D208 水の過冷却解消に及ぼす気泡核の影響に関する研究 : 水中に存在する気泡数の測定(オーガナイズドセッション14 : 固・液相変化を伴う熱・物質移動及び流動の基礎と応用)

Abstract

In order to clarify the effect of bubbles on freezing of supercooled water, two kinds ol experiments were carried out. In the first experiment, diameters and the number of bubbles in the water samples were measured using a CCD camera. The water samples had a free surface to observe and count the number of bubbles. In the second experiment, the degree of supercooling at freezing of supercooled water was measured. Water samples were covered with silicone oil to trap bubbles in the water. In each experiment, two kinds of water sample conditions were prepared. Ultra pure water was used and air was saturated at the room temperature. The volume of the water samples was 1cm^3 and bubbles were introduced into water samples. In the case of condition (1), the holding time period before starting the experiments was 0 hour at free surface. On the other hand, in the case of condition (2), the holding time was 100 hours at free surface. It was found that a lot and wide range of bubbles existed in the water samples in the case of the holding time of 0 hour at free surface. On the other hand, there were few number of bubbles in the case of the holding time of 100 hours. Meanwhile, degree of supercooling at freezing was high in the case of the holding time of 100 hours compared to the one of the holding time of 0 hour. The reason was suggested that the bubbles in the water can be released from the surface in the case of lOOhours and trapped at the oil-water interface in the case of Ohour. Hence, it was clarified that bubbles had effects on the freezing of supercooled water.