MODELING THE EFFECTS OF FUEL ROD CRUD FORMATION ON BOILING HEAT TRANSFER IN A PRESSURIZED WATER REACTOR USING EULERIAN TWO-FLUID CFD

Open Access
Author:
Guzzetta, Ashley Susan
Graduate Program:
Nuclear Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Maria Nikolova Avramova, Thesis Advisor
  • Robert Francis Kunz, Thesis Advisor
Keywords:
  • nuclear
  • pressurized water reactors
  • crud model
  • subcooled boiling
  • heat transfer
  • CFD
  • crud formation
Abstract:
This research focuses on Computational Fluid Dynamics (CFD) modeling of subcooled boiling in crudded nuclear reactor coolant passages. An Eulerian multiphase subcooled boiling model was implemented in a multidimensional CFD code to predict the heat transfer in vertical coolant passages with inlet subcooling, with and without crud deposits present on the heated surface. A subcooled nucleate boiling model based on partitioning of the relevant models of heat transfer is implemented. Specifically, models for sensible heating and quenching heating of the liquid, and heat and mass transfer modeling of evaporation and condensation are implemented in concert with the baseline interfacial dynamics models (i.e. drag, dispersion) in the code. This boiling model, adopted from the work of Podowski (1), is applicable to uncrudded/clean channel surfaces. The model was validated against two sets of experimental data and results compare favorably with the measurements. In this thesis, a heat-apportionment based nucleate boiling model has been developed to model crudded systems. Crud conductivity, surface roughness, nucleation site density and frequency, bubble departure diameter, and crud porosity were accounted for, the latter in the context of modeling of wick boiling associated with the “chimney” structures that occur in crudded boiling. By comparing results of the crudded model to experimental data, it was observed that the model captures the essential heat transfer characteristics present in subcooled nucleate boiling of crudded systems.