Enhancement of film condensation using porous fins

Abstract

The effect of porous fins on film condensation on a horizontal tube was examined experimentally. It was demonstrated that the porous fins are effective in thinning the liquid film via a surface tension driven flow and hence enhancing the condensation rate. The experiments were limited to condensation of saturated vapor with surface subcooling up to 14°C. The results obtained using 95% porosity fins and R-ll revealed that, at the optimum fin spacing, the condensation rate can be increased by as much as two times that for a plain tube. It was observed that the liquid film behaves differently for different fin spacings. At small fin spacing (3.2-6.4 mm), a thin, apparently stable film was present. The film was nearly uniform and all of the condensate drained through the porous fins. At larger fin spacing (>9.5 mm) dripping from the tube itself as well as drainage through the porous fins occurred. The maximum condensation rate occurred at a fin spacing of 9.5 mm (/8 in.).