Photographic study on transitions from non-boiling and nucleate boiling regimes to film boiling due to increasing heat inputs in liquid nitrogen and water Sakurai, A; Shiotsu, M; Hata, K [Kyoto Univ. (Japan)]; Fukuda, K 42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES; PHOTOGRAPHY; NUCLEATE BOILING; FILM BOILING; NITROGEN; LIQUIDS; WATER; HEAT TRANSFER; CRITICAL HEAT FLUX; VAPORS; BUBBLES; PRESSURIZATION; SURFACES; SUPERHEATING The behavior of vapor bubbles and vapor film during the transition from non-boiling regime such as natural convection or transient conduction regimes to film boiling on a 1.2 mm diameter platinum horizontal cylinder in liquid nitrogen and in water due to the exponentially increasing heat inputs from a quasi-steady state to a very rapidly increasing one was examined using a high speed video camera. The water experiments were performed for the cases without and with pre-pressurization before each experimental run. It was confirmed by the observation of vapor behavior that the direct transitions in liquid nitrogen and in pre-pressurized water occur due to the explosive-like heterogeneous spontaneous nucleation (HSN) in originally flooded cavities not only in the transient conduction regime but also in the quasi-steady increasing natural convection regime without the vapor bubbles from active cavities entraining vapor. It was also confirmed that the semi-direct transition from conduction regime to film boiling with nucleate boiling due to the rapidly increasing heat inputs in water occurs due to the HSN with nucleate boiling at around the lower limit of HSN surface superheat in water even for the non-prepressure case. The lower limit of HSN surface superheat was measured as an initial boiling surface superheat caused by a quasi-steadily increasing heat input for the case with pre-pressurization before each experimental run. (author) Atomic Energy Society of Japan, Tokyo (Japan) Atomic Energy Society of Japan, Tokyo (Japan) Japan 1998-12-31 English Conference Conference: NURETH-8: 8. international topical meeting on nuclear reactor thermal-hydraulics, Kyoto (Japan), 30 Sep - 4 Oct 1997; Other Information: DN: Published in 3 volumes; PBD: 1997; Related Information: Is Part Of Eighth international topical meeting on nuclear reactor thermal-hydraulics; PB: 1890 p. Medium: X; Size: pp. 1038-1049 https://doi.org/ [] CONF-970922- TRN: JP9910089 JPN; SCA: 420400; PA: JPN-99:010089; EDB-99:042561; SN: 99002080210 2008-02-04 330910