Enhanced Phase-Change Condensation Using Inverse Opals

Abstract

Phase-change condensation is commonplace in power and process engineering. Due to high surface energy, most condenser surfaces exhibit filmwise mode wherein the condensate is removed due to gravity when the weight overcomes pinning forces. Here, we use cracks (fabrication defects), which form when a copper tube is coated with inverse opals, to transport the condensate away from the condensing surface. Our visualization and experiments show that the cracks have high hydraulic conductivity that preferentially transports the condensate towards the ends of the copper tube. This improves the heat transfer coefficient to ~ 80 kW/m2·K from ~ 12 kW/m2·K for filmwise condensation on smooth copper tubes. Additionally, when the porous inverse opals are impregnated with a lubrication film, the heat transfer coefficient increases by an additional 30% to 103 kW/m2·K. Repeated experiments show that our material design is durable. The insights gained from this work informs the rational design of condenser surfaces.