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Journal Articles

Macrolayer formation model for prediction of critical heat flux in saturated and subcooled pool boiling

Ono, Ayako; Sakashita, Hiroto*; Yoshida, Hiroyuki

Heat Transfer Engineering, 42(21), p.1775 - 1788, 2021/00

 Times Cited Count:3 Percentile:26.77(Thermodynamics)

In this study, the macrolayer formation model is proposed to predict the critical heat flux in the saturated and subcooled pool boiling based on the macrolayer dryout model. This model concept is based on the results of the previous experiments. In the model, the nucleation site is assumed to distribute based on the Poisson distribution. Combining the proposed macrolayer formation model and macrolayer dryout model, the CHFs up to subcooling 40K were predicted and they are successfully good agreement with the experimental data. Moreover, the concept of the model was confirmed by the numerical simulation using the TPFIT.

Journal Articles

Transient behavior of gas entrainment caused by surface vortex

Ezure, Toshiki; Kimura, Nobuyuki; Hayashi, Kenji; Kamide, Hideki

Heat Transfer Engineering, 29(8), p.659 - 666, 2008/08

 Times Cited Count:19 Percentile:63.94(Thermodynamics)

A compact sodium cooled reactor is one of important candidates as FBRs and has been investigated in the feasibility study of FBR cycle. According to the compact sizing of reactor vessel, gas entrainment at the free surface of sodium coolant becomes one of the significant issues for reactor design, and it is required to clarify the criterion of gas entrainment at free surface and the tolerance. In the present study, some visualization experiments were performed in a water-air system focusing on the gas entrainment due to surface vortex and its transient phenomena. Influences of horizontal velocity were clarified by the visualization. Time trends of circulation and length of gas core for the intermittent surface vortices were measured by the particle image velocimetry and visualization. It was found that the gas core length extends with time delay to the increase of circulation around the vortex.

Journal Articles

Proposal of design criteria for gas entrainment from vortex dimples based on a computational fluid dynamics method

Sakai, Takaaki; Eguchi, Yuzuru*; Monji, Hideaki*; Ito, Kei; Ohshima, Hiroyuki

Heat Transfer Engineering, 29(8), p.731 - 739, 2008/08

 Times Cited Count:37 Percentile:80.63(Thermodynamics)

Design criteria for gas entrainments (GE) from the liquid surface in a fast breeder reactor system were proposed in this paper for the two types of GE phenomena from a vortex dimple based on a computational fluid dynamics (CFD) method. The first gas entrainment phenomenon is a gas core extension directly to the outlet piping level, which induces large amount of GE to the flow system. The second is continuous bubble detachments from the tip of the vortex dimple. Based on CFD calculations for elemental experiments of the surface vortex, local CFD non-dimensional numbers were defined as the design criteria to prevent GE. In conclusion, it was found that the CFD non-dimensional numbers are useful for the design parameters of GE prevention.

Journal Articles

Thermal feasibility analyses for the 1356 MWe high conversion-type innovative water reactor for flexible fuel cycle

Liu, W.; Onuki, Akira; Yoshida, Hiroyuki; Kureta, Masatoshi; Takase, Kazuyuki; Akimoto, Hajime

Heat Transfer Engineering, 29(8), p.704 - 711, 2008/08

 Times Cited Count:2 Percentile:17.62(Thermodynamics)

With using the research achievements on thermal-hydraulic characteristics so far derived for the target tight lattice core, this paper studies the thermal feasibility of the designed 1356 MWe FLWR core using a modified transient analysis code TRAC-BF1. The newest critical power correlation developed at JAEA for tight lattice rod bundles is implemented to judge the occurrence of boiling transition from nucleate boiling to film boiling. The pressure drop in two-phase flow region is evaluated by Martinelli-Nelson two-phase multiplier. In the analyses, the 900 fuel assemblies in the designed core are modeled into 12 fuel channels according to the relative mass and power distributions. Analyses to the postulated abnormal transient events that may be possibly met in the operation of the FLWR are performed with $$Delta$$MCPRs being evaluated. The necessary coolant flow rate then is calculated based on the evaluated $$Delta$$MCPRs. As the results, for a natural circulation type FLWR, the operation limited MCPR is 1.19. For a forced circulation type FLWR, the one is 1.32.

Journal Articles

Development of thermal-hydraulic code coupled with heat conduction in structure for thermal striping phenomena; Development of calculation module for temperature distribution in structure

Tanaka, Masaaki; Ohshima, Hiroyuki

Proceedings of 2007 ASME-JSME Thermal Engineering Conference and Summer Heat Transfer Conference (CD-ROM), 10 Pages, 2007/07

An analysis program (MUGTHES) for fluid-structure thermal interaction has been developed to evaluate the thermal striping phenomena and to establish the evaluation method. MUGTHES can treat thermal-hydraulic field and temperature field in structure simultaneously. In this paper, detailed description of the evaluation method of spatial differential terms in the equations was described. Numerical simulations were performed in order to verify the discretization method in BFC system and the calculation method for thermal interaction between two calculation regions.

Journal Articles

Application of electromagnetic velocity meter for measuring liquid velocity distribution in air-water two-phase flow along a large vertical pipe

Onuki, Akira;

Proc. of ASME Heat Transfer and Fluids Engineering Divisions (HTD-Vol. 321,FED-Vol. 233), 0, p.473 - 478, 1995/00

no abstracts in English

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