In the range of pressure from 24 MPa to 32 MPa

mass flow rate from 420kg/(m2·s)to 800kg/(m2·s)

and heat flux at outer wall from 150kW/m2 to 360kW/m2

experiments were conducted to investigate the heat transfer characteristics of water in a vertical upward rifled tube.The temperature distribution in the tube wall was obtained.The effects of heat flux at outer wall

mass flux and pressure on heat transfer coefficient and temperature at inner wall were analyzed

and the corresponding empirical correlations were presented.The experimental results show that at subcritical pressures

the wall temperature increases monotonically with the bulk fluid enthalpy.The wall temperature rises slowly in the pseudo-critical enthalpy region

which implies that the heat transfer is enhanced.With the increase of outer wall heat flux and pressure and with the decrease of mass flux

the wall temperature rises.Meanwhile

the heat transfer coefficient goes down.