Analysis of heat and mass transfer characteristics of supercritical CO2 in vertical U-tube

Abstract

The heat and mass exchange of CO2 in a vertical U-tube under supercritical pressure was simulated. The effects of the geometry of the bend area, The center arc radius of the bend area and the different bend orientations on the flow heat transfer of supercritical CO2 in the U-tube were analyzed. The results show that in the bend area, the flow is affected by the combined action of centrifugal force and gravity, as well as the pipe structure, so the flow mixing is intense, and the heat transfer capacity is significantly enhanced. When the direction of the bend changes, the interaction between centrifugal force and gravity will affect the heat transfer at pipe bending. When the central arc radius r of the bend area increases from 0.5D to 3D, the heat transfer at the bend can be strengthened, but will weaken the heat transfer at the bend outlet area.