Condensation frosting on meter-scale superhydrophobic and superhydrophilic heat exchangers

•Applied low cost superhydrophobic coating to meter-scale heat exchangers.•Superhydrophobic heat exchangers (SHPHX) delayed frost growth significantly.•SHPHX decreased defrosting times over a long period of time.•SHPHX consistently retained less water compared to uncoated heat exchangers. Frost formation on heat transfer equipment such as air-source heat pump evaporators can result in drastic efficiency penalties. The performance reduction is a result of the insulating nature of ice and the increased fan power required to pump air through the constricted channels between frosted fins. Furthermore, the need to defrost adds appreciable energy use to the system. In this study, we develop a nanoengineered coating process that can be scalably applied to meter-scale, fully-assembled, aluminum heat exchangers. We demonstrate the coating on a decimeter-scale copper-tube aluminum-fin commercial heat exchanger having a 25 × 15 cm face area, and 9 corrugated fins per inch. The frosting characteristics on the unaltered heat exchanger are compared to identical components with superhydrophobic and superhydrophilic coatings for a range of inlet coolant temperatures (−5 to −10 °C) and ambient humidities (30 to 50%). The results show that a superhydrophobic heat exchanger can decrease frost accumulation, maintain heat transfer rates above half of the maximum capacity three times longer, reduce the required defrosting time and energy by 50%, and reduce the amount of water retained by 75% when compared to its uncoated and superhydrophilic counterparts.