Prediction of sliding bubble coalescence rate during subcooled flow boiling in narrow rectangular channel

• Published in: International journal of heat and mass transfer 2022-11, Vol.196, p.123244, Article 123244
• Main Authors: Zhang, Lin, Liu, Hanzhou, Liu, Xiaojing, Chen, Deqi
• Format: Article
• Language: English
• Subjects: Bubble coalescence rate; Rectangular narrow channel; Subcooled flow boiling; Visual experiment
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2022.123244

•Boiling experiment based on a full transparent test section is carried out to investigate the bubble coalescence rate in flow boiling.•The interfacial contact velocity at the moment of bubble coalescence increases due to the variation of bubble size in slide process during the subcooled boiling.•The bubble coalescence critical velocity model was improved to predict sliding bubble coalescence rate during subcooled flow boiling. Prediction of bubble coalescence rate during subcooled boiling is significant for the simulation of void fraction and heat transfer capacity in the flow channel. In this paper, the boiling visualization experiment based on a four-sides visible test section was carried out to investigate coalescence characteristics of sliding bubbles and predict bubble coalescence rate during subcooled flow boiling in narrow rectangular channel. The experimental phenomena shown that phase interfacial contact velocity at the moment of bubble coalescence increases due to the variation of bubble size in the slide process during the subcooled boiling, which prominently alters the bubble coalescence rate. Besides, bubble collision mainly comes from the relative motion between bubbles due to buoyancy difference and turbulence in this study. Herein, we proposed a correlation of bubble collision frequency by considering the characteristics of rectangular narrow channel. Finally, the bubble coalescence critical velocity model was improved to predict sliding bubble coalescence rate within an error of ±25% during subcooled flow boiling in narrow rectangular channel.