Performance evaluation of flow boiling CHF correlations in short-heated channel

Abstract

This study investigates critical heat flux (CHF) in a horizontal saturated flow boiling water loop with a downward-facing heated surface in a macro-channel (40 mm × 10 mm cross-section) at atmospheric pressure. CHF models and correlations were evaluated against a new dataset spanning mass fluxes from $120–640kg/m²·s$ and materials such as non-oxidized and oxidized copper and carbon steel. While several correlations accurately predicted CHF, many overlooked the effects of surface conditions and orientation, exposing gaps in existing methods. The study also examines radiation-induced surface activation (RISA) under electron beam and γ-ray irradiation. Results show γ-ray irradiation enhances CHF by up to 47% across metals, while electron beam irradiation has material-dependent effects: aluminum maintains stable CHF, but copper and silver exhibit an initial decrease followed by an increase at higher doses. This study provides insights of CHF behavior on downward-facing surfaces and for irradiated materials, offering guidance for selecting CHF models and informing nuclear safety applications, particularly in-vessel retention (IVR) strategies.