Hydrophobic surface embedded with arrayed hydrophilic dots can be prepared on a copper surface with mesh screen and Teflon solution. Completely hydrophilic copper surface

completely hydrophobic Teflon-coated surface and hydrophobic-hydrophilic hybrid surfaces are taken into consideration which are served as the bottom heat transfer area of 1.5 mm hydraulic diameter rectangular mini-channels. In this experiment

vapor mass velocity ranges from 10 kg·m-2·s-1 to 60 kg·m-2·s-1

while the vapor quality from 0.3 to 1. According to the experimental investigation

steam condensation heat transfer coefficient on hybrid surface is about 454.6% higher than that of completely hydrophilic surface and 107.3% higher than completely hydrophobic surface at most. High speed camera provided the photos of two-phase flow pattern

especially the periodic behavior of the droplets nucleation

coalescence and flushing which can explain the mechanism of heat transfer enhancement.