Quantitative analysis of anti-freezing characteristics of superhydrophobic surfaces according to initial ice nuclei formation time and freezing propagation velocity

In order to quantitatively analyze the anti-freezing characteristics of superhydrophobic and bare surfaces, the freezing delay properties of the surfaces were experimentally investigated under various operating conditions by placing sessile droplets on their surface. The freezing delay time was calculated using the experimental results and analyzed by employing a stochastic method. The formation time of initial ice nuclei and freezing propagation velocity at a macroscopic level were proposed as measures of surface anti-freezing characteristics. The anti-freezing properties of the bare and superhydrophobic surfaces were analyzed using the proposed quantitative measures. Consequently, the tendency of quantitative results was consistent with that of the qualitative ones according to the changes of the operating conditions (air inlet velocity, relative humidity, and surface temperature). Moreover, the superior anti-freezing performance of the superhydrophobic surface was quantitatively confirmed by the initial ice nuclei formation time, which was delayed by 22-92%, and the freezing propagation velocity, which decreased by 17-30%.