An experimental, theoretical and numerical investigation of corona wind heat transfer enhancement

Abstract

Corona wind heat transfer enhancement is a non-mechanical means of augmenting transfer coefficients in free and low-velocity convection flow fields. Ions formed near the surface of a high-voltage electrode are forced along the electric field lines toward the nearby ground, inducing fluid motion and thereby enhancing convection. This study examines experimentally the resultant heat transfer in the needle-plate, wire-plate and multiple wire-plate configurations. Heat transfer coefficients as high as 70 W/m2K are reported. Joule heating of the air is measured, and found to generate a temperature increases of up to 3'C. The optimum needle and wire heights are found, and the trends in wire-plate performance are examined. A numerical procedure for solving the coupled Poisson and charge conservation equations in the wire-plate geometry is developed. A non-dimensional parameter is defined which allows the dominance of electrostatic over buoyancy forces to be demonstrated. This allows the energy equation to be decoupled from the momentum equation. The SIMPLEC procedure with uneven grid spacing is used to model the resultant flow field. The energy equation is solved in order to calculate the resultant heat transfer coefficients. Excellent agreement between experimental and computed heat transfer coefficients is observed. Novel electrode configurations are considered, and two promising electrode designs are presented.