Forced convective heat transfer to turbulent CO2 in the supercritical region

Measurements were made of the wall temperatures of a 4·56 m long, 2·28 × 10−2 m dia. tube with heat transfer to turbulent flow of CO2 at supercritical pressure. In some experiments the change in state of the CO2 between the inlet and the outlet of the tube, covered the full supercritical range between the liquid and the gaseous phases and in others the effect of varying the inlet state through the supercritical region, was investigated. Measurements were made with both vertically upward and downward flow through the tube to determine the effect of changing the direction of the flow relative to bouyancy forces. A comprehensive set of data was obtained for pressures from 7.44 × 106 to 10·32 × 106 N/m2, heat fluxes from 0·8 × 104 to 35 × 104 W/m2 and mass flows from 0·127 to 0·695 kg/s. Deviations of the local heat transfer from that for normal gaseous or liquid CO2 ranged from factor of two deteriorations to order of magnitude improvements.