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Journal Articles

Toward mechanistic evaluation of critical heat flux in nuclear reactors, 2; Recent studies and future challenges toward mechanistic and reliable CHF evaluation

Okawa, Tomio*; Mori, Shoji*; Liu, W.*; Ose, Yasuo*; Yoshida, Hiroyuki; Ono, Ayako

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 63(12), p.820 - 824, 2021/12

The evaluation method of the critical heat flux based on the mechanism is needed for the efficient design and development of fuel in reactors and the appropriate safety evaluation. In this paper, the current researches relating to the mechanism of the critical heat flux are reviewed, and the issue to be considered in the future are discussed.

Journal Articles

Droplet generation during spray impact onto a downward-facing solid surface

Zhan, Y.*; Sun, G.*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Takata, Takashi

Experimental Thermal and Fluid Science, 126, p.110402_1 - 110402_8, 2021/08

 Times Cited Count:0 Percentile:0.01(Thermodynamics)

Journal Articles

Experimental study on secondary droplets produced during liquid jet impingement onto a horizon solid surface

Zhan, Y.*; Kuwata, Yusuke*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Takata, Takashi

Experimental Thermal and Fluid Science, 120, p.110249_1 - 110249_12, 2021/01

 Times Cited Count:2 Percentile:73.11(Thermodynamics)

Journal Articles

Effects of surface tension and viscosity on liquid jet breakup

Zhan, Y.*; Kuwata, Yusuke*; Maruyama, Kiyotaka*; Okawa, Tomio*; Enoki, Koji*; Aoyagi, Mitsuhiro; Takata, Takashi

Experimental Thermal and Fluid Science, 112, p.109953_1 - 109953_8, 2020/04

 Times Cited Count:5 Percentile:75.81(Thermodynamics)

Journal Articles

Droplet generation during liquid jet impingement onto a horizontal plate

Zhan, Y.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Takata, Takashi

Experimental Thermal and Fluid Science, 98, p.86 - 94, 2018/11

 Times Cited Count:7 Percentile:54.73(Thermodynamics)

Journal Articles

A Study on splashing during liquid jet impingement onto a horizontal plate

Kuwata, Yusuke*; Zhan, Y.*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Takata, Takashi

Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-12) (USB Flash Drive), 10 Pages, 2018/10

This study aims improvement of safety analysis for sodium fire accidents in sodium-cooled fast reactors. In the experiment, effect of viscosity on liquid jet impact on solid surface was studied.

Journal Articles

Splash during liquid jet impingement onto a horizontal plate

Zhan, Y.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Ohno, Shuji; Aoyagi, Mitsuhiro; Takata, Takashi

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 6 Pages, 2017/07

It is important to set the amount of sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. In the present work, fundamental experiments are performed to measure the splash ratio during the vertical water jet impact onto a horizontal wall. It is shown that the splash ratio can be correlated well as a function of the impact Weber number and dimensionless impact frequency.

Journal Articles

Production of droplets during liquid jet impingement onto a flat plate

Yi, Z.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Ohno, Shuji; Aoyagi, Mitsuhiro; Takata, Takashi

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 7 Pages, 2016/11

It is important to set the amount of sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. In the present work, fundamental experiments were performed to measure the splash ratio during the vertical water jet impact onto a horizontal wall. It was shown that the splash ratio can be correlated well as a function of the impact Weber number, the Strouhal number and the Ohnesorge number of the droplets impinging the liquid film.

Journal Articles

Experimental study on splashing during liquid jet impingement onto a liquid film

Yi, Z.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Ohno, Shuji; Aoyagi, Mitsuhiro

Proceedings of 24th International Conference on Nuclear Engineering (ICONE-24) (DVD-ROM), 7 Pages, 2016/06

It is important to set the amount of sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. In the present work, fundamental experiments were performed to measure the splash ratio during the vertical water jet impact onto a horizontal wall. It was shown that the splash ratio can be correlated well as a function of the impact Weber number and the Strouhal number of the droplets impinging the liquid film.

Oral presentation

Study on droplet generation at the time of a water jet, the liquid film collision

Oya, Naoki*; Okawa, Tomio*; Ohno, Shuji; Aoyagi, Mitsuhiro

no journal, , 

It is important to set the diameter of leakage sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. We performed a fundamental experiment with water in order to clarify mechanism of droplet generation in this study. Impinging water jet on a flat plate was tested for various cases of jet velocity, nozzle diameter and nozzle height. The impinging behavior was visualized by means of a high-speed video camera. We measured the amount of generated droplet and the maximum droplet diameter. Observed jet flow was categorized into following three modes: drop mode which is droplet state flow, jet mode which is straight flow and lump mode which is partially constricted flow. Both the amount of generated droplet and the maximum droplet diameter increased in the following order: jet, drop and lump modes.

