Effect of oscillatory EHD on the heat transfer performance of a flat plate

The present study investigates the effect of oscillatory EHD on the heat transfer performance of a flat plate. A needle type electrode with positive polarity is used to generate ionic wind with applied voltage ranging from 4 to 9.5 kV. The wave forms of the input voltage are either steady or stepped and the frequency ranges from 0.5 to 2 Hz with the separation distance between the electrode and the test plate being 5 and 15 mm, respectively. It is found that at the same applied voltage, the heat transfer performance subject to the oscillatory EHD is always inferior to that of the steady EHD for all frequencies. A parabolic dependence of the ionic current with the supplied voltage is seen under steady EHD operation. However, the ionic current vs. supplied voltage shows a rather linear dependence pertaining to the oscillatory EHD. For a smaller separation distance of 5 mm, the heat transfer performance for f = 0.5 Hz is slightly higher than that of f = 2 Hz. However, the trend is reversed when the separation distance is increased to 15 mm. (C) 2013 Elsevier Ltd. All rights reserved.