Experimental results for etectrohydrodynamic (EHD) effects on nucleate boiling at passively enhanced surfaces, such as Thermoexcel-HE and Gewa-T, are reported. The experiments were carried out using a single-tube test rig by applying a 0- to 30- kV dc potential to a dielectric liquid (Refrigerant-114). The EHD effect on the enhanced surfaces is compared with results of earlier experiments on smooth and Thermoexcel-C tubes and discussed. The results indicate that the boiling hysteresis at these passively enhanced surfaces can be eliminated and the nucleate boiling can be further enhanced and controlled by applying an electric field. An explanation of bubble initiation at low superheat by an electric field is offered in terms of the effect of the field on bubble critical radius.
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