Investigation of transition mode phenomenon from dropwise to filmwise steam condensation

摘要

Experimental results of a study of transition from dropwise to filmwise steam condensation are presented in this report. Dropwise condensation was stimulated by fluorine-containing disulfide. This type of organic stimulator create a monomolecular coating on the heat exchange surface. This coating has a finite life time. After some thousands of hours of heat exchange surface operation the organic coating began to destruct. As a result dropwise condensation little by little transforms to filmwise. Photograph observation this phenomenon was carried out through an optical system with a magnification up to 262. For different time intervals the portion of the heat exchange surface with different condensate modes (dropwise and film) were determined. The average heat removal coefficients have been determined by using the heat conduction models through drops and local films. The available time parameters information about condensate modes also was took into consideration. It can be noted that there was a satisfactory agreement between experimental and calculation results.