ABSTRACT
Convective boiling beyond critical-heat-flux (CHF) is encountered in a number of applications, including steam generators, nuclear reactors, cryogenic systems, and metallurgical processing. Post-CHF boiling is traditionally divided into the regimes of flow film boiling and transition boiling. Both regimes are further categorized according to the distribution of the vapor and liquid phases. At subcooled or low vapor qualities, with low void fractions, post-CHF heat transfer occurs with inverted annular flow, wherein a liquid core is surrounded by a vapor film at the hot channel wall. At high void fractions with moderate to high vapor qualities, post-CHF heat transfer occurs with dispersed flow, wherein the liquid phase is distributed as entrained droplets in the vapor phase. The chapter presents a framework to examine phenomenological questions pertinent to the understanding of the transport mechanisms in convective post-dryout boiling heat transfer.
