Experimental and LBM simulation study on the bubble dynamic behaviors in subcooled flow boiling

Bubble dynamic behavior is a fundamental issue in comprehending flow boiling process. In this paper, the bubble characteristics are studied in depth through experiment in conjunction with the Lattice Boltzmann method (LBM). Firstly, the visualized experiment in rectangular channels with double heating plates is performed during subcooled flow boiling. High-speed camera is employed to directly capture the macroscopic bubble dynamic behaviors under different working conditions. Furthermore, LBM model with a novel hybrid boundary scheme is developed to investigate mesoscopic bubble characteristics, including contact diameter, microlayer thickness profile and superheated layer thickness. The bubble diameter from LBM model is compared to experimental data with a mean relative error of 10.8%. The results of the current research find that the bubbles nucleating on the inside channel have smaller contact diameter ratio and larger inclined angle. Finally, combining macroscopic experiments and mesoscopic LBM studies, a model of the bubble growth rate is proposed for predicting bubble growth behavior. In the process of model development, three aspects for deciding the bubble growth rate are considered, including microlayer evaporation, heat diffusion from the superheated liquid layer, and condensation at bubble dome caused by subcooled flow boiling. The prediction model agrees well with the experimental results, with a mean relative error of 14.7%. The established bubble growth model will help to predict the heat transfer process during flow boiling.