TRANSITION MODES OF FILM-TO-DROPWISE CONDENSATION.

The object of the study is to clarify the transition modes of film-to-dropwise condensation on the lyophobic surface. From the measured results of the propylene glycol vapor for three surface edge conditions, changing the wettability, i. e. , for wetting, partially non-wetting and non-wetting edge conditions, the transition modes were greatly affected by these conditions. Comparing the curves for decreasing surface subcooling modes were greatly affected by these conditions. Comparing the curves for decreasing surface subcooling with those for increasing subcooling, the reversible curves and the hysteresis curves, depending on the edge conditions, were obtained in the case where the overall cooling-side conductances were large enough to obtain the continuous curves for the increasing subcooling process. When the overall cooling-side conductances were small and the condensation curves had jumping regions, the hysteresis curves were essentially obtained for any edge conditions. The transition modes, for decreasing subcooling cases, were closely related to the variations of the condensation aspects, and were controlled by the edge conditions and the instability in an overall heat transfer system.