CFD Simulations of an Air-Conditioned Radiological Materials Staging Room: Comparison Between COMSOL and ANSYS Codes
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Authors
Pulciano, Frank J
Issue Date
2023
Type
Thesis
Language
Keywords
Alternative Title
Abstract
Heat-generating radiological material packages, such as the 9975 package and other packages, are stored in facilities managed by the National Nuclear Security Administration (NNSA). These packages must be stored in a ventilated facility to prevent the packages, internal components, and outer surfaces from reaching prescribed limits. The objective of this work is to conduct steady-state computational fluid dynamics (CFD) simulations of a potential ventilated radiological-material-package staging facility to assess the surface temperatures of the packages using two CFD codes: ANSYS/Fluent finite volume and COMSOL finite element codes. The simulated facility contains 640 heat-generating 9975 packages, arranged in four rows and eight levels, equipped with a ventilation system and lighting. The outer walls of the facility are assumed to be completely insulated. The packages are modeled as Celotex insulation, each of them generating 19 W of heat. Due to the computational demands of COMSOL, the simulations excluded the modeling of natural convection and the shelving structure supporting the packages in both ANSYS and COMSOL simulations. For both CFD codes, three numerical meshes are generated and mesh sensitivities are conducted to determine the optimal meshes. The package maximum temperatures obtained using the optimal mesh for each code are compared and the differences are analyzed. The results show that the temperatures and flows in the staging facility vary depending on the CFD code used. ANSYS/Fluent predicts maximum package surface temperatures that are on average 5°C higher than COMSOL. Also, ANSYS/Fluent predicts the location of the hottest package to be near the back of the facility, while COMSOL predicts it toward the front. Additional simulations using both codes, isolating conduction, convection, and radiation heat transfers have been conducted. The results showed that the two codes predict the same package surface temperatures when only conduction heat transfer is considered. However, discrepancies emerged when convection and radiation were included.