Thermal Transfer in Turbulent Gas Streams. Effect of Turbulence on Local Transport From Spheres

Abstract

The present investigation was undertaken because of the paucity of data concerning the effect of level of turbulence upon local thermal transport from spheres in a free stream. A series of measurements was made of the local thermal transport in the forward hemisphere and a part of the after hemisphere of a silver sphere 0.5 in. diam. The measurements were made in an undisturbed air stream and at several positions in the wake of a grid inserted in the air stream. The apparent level of longitudinal turbulence was varied between 0.013 and 0.15 for Reynolds numbers up to 3600. At an apparent level of turbulence of 0.013 and a Reynolds number of 3600, the local thermal transfer varied by a factor of eight around the sphere. Increasing the apparent level of turbulence to 0.15 increased the over-all thermal transfer 20 per cent. The local thermal transfer varied by a factor of five at the latter level of turbulence.