A customized Computational Fluid Dynamics (CFD) model of supercritical water (SCW) heat transfer in a vertical tube upward flow is developed and validated using experimental data obtained under the operating conditions typical for SCW cooled reactors (SCWRs): at a pressure of 24 MPa, an inner tube diameter of 10 mm, an inlet temperature of 320 or 350 °C and a heated tube length of 4 m. The three values of mass flux (500, 1000 and 1500 kg/m2s) and various values of wall heat flux (from 141 to 729 kW/m2) are considered. Physical properties of SCW are calculated by using the REFPROP software from National Institute of Standards and Technology (NIST). The model has been incorporated into the commercial general-purpose CFD software, PHOENICS. Various turbulence models and numerical grid settings are tested. The study has demonstrated a good agreement between the CFD predictions and the experimental data on the inside tube wall temperature and heat transfer coefficient with use of a two-layer low-Reynolds-number k-e turbulence model. Practical recommendations are made regarding potential model applications in 3D analyses of SCWRs.