Publications Details

On enhancing VHTR lower plenum heat transfer and mixing via swirling jets

Rodriguez, Sal B.; El-Genk, Mohamed S.

High and very-high temperature gas-cooled reactors bring about unique challenges such as hot spots in the lower plate and thermal stratification in the lower plenum (LP). Analysis performed using Sandia National Laboratories' (SNL) Fuego computational fluid dynamics (CFD) code shows that these issues can be mitigated using static swirling inserts at the exit of the helium coolant channels to the LP. A full-scale, half-symmetry LP section is modeled using a numerical mesh that consists of 5.5 million hexahedral elements. The LP model includes the graphite support posts, the helium flow channel jets, the bottom plate, and the exterior walls. Calculations are performed for both conventional jets and clockwise and counter-clockwise swirling jets and varying swirl number, S, from 0 to 2.49. Calculations show that increasing S increases mixing and enhances heat transfer, thus reducing the likelihood of forming hot spots and thermal stratification in the LP.