BLIND AND AFTERMATH NUMERICAL ANALYSES OF SUPERCRITICAL WATER FLOW AND HEAT TRANSFER IN 1/12 OF 7- ROD BUNDLE WITH SPACERS

摘要

Application of supercritical water to conventional power plants has provided nuclear community with some experience which can be used in development of future generation of nuclear power plants. Nevertheless there are some specific features of nuclear power plants which should be studied during preparations of pilot designs. In 2013, the Gen-Ⅳ International Forum initiated a numerical benchmark based on experimental data obtained in a 7-rod bundle with spacers. It was a "blind" benchmark; the experimental data from a supercritical water test facility at Japan Atomic Energy Agency (JAEA) were revealed to participants during a meeting in June 25-26, 2014 at Delft. This paper deals with numerical results, obtained at Research Centre Rez during the "blind" phase of the benchmark and also results of some aftermath computations. Main goal was to test ability of the ANSYS FLUENT 12 code to simulate supercritical water flow and heat transfer in rod bundles using moderate-size computational grids. In order to limit the range of involved parameters, only one model of turbulence (SST k-ω) was selected; physical properties of supercritical water were calculated by REPROP 7 package. Mainly the results for Case B2 where water temperature crosses the pseudo critical temperature are presented here. Several computational grids with increasing size were produced with GAMBIT 2.4.6 preprocessor, and skewness, aspect ratio and size change were selected as monitored characteristics of grid quality. Due to hardware limitations, only 1/12 of the bundle was modeled. In all blind calculations, heat transfer deterioration region appeared when case B2 was simulated. The main results (wall temperatures) obtained using all grids were compared with measured data. Aftermath simulations were focused on determination of effects of buoyancy and spacers on heat transfer phenomena.