[3G01-06] Critical Heat Flux

[3G03] CHF and Near-Wall Boiling Behaviors in Flow Boiling on a Vertical Surface

*Hiroto Sakashita¹ (1. Hokkaido University)

Keywords:Flow boiling, Critical heat flux, Liquid-vaper behavior, Conductance probe, Liquid layer thickness

This study examines the trigger mechanism of the CHF for forced convection boiling of water on a vertical surface based on measurements of the liquid-vapor behaviors near heating surface by using a conductance probe. The probe signals and the void fraction distributions showed that a liquid layer remains beneath the vapor masses moving upward along the heating surface at high heat fluxes. Liquid velocity has little effect on the liquid layer thickness and greatly influences the vapor mass passage period. The measured data of CHF were well predicted base on a liquid layer dryout model where CHF is triggered by the dryout of the liquid layer during the period when the vapor mass passes.