Heat transfer deterioration (HTD) phenomena in supercritical water is one of the most thermal hydraulic critical issues for supercritical reactors. The onset of heat transfer deterioration and bouncy effect have been studied in details, however limited work has been done on the mechanism of HTD occurrence. In this work, three dimensional analysis of velocity and temperature boundary layers under heat transfer deterioration conditions is conducted. The effect of thermo physical water properties changes inside the fluid boundary layer and its effect on the heat transfer coefficient is studied. Analogy between HTD and critical heat flux condition in subcritical boiling is observed and reported. Under HTD conditions, clotting or sudden stopping of the flow inside the tube is predicted due to the severe variation in density and other thermo physical properties in the tubes radial direction.
