Ice Nucleation in the Presence of Electric Fields: An Experimental Study 2019-01-2020

Ice accretion poses a severe problem for various applications occurring in the transportation or electric power supply sectors and often arise due to the freezing of supercooled water drops on a solid surface. The first priority in all applications is a secure operation and high reliability, especially for electric power supply systems. Ice accretion on high voltage insulators mostly occurs in colder regions and may lead to an interruption of the power supply due to an altered shape of the insulator. The adhered ice potentially causes a partial or complete failure of the insulation, can increase the surface conductivity, or can affect the mechanical stability of the pylons. In the present study, ice nucleation in sessile water droplets is investigated under the impact of electric fields to determine their influence on heterogeneous nucleation. The experimental setup enables simultaneous observation of multiple drops under well-defined conditions with and without an electric field, and at temperatures down to -40 °C. A single experimental run contains 50 drops exposed to the same conditions. The drops are produced with a well-defined size using a drop-on-demand droplet generator. Based on multiple experimental runs the nucleation behavior is analyzed using statistical methods to determine the drop survival curves and nucleation site densities for varying conditions. Besides the influence of the electric field, the influence of the cooling rate is investigated in the range of 1 K/min and 5 K/min. A comparison of the experiments with and without an electric field is used to elaborate its influence on heterogeneous ice nucleation.