Transient burn-out in liquid helium with rapid rise of heat flux

This Paper presents the results of experimental and theoretical investigations of transient burn-out in liquid helium moving freely. Heat input in the open vertical channel with liquid helium was increased linearly. The rate of increase of heat flux was varied from 100 to 23 000 W m −2 s −1, ensuring both quasi-steady and transient conditions. When heat input rose rapidly, burn-out simultaneously appeared over the entire channel length. This can be explained by the peculiarities of unsteady hydrodynamics. A physical model of transient boiling burn-out in a pool and in channels is presented. Relationships for some forms of heat flux variation in time have been derived on the basis of this model. Present experimental data and results of other authors are verified by means of the developed model.