Nuclear Technology / Volume 158 / Number 2 / May 2007 / Pages 229-236
Technical Paper / Nuclear Reactor Thermal Hydraulics
Computational fluid dynamics (CFD) analysis is carried out for heat transfer of lead-bismuth eutectic flows in rod bundles. The effect of different parameters, such as turbulence models, on the numerical results is investigated. The effect of meshes on the heat transfer is much smaller when using the [curly epsilon]-type turbulence models than when using the -type turbulence models. Based on the results achieved, the Reynolds stress model of Speziale with fine-mesh structures, i.e., y1+ 15, is recommended for further CFD analysis of heavy liquid-metal (HLM) flows in rod bundles. A strong circumferential nonuniformity of heat transfer is observed in tight rod bundles, especially in square lattices. The secondary flow leads to a reduction in the nonuniformity of heat transfer. Related to the overall average Nusselt number, CFD codes give similar results for both triangular and square rod bundles when the Peclet number and the pitch-to-diameter ratio have the same values in both bundle configurations. Comparison of the CFD results with bundle test data in mercury clearly indicates that the turbulent Prandtl number for HLM flows in rod bundles is smaller than that in circular tubes. It has values close to 1.0 at high Peclet number conditions and increases by decreasing Peclet number.