Enhanced thermal uniformity and stability in pool boiling heat transfer using ultrasonic actuation

Recent issues in boiling heat transfer include enhancing not only heat transfer performance but also heat transfer uniformity and stability of the surface for using it as a practical cooling application. In this study, we demonstrate that ultrasonic actuation can be used to enhance the boiling heat transfer and thermal stability while also improving the temporal and spatial temperature uniformity through the acoustic field and acoustic streaming effect. The acoustic field is shown to enhance the instability between the bubble and heater interface, resulting in an increased dissipation rate of smaller bubbles and an increased, stable heat dissipation capacity. Through the particle image velocimetry (PIV), we observe the formation of convective flow and an enhancement of bubble mobility near the surface. It makes that, when ultrasonic actuation is used in the partial nucleate boiling region, the heat transfer coefficient is increased by 17%, and the temporal and spatial temperature variations are reduced to less than 70% and 65%, respectively, compared to that of the reference data. This study will help to enhance the understanding of boiling heat transfer under ultrasonic actuation.