Experimental study on freezing characteristics of droplet impact on cold cylindrical surfaces

The freezing process of droplet impact on cold cylindrical surfaces are experimentally investigated using high-speed photography. Effects of Weber number (9.93–357.44) and surface temperature (−25 ∼ −5 °C) on the freezing characteristics are analyzed. The results show that, there are five different freezing morphologies after impacting cold cylindrical surfaces: semi-sphere, cone, single-bridge double-ear, double-bridge double-ear, and central concave ring. As Weber number (We) increases or surface temperature decreases, the freezing delay time, freezing time, and total freezing time are shortened, while the freezing velocity and the exterior freezing front moving speed increase. When the freezing morphology is semi-sphere or cone, the exterior freezing front moving speed in axial direction is smaller than that in circumferential direction. When the freezing morphology is single-bridge double-ear, double-bridge double-ear, or central concave ring, the movement of exterior freezing front can be divided into two stages: rapid development stage and slow convergence stage. The exterior freezing front in axial direction moves faster than that in circumferential direction during the rapid development stage. In this paper, the differences of icing in axial and circumferential directions on cylindrical surfaces are analyzed. The freezing characteristics and mechanisms under the influence of curvature are revealed.