Enhancement of dryout heat flux in a particle debris bed with downcomers

This paper presents the results of the experimental investigation on dryout heat flux of a particulate debris bed. A series of experiments were performed on the POMECO (POrous MEdia COolability) facility for both homogeneous and stratified porous particle debris beds. The porous beds were made of different sand particles. The porosity of particle bed was varied from 25 to 40%, and the average particle size from 0.2 to 1 mm. Experimental results show that the installation of a downcomer in the particle beds can enhance significantly the dryout heat flux for both homogeneous and stratified particle beds. It is found that up to 600% enhancement of dryout heat flux in the present particle beds can be reached. The configurations of downcomers have significant impact on the performance of the dryout heat flux enhancement. The presence of holes on the downcomer can remarkably improve the dryout heat flux, especially for the particle bed with large size or porosity. More holes provide larger channel area for water to penetrate into the particle bed, so lead to higher dryout heat flux. Generally, larger effective cross-section area of downcomer per particle bed area provides bigger enhancement of dryout heat flux.