Grooved hybrid copper surfaces for condensation heat transfer.

Condensation is commonly utilized in numerous thermal management applications and has two modes termed filmwise and dropwise, the latter providing superior heat transfer performance. However dropwise condensation is usually limited by its dependence on gravitational shedding of condensate. To combat this, hybrid surfaces consisting of regions of different wettability have emerged as a promising solution. Of such designs, hybrid grooved surfaces consisting of grooves with varying wettability in the groove valleys and ridge tops are of current interest. To date, most such surfaces have been silicon-based and over flat substrates. In this work, condensation experiments are performed on a copper tube with fabricated grooved hybrid surfaces. The aim is to take advantage of anisotropic wetting due to the presence of grooves and condensate drainage from higher wettability regions. The experimental results quantify the heat transfer with the degree of subcooling. At the same time, droplet dynamics were studied on the hydrophobic-hydrophilic surfaces, showing several droplet growth and departure mechanisms leading to effective heat transfer.