HYPERVAPOTRON TECHNIQUE IN SUBCOOLED FLOW BOILING CHF

Fusion reactor thermal hydraulics requires suitable techniques for the removal of extremely high heat fluxes, of the order of some tens of megawatts per square meter. One possible technique, the hypervapotron, to enhance the critical heat flux (CHF) in subcooled flow boiling (already characterized by high values of CHF) was studied using water flowing in a horizontal annular test section designed for visualization. A full characterization of the hypervapotron effect as a function of geometry and fluid thermal hydraulic conditions was accomplished by making use of a high-speed videotape. The hypervapotron technique is suitable for the removal of high heat fluxes (up to about 30 MW/m2) wherever high values of fluid velocity and subcooling are not practical. In fact, it is typically employed at low values of liquid velocity and subcooling that in turn directly affect enhancement of the CHF in subcooled flow boiling.