Mechanism of bubble nucleation and growth during nucleate boiling on microcavity surfaces

The enhancement of heat transfer using engineered microstructured surfaces holds significant potential for applications in high heat flux components. To investigate the impact of microstructure scale on bubble nucleation and growth at the microscale, three types of microcavity surfaces, each with an identical surface area-to-volume ratio, were fabricated on monocrystalline silicon plates. The nucleation and growth of bubbles on these microstructured surfaces, as well as on smooth surfaces, were observed during pool boiling experiments using a metallurgical microscope and high-speed photography with de-ionized water. The experimental results indicate that both the temperature and diameter of nucleated bubbles are significantly influenced by the scale of the microstructure. These observations are consistent with predictions from the Young–Laplace equation, confirming that the scale of the microstructure plays a pivotal role in enhancing boiling heat transfer. However, existing bubble growth models exhibit discrepancies when compared to the experimental data. To address this, a new bubble growth model, based on energy conservation principles and microstructure characterization parameters, is proposed. This model accurately predicts bubble growth behavior on microstructured surfaces, with a mean absolute deviation of 11.7%. The microstructure enhances heat transfer both from the wall to the bubble and from the wall to the adjacent superheated liquid layer. The expansion of the vapor/liquid interface is an important factor in the growth of bubble diameter on microstructured surfaces.