On the periodic nature of two-phase pool boiling structure

Abstract

[Abstract]: This work shows that the two-phase boiling structure emerging from the hot surface is periodic for almost the full range of the boiling curve. We conduct a non-conventional analysis of the two-phase structure based on its evolution over time. Given the periodic nature of the pool boiling structure, we developed a proposal for the physical mechanisms responsible for the observed behavior. This work uses a previously published boiling study on saturated HFE-7100 at 100 kPa with a copper surface having a 24 nm average roughness. Six videos along the boiling curve constitute the basis of this analysis. The videos comprise the full range of the boiling curve, from the fully developed regime to the critical heat flux. Three regions were found: a thin layer by the boiling surface with strong frequencies; a region with two marked frequencies; and a region influenced by free surface. The spectral analysis of the two-phase structure reveals six different periodic structures in the second region: the bubble package, the scrambled package, the broken package, the remaining package, the dissolved package, and the two-phase stream. Each of these structures has their own features and frequencies. Spectral analysis reveals that there are two dominant harmonics in the pool boiling structure. The highest frequency corresponds to the structure near the hot surface, whereas the lowest one is related to the detached structures away from the hot surface. This spectral framework provides a new perspective for characterizing the two-phase structure and offers new insight into pool boiling.