Ice adhesion and accretion on power lines is a severe problem that can pose a threat to the electric power transmission, and this icing phenomenon is significantly related to the impact dynamics of freezing rain droplets. In the current paper, this process was studied by using a CFD way, and the model was verified by an experiment with a high-speed camera. The detail droplet impact processes on the surface of a very commonly used overhead power line (the ACSR-type cable) were analyzed. The effects of surface wettability (θ = 67°~135°) and initial droplet impact velocity (We = 22~219) on the evolution of the liquid-solid contact area during the whole process and the amount of the residual liquid on the power line surface after impact were studied. Meanwhile, the influence of the surface structure of the ACSR power line on the droplet impact dynamics was analyzed. Results show that the capturing of impact droplets can be enhanced by the grooved structures on a hydrophilic ACSR power line surface, while differently the expelling of impact droplets can be enhanced by these grooved structures on a hydrophobic ACSR power line surface. By analyzing the possible influence of the surface structure of an ACSR power line on the phase transition of the impact droplets, these grooved structures could facilitate the formation of ice nucleation which can finally lead to the ice adhesion and accretion on an ACSR power line is more serious than that on a traditional smooth cylindrical power line.

Poor performance in the condensers in power plants and chemical plants is due to the fact that condensed water is deposited on the heat transfer pipes. The dynamics of condensed water droplets forming on the surface of heat transfer pipes have a significant effect on the heat transfer efficiency of heat exchangers. In the present study, a numerical approach using a coupled level-set and volume of fluid (CLSVOF) method was adopted to investigate the impact of water droplets on cylindrical pipes. The numerical model was verified by an experiment, and both sets of results showed qualitative and quantitative agreements. The effects of the surface wettability, impact velocity and relative size of the droplet to the pipe on the droplet impact dynamics are systematically investigated. Moreover, the regularities of the contact area between the liquid and the pipe during the impacting process as well as the volume of residual liquid remaining on the pipe post-impact are also analyzed; these two parameters are the key factors which affect the heat transfer efficiency of heat transfer pipes, and they cannot be acquired very accurately using experiments.