator—an electrohydrodynamic (EHD) system—employing needle-to-cylinder configurations to improve natural convection around a heated cylinder. Three configurations were investigated: a single vertical wire electrode, a single lateral wire electrode, and two lateral wire electrodes, positioned perpendicular to the cylindrical surface at varying distances. Voltages ranging from 0 to 9000 V were applied to produce a corona wind jet. The findings revealed that lateral wire electrode configurations significantly enhanced natural convection heat transfer, achieving an average Nusselt number improvement exceeding 51.17 % at 8000 V compared to natural convection alone. Among these, the single lateral electrode configuration demonstrated superior performance, yielding a 13.87 % higher average Nusselt number than the vertical electrode configuration. It was observed that the corona wind jet initially impinged on the heated cylinder; however, increasing the distance between the electrode tip and the cylinder caused the jet to rise due to buoyancy, reducing its cooling effectiveness. Despite this limitation, the lateral electrode configurations effectively enhanced natural convection. The experimental results were utilized to develop a practical Nusselt number correlation that integrates voltage, electrode tip distance, distance of two electrodes, and cylinder diameter. The proposed model demonstrated high accuracy, with R² values ranging from 0.81 to 0.94, offering a valuable tool for designing efficient cooling systems for electrical devices.