Investigation into the packing structure of binary pebble beds using X-ray tomography

The packing structure of pebble beds has a significant influence on their macroscopic thermal and mechanical performance. An advanced experimental X-ray tomography technique was applied to study the structural properties of binary pebble beds. Based on the reconstructed geometry, structural properties were analyzed employing different approaches. The bulk porosity predicted by DEM simulations agreed well with the values obtained experimentally. The radial porosity distribution of the binary pebble beds was found to have a regular and typical oscillatory characteristic near the wall. In addition, a correlation within the experimental range was derived to predict the average coordination number of binary pebble beds. The distribution of contact angles for binary pebble beds has the same features as the distribution for unitary pebble beds. Understanding the local structural properties of a binary pebble bed will significantly help its application in heat transfer and mechanics.