Numerical study on heat transfer and flow oscillations of supercritical-pressure water in helical tubes

A deep understanding of flow oscillations of supercritical fluids in helical tubes is of great significance for the safety of supercritical steam generators. A numerical study was conducted on the flow oscillations of water in helical tubes with various wall heat capacities and helix diameters at a supercritical pressure of 24.5 MPa. For steady-state calculations, the flow and heat transfer characteristics of supercritical-pressure water were investigated in 2-mm-thick helical tubes with various helix diameters. For transient calculations, the mass flow rate oscillated intensely beyond a heating power threshold in the tube with zero-thickness wall, while the flow characteristics in tubes with finite-thickness walls with various wall heat capacities were significantly different. The flow and heat transfer characteristics are presented during the heating process at various times under flow oscillations. The flow oscillations in helical tubes with various helix diameters are also analyzed to determine the effects of the centrifugal force.