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Journal Articles

Numerical interpretation of hydrogen thermal desorption spectra for iron with hydrogen-enhanced strain-induced vacancies

Ebihara, Kenichi; Sugiyama, Yuri*; Matsumoto, Ryosuke*; Takai, Kenichi*; Suzudo, Tomoaki

Metallurgical and Materials Transactions A, 52(1), p.257 - 269, 2021/01

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

We simulated the thermal desorption spectra of a small-size iron specimen to which was applied during charging with hydrogen atoms using a model incorporating the behavior of vacancies and vacancy clusters. The model considered up to vacancy clusters $$V_9$$, which is composed of nine vacancies and employed the parameters based on atomistic calculations, including the H trapping energy of vacancies and vacancy clusters that we estimated using the molecular static calculation. As a result, we revealed that the model could, on the whole, reproduced the experimental spectra except two characteristic differences, and also the dependence of the spectra on the aging temperature. By examining the cause of the differences, the possibilities that the diffusion of clusters of $$V_2$$ and $$V_3$$ is slower than the model and that vacancy clusters are generated by applying strain and H charging concurrently were indicated.

Journal Articles

Numerical analysis of turbulent flow in periodically arranged ribs

Okagaki, Yuria*; Sugiyama, Hitoshi*; Kato, Naoto*; Hino, Ryutaro

Jidosha Gijutsukai Rombunshu, 43(4), p.949 - 955, 2012/07

Turbulent heat transfer enhancement using periodically arranged ribs processed on the graphite sleeve of a fuel rod aims to increase heat generation density of the fuel rod, which can potentially improve the economics of a block type high-temperature gas-cooled reactor. Rectangular cross section of rib is selected because of easy processing. Furthermore, it is important to find optimum rib topology such as pitch and height to maximize turbulent heat transfer performance. In order to develop a turbulent model as a design tool for rib-roughened fuel rod, numerical analysis has been conducted to verify applicability of an algebraic Reynolds stress model, which is computationally efficient, to non-isotropic turbulent flow in rib roughened channels. The results of the analysis on a square duct with periodically arranged ribs on the bottom wall are shown to reproduce very well the flow characteristics such as flow separation and reattachment behind the ribs. The model is therefore expected to be applicable to rib-enhanced fuel rod design.

Journal Articles

Numerical analysis of turbulent flow with heat transfer in a square duct with 45 degree ribs

Okagaki, Yuria*; Sugiyama, Hitoshi*; Kato, Naoto*; Terada, Atsuhiko; Hino, Ryutaro

Proceedings of 19th International Conference on Nuclear Engineering (ICONE-19) (CD-ROM), 8 Pages, 2011/10

Turbulent flow and heat transfer characteristics in a square duct of 100 mm height with 45 degree square ribs of 10 mm height was analyzed numerically by using algebraic Reynolds stress model including the fixed turbulent Prandtl number and algebraic turbulent heat flux models. In this research, analytical results were compared with the experimental and predicted data reported by Bonhoff et al, which were measured and analyzed turbulent flow fields at Reynolds number 50000 based on bulk velocity and duct height by means of a PIV system and a Reynolds stress model. As a result of this study, it was verified that the presented method was able to predict turbulent flow in duct with ribs through the comparison of calculated results with the experimental data.

Journal Articles

Numerical analysis of turbulent flow in a periodically arranged ribs

Okagaki, Yuria*; Sugiyama, Hitoshi*; Hino, Ryutaro; Kato, Naoto*; Terada, Atsuhiko

Nippon Kikai Gakkai Kanto Shibu Burokku Godo Koenkai Koen Rombunshu, p.35 - 36, 2011/09

Turbulent flow and heat transfer characteristics in a square duct of square ribs was analyzed numerically by using algebraic Reynolds stress model. In this research, as the first step of design code development for HTGR heat exchanger equipment, analytical results were compared with the experimental and predicted data reported by Casarsa et al., which were measured by means of a PIV system.

Oral presentation

Numerical study on the hydrogen thermal desorption of an iron specimen including strain-induced vacancies

Ebihara, Kenichi; Sugiyama, Yuri*; Takai, Kenichi*; Matsumoto, Ryosuke*; Suzudo, Tomoaki

no journal, , 

no abstracts in English

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