Saturated Pool Boiling Heat Transfer of R-141b on Al2O3 Nano-Structured Surfaces Fabricated by Dip-Coating Method

In pool boiling applications, appropriate surface properties of the heating surface are crucial for improving the heat transfer. In this study, two different Al₂O₃ nano-structured surfaces were fabricated using dip-coating method by controlling coating thickness, and adopted to conduct pool boiling experiments with R-141b. Prepared Al₂O₃ nano-structured surfaces were characterized by scanning electron microscopy (SEM), elemental dispersive spectroscopy (EDS), ellipsometer, contact angle meter, and 2D profilometer to investigate the surface morphology, elemental composition, thickness, angle of contact, and surface roughness, respectively. Based on the surface characterization and boiling curves, the effects of coating thickness (300 nm and 400 nm) on the pool boiling heat transfer were examined. The heat transfer coefficient (HTC) of Al₂O₃ nano-structured surface (S2) was the highest, followed by those of Al₂O₃nano-structured surface (S1), and plain copper surface. The outstanding heat transfer performance of Al₂O₃ nano-structured surfaces is mainly associated with enhanced surface wettability and increased active nucleation site density.