Self-evaporation phenomenon of water accompanied by a circulation flow in a vessel - 1st report examination of the self-evaporation phenomena through visualization experiments

摘要

Characteristics of the self-evaporation of hot water in a vertical vessel with internal baffles were investigated experimentally by using a visual hot model. The experiment apparatus was designed by modeling Kuths' varying pressure steam accumulator, and consisted of a vertical straight vessel (100mm in diameter and 1500mm in height) and internal baffles such as a straight pipe (60mm in diameter) and tapered tubes which were installed concentric to the vessel. Self-evaporation experiments were executed under vacuum pressure conditions. It was found that a permanent circulation of hot water was naturally induced in the vessel macroscopically, and nucleation took place within the upper part of the internal baffles near the water surface along this water circulation. Self-evaporation could go on steadily and the temperature uniformity in hot water layer could be improved remarkably in comparison with the case with no internal baffles. In this case, large portion of the self-evaporation of hot water resulted from the hydraulic pressure loss during the upward flow motion in the inner pipe.