Heat Transfer Characteristic Of Water In Vicinity Of Pseudo Critical Of Scwr Core

Nuclear energy is clean and efficient.After 60 years of development,its application in power plants is mature.As one of the Generation-? reactor concepts,the supercritical pressure water-cooled reactor(SCWR)has drawn more and more attention due to its simpler,more compact structure and higher thermal efficiency in comparison with the existing LWRs.The grid spacer is an indispensable part to precisely position and support fuel rods in a rod bundle.It has been proved that grid spacer is influential in the local thermal hydraulic characteristics.These impacts must be learned deeply in the design of fuel assembly in SCWR.Due to very high cost and several technical problems,it is difficult to carry out the experimental research on the heat transfer performance of supercritical water inside a fuel rod bundle.And the corresponding data is little.The CFD analysis,however,is able to provide an alternative way to the experimental research that allows us to comprehensively and deeply explore this field with much lower cost on both economy and time.It is of great significance that using CFD simulation to analysis the thermal hydraulic characteristics in sub-channel of SCWR core.In this paper,we study on working medium in Vicinity of Pseudo Critical.The turbulence model is Reynolds Stress SSG model working in with automatic wall function,and it is validated.We use structured mesh to discrete the fluid domain.The difference of the results between sub-channel with and without grid spacer were contrasted.The effect of grid spacer on thermal hydraulic in sub-channel is analyzed in transverse temperature distribution,the formation of vortex,second flow,pressure drop,buoyancy and flow acceleration.It turned out that the split vanes contribute to the mixing of fluid in the sub-channel and neighbouring sub-channels.Turbulent flow in the sub-channel has strong circumferential nonuniformity,which causes the distribution of pressure and temperature uneven and enhance the local heat transfer in the downstream of grid spacer.The highest cladding temperature appears at the narrow gap of the sub-channel without grid spacer.However,it appears at the angular position of-10°in sub-channel with grid spacer attached by split vanes.The vane guides the fluid and leads to the change of velocity and pressure field in the downstream of grid spacer,and cause strong second flow.Moreover,it also brings differential pressure in cross-flow and different kinds of vortex.The movement of these vortexes impacts on the heat transfer in the sub-channel.The split vanes have some effects on buoyancy and flow acceleration.However,in its entirety,the buoyancy and flow acceleration in the conditions we conducted is so small that can be neglected.