EXPERIMENTAL STUDY OF FORCED CONVECTIVE HEAT TRANSFER IN COMPOSITE PACKED BEDS OF SPHERES
In the present paper, the forced convective heat transfer was experimentally studied in a square channel fully
filled with steel spherical particles. Three kinds of randomly packed beds were constructed, including two
kinds of uniform packings with mono-sized particles of dp=6mm or 12mm, respectively, and a kind of
composite packing with both particles of dp=6mm and 12mm. The packing structures of these packed beds
were reconstructed with discrete element method (DEM), and the radial porosity distributions were analyzed
and compared with each other. Furthermore, the pressure drop, heat transfer and overall heat transfer
performances of different packings were also carefully investigated. Firstly, it is found that, for mono-sized
packing, the packed bed with lower tube to particle diameter ratio (D/dp) would be less compact and the tube-wall
effect would be remarkable. With composite packing method, the tube-wall effect in the packed bed with low D/dp
would be restrained in the near tube wall region and the air flow rate in inner region would be enhanced. Secondly,
the pressure drop and heat transfer capacity of mono-sized packing with large D/dp were found to be much
higher than those of packing with low D/dp, while the overall heat transfer capacities were close with each other.
With compositing packing method, both heat transfer and overall heat transfer capacities would be improved
for the packed bed with low D/dp.