Study Of Hydraulic Performance Of Rod Bundles With Spacer Grids

This paper studied hydraulic performance of the flow field of 5×5 rod bundles with spacer grids by Large Eddy Simulation(LES)in order to validate the applicability of LES in hydraulic performance study of spacer grids and to analyze the hydraulic performance of two different spacer grids,Split-type and Swirl-type,through the comparison between calculation results and experiment data.SST k-ω model was adopted in this paper as a comparison in order to investigate the accuracy and advantages of LES.By comparing the simulation results and the experiment data,it can be proved that the LES method can get more accuracy results than SST k-ω model dose.The LES can capture the specific information of complex flow field.That is to say the large eddy simulation has good applicability in hydraulic performance study of spacer grids.Depending on the results above,models with drum and with square duct were simulated separately with LES.The result shows that the information on the measurement section cannot show the effects of the spacer grids,the drum has effect on the parameters as well,it is suggested that the measurement section should be moved forward so that the effects of the spacer grids can be analyzed reasonably.At last,the hydraulic performance of the two spacer grids was studied with LES method.The result shows that both of the two spacer grids have fierce mix effect during sub-channels,under the influence of spacer grids,vortex flow is generated in sub-channels and reduces as the measurement distance increasing.The Swirl-type spacer grid induced fiercer vortex near the wall,and the vortex flow last longer distance.In the matter of axial velocity,the Split-type spacer grid makes the axial velocity more uniform and has larger resistance coefficient,which is due to the larger projected area towards the flow direction.