Simulation and experimental analysis of purge gas flow characteristic for pebble bed

Abstract In a solid breeder blanket as a functional material, the lithium ceramics are kept in the form of a pebble bed. Helium is used as a purge gas, which flows through the pebble bed. The flow characteristics are essential in designing and running the breeding blanket efficiently, depending on the pebble bed arrangement. In the present study, a computational model of unitary pebble bed was engineered using DDPM-DEM (Dense Dispersed Phase Model-Discrete Element Method) to study the purge gas flow characteristics of the pebble bed. A similar packed bed was engineered using a porous media approach. The parameters which affect the flow characteristics are porosity, pressure distribution, pressure drop, and wall effect. Nitrogen and helium were used as purge gas to study the flow characteristics of a pebble bed. The simulations with the laminar and k-ɛ model were performed at different inlet velocities, and flow characteristics of a packed bed were observed. The comparison shows that the pressure drop simulation results agree with the Ergun equation's predicted pressure drop. Also, a previously developed experimental facility has been used to validate the simulation results. Artificial Neural Network (ANN) is used to predict the pressure drop as a complementary approach. DDPM-DEM analysis helps to predict the pressure drop which enables us to finalize the design parameters of canister, pebble size, finally the size of the pebble bed, packing fraction etc. Simulation results were also compared with the experimental results and ANN model, which were in good agreement.