Heat Transfer to Stationary and Rolling Droplets on Carbon Nanotube Superhydrophobic Surfaces

Orem, UT

Superhydrophobic (SH) surfaces significantly alter heat transfer characteristics by minimizing liquid-solid contact. This study investigates transient heat transfer to stationary and rolling water droplets on heated SH surfaces comprising nanostructured carbon nanotube (CNT) forests and two-tier micro/nanostructured geometries. Droplets (20–50 μL) were deposited onto surfaces heated to 80°C at inclination angles ranging from 0 to 5°. Infrared thermography and image processing were utilized to determine droplet heating effectiveness as influenced by CNT height (65–180 μm), CNT diameter (25–65 nm), cavity fraction (0.5–0.85), and inclination angle. Results indicate that heating effectiveness is primarily driven by inclination angle and CNT diameter. Smooth nanostructured CNT surfaces reduced heating effectiveness by approximately 70% compared to smooth Teflon-coated SH surfaces. Furthermore, two-tier structured surfaces reduced heat transfer by an additional 38% relative to the smooth CNT surfaces. These results offer new insights into dynamic droplet thermal transport on SH nanostructured surfaces, which is useful for optimizing SH surfaces using grown CNTs.