ON THE ENHANCEMENT OF FILMWISE CONDENSATION HEAT TRANSFER BY MEANS OF THE COEXISTENCE WITH DROPWISE CONDENSATION SECTIONS

This article describes work aimed at obtaining higher filmwise condensation heat flux by distributing dropwise condensation surfaces of optimal width promoted by an organic coating among filmwise surfaces, and to get higher mean overall heat transfer coefficients in condensing systems. Several different spacings were examined for the horizontal orientation, arranging a dropwise section above a filmwise one, to make clear the effect of the drops falling down to the filmwise section. The heat flux of the filmwise part increased with increasing the height of the dropwise part up to 2 mm, but then decreased above that. The extent of the filmwise part that was augmented by drops was also tested by changing the width of the filmwise section sandwiched between dropwise sections of constant width. The heat flux of the filmwise part increased abruptly at a width between 5 and 3 mm. Consequently, it was shown that there exists an optimum width for each section for enhancing condensation heat transfer in the filmwise sections.