Self-healing, Slippery Surfaces for HVAC&R Systems

Enhancing water shedding behavior on aluminum surfaces is important in the design of energy-efficient heat exchangers. In this work, a method for fabricating oil-infused aluminum surfaces for HVAC&R systems is described for the purpose of exploiting the slippery nature of such surfaces, thereby improving the overall surface wettability. A microstructured, porous aluminum fin stocks with heterogeneous hydrophobic coating are infused with a secondary liquid acting as a lubricant that enhances slippery, liquid repellant and self-healing behavior. The objective of this work is to study the feasibility of using these surfaces to more effectively manage condensate/frost formation on heat exchangers. The effects of the underlying oil-infused microstructure and hydrophobic coating on the behavior of droplets are studied. Although the slippery surfaces are observed to decrease the contact angle of droplets, they promote mobility by reducing the interfacial energy and friction force. From preliminary experiments, critical inclination angles of small droplets (volume ≤30 μl) are reduced by more than 40° compared to baseline surfaces. Moreover, slippery surfaces delay the frost formation, and have only one fourth of the baseline water retention after self-defrosting. Therefore, such properties provide potential for improving the water drainage behavior for HVAC&R systems.