Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Ono, Ayako; Sakashita, Hiroto*; Yamashita, Susumu; Suzuki, Takayuki*; Yoshida, Hiroyuki
Mechanical Engineering Journal (Internet), 11(4), p.24-00188_1 - 24-00188_12, 2024/07
Japan Atomic Energy Agency (JAEA) is developing the evaluation method for a two-phase flow in the reactor core using simulation codes based on the Volume Of Fluid (VOF) method. JAEA started developing a Simplified Boiling Model (SBM) for the large-scale two-phase flow in the fuel assemblies. In the SBM, the motion and growth equations of the bubble are solved to obtain their diameter and time length at the detachment, of which size scale is within/around the calculation grid size of the numerical simulation. JUPITER calculates the bubble behavior with a scale of more than several 
m. In this study, the convection boiling on a vertical heating surface is simulated using the developed SBM. The comparison between the simulation and experimental results showed good reproducibility of the heat flux and velocity dependency on the passage period of the bubble.
Ono, Ayako; Sakashita, Hiroto*; Yamashita, Susumu; Suzuki, Takayuki*; Yoshida, Hiroyuki
Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 7 Pages, 2022/10
The new prediction method of critical heat flux (CHF) of the fuel assemblies based on the mechanism is proposed in this study. The prediction method of CHF based on the mechanism has been needed for a long time to enhance the safety analysis and reduce the design cost. From several experimental findings of the liquid-vapor behavior near the heating surface from the nucleate boiling to the CHF, the authors consider that the macrolayer dryout model will be appropriate to predict the CHF under the reactor condition. The prediction method of the macrolayer thickness and the passage period of vapor mass in the fuel assemblies are needed to predict CHF from the macrolayer dryout model. In this study, the CHF under the forced convection is evaluated by combining the prediction methods for the macrolayer thickness and passage period of vapor mass, which are proposed by authors. The prediction of the CHF under the forced convection is examined and compared with the experimental data.
Ono, Ayako; Yamashita, Susumu; Sakashita, Hiroto*; Suzuki, Takayuki*; Yoshida, Hiroyuki
Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 12 Pages, 2022/09
Japan Atomic Energy Agency is developing the computational fluid dynamics code, JUPITER, based on the volume of fluid (VOF) method to analyze detailed thermal-hydraulics in a reactor. The detailed numerical simulation of boiling from a heating surface needs a substantial computational cost to resolve the microscale thermal-hydraulic phenomena such as the bubble generation from a cavity and evaporation of a micro-layer. This study developed the simplified boiling model from the heating surface to reduce the computational cost, which will apply to the detailed simulation code based on the surface tracking method such as JUPITER. We applied the simplified boiling model to JUPITER, and compared the simulation results with the experimental data of the vertical heating surface in the forced convection. We confirmed the degree of their reproducibility, and the issues to be modified were extracted.
Ono, Ayako; Yamashita, Susumu; Sakashita, Hiroto*; Suzuki, Takayuki*; Yoshida, Hiroyuki
Dai-26-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2022/07
JAEA is implementing a simulation of a two-phase flow in the reactor core by TPFIT and JUPITER which are developed by JAEA based on the surface tracking method. However, it is impossible to simulate a boiling on the heating surface in the large-scale domain by this type of simulation method since the simulation of boiling based on the surface tracking method needs the fine mesh which sufficiently resolves the initiation of boiling. Therefore, JAEA started to develop the simplified boiling model applied for the two-phase flow in the fuel assemblies. In this study, the simulation results of the convection boiling on a vertical heating surface and the comparison between the simulation results and experimental results are shown.
Ono, Ayako; Sakashita, Hiroto*; Yoshida, Hiroyuki
Heat Transfer Engineering, 42(21), p.1775 - 1788, 2021/00
Times Cited Count：5 Percentile：26.01(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.
Onuki, Akira; Nakamura, Hideo; Kawamura, Shinichi*; Saishu, Sadanori*
Nihon Kikai Gakkai Netsu Kogaku Koenkai Koen Rombunshu, p.31 - 32, 2001/11
A passive containment cooling system (PCCS) is under planning to use in a next-generation-type BWR for long-term cooling by condensing steam using horizontal heat exchangers. Heat transfer behavior in a secondary water pool is one of important phenomena governing heat removal performance of the PCCS. Boiling and condensation can be supposed under high heat flux regions and the characteristics of the two-phase natural circulation should be evaluated. This study investigated effects of pool size on the characteristics by multi-dimensional two-fluid model code ACE-3D. It was found from the analyses that the pool size gives no significant influences for the characteristics in tube bundle under local-boiling mode.
Kinoshita, Hidetaka; Nariai, Hideki*; Inasaka, Fujio*
JSME International Journal, Series B, 44(1), p.81 - 89, 2001/01
no abstracts in English
Onuki, Akira; Nakamura, Hideo; Anoda, Yoshinari; Obata, Hiroyuki*; Saishu, Sadanori*
Proceedings of 9th International Conference on Nuclear Engineering (ICONE-9) (CD-ROM), 10 Pages, 2001/00
A passive containment cooling system (PCCS) is under planning to use in a next-generation-type BWR for long-term cooling by condensing steam using horizontal heat exchangers. Heat transfer behavior in a secondary water pool is one of important phenomena governing heat removal performance of the PCCS. Boiling and condensation can be supposed under high heat flux regions and the two-phase natural circulation might enhance the heat transfer due to an increase of flow rate and a flow agitation. However, some heat transfer tubes might be covered only by steam and the heat transfer is degraded in such region (Steam-blanket effect). This study evaluated the characteristics of the heat transfer behavior in the secondary water pool by multi-dimensional two-fluid model code ACE-3D. It was found from the analyses that no any heat transfer tubes are covered only by steam and the heat transfer is enhanced due to the nucleate boiling and the increase of local liquid flow rate.
Onuki, Akira;
Proc. of 5th Int. Topical Meeting on Nuclear Thermal Hydraulics,Operations and Safety, 00(00), p.1 - 6, 1997/04
no abstracts in English
; Abe, Yutaka*; ; ; Yamano, N.; Sugimoto, Jun
JAERI-Research 96-032, 152 Pages, 1996/06
JAERI-Research-96-032.pdf:4.05MB
no abstracts in English
B.Basoglu*; Okuno, Hiroshi; Yamamoto, Toshihiro; Nomura, Yasushi
PHYSOR 96: Int. Conf. on the Physics of Reactors, 4, p.L110 - L119, 1996/00
no abstracts in English
Osakabe, Masahiro; Sudo, Yukio
Journal of Nuclear Science and Technology, 21(2), p.115 - 125, 1984/00
Times Cited Count：2 Percentile：29.62(Nuclear Science & Technology)no abstracts in English
JAERI-M 83-098, 21 Pages, 1983/07
no abstracts in English
Ono, Ayako; Sakashita, Hiroto*
no journal, ,
A macrolayer formation model for saturated and subcooled pool boiling is proposed, which is developed based on the visual observation of boiling behavior. The distribution of nucleation sites is assumed to distribute based on Poisson distribution. The predicted macrolayer thicknesses are used for the prediction of CHFs in saturated and subcooled pool boiling based on the macrolayer dryout model. The combination of the macrolayer dryout model and macrolayer formation model is able to predict the CHF well at least up to subcooling 40K.
