Comprehensive experimental thermal analysis of single bubble nucleation in vertical flow boiling: Whole field temperature and microlayer dynamics

• Published in: International journal of heat and mass transfer Vol. 233; p. 126006
• Main Authors: Moiz, Mohd, Vadlamudi, Sai Raja Gopal, Srivastava, Atul
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-11-2024
• Subjects: Bubble dynamics; Contact line dynamics; Evaporative heat transfer coefficient; Flow boiling; Heat transfer; Microlayer evaporation; Microlayer evaporation; Bubble dynamics; Flow boiling; Evaporative heat transfer coefficient; Contact line dynamics; Heat transfer
• ISSN: 0017-9310
• DOI: 10.1016/j.ijheatmasstransfer.2024.126006

•Microlayer dynamics and thermal analysis of single bubble nucleation.•Experiments under nucleate flow boiling regime.•Simultaneous application of gradients-based imaging techniques.•Quantification of microlayer evaporation contribution towards total heat transfer using thin-film interferometry.•Dry patch dynamics and comparison with theoretical predictions.
Nucleate boiling, an important heat transfer phenomenon, holds significance in the thermal management of numerous engineering applications. Understanding and predicting its heat transfer characteristics are vital for system optimization. The formation of a microlayer, resulting from rapid bubble growth on a heater substrate, subsequently facilitates further bubble growth through evaporation playing a critical role in overall bubble dynamics. This study examines the intricate relationship between bubble and microlayer dynamics and their impact on heat transfer rates. Experimental work is conducted for varying heat fluxes using rainbow schlieren deflectometry (RSD) and thin-film interferometry (TFI) in tandem for simultaneous mapping of key parameters: bubble dynamics, microlayer dynamics, and two-dimensional temperature field in vertical flow boiling. The analysis of these parameters has provided significant insights into some fundamental aspects of boiling. Firstly, this study emphasizes that the bubble growth rate models need to take into initial microlayer thickness in accurately predicting bubble growth dynamics. The iteratively obtained constant Ceff (describing the initial microlayer thickness) for bubble growth models matches well the value of Ceff obtained experimentally from thin film interferograms. Additionally, this study also validates the applicability of the kinetic theory-based model in predicting the evaporative heat transfer coefficient during the initial stage of flow boiling, while demonstrating that the accommodation coefficient is ∼0.04 for the investigated range of heat fluxes. Subsequently, using the experimentally obtained evaporative heat transfer coefficient, further insights are provided into the dry patch dynamics. Experimental dry patch dynamics were in good agreement with theoretical predictions up to the rewetting phase. The results also indicate a substantial contribution of microlayer evaporation, constituting approximately 34 % of the total heat flux.