High-fidelity simulation of pebble beds: Toward an improved understanding of the wall channeling effect

David Reger, Elia Merzari, Saya Lee, Paolo Balestra, Yassin A. Hassan

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations

Abstract

Wall channeling is a phenomena of interest for Pebble Bed Reactors (PBRs) where flow is diverted into high-porosity regions near the wall.This diversion of flow can have a significant impact on maximum fuel temperatures and core bypass flow.Porous media models that are currently used to model PBRs for design scoping and transient simulation are lacking in their capabilities to model the wall channel effect.Recent efforts at Penn State have produced an im-proved porous media pressure drop equation that is more capable of modeling the velocity variations caused by the wall channel effect in a porous media model.Several pebble beds were divided into concentric rings of 0.05Dpeb, and average flow quantities and porosities were extracted for the ring.A correlation between the form loss coefficient and the local ring porosity was found, allowing for the addition of a correction factor to the form loss term of the KTA equation.The developed correlation was purely empirical, and thus a more thorough understanding of the underlying flow phenomena is desired.This study investigates geometric and flow features that can explain the observed correla-tion between the form coefficient and the local porosity that was used to generate the improved pressure drop equation.The solid surface area to volume ratio Sv along with the production of Turbulent Kinetic Energy (TKE) is analyzed.A relationship between Sv and the local porosity and an inverse relationship between the negative TKE production and the local porosity were found, pointing to the idea that inertial effects caused by different pore geometry in each ring contribute to the variation of the form constant with the local porosity.

Original languageEnglish (US)
Title of host publicationProceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023
PublisherAmerican Nuclear Society
Pages3140-3154
Number of pages15
ISBN (Electronic)9780894487934
DOIs
StatePublished - 2023
Event20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023 - Washington, United States
Duration: Aug 20 2023Aug 25 2023

Publication series

NameProceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023

Conference

Conference20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023
Country/TerritoryUnited States
CityWashington
Period8/20/238/25/23

All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Instrumentation

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