Experimental investigation of the pressure drop of CO2 flow at supercritical pressures in a heated 4 mm smooth pipe with different orientations

The application of supercritical fluids as an alternative heat transfer medium in thermal processes is becoming increasingly important, whereby the understanding of their pressure drop characteristics is essential for the process and component design. With a total of 96 experiments, this publication shows a systematic analysis of the pressure drop of CO₂ flow at supercritical pressures in a heated smooth pipe with an inner diameter of 4 mm, at a pressure of 7.75 MPa, mass fluxes up to 2000 kg/m²s and heat fluxes up to 235 kW/m². The hydrostatic pressure drop accounts for between 4 % and 24 % of the total pressure drop and the pressure drop due to flow acceleration for between 12 % and 30 %, with the frictional pressure drop accounting for the largest percentage. It was found that the Filonenko correlation can predict the pipe friction pressure drop in the investigated parameter range with a mean absolute deviation of 7 %.