Experimental Analysis on Reliability of Needle Electrodes in Ionic Wind

Electrohydrodynamic (EHD) cooling has gained prominence in recent years as a solid-state cooling technology due to lack of moving parts, low power consumption, silent operation, and superior thermal performance over passive cooling techniques. A common embodiment of such a cooling arrangement involves needles and finned heat sink acting as emitter and collector electrodes, respectively, to generate ionic wind. One of the major factors that affect the reliability of these air movers is the degradation of the needles over time. In this research, we have experimentally investigated the reliability of stainless-steel needles and characterized its performance over 60 cycles of operation. The results show considerable reduction in heat transfer as evidenced from the increase heat source temperature or thermal resistance. The cooling enhancement due to dc ionic wind dropped from a factor of 2.6-2.05. The surface of the needles was examined under a microscope and found to undergo oxidation, wear out, and micropitting when subjected to such repeated operations under high voltage. The degradation in thermal performance could be correlated to the change in the surface finish of the needles. The results point to the importance of ensuring the reliability of dc ionic winds produced under corona discharge for the cooling of electronic devices.