Microscale Heat Transfer Enhancement Utilizing EHD Effects

The augmentation of direct heat removal from small-scale heating elements by an electrohy drodynamically (EHD)-induced flow was experimentally investigated. The shape of electrodes, polarity, electric field strength and electric conductivity of a working fluid were systematically changed to clarify the heat transfer mechanism. By applying electric field, the increase of the heat transfer coefficient of FC-72 (CFC) for a 25 mm² heating element was enhanced 1.8 times at maximum compared to those with no electric field. For a 0.25 mm² heating element, it remained at 1.2 times. However, the heat transfer coefficient for the 0.25 mm² heating element is about 15 times greater compared with that for 25 mm² due to the fin effect of the substrate. By using a mixture of R113 and ethanol, the heat transfer coefficient was increased about 10 times at maximum compared to those with no electric field, which was proportional to the power consumption.