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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.contributorPeles, Yoav
dc.contributorBolotnov, Igor
dc.contributor.authorJiao, Hong
dc.date.accessioned2021-11-03T08:32:27Z
dc.date.available2021-11-03T08:32:27Z
dc.date.created2016-02-26T09:06:51Z
dc.date.issued2015-12
dc.identifier.urihttps://hdl.handle.net/20.500.13015/1613
dc.descriptionDecember 2015
dc.descriptionSchool of Engineering
dc.description.abstractThe subject of subcooled flow boiling analysis encompasses a wide range of topics. A literature review suggests that several important aspects of subcooled boiling need further understanding, such as the bubble growth rate, departure point and maximum size, condensation in subcooled liquid, heat transfer in general, critical heat flux, etc. The proposed NPHASE/Level-Set modeling package has been used to simulate several phenomena in this area. Simulations of bubble condensation/evaporation after departure have been first carried out, combined with a stand-alone numerical analysis of local Nussselt number variations for flow over different shapes, such as ellipsoids and spheres. The comparison with experimental data has shown good agreement. Simulations of multiple bubbles flows have also been conducted. Concerning the issue of bubble shape before departure, the results from the NPHASE/Level Set Method and the Young-Laplace-based theoretical model have been compared against each other, showing very good agreement. Then, simulations of bubble growth on a heated surface have been carried out. These simulations demonstrated the robustness of the new algorithm for the modeling of simultaneous evaporation and condensation, as well as the capability of the package to capture several subcooled boiling phenomena before and after bubble departure. One can expect that in the future the proposed method will facilitate the development and validation of multiphase closure models of subcooled boiling flows.
dc.description.abstractThe focus of this work is on the development and implementation of interface-tracking based models of subcooled boiling phenomena. The major work include a theoretical model to predict 3D quasi-static bubble/droplet shapes of various inclinations; a flexible and robust phase change modeling approach based on the Level Set Method; the implementation of the new method into the NPHASE-CMFD Computational Multiphase Fluid Dynamics code, and the analysis of several aspects of subcooled boiling flows. One of the advantages of the-interface-tracking based method is the avoidance of using phenomenological closure models, which makes it an attractive tool for validating various models of boiling.
dc.description.abstractModeling and simulation of flow and heat transfer at two-phase conditions pose several challenges due to the complexity of the underlying driving mechanisms. Development of mechanistic modeling approaches has gained much momentum in recent years, compared with traditional empirical correlations. These approaches include the implementation of mechanistic closure models into averaging-based governing equations, and direct simulations of multiphase flow using various interface tracking techniques.
dc.description.abstractThe proposed evaporation/condensation model for the level set interface tracking technique includes a local pseudo-heat-transfer- coefficient concept, and proves advantageous from both the numerical and physical points of views. The method has been implemented in the NPHASE-CMFD package and validated against several 1D to 3D problems. The corresponding phase-change model is the basis of a study on several aspects of subcooled boiling phenomena.
dc.description.abstractA theoretical analysis of bubble/droplet shape before departure is also introduced. The shape of bubbles departing from a solid wall is a key aspect of the high-subcooling phase of forced-convection boiling, during which bubbles still remain attached to the heated surface. The proposed computational model is based on force balance equations of the Young- Laplace type. A finite-difference-based solver has been developed in Matlab. The method has been validated against several experimental data of droplet/bubble shapes on horizontal or inclined surfaces. The methodology adopted in this chapter also functions as a comparison basis for similar simulations performed using the NPHASE/Level Set package.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectMechanical engineering
dc.titleMechanistic model of bubble dynamics at subcooled boiling conditions
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid177048
dc.digitool.pid177049
dc.digitool.pid177050
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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