Critical heat flux at low velocity and pressure conditions

The purpose of this study is to provide some systematic understanding on critical heat flux (CHF) at low velocity and pressure conditions in which the effects of gravity and flow instability are remarkable. Experimental data obtained previously for water in an annulus, rectangular ducts and a round tube are briefly reviewed and augmented in collaboration with existing data and correlations to extract more generic information. The effect of channel geometry is then discussed. The effect of channel geometry turned out to be significant at intermediate mass velocities. The difference in CHF at these mass velocities between a round tube and the other channel geometries was attributed mainly to the existence of unheated wall which causes a nonuniform distribution of liquid film. (author)