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Swirling jets for the mitigation of hot spots and thermal Sstratification in the VHTR lower plenum


Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/12873

Swirling jets for the mitigation of hot spots and thermal Sstratification in the VHTR lower plenum

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dc.contributor.author rodriguez, salvador
dc.date.accessioned 2011-07-02T17:38:44Z
dc.date.available 2011-07-02T17:38:44Z
dc.date.issued 2011-07-02
dc.date.submitted May 2011
dc.identifier.uri http://hdl.handle.net/1928/12873
dc.description.abstract The literature indicates that a prismatic-core very high temperature reactor can experience thermal stratification and hot spot issues in the lower plenum (LP). This research hypothesizes that the complex thermalhydraulic phenomena in the LP requires a sophisticated computational fluid dynamics (CFD) code with state-of-the-art turbulence models and advanced swirling jet technology to mitigate the two issues. The primary research goals were to increase the heat transfer and mixing capacity of swirling jets, extend swirling jet theory, and to apply those advancements for the mitigation of the thermalhydraulic issues. First, it was demonstrated that the Fuego CFD code successfully modeled a set of key LP thermalhydraulic phenomena. Thereafter, a helicoid vortex swirl model was developed to investigate the impact of the swirl number (S) on mixing and heat transfer. The development of azimuthal and axial velocities that are purely functions of S permitted the analysis of the central recirculation zone’s (CRZ) impact on the LP flow field. At this point, several characteristics were found in common between the helicoid vortex and other axisymmetric, Newtonian, incompressible vortices found in the literature. This observation resulted in a more fundamental understanding of how vortices behave, and which traits can be exploited for the purpose of maximizing heat transfer and mixing. Because the CRZ is a strong function of the azimuthal and axial velocities, shaping those velocity profiles had a substantial impact on the flow field. Eventually, this led to the discovery that vortices may be expressed as alternating series that expand geometrically with odd exponents. This helped corroborate that the 15 axisymmetric vortices discussed in this research are part of a vortex family with seven common traits. This also led to the development of new vortices that are based on one or two series terms that satisfy the Navier-Stokes equations and conservation of mass. In addition, the impact of Reynolds number and swirl decay were explored in order to further quantify their impact on mixing and heat transfer. Finally, the above theories and modeling insights were applied towards a comprehensive set of LP calculations that showed that the swirling jets mitigated the entrainment and hot spot issues, while resulting in a reasonable pressure drop. en_US
dc.description.sponsorship sandia national laboratories en_US
dc.language.iso en_US en_US
dc.subject swirling jet vortex turbulence mixing vhtr nuclear lower plenum cfd crz en_US
dc.subject helicoid en_US
dc.subject.lcsh Nuclear reactors ǂx Fluid dynamics.
dc.subject.lcsh Plasma turbulence.
dc.subject.lcsh Jets--Fluid dynamics.
dc.subject.lcsh Superheating reactors.
dc.title Swirling jets for the mitigation of hot spots and thermal Sstratification in the VHTR lower plenum en_US
dc.type Dissertation en_US
dc.description.degree nuclear engineering en_US
dc.description.level Doctoral en_US
dc.description.department University of New Mexico. Dept. of Chemical and Nuclear Engineering en_US
dc.description.advisor el-genk, mohamed
dc.description.committee-member petsev, dimiter
dc.description.committee-member steinberg, stanly
dc.description.committee-member de oliveira, cassiano
dc.description.committee-member hassan, basil

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