Natural convective heat transfer influence between two spheres in a packed bed

Abstract

The influence on heat transfer between two spheres in a packed bed was investigated with horizontal and vertical pitches using the copper sulfate‑sulfuric acid (CuSO4-H2SO4) electroplating system. The natural convective heat transfer of two spheres in an open pool was also analyzed for a comparative purpose. Both the bed diameter-to-sphere diameter ratios (D/d) and the bed height-to-sphere diameter ratios (H/d) were fixed at 10. The sphere diameter was 0.0158 m, which is consistent with Grd of 1.66 × 105. All the possible geometric arrangements of the two spheres in a rhombohedral packing were simulated. In an open pool, the natural convection of the two heating spheres was influenced by initial velocity, preheating and stagnant flow effects. The heat transfers of the lower and upper spheres were either weakened due to the stagnant flow and preheating effects or improved due to the initial velocity effect. In a packed bed, similar tendency but weaker influences were observed due to the friction loss and separation of the plume by adjacent spheres. The visualization of local heat transfers of spheres performed by copper plating patterns, showed the breakup of thermal boundary layer of spheres in packed bed.