When a water-ethanol binary mixture vapor condenses on a vertical flat plate

the condensate film rises locally and creats many drops on the film.Many researchers called such a phenomenon non-film condensation

pseudo-dropwise condensation or Marangoni condensation.The purpose of this paper was to experimentally study the effect of vapor pressure on Marangoni condensation.At the same vapor speed u=4 m·s-1 and three different vapor pressures

i.e.

31.16 kPa

47.36 kPa and 84.53 kPa respectively

the condensation processes of the vapors of water

ethanol and water-ethanol mixture on a brass block were studied and the variation of condensation mode was observed.The results showed that

at the same vapor concentration/speed and surface subcooling

the heat transfer coefficients of high vapor pressure were larger than those of low vapor pressure.Furthermore

at different concentrations

the vapor pressure had different effects on condensation.For water-ethanol mixture vapors of extremely high or low concentration of 22%，51%

and 0.5%

1%

the vapor pressure had little effect on the condensation heat transfer

but for mixture vapors of 5.1% and 9.83%

heat transfer coefficients increased obviously with the vapor pressure.