ICONE19-43586 Effectiveness of natural circulation on molecular diffusion of two component gases in a stratified fluid layer

Takeda, Tetsuaki; Isomi, Hirotaka; Hanazawa, Hiroki; Mizuno, Hiroki

doi:10.1299/jsmeicone.2011.19._icone1943_238

Cited by 2 publications

(2 citation statements)

References 9 publications

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“…Authors also have reported the transport phenomena by the molecular diffusion were affected by not only the localized natural convection but also natural circulation of the gas mixture. The localized natural convection may affect to the onset time of the natural circulation (10) .…”

Section: Fig1 Experimental Apparatusmentioning

confidence: 99%

Study on the Effect of One-Dimensional Natural Circulation on the Mixing Process of Two Component Gases

Funatani

Takeda

2014

Volume 2A: Thermal Hydraulics

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This study is to investigate the effect of one-dimensional natural circulation on the mixing process of two component gases by evaluating the onset time of natural circulation through the apparatus under the stable density stratified fluid layer. The experimental apparatus consists of a reverse U-shaped vertical slot and a storage tank. The left side vertical slot consists of the heated wall and the cooled wall. The right side vertical slot consists of the two cooled walls. Temperature difference between the vertical walls was set to 50, 70, and 100 K. In this study, the combination of the two component gases is He/Ar and density ratio of each component is 1.4/10. The heavy gas was filled with the storage tank and light gas was filled with the reverse U-shaped vertical slot. Before the experiment starts, the localized natural convection was generated in the heated side vertical slot. After the experiment starts, the heavy gas will be transported to the slot by the molecular diffusion and natural convection. And then, natural circulation occurs abruptly through the reverse U-shaped passage. The mixing process of two component gases and the onset time of natural circulation in the vertical fluid layer were affected not only by the localized natural convection but also by the molecular diffusion. The wall and gas temperatures were measured by thermocouples and the velocity of natural convection was measured to evaluate the characteristics of the mixing process and the natural convection. These experimental results show that generation time of natural circulation was affected by molecular diffusion and localized natural convection. When the two components of gases have large density ratios and large Gr numbers, the mixing process of two components of gases was affected by more intensively molecular diffusion than localized natural convection when temperature difference was 50K. The mixing process of two component gas was affected by more intensively localized natural convection than molecular diffusion when temperature difference was 70 to 100K. However, two component gases were affected by more intensively molecular diffusion than localized natural convection at small density ratios and small Gr numbers.

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Section: Fig1 Experimental Apparatusmentioning

confidence: 99%

Study on the Effect of One-Dimensional Natural Circulation on the Mixing Process of Two Component Gases

Funatani

Takeda

2014

Volume 2A: Thermal Hydraulics

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“…The report described the process of air ingress during the first stage of a primary pipe rupture accident, and provided experimental results regarding the influence of localized natural circulation in the parallel channels on the air ingress process. Localized natural convection may affect the onset time of natural circulation [12][13][14]. In order to predict or analyze the air ingress phenomena during the depressurization accident in the VHTR, it is important to examine the influence of localized natural convection and molecular diffusion on the mixing process.…”

Section: Introductionmentioning

confidence: 99%

Process of Air Ingress during a Depressurization Accident of GTHTR300

Shiga

Tanaka

Takada

2018

Science and Technology of Nuclear Installations

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A depressurization accident is the design-basis accidents of a gas turbine high temperature reactor, GTHTR300, which is JAEA’s design and one of the Very-High-Temperature Reactors (VHTR). When a primary pipe rupture accident occurs, air is expected to enter the reactor core from the breach and oxidize in-core graphite structures. Therefore, it is important to know a mixing process of different kinds of gases in the stable and unstable density stratified fluid layer. In order to predict or analyze the air ingress phenomena during the depressurization accident, we have conducted an experiment to obtain the mixing process of two component gases and the characteristics of natural circulation. The experimental apparatus consists of a storage tank and a reverse U-shaped vertical rectangular passage. One side wall of the high temperature side vertical passage is heated and the other side wall is cooled. The other experimental apparatus consists of a cylindrical double coaxial vessel and a horizontal double coaxial pipe. The outside of the double coaxial vessel is cooled and the inside is heated. The results obtained in this study are as follows. When the primary pipe is connected at the bottom of the reactor pressure vessel, onset time of natural circulation of air is affected by not only molecular diffusion but also localized natural convection. When the wall temperature difference is large, onset time of natural circulation of air is strongly affected by natural convection rather than molecular diffusion. When the primary pipe is connected at the side of the reactor pressure vessel, air will enter the bottom space in the reactor pressure vessel by counter-current flow at the coaxial double pipe break part immediately. Afterward, air will enter the reactor core by localized natural convection and molecular diffusion.

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ICONE19-43586 Effectiveness of natural circulation on molecular diffusion of two component gases in a stratified fluid layer

Cited by 2 publications

References 9 publications

Study on the Effect of One-Dimensional Natural Circulation on the Mixing Process of Two Component Gases

Study on the Effect of One-Dimensional Natural Circulation on the Mixing Process of Two Component Gases

Process of Air Ingress during a Depressurization Accident of GTHTR300

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