Hydrothermal spallation drilling is a possible alternative drilling technology based on the characteristics of certain rock types to disintegrate continuously into small fragments when exposed to high thermal loads. Impinging supercritical water jets or hydrothermal flames are favored to provide the required heat for thermal fragmentation. Hence, stagnation flow heat transfer under supercritical pressures of water was investigated by means of two calorimetric sensor devices covering a wide range of heat fluxes and surface temperatures. A numerical model based on ANSYS FLUENT was established to predict the heat transfer in conjunction with the Shear-Stress Transport k-omega turbulence model and the REFPROP database to calculate the thermo-physical properties. Finally, area-averaged heat transfer coefficients in the stagnation region of impinging hot water jets were determined by numerical simulations and validated against experimental measurements. Generally, the experimental trends were predicted correctly by the numerical model although the absolute heat transfer was overestimated. (C) 2015 Elsevier B.V. All rights reserved.