Separate effects experiments for air-ingress in helium filled vessel

Kim, Seung-Jin; Yadav, Mohan; Talley, Justin D.; Ireland, A.; Bajorek, Stephen M.

doi:10.1016/j.expthermflusci.2013.02.022

Cited by 3 publications

(1 citation statement)

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“…Unfortunately, there is currently a very limited amount of experimental data in the established literature that can be used to understand this transition from diffusion to natural circulation and validate numerical models. In a separate-effects experimental study on isothermal air ingress through horizontal ports in a helium filled scaled-vessel [17], it was found that it would take several minutes to fill the entire test chamber -a result that differs from the numerical predictions by Oh et al [5,12]. The predictive modeling of this process is quite challenging because the CFD codes don't have appropriate models for properties such as molecular diffusion in binary mixtures.…”

Section: Introductionmentioning

confidence: 96%

Transition from molecular diffusion to natural circulation mode air-ingress in high temperature helium loop

Gould

Franken

Bindra

et al. 2017

Annals of Nuclear Energy

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High Temperature Gas-cooled Reactors (HTGRs) have significantly robust passive heat removal capabilities owing largely to conduction and radiation heat transfer through graphite-fuel matrix and reactor vessel wall respectively. However, these capabilities may be significantly impacted if air was to replace Helium in the high temperature graphite under accident scenarios. In case of break in the coolant system high pressure Helium will escape into the reactor cavity leading to depressurization of the reactor. This will allow air from reactor cavity to enter the plenum or core of HTGRs via different mechanisms-diffusion, gravity currents, or natural circulation. Experimental studies were conducted in a geometrically scaled setup with a shape of small English letter 'h', to depict the role of upper plenum in this process. Main focus of these studies was to understand and observe the transition time from diffusion to natural circulation. Thermal camera is used to identify this transition and flow transducer is used to measure the flow rates. The experimental results on incipience time of natural convection after a chamber pre-filled with Helium is opened to atmosphere are qualitatively similar to observations reported in literature using 'inverse U' shaped experimental setup, but also show distinct quantitative effect of extended leg on the transition times. Prior to onset of natural circulation (ONC), molecular diffusion plays the significant role in air-ingress. However, at higher temperatures convection currents may be influencing air ingress and in-turn ONC times.

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Section: Introductionmentioning

confidence: 96%