ACTIVE ENHANCEMENT OF EVAPORATION OF A LIQUID-DROP ON A HOT SOLID-SURFACE USING A STATIC ELECTRIC-FIELD

This study aims at further improvement of evaporation or boiling heat transfer using an electric field. Active enhancement using an electric field would be extremely effective in film boiling, but favorable eff ects would be expected on nucleate and transition boiling, and on the maximum and minimum heat fluxes. In this paper the results of our prec eding studies are first summarized. We have found that the application of an electric field enhances, to a great extent, the evaporation of a liquid drop on a hot solid surface. The time needed for a single dro p to evaporate completely reduces to one-twentieth of that for evapora tion without an electric field, when 300 V is applied to a drop of eth anol. The results of an additional experiment are presented in this pa per. The heat transfer coefficient during evaporation of a liquid drop on a platinum surface is measured while the volume of the drop suspen ded at the tip of a thin needle nozzle is kept constant. The voltage a pplied between the drop and the heat transfer surface is varied from 0 V to 2000 V (for R113) or to 250 V (for ethanol). The maximum enhance ment ratios of the evaporative heat transfer coefficients at the highe st voltages are 7.6 for ethanol and 2.8 for R113.