Experimental study of dropwise condensation on plasma-ion implanted stainless steel tubes

Plasma-ion implantation was used to achieve stable dropwise condensation of saturated steam on stainless steel tubes. For the investigation of the efficiency of plasma-ion implantation regarding the condensation process a condenser was constructed in order to measure the heat flux density q˙ and the heat transfer coefficient hc for the condensation of steam on the outside surface of a single horizontal tube. For tubes implanted with a nitrogen ion dose of 1016 cm−2, the heat transfer coefficient hc was found to be larger, by a factor of 3.2, in comparison to values theoretically calculated by the corrected Nusselt film theory. The heat flux density q˙ and the heat transfer coefficient hc were found to increase with increasing ion dose and steam pressure. The heat transfer coefficient decreases with increasing surface subcooling as it has been found in former work for dropwise condensation on ion implanted vertical plates.