HEAT TRANSFER IN THE SEPARATION AND WAKE REGIONS OF A GAS-PARTICLE CROSS FLOW
This paper reports the results of a study of the effect of flow Reynolds number on suspension heat transfer in the separation and wake regions of tubes subject to a gas-particle cross flow. Results are presented for tubes located in the first three rows of a staggered tube array with air flow rates corresponding to Reynolds numbers of 7000, 10000 and 14000. Glass beads of mass median diameter 127 µm are used at solids mass loading ratios ranging from 0.25 to 0.9kg/kg. Although the effect of particles on heat transfer varies somewhat with Reynolds number and solids concentration, it was found for all test conditions that the wake region of tubes in the second and third rows was narrower for the suspension flows. This change has been attributed to a delay in boundary layer separation due to momentum transfer from the particles which leads to a reduction in local turbulence levels and reduces heat transfer over the rear of that tube and the front of downstream tubes. In addition, the heat transfer data presented for the highest Reynolds number suggest that the presence of the particles in the flow reduces local turbulence levels to such an extent that transition to turbulence within the boundary layer is inhibited.