Heat transfer experiments on subcooled water flow boiling were carried out in a vertical upward circular channel, which was set off-center in a rectangular nickel block. Particular attention was paid to the heat transfer of water under high and heat fluxes and high mass fluxes under one-side heating conditions, with respect to the heat removal technologies for the divertor in the International Thermonuclear Experimental Reactor (ITER). The test section was electrically heated by a large AC power supply with an effective heated length of 360 mm. The test parameters covered pressures of 3-5 MPa, mass fluxes of 3000-8000 kg.m(-2).s(-1), inlet bulk temperatures of 40-220 degrees C, and equivalent heat fluxes up to 8 MW.m(-2). The effects of the parameters on the heat transfer coefficients have been discussed in detail, from single-phase forced convention to fully developed nucleate boiling. A series of heat transfer correlations were evaluated using the experimental data, and most of the correlations did not adequately fit the experimental results. A modified Liu-Winterton correlation and modified Jens-Lottes correlation were used to predict the heat transfer coefficients in the partially boiling region and fully developed boiling region, respectively. The average errors (AEs) of the two correlations were -0.28% and 0.6%, and the root mean square errors (RMSEs) of them were 7.93% and 2.89%. (C) 2017 Elsevier Ltd. All rights reserved.