Transient pool boiling heat transfer during rapid cooling under saturated water condition

Abstract

The transient pool boiling heat transfer during rapid cooling was investigated under the saturated water condition. The quenching method was applied, and the vertical rodlet was used as the test specimen. The effects of material property, test specimen size, groove structure, and chromium coating were studied. The small heat capacity and small volume-to-area ratio (VAR) made the quenching duration shorter. In the groove-structured test specimen, the vapor film on the structured portion collapsed earlier than on the plain portion, which could be due to the small local VAR of the structured portion. It caused the groove-structured test specimen to exhibit a shorter quenching duration than the plain test specimen, though both test specimens had almost the same averaged VAR. This implies that the quenching duration and position of the vapor film rupture can be actively controlled by the surface structure. The influence of chromium coating on the quenching duration was preliminarily tested using niobium for accident tolerant fuel (ATF) application in a nuclear light water reactor. The chromium-coated niobium test specimen exhibited a somewhat longer quenching duration than the non-coated one.