強制流動沸騰における非凝縮性ガスが気泡生成に及ぼす影響

抄録

It is not clear how the dissolved air works and affects heat transfer because the phenomenon is complicated with respect to forced flow boiling. This paper deals with subcooled flow boiling experiments using different inlet subcool temperature in the Perfluorohexane (PFH) in order to clarify its effects on flow boiling heat transfer through a tube with an inner diameter of 4 mm, excess temperature, boiling curve. In order to investigate the factors of the influence, we investigated the change of the boiling curve at local heat transfer coefficient, and the temperature distribution in the axial direction of the metal heat transfer tube. As a result, dissolved air was shown to affect boiling characteristics as boiling curve. In particular, dissolved air significantly affected the boiling curve in the low heat flux region. We found a two-stage overheating drop before occurrence of developed nucleate boiling in case of saturated dissolved air condition. Dissolved air also significantly affects the onset of boiling. These effects lead to increasing generation of bubble. It is considered that nucleate boiling disappears near the inlet of the metal heat transfer tube due to the high inlet subcool temperature, and then the second nucleate boiling occurs.