A comprehensive review of nucleate boiling fundamentals applied to thin film annular flow

• Identification of the driving mechanisms influencing boiling in thin annular liquid films. • Critical review of flow boiling heat transfer coefficient correlations, with an emphasis on nucleate boiling contributions. • Comparison of possible mechanisms that promote nucleate boiling beneath disturbance waves. • Evaluation of current limitations and opportunities in heat flux partitioning models for annular flow boiling. Nucleate boiling in thin film annular flow is a complex phenomenon influenced by a variety of heat transfer mechanisms. While the fundamentals are rooted in the comparatively well-understood fields of pool and flow boiling, thin film flow boiling introduces additional challenges that make the heat transfer behavior hard to predict. Specifically, the relative importance of the heat transfer mechanisms controlling nucleate boiling in thin annular films and their roles in flow regime transitions remains inadequately understood. In light of this, the foundational aspects of nucleate boiling and the relationship between flow parameters – such as liquid film thickness, system pressure, surface tension, channel geometry, mass flow rate, and applied heat flux – and the intensity of nucleate boiling in thin annular films are analyzed. The importance of these parameters is demonstrated through the presentation of multiple correlations, with a critical examination of the limitations inherent in correlation-based modeling. Additionally, recent research has identified disturbance waves as a significant factor in enhancing bubble nucleation, yet the underlying mechanisms driving this phenomenon remain undefined. Therefore, the insights and deficiencies of three theories seeking to explain wave-based nucleation are extensively considered. This research aims to introduce and categorize the wide breadth of literature regarding thin film annular flow nucleate boiling to identify gaps in understanding and facilitate future physics-based modeling efforts.