Heated Liquid Film Flow and its Breakdown Caused by Marangoni Convection : 1st Report, The Characteristic Flow of Pure Water

Abstract

The flow characteristic of pure water partly heated on the surface was experimentally investigated by using a holographic interferometer. An extremely low velocity of water surface flow compared with that of any other liquid had been previously observed. In this experiment the water surface was cleaned by sucking out the surface layer before heating. The measured surface velocity is about one order of magnitude higher than that of water without cleaning the surface and is consistent with the velocity expected by Marangoni convection which was calculated by temperature distribution of the water surface. The flow characteristic of pure water is not dependent on the absolute value of surface tension force, as was previously thought, but on the surface condition. If the surface is spoiled by a contaminant such an oil, dust or any other inhibiting elements, Rayleigh convection dominates the flow pattern. The effects of liquid film thickness on flow pattern and on temperature distribution in liquid phase was also discussed in relation to film breakdown.