The numerical method was used to study bubble sliding characteristics and dynamics of R134a during subcooled flow boiling in a narrow gap. In the numerical method, the volume of fraction (VOF) model, level set method, Lee phase change model and the SST k − ω turbulent model were adopted for the construction of the subcooled flow boiling model. In order to explore bubble sliding dynamics during subcooled flow boiling, the bubble sliding model was introduced. The bubble velocity, bubble departure diameter, sliding distance and bubble sliding dynamics were investigated at 0.2 to 5 m/s inlet velocities. The simulation results showed that the bubble velocity at the flow direction was the most important contribution to bubble velocity. Additionally, the bubble velocity of 12 bubbles mostly oscillated with time during the sliding process at 0.2 to 0.6 m/s inlet velocities, while the bubble velocity increased during the sliding process due to the bubble having had a certain inertia at 2 to 5 m/s inlet velocities. It was also found that the average bubble velocity in flow direction accounted for about 80% of the mainstream velocities at 0.2 to 5 m/s. In the investigation of bubble sliding distance and departure diameter, it was concluded that the ratio of the maximum sliding distance to the minimum sliding distance was close to two at inlet velocities of 0.3 to 5 m/s. Moreover, with increasing inlet velocity, the average sliding distance increased significantly. The average bubble departure diameter obviously increased from 0.2 to 0.5 m/s inlet velocity and greatly reduced after 0.6 m/s. Finally, the investigations of the bubble sliding dynamics showed that the surface tension dominated the bubble sliding process at 0.2 to 0.6 m/s inlet velocities. However, the drag force dominated the bubble sliding process at 2 to 5 m/s inlet velocities.

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Because of the important role of multiphase flow in many fields and its complexity, the study of boiling heat transfer of two-phase flow has become an important topic of current research. Under the background of double carbon, energy saving and emission reduction are a hot direction in the current refrigeration industry. Therefore, studying the boiling heat transfer of two-phase flow is helpful to strengthen heat transfer and design more efficient heat exchangers. In this paper, the research progress of subcooled flow boiling based on CFD is reviewed. Firstly, the mechanism of subcooled flow boiling and the current research contents are introduced. Secondly, the development of incompressible flow and two-phase flow solving algorithms is reviewed, and the advantages and disadvantages of each algorithm are analysed and compared. Finally, a research method is selected to provide a basis for the simulation of subcooled flow boiling in the tube.