Effect of internal helical-rib roughness on mixed convection flow and heat transfer in heated horizontal pipe flow of supercritical water

A designed wall roughness approach to improve turbulent heat transfer to supercritical CO2 flowing in horizontal tubes

“…It was reported that while the filled metal foams remarkably enhance the sCO 2 heat transfer and result in a more uniform wall temperature along the tube circumference, the flow resistance increased by 50-100%, leading to significant excess pressure drops. Li et al [32] introduced internal helical-ribs to improve the supercritical heat transfer in horizontal pipes to note an improved heat transfer along the top wall thereby reducing the temperature difference over the circumference albeit at the expense of 20-100% extra pressure drop. To optimize a heat exchanger design the interplay between heat transfer coefficient and pressure drop has to be carefully investigated especially for sCO 2 tubes with large diameters [33].…”