The effect of turbulence parameters and support position on the heat transfer from spheres

Abstract Measurements are reported which show the influence of the turbulence intensity, the scale of turbulence, and the position of the support, on the average heat transfer from spheres to an air stream. The Reynolds number range was from about 3·6 × 10 3 to 5·2 × 10 4 . The turbulence intensity and the scale of turbulence distributions downstream from three grids, behind which the heat-transfer measurements were later made, were measured for velocities from 4·6 to 18·3 m/s. The heat-transfer measurements showed that the average Nusselt number increased with the turbulence intensity, and with the ratio of the sphere diameter to the scale of turbulence for values up to at least five. Nusselt numbers, obtained using a crossflow support, were found to be about 10 per cent higher than those obtained using a rear support. Equations relating the average Nusselt number to the Reynolds number, for a low-turbulence free stream, are given.

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