Dynamics of inner bubble during water droplet evaporation on conical micro-pillars surfaces. (February 2022)

• Record Type: Journal Article
• Authors: Gao, Linsong; Lyu, Jizu; Zhou, Zhifu; Li, Yang; Gao, Dongdong; Shi, Lin; Lv, Xuecheng; Li, Yubai
• Is Part Of: International communications in heat and mass transfer. Volume 131(2022)
• Publication Date: 2022-02
• Subjects: Droplet evaporation -- Bubble dynamics -- Strong turbulent fluctuation -- Conical micro-pillars; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Heat -- Transmission; Mass transfer; Periodicals; 621.4022
• DOI: 10.1016/j.icheatmasstransfer.2021.105841
• Languages: English
• ISSNs: 0735-1933

Abstract

Abstract: The experiments are conducted to investigate the geometrical parameters' effects of the water droplet evaporation process on the conical micro-pillars surfaces. Four conical micro-pillars surfaces with different pitches of adjacent micro-pillars (200, 300, 400 and 500 μm) are fabricated by nanosecond laser micro-nano processing technology on the copper surface. The results indicate that micro-pillars structures significantly enhance the droplet evaporation rate for the modified surfaces comparing to the smooth surface due to the easier initiation and more rapid growth of the bubbles. Conical micro-pillars surface with pitch of 500 μm has the largest solid-liquid interface among the studied conical micro-pillars surfaces. Meanwhile, some satellite bubbles depart from heated surface at the surface temperature of 107.8 °C, leading to the best nucleate boiling of droplet. On the other hand, a coalesced vapor bubble is observed in the tests on the other micro-pillars surfaces, which increases thermal resistance at the solid-liquid interface and hinders heat transfer from the heated surface to the droplet. The phenomenon of bubble oscillation occurs due to the combined effects of bubble evaporation and condensation. And this process repeats for several time at the early stage of evaporation. In addition, a strong turbulent fluctuation is formed after the breakup of vapor bubble on conical micro-pillars surfaces at the surface temperature of 107.8 °C. The observed strong turbulent fluctuation is also observed at higher surface temperature.