Pool boiling heat transfer enhancement with electrowetting

Electrowetting (EW) has drawn significant research interests in droplet-based microfluidics, and most applications focus on electronic displays, lab-on-a-chip devices and electro-optical switches, etc. This paper presents a new application of EW in enhancing pool boiling heat transfer. The working approach capitalizes on the complimentary roles of hydrophobicity and hydrophilicity played in boiling and takes advantage of the ability of EW to alter the surface wettability dynamically and reversely. In this work, the effects of alternating current EW (ACEW) on the heat transfer characteristics of various boiling regimes, including the onset of nucleate boiling (ONB), fully developed nucleate boiling, and film boiling at critical heat flux (CHF) conditions, are investigated. A synchronized high-speed optical imaging and infrared (IR) thermography approach is taken to obtain simultaneous measurements of the bubble dynamics and the wall temperature and heat flux distributions on the boiling surface. Based on the experimental data, boiling curves are constructed and the boiling heat transfer coefficients (BHTCs) are computed. Comparisons with the boiling characteristics of the baseline surface without ACEW demonstrate the efficacy of ACEW in enhancing the performance of pool boiling heat transfer. Some insights are also offered to understand the physics of the ACEW-enhanced boiling behaviors.