Observation of Steam Condensation on Thin Vertical Tubes

Abstract

The observation and the measurement of the steam condensation phenomena on the wetted outer surface of the thin tubes arranged vertically were carried out. It was clarified that the condentate modes were affected by the surface tension of the condensate and the wavy shape of the condensate surafce appeared due to the surface tention instability for thin tubes. That is, while the smooth surfaces of condensate with uniform thickness were observed for the tube of 1 mm in outer diameter, the wavy shape with non-uniform thickness appered for 0.5 and 0.4mm in diameter. The wavy shape became remarkable with decrease of the tube diameter. Although the weve lengths of the instability under low condensation rate almost coincided with the analysis of Rayleigh for free liquid jet, they increasd with increases of the condensation rate and the axial length from the top.