Numerical study on acoustic characteristics of flow boiling in a helical tube

• Published in: Applied thermal engineering 2024-06, Vol.247, p.123090, Article 123090
• Main Authors: Chen, Chao-Guo, Li, Xiao-Bin, Zhang, Hong-Na, Li, Feng-Chen
• Format: Article
• Language: English
• Subjects: Boiling acoustics; Boiling patterns; Flow boiling; Frequency bands; Helical tube
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2024.123090

•Flow boiling of R141b and its acoustic features are simulated and analysed.•Boiling acoustics are determined by flow pattern, wall superheat and flowrate.•Boiling acoustic characteristics with flow pattern variation are discussed.•Wavy flow is characterized by low-frequency, but plug flow and slug flow are not.•Flow boiling regimes could be identified by acoustic emission. Helically coiled steam generators have advantages of strong heat transfer capacity, compact structure, and low thermal stress, and are widely used in many engineering fields. However, the heat transfer performance is still limited by the critical heat flux, beyond which boiling deterioration is an important cause of safety accidents. Both engineering and experimental studies have found that complex noises could be frequently generated during the occurrence of boiling crisis. In this paper, the acoustic characteristics of both subcooled and saturated flow boiling in a helical tube were numerically investigated, by using the volume of fluid scheme and acoustic model. The distribution of the vapor-liquid phase, flow pattern transition, and acoustic frequency band characteristics during boiling were analyzed under different wall temperatures (varied superheat), inlet subcooling, and flowrates. It’s found that the flow pattern under low mass flowrate was plug flow, slug flow, and wavy flow. All the three flow patterns have unique boiling acoustic features. The plug flow, consisted by a large number of small bubbles, shows the distinct high-frequency band characteristics of the boiling acoustics. The wavy flow, which is composed mainly by large bubbles, exhibits a significant low-frequency band characteristics of the boiling acoustics.