Flow Characteristics And Heat Transfer Study Of Purge Gas In The Pebble Beds Of Water Cooled Ceramic Blanket

Blanket plays an important role in tritium proliferation and heat extraction in fusion reactor,and plays an important role in the normal operation of fusion reactor.WaterCooled Ceramic Blanket(WCCB)is one of the three blanket candidate schemes proposed by China Fusion Engineering Test Reactor(CFETR).In it,lithium titanate(Li2TiO3)and beryllium small ball(Be12Ti)particle binary random packed pebble bed are used as tritium proliferator and pure Be mono-sized pebble bed is used as neutron multiplier.The two are arranged in zones,and helium is used as purge gas to extract tritium produced in the blanket.The flow and heat transfer characteristics of the purge gas in the pebble bed will directly affect the tritium extraction efficiency,and then affect the design parameters of the blanket.Therefore,it is necessary to conduct in-depth research on the flow parameters and heat transfer characteristics of the purge gas in the water-cooled ceramic blanket,so as to determine whether it is necessary to add a preheating device to preheat the purge gas and effectively improve the tritium production efficiency in the pebble bed.Based on the above purposes,this paper has carried out the following research:Firstly,based on the DEM-CFD coupling method,the flow characteristics of monosized pebble bed are numerically studied,and the effectiveness of DEM-CFD method is verified.The velocity and pressure drop of purge gas and the heat exchange between purge gas and particle surface are analyzed.The effects of particle surface friction coefficient on the accumulation results of pebble bed and the flow characteristics of purge gas are studied,The results show that with the increase of the purge gas flow rate at the inlet,the purge gas flow rate and pressure drop in the mono-sized pebble bed also increase,but the regional distribution in the pebble bed does not change significantly;The increase of particle surface friction coefficient will reduce the filling rate of monosized pebble bed,and the flow characteristics of purge gas will not change,the maximum flow rate is about 12 times of the inlet velocity,and the pressure drop is 1.33KPa/m;When the particle surface friction height increases,the flow characteristic parameters of purge gas decrease;The heat exchange between the purge gas and the pebble bed is small,and the influence on the working ambient temperature of the pebble bed can be ignored.Then,the binary pebble bed is also modeled by DEM-CFD method.The diameter ratio of particles in the pebble bed is 6:1.The flow characteristics of purge gas and the influence of particle surface friction on the flow characteristics of purge gas are studied,and the detailed parameters of purge gas flow characteristics and heat exchange in the pebble bed are obtained:The maximum flow rate of purge gas in the binary pebble bed is about 23 times of the inlet velocity,and the pressure drop is 11KPa/m,which is about 9 times of that in the mono-sized pebble bed;The particle surface temperature in the binary pebble bed decreased by 1.5℃.In this paper,the flow and heat transfer characteristics of purge gas in the pebble bed are studied,and the specific parameter values are obtained through numerical simulation,which verifies the influence of the heat transfer behavior between purge gas and pebble bed on the working environment of pebble bed,and provides a theoretical reference for the structural design of blanket module and the analysis of tritium extraction efficiency.Figure[62]Table[11]Reference[65]...