High fidelity experimental and numerical results are presented to understand fluctuating thermal stratification fronts in liquid metal plena with cold jet injection from the bottom. During cold injection events (as seen during certain transients important to safety in the upper plena of liquid metal cooled reactors) the behavior of the stratification front can dictate natural circulation performance and the thermal fatigue experienced by adjacent solid structures caused by large, rapid thermal changes that can be enhanced when the local front behavior oscillates.&nbsp; While work has already been established for fluids like air and water, research on low Pr fluids ( Pr &lt;&lt;1) (e.g. liquid metals) has fewer experimental data sets with even fewer under plenum inlet conditions that promote this oscillatory behavior. In order to parameterize the magnitude and frequency of the fluid temperature behavior in liquid metal, experimental and numerical tests were conducted. The Gallium Thermal-hydraulic Experiment (GaTE) facility is outfitted with Rayleigh and acoustic backscattering measurement techniques used to generate the high fidelity distributed temperature and flow field data (respectively) in a liquid metal plenum (a 1/20th scale plenum of the Department of Energy’s sodium cooled Advanced Burner Test Reactor design). The high spatial and temporal resolution of the sensors are required to capture the temperature gradient and fluctuations of temperature and velocity to allow a more direct comparison to the numerical simulations. &nbsp;For these simulations the coupled mass, energy, and momentum equations under the large eddy simulation (LES) framework were solved with the wall-adapting local eddy-viscosity (WALE) model for sub-grid scale formulations. With validated agreement between both sets of data, the relationship between buoyancy, inertia, and stratification fluctuation behavior is assessed in the context of low Pr fluids. To quantify the relationship between buoyancy and inertia, the local turbulent kinetic energy budget (in terms of the flux Richardson number Ri f,(z,r, θ)  = g βw'T'/u'w'(dU/dz) is determined and contrasted to stratification front dynamics as it evolves through the plenum. The magnitude and frequency of the local front fluctuation behavior is compared to bulk plenum inlet conditions such that these global parameters can be used to provide the relative impact to solid structure fatigue for different transient conditions.


ICONE Competition - ICONE28-POWER2020-16661: Experimental Validation of Cfd Models Capturing the Thermal-Hydraulics in Liquid Metal Cooled Reactor Plena

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

POWER-ICONE - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.