Experimental and numerical study on helium flow characteristics in randomly packed pebble bed

Abstract

The high temperature gas cooled reactor (HTGR) with a packed pebble bed core has been one of the fourth generation reactors. The helium cooled pebble bed (HCPB) blanket packed spherical pebbles of lithium orthosilicate (Li4SiO4) has been recommended to Chinese Fusion Engineering Test Reactors (CFETR). Helium flow characteristics in spherical pebble bed are the key issues to design the pumping power. In this work, helium flow characteristics in a rectangular pebble bed channel filled with stainless steel particles whose diameters are 0.5 mm, 0.8 mm, 1.0 mm, 1.5 mm, and 2.0 mm, respectively, were investigated experimentally and numerically. The experimental results show that the compressibility cannot be neglected and it has an important influence on flow characteristics in the conditions with the enough large ratio of pressure drop to system pressure. Ergun correlation was compared with experimental values, and Ergun correlation modified with compressibility was deduced. The results show that Ergun correlation modified with compressibility can improve the ability to predict experimental values. The numerical results show that the particle friction factors modified with compressibility (fp*) in a rectangular pebble bed channel randomly filled with spherical particles can be predicted by using the models with SC-1, BCC-1, and FCC-1 arrangements. This work would provide some supports for the design of the helium supply system of the packed bed reactors.