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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorPodowski, M.
dc.contributorJi, Wei
dc.contributorSahni, Onkar
dc.contributorBolotnov, Igor
dc.contributorBurdick, Gretchen
dc.contributor.authorWaite, Brian M.
dc.date.accessioned2021-11-03T09:00:57Z
dc.date.available2021-11-03T09:00:57Z
dc.date.created2018-07-27T15:11:21Z
dc.date.issued2018-05
dc.identifier.urihttps://hdl.handle.net/20.500.13015/2215
dc.descriptionMay 2018
dc.descriptionSchool of Engineering
dc.description.abstractOverall, the study provides a greater understanding of multiphase flow in a nuclear reactor. The consistent physical approach that started with simpler problems and slowly expanded to a more involved analysis provided confidence and understanding of the models before proceeding to the next step. Rod bundle simulations with spacers have shown the importance of modeling the full geometry to capture more of the physical phenomena in the core. The modeling process must carefully consider the bubble size and shape as it has a large impact on the void distribution and development behavior downstream from the spacers. The numerical analyses examining the effects of spacer grids on boiling heat transfer is one of the first such studies.
dc.description.abstractThe most prevalent type of nuclear reactor in the world uses light water as the coolant and moderator. The vast wealth of knowledge already generated, due to years of research completed on light water reactors (LWRs), has greatly improved them from the original designs. The large amount of design and operation experience gained means that the use of light water reactors is likely going to continue for the foreseeable future. Improvements to the thermal hydraulics within these designs, using advanced models and tools, can allow current and future reactors to operate with higher fidelity. Nuclear reactor spacer grids have a large effect on the coolant distribution in the core. Historically, a majority of the effort in analyzing these complex designs focused on single-phase heat transfer rather than multiphase flow conditions. The focus of this work is to characterize and model the underlying physics governing multiphase flow and heat transfer around spacer grids in a rod bundle geometry. The complexity of the geometry introduces several new challenges.
dc.description.abstractThis work discusses the formulation of a two-phase dispersed field model and corresponding interfacial momentum closures, with an emphasis on the influence of bubble conditions within the channels. Reynolds-averaged Navier-Stokes level analyses are completed with the NPHASE-CMFD code which employs a multiphase formulation of the $k-\epsilon$ turbulence model. This study addresses many computational challenges that the complexity of the spacer grid geometry offers, such as grid formulation and boundary condition testing.
dc.description.abstractAn adiabatic two-field model was validated for flow around spacers in a 16-channel rod bundle (5x5) against experimental data. This methodology incorporates the uncertainties of the experimental methods and the bubble conditions within the flow. The large rod bundle simulations prove RANS methods are useful for these scenarios as a modest computational cost can achieve a high level of accuracy. The implications of non-fully-developed flow downstream of the spacer are thoroughly discussed.
dc.description.abstractThe adiabatic model consisting of the mass and momentum conservation equations is combined with the energy equation to show the effects of spacers on subcooled boiling heat transfer. A new model for wall temperature and bubble production in boiling channels is proposed. Results of the new model are compared against experimental data and show good agreement. Spacer grids have been shown to increase bubble condensation and reduce bubble production in the reactor channel due to the enhanced mixing caused by the flow blockages.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectNuclear engineering and science
dc.titleMechanistic modeling of two-phase flow and heat transfer around light water reactor spacer grids
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid179052
dc.digitool.pid179053
dc.digitool.pid179054
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDept. of Mechanical, Aerospace, and Nuclear Engineering


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