Manufacturing of microstructures with preventing frost accretion effect: Interaction of microstructures, wettability, and ultrasonic vibration

Frost formation is one of the natural phenomena and it causes many industrial problems. Frost has been usually removed by heating and deicer spraying to melt but they have recently been concerned about the defrost cost. Therefore, we tried to clarify the effect of preventing frost growth on the surface wettability and the microstructures on the cooling surface. Firstly, four samples with different wettabilities, as-mirror-finishing, hydrophilic, hydrophobic and superhydrophobic, were prepared by mirror-finishing and coating and two types of experiments, with and without ultrasonic vibration, were conducted. The results showed that the hydrophobic surface improved the frost reduction effect with the ultrasonic vibration because it might lower the mechanical strength of frost. On the other hand, the frost grew strongly on the hydrophilic surface and was not separated from its surface. Then, microstructured samples, rectangle-shaped projection on the surfaces, were created and experimented with cooling. The results suggested that the frost grew on the top of the structures due to the water supply caused by the heat convection.