[2L16-19] Gas-liquid Two Phase Flow 2

[2L19] CHF and Liquid-Vapor Structure near Heating Surface in Subcooled Flow Boiling on a Vertical Surface

*Takashi Furuhashi¹, Hiroto Sakashita¹ (1. Hokkaido Univ.)

Keywords:Critical heat flux, Flow boiling, Subcooling, Liquid layer thickness, Void fraction, Conductance probe

This study examines the trigger mechanism of the DNB-type CHF for subcooled flow boiling of water on a vertical surface. The liquid-vapor behaviors close to the heating surface were measured by using a conductance probe in the range of subcooling 2.5 to 15K at flow velocity of 0.5m/s. It was found that at high heat fluxes a liquid layer remains beneath the vapor masses moving upward along the heating surface, and the vapor mass passage period decreases sharply with the increase in subcooling. The measured data of CHF were well predicted based on the macrolayer dryout model where CHF is triggered by the dryout of the liquid layer during the period when the vapor mass passes.