ENHANCED STEAM CONDENSATION HEAT TRANSFER ON A HONEYCOMB-LIKE MICROPOROUS SUPERHYDROPHOBIC SURFACE UNDER DIFFERENT CONDENSING PRESSURES

摘要

Steam condensation heat transfer was studied over a honeycomb-like microporous superhydrophobic surface under various pressures, in order to elucidate the effects of pressure on the jumping-droplet condensation behaviors. The condensing pressure was varied from 4 kPa to 13 kPa. based on the typical operating conditions of condensers in power plants. Stable coalescence-induced droplet jumping was realized on the honeycomb-like superhydrophobic surface over this range of pressure, leading to a great enhancement on the condensation heat transfer as compared to that on the common hydrophobic surface, especially at small degrees of subcooling (e.g.. ＜10 K). The frequency and number of jumping droplets were observed to decrease at lower pressures because of the less amount of condensate produced, and at higher degrees of subcooling due to the occurrence of surface flooding. The increasing condensing pressure was found to lead to a later onset of surface flooding. The results indicated that the honeycomb-like superhydrophobic surface has a great potential for industrial condensation equipment operating at multiple pressures owing to its superior performance and facile fabrication.