Experimental Study of Forced Convective Heat Transfer in Packed Beds With Uniform and Non-Uniform Spheres
In the present paper, the forced convective heat transfer was experimentally studied in packed beds with uniform and non-uniform spheres. The pore structures of different packings were reconstructed with discrete element method, and the lateral porosity distributions were analyzed. Furthermore, the pressure drop, heat transfer and overall heat transfer performances of different packings were investigated and compared with each other. Firstly, it is found that, using laterally layered composite packing (LLM), smaller pores would be formed close to the tube wall and big flow channels would be formed in the inner-tube region, which would reduce the tube-wall effect in the near tube wall region of packed bed. When compared with mono-sized packing with lower tube to particle diameter ratio, both the heat transfer and overall heat transfer capacities would be improved with LLM packing method. Secondly, it is found that, using randomly composite packing (RCM) or axially layered composite packing (ALM), both the lateral porosity magnitude and amplitude of packed bed are lower than those of mono-sized packing with higher tube to particle diameter ratio in the near tube-wall region. The tube-wall effect would be further reduced, and both the heat transfer and overall heat transfer capacities would also be improved with RCM and ALM packing methods.