| China Advanced Research Reactor (CARR), which is being designed and constructed, is a high performing and multipurpose inverse neutron trap pool research reactor. The reactor is cooled and moderated by light water, reflected by heavy water. The compact core, large core volume power density, heavy heat load of the fuel plate, and high speed of the coolant flow velocity, bring new challenges to the thermal-hydraulic design. How to efficiently take the heat produced by the fuels and structures out of the core, to maintain the temperature of the fuel and structure in the permission range, is important part of the reactor designing. This paper performed benchmarking Computational Fluid Dynamics (CFD) for application to CARR core, and finished the numerical simulation of the flow and temperature field of the core components with CFD method. The results have been applied to the thermo-hydraulic deigning, safety and mechanics analysis. The commercial CFD software CFX4.4 and CFX5.5 were adopted to finish the study.1st, the benchmarking was carried. The CARR fuel assemblies are constituted with plate fuel elements. The reactor core is mainly compounded with long narrow rectangular coolant channels. The main purpose of the benchmarking on this special coolant channels, is to improve the accuracy and creditability of the CFD calculation results. The study is processed on a typical core coolant channel, refer to experimental data and experience relations, mainly analyzes the influence of the wall function (including the Standard Wall Function and Scalable Wall Function of CFX), the spacing of the near wall grids, and turbulence models (including standard k-εmodel, RNG k-εmodel, and Reynolds stress model) on the main parameters, such as pressure drop (ΔP) and heat transfer coefficient (h). The analysis indicates that, numerical simulation of CARR core channels choosing standard k-εmodels, Scalable Wall Function, and suitable near wall grid spacing (y+ between 30～180), forΔP and h, compared with the experiment and experience relations, the discrepancy is about 5%.2nd, the simulation of CARR core flow and temperature fields. The core of CARR is composed of 17 standard fuel assemblies, 4 follower fuel assemblies and other core structures. If stimulate the whole core in one model, it would product a lot of calculation grids, and need the computer with large ROM and high speed CPU. Without those equipments, this study is performed on personal computer. So the separated districts method is adopted to finish the work, which is to divide the core into three kinds of districts, including standard fuel assembly district, follower fuel assembly district, and core vessel & insert district, and simulate those districts separately. The flow and temperature fields of fuel assembly and core structures in different places of the core or under different conditions could be obtained by changing some calculation's input parameters, such as flow rate, heat power, etc. The hydraulic characteristic and in-assembly flow distribution of the standard fuel assembly are simulated, and agree well with the experience correlations' results and the experimental data. Under the design conditions, for the standard and follower fuel assemblies, the top temperatures of the fuel meat and cladding are both lower than the restricting values, the highest temperature on the outer surface of the cladding is lower than the local onset temperature of nuclear boiling and coolant saturation temperature and the residue is significant, the coolant will not boil. The highest temperature in core vessel & insert is also lower than the design restricting value.In general, through the benchmarking, the numerical simulation accuracy is improved, the results of CARR core simulations have been applied in the CARR design, and also the valuable experience of using CFD for the following work is accumulated. |
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