In this study, the EHD (electrohydrodynamic) enhancement of heat transfer in open vertical rectangular capillary microgrooves heat sink was studied, and with the help of a high-speed digital camera with maximum speed of 100,000 frames per second, the nucleate boiling phenomena in microgrooves were also visually investigated. The tests results have shown: (1) the input heat flux has no influences on the threshold voltage basically, while the absolute temperature drop A T of the lower or higher input heat fluxes were smaller than that of the midrange ones. (2) the threshold voltage was getting small with the decreasing distance between the electrodes, meanwhile the absolute temperature drop Δ T was growing larger and larger. (3)the threshold voltages of NO.1 microgrooves(the dimensions are listed in Table 1) were lower than that of NO.2, and Δ T of NO.1 microgrooves was larger than that of NO.2. (4) the bubble growth process was becoming longer with the increasing applied voltage.
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