Enhancement of external forced convection by ionic wind

An ionic wind is formed when air ions are accelerated by an electric field and exchange momentum with neutral air molecules, causing air flow. Because ionic winds can generate flow with no moving parts and have low power consumption, they offer an attractive method for enhancing convection heat transfer from a surface. In the present work, corona discharges are generated between a steel wire and copper-tape electrode pair on a flat plate, perpendicular to the bulk flow direction such that the ensuing ionic wind is in the direction of the bulk flow. The corona discharge current is characterized, and experimental measurements of heat transfer from a flat plate are reported. Infrared images demonstrate that the cooling occurs along the entire length of the wire, and local heat transfer coefficients are shown to increase by more than 200% above those obtained from bulk flow alone. The magnitude of the corona current and the heat flux on the flat plate are varied. The heat transfer coefficient is shown to be related to the fourth root of the corona current both analytically and experimentally, and heat transfer enhancement is seen to be solely a hydrodynamic effect. Variation of the spacing between electrodes demonstrates that while the local peak enhancement is largely unaffected, the area of heat transfer enhancement is dependent on this spacing.