Oral presentation

Study on droplet generation of the surface collision jet

Oya, Naoki*; Okawa, Tomio*; Enoki, Koji*; Ohno, Shuji; Aoyagi, Mitsuhiro

no journal, , 

It is important to set the diameter of leakage sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. We performed a fundamental experiment with water in order to clarify mechanism of droplet generation in this study. Impinging water jet on a flat plate was tested for various cases of jet velocity, nozzle diameter and nozzle height. The impinging behavior was visualized by using a high-speed video camera. We measured the amount of generated droplet and the maximum droplet diameter. Observed jet flow was categorized into following three modes: drop mode which is droplet state flow, jet mode which is straight flow and lump mode which is partially constricted flow. The amount of generated droplet had a strong correlation with the impact frequency. Larger droplet diameter was observed for the drop and lump modes.

Oral presentation

Splashing during liquid jet impact onto a horizontal wall

Okawa, Tomio*; Oya, Naoki*; Yi, Z.*; Enoki, Koji*; Ohno, Shuji; Aoyagi, Mitsuhiro

no journal, , 

It is important to set the amount of sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. In the present work, fundamental experiments were performed to measure the rate of splashing during the vertical water jet impact onto a horizontal wall. It was found that the splashing rate is negligibly small when the water jet is continuous at the impact point. Whilst, the splashing rate increased rapidly with an increase in the jet velocity when the jet was broken into droplets at the impact point. Therefore, when the fall height is longer than the breakup length, it was suggested that the dimensionless splashing rate scaled by the liquid jet flow rate can be expressed as a function of the modified Weber number of the primary droplets impacting the target. A semi-empirical method to estimate the splashing rate during liquid jet impact onto a horizontal wall was proposed based on linear stability theory.

Oral presentation

Study on surface collision of the liquid jet

Oya, Naoki*; Okawa, Tomio*; Enoki, Koji*; Ohno, Shuji; Aoyagi, Mitsuhiro

no journal, , 

This study aimed at improvement of sodium fire analysis method for coolant leakage in sodium-cooled fast reactor. A semi-empirical method to estimate the splashing rate during liquid jet impact onto a horizontal wall was proposed based on consideration of splashing mechanism.

Oral presentation

Droplet generation during liquid jet collision onto solid surface

Oya, Naoki*; Zhan, Y.*; Okawa, Tomio*; Enoki, Koji*; Aoyagi, Mitsuhiro; Ohno, Shuji; Takata, Takashi

no journal, , 

This study aims improvement of safety analysis for sodium fire accidents in sodium-cooled fast reactors. In the experiment, droplets were generated by collision of downward liquid jet onto a horizontal solid surface. We studied the mechanism of droplet generation and the empirical correlation of droplet amount.

Oral presentation

Splashing droplets during liquid jet collision onto solid surface

Zhan, Y.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Ohno, Shuji; Takata, Takashi

no journal, , 

This study aims improvement of safety analysis for sodium fire accidents in sodium-cooled fast reactors. In the experiment, droplets were generated by collision of downward liquid jet onto a horizontal solid surface. We studied the mechanism of droplet generation and the empirical correlation of droplet amount.

Oral presentation

Study on splashing phenomenon of liquid jet collision

Zhan, Y.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Ohno, Shuji; Takata, Takashi

no journal, , 

This study aims improvement of safety analysis for sodium fire accidents in sodium-cooled fast reactors. In the experiment, droplets were generated by collision of downward liquid jet onto a horizontal solid surface. We studied the mechanism of droplet generation and the empirical correlation of droplet amount.

Oral presentation

Effect of viscosity on liquid jet impact on solid surface

Kuwata, Yusuke*; Zhan, Y.*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Takata, Takashi

no journal, , 

This study aims improvement of safety analysis for sodium fire accidents in sodium-cooled fast reactors. In the experiment, effect of viscosity on liquid jet impact on solid surface was studied.

Oral presentation

Study on splashing droplets during the breakup liquid jet collision onto solid surface

Zhan, Y.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Ohno, Shuji; Takata, Takashi

no journal, , 

This study aims improvement of safety analysis for sodium fire accidents in sodium-cooled fast reactors. In the experiment, droplets were generated by collision of breakup liquid jet onto a solid surface. We studied the mechanism of droplet generation and the empirical correlation of droplet amount.

Oral presentation

Splashing droplets during liquid jet collision onto solid surface

Zhan, Y.*; Kuwata, Yusuke*; Maruyama, Kiyotaka*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Takata, Takashi

no journal, , 

This study aims improvement of safety analysis for sodium fire accidents in sodium-cooled fast reactors. In the experiment, splashing droplets are investigated by observation of liquid jet collision onto a solid surface.

Oral presentation

Study on droplet generation during upward liquid jet collision onto ceiling surface

Zhan, Y.*; Maruyama, Kiyotaka*; Kuwata, Yusuke*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Takata, Takashi

no journal, , 

This study aims improvement of safety analysis for sodium fire accidents in sodium-cooled fast reactors. In the experiment, falling droplets are investigated by observation of upward liquid jet collision onto a solid surface.

22 (Records 1-20 displayed on this page)