Dropwise condensation heat transfer on hydrophobic sine-shape micro-grooved surfaces

In this study, Sine-shape micro-grooved surfaces with depth of 12 - 24 μm and width 30 - 60 μm were precisely and smoothly fabricated using 3D printing. The hydrophobicity and the heat transfer characteristics of dropwise condensation on the micro-grooved surfaces were investigated experimentally, and the coalescence and sweeping process of droplets on micro-grooved surfaces was thermodynamically analyzed. As the results show, the wetting behavior and heat transfer characteristics on the micro-grooved surfaces presented anisotropic characteristics, the static contact angle in perpendicular direction θ↓ was significantly larger than that in parallel direction θ_//. In heat transfer experiment, the plates were set vertically and the grooves were arranged in two positions, vertical and horizontal. For the vertically grooved surface, the sweeping effect of falling drop was enhanced by the vertical groove and the heat transfer during dropwise condensation was increased to 30% - 50%, and a better heat transfer performance can be achieved when the ratio of height to pitch increases. Different from vertical grooved surface, the experimental results obtained from horizontal grooved surface was similar to the results of smooth surface. This may be due to the dual effect of horizontal grooves, promoting droplet coalescence and hindering the departure process.