Nucleate boiling “frontiers": Boiling inception and boiling crisis

This paper has the (ambitious) aim to review and discuss the fundamental theories and the more recent findings at the "frontiers" of nucleate boiling, i.e. its boundaries: nucleation onset and CHF, where its efficient performance is terminated. Nucleate boiling and is dominated by bubble dynamics, however in the past years it has become increasingly evident that multiple thermal and chemical interactions with the heated surface cannot be discounted. In the recent past, the development of new and sophisticated diagnostic techniques has allowed a substantial gain of knowledge of the phenomena taking place at micro- and meso-scale on the boiling surface. At the same time, new technologies allowed for performing experimentation in exotic environments like the variable-gravity ones, or for developing of innovative surfaces of controlled morphology. The investigation on ultrasmooth, superhyprophobic and nano-structured surfaces on one hand opened new promising fields for industrial application, and on the other hand disclosed new features that forced to "re-think" and integrate the basic knowledge on boiling heat transfer, developed in the past 60 years. New theories and explanations have been set forth to account for new experimental findings, but at the same time the need arises to take into account and "re-discover" old and valuable contributions, often forgotten or hidden in aged and dusty xerox papers in our shelves.