Electrohydrodynamical(EHD) Research of Saturated Pool Boiling Heat Transfer.

Abstract

The enhancement of the saturated pool boiling heat transfer utilizing electric field has been studied. By selecting a small-scale heat transfer surface of 5 mm in diameter, the nucleate boiling heat transfer without the enhancement effect of the movement of boiling bubbles along the heat transfer surface has been realized to quantitatively examine the bubble deformation effect of the applied electric field. The boiling curves which have been experimentally obtained showed the enhancement ratio to be about twice that in the case where no electric field is applied. Therefore, by comparing these data with our previously obtained nucleate boiling curves on the larger heat transfer surface of 50 mm in diameter, which showed the enhancement ratio of about 50 times, it has been clarified that the effect of the deformation of bubbles in the electric field making the larger bottom area would cause the enhancement ratio of about twice and that the effects of violent motion of the bubbles along the surface would cause the additional increase of the enhancement ratio. To measure the thickness of the liquid film on the heat transfer surface under the boiling bubble, a capacitance probe has been devised by use of a heterodyne detector. Based on the results obtained using this capacitance proble, the high wall superheat increases the time of dissipation of liquid film in the case without the applied electric field. However, the liquid film on the heat transfer surface does not dissipate in high wall superheat due to continuous supply of liquid with applied electric field.