EXPERIMENTAL INVESTIGATION OF CORONA WIND HEAT-TRANSFER ENHANCEMENT WITH A HEATED HORIZONTAL FLAT-PLATE

Corona wind enhancement of free convection was investigated with the needle-plate geometry in air. High voltage was applied to a needle suspended above a heated plate, and heat transfer coefficients were computed by measuring the plate surface tempera ture distribution with an infrared camera. Local heat transfer coefficients greater; than 65 W/m(2) K were measured, an enhancement of more than 25:1 over natural convection. The enhancement extended over a significant area, often reaching beyond the 30 cm measurement radius at high power levels, Joule heating significantly reduced the effective impingement point heat transfer coefficient. The corona wind was found to be more efficient with positive potential than with negative. The heat transfer efficiency, was optimized with respect to electrode height and applied voltage. The needle-place heat transfer effectiveness improved rapidly with Increasing height, and became relatively insensitive to height above a threshold value of about 5 cm.