Turbulent heat transfer of highly buoyant supercritical CO2 flow in various horizontal pipes

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

“…Computational fluid dynamics (CFD) simulations, direct numerical simulations (DNS) and Reynolds-Averaged Navier-Stokes (RANS) modeling [21][22][23][24], demonstrated that this impairment is attributed to buoyancy-induced secondary flows taking the accumulated lighter and hotter sCO 2 fluids to the top wall. Wang et al [25] investigated the effect of tube diameter (4.6-22 mm) on turbulent heat transfer to sCO 2 flowing in horizontal tubes and concluded that the overall heat transfer performance was negatively influenced by the strong buoyancy induced by property variation even for pipes of small diameter. In view of the above, the asymmetric tube wall temperature distribution, observed by experimental and numerical papers, can lead to thermal stress and fatigue affecting the tube longevity and structural integrity thereby presenting a safety concern and increasing the operation and maintenance cost in the long run.…”