Evaluation of the Critical Heat Flux Under Conditions of High Subcooling and High Velocity in Small Diameter Channels

The critical heat flux (CHF) under conditions of high subcooling and high velocity in small diameter channels was systematically evaluated to obtain a reliable CHF correlation which can be used to predict CHFs higher than 50 MW/m2 in the design of high performance nuclear research reactors, the accelerator target and the first wall and diverter of the fusion reactor etc.. The major test conditions of the existing CHF experiments investigated in this study were a channel diameter or gap of 0.3 to 4mm, a channel length-to-diameter ratio of 15 to 97, a pressure of 0.1 to 7.1 MPa, an inlet water subcooling of 13 to 210°C and a water mass flux of 124 to 90000kg/(m2·s), resulting in a CHF of 4.2 to 224MW/m2. The existing experimental data were compared with the analytical CHF solution which was derived by the author for the channel flow under high subcooling and high velocity of water at atmospheric pressure. As a result, the effect of the channel diameter on CHF was clarified quantitatively and a correlation of CHF was newly proposed, which can be used to predict the existing CHF data within an error of about ±35 percent, reflecting the effect of the pressure properly.