Heat transfer and pressure-drop characteristics of a gas-solid suspension flow in a horizontal circular tube were investigated using glass spheres of two sizes, 30 and 200 micron. The airflow rate was held constant at three different values in a 0.71-in-ID tube such that Reynolds numbers of 10,000, 15,000, and 30,000 were produced. Solid loading ratios on a mass basis were as large as 7. The purpose of the investigation was to observe the effect of stratification on the heat transfer characteristics of the system. The pressure-drop results indicate that the solids were suspended in all cases, but the heat transfer data slum significant difference between the temperature of the tube wall at the top and bottom with the small particles. Nusselt numbers were as much as 2-1/2 times larger on the bottom side than on the top side. No such effect was produced with the large particles. The pressure-drop data indicate significant wall interaction for the large size, but not for the small size.

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