1995 Volume 35 Issue 12 Pages 1438-1443
Convective heat transfer coefficients between a spherical particle and fluid for two flow systems (solid-liquid, -gas) were measured and were calculated with computer simulation at relatively low Reynolds numbers, and the applicabilities of empirical equation, for example, Ranz & Marshall's equation, to the estimations of convective heat transfer coefficients of these systems were investigated.
An aluminum sphere, 32 mm in diameter, which was kept at about 60°C initially for solid-water system and at 30°C for solid-air system, was dipped into each fluid flow and the relationships between the Nusselt number, Nu, and the Reynolds number, Rep, were obtained. Convective heat transfer coefficients were calculated with computer simulation and were compared with experimental results.
For solid-water systems, convective heat transfer coefficient was as large as the value estimated by Ranz & Marshall's equation for the range 300<Rep, but for lower Reynolds number region, heat transfer coefficients were slightly larger than the value calculated by Ranz & Marshall's equation. Although Reynolds number measured in solid-air system was small, heat transfer coefficient was as large large as ones calculated with following empirical equation.