Movement Of Different Types Of Particulate Matter In Supercritical Water

Supercritical water reactor(SCWR)is the only water reactor of the four generations and six types selected in the world.At present,the technology of supercritical boiler and ultra-supercritical boiler is mature.At the same time,natural circulation is an important part of the passive safety system of supercritical water reactor.Due to various reasons,there will be a large number of corrosive particles in the pipeline,which will accumulate on the wall of pipeline and affect the heat transfer efficiency,posing great potential safety hazards to the safe and stable operation of the reactor.Due to the different principles of particle generation and environment,the types of particles are quite different.Therefore,it is of great significance to study the deposition movement of different types of particles in supercritical water for the normal and safe operation of various power plant equipment.Complete the construction of a fine particle motion deposition experimental platform system in supercritical water.On the basis of solving the sealing and reliability of the interface,ensure the normal and stable operation of the system after the fluid reaches the supercritical state.In addition,the gantry is provided with a visible window to observe the movement of fluid and particles in a visual way,thus successfully solving the difficult problems of easy leakage of the visible window,inability of visible materials to bear ultra-high temperature and high pressure,etc.Based on the principle of passive natural circulation,the experimental loop is provided with a preheating section and a heating section for heating to ensure reaching a supercritical state,and a cooling section is adopted for cooling to ensure that the loop can generate density difference as a driving force for circulating flow.During the experiment,the working pressure was as high as 27.5MPa;The maximum flow rate of the system is up to 6.5 kg/h;The temperature of the fluid reaches 657K and the fluid reaches supercritical state.Based on the established experimental platform,ICEM CFD was used to model and mesh the natural circulation loop of supercritical water.CFX was used to calculate and study the effects of particle concentration,particle size and density on particle motion deposition.Experimental and analytical results verify the rationality of the simulation calculation.The importance of influencing factors of particle deposition rate in pipelines was studied by using the SWGRA program compiled by grey correlation analysis method,and the influence of particle types in supercritical water on particle deposition movement was quantitatively analyzed.According to the research,the particle movement and deposition laws are obtained.The particle deposition phenomenon is obvious in the experiment,a small amount of particles are deposited on the wall surface of the vertical section,and a large amount of particles are deposited on the bottom of the bent pipe.The fluid velocity increases with the increase of particle concentration,the decrease of particle size and the decrease of particle density.The particle deposition rate increases with the increase of particle concentration,particle size and particle density.The degree of influence on particle deposition is:particle size>initial concentration>density.The initial concentration of particulate matter increases and the friction force increases,which makes the particulate matter difficult to be removed by fluid after deposition,resulting in higher deposition rate.The acceleration of large particle size in the horizontal direction is smaller,and the particle tracking is lower,resulting in higher deposition rate.The follow-up of high-density particles to the fluid is reduced,and more particles are deposited on horizontal pipeline.Compared with the fluid with lower pressure and temperature,supercritical water has higher pressure and temperature,which leads to greater thermal swimming force and turbulent flow force of the fluid,thus causing more obvious deposition phenomenon.