Heat-transfer measurements were made along the wall in the thermal entrance region of a high-temperature turbulent airflow through a cooled tube 8.6 dia long. There was simultaneous development of the velocity and temperature profiles along the tube, the boundary-layer thickness at the inlet being small, compared to the tube radius. The measurements, made over a range of Reynolds numbers based on the tube diameter ReD from 7 × 104 to 106 and wall-to-gas temperature ratio Tw/Tt from 1/3 to 2/3, included natural boundary-layer transition data in the laminar, transition, and turbulent boundary-layer regions, and forced transition data obtained with a trip at the tube inlet. Although the inability to predict boundary-layer transition precludes a general correlation of the data, a fair correlation of the transitional data was obtained by accounting for the effective origin of the boundary layer. Transition Reynolds numbers, on the order of those found for flow over a flat plate, increased with ReD and decreased with wall cooling; i e., decreasing Tw/Tv In the turbulent boundary-layer region, both the natural transition data and tripped data were in general correspondence with the trend of a constant-property flat-plate prediction. However, the turbulent boundary-layer heat-transfer group with properties evaluated at the core flow temperature increased with wall cooling. Other investigations in the turbulent flow region are discussed in light of these measurements.

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