Research on the phase transition process of sessile droplet on carbon fiber cold surface

The droplet phase transition process on the cold surface of a T300 carbon fiber substrate was studied by observing the droplet freezing process. Through the construction of visualized experimental device, the change in the droplet phase transition time under different experimental conditions, the progression of the solid-liquid interface during the phase transition process, the droplet deformation rate, and the ratio of growth of the interface height after the phase interface appears were experimentally obtained. The influence of different surface temperatures and different droplet volumes on the phase transition process was investigated. The experimental results show that the phase interface shows an irregular profile during the phase transition of the sessile droplet on the cold surface of the carbon fiber substrate, it presents a wave-shape early and smooth concave-shape later. The influence of droplet volume on the phase transition time is not a simple linear relationship. The height of the solid-liquid phase interface during the droplet phase transition process first grows rapidly, then slowly, and then fast once again. In other words, the growth rate of the phase interface is relatively fast when the phase transition has just occurred and the when the bulged tip is formed. At different cold surface temperatures, the droplet deformation rate with a volume of 10μL is basically the same, which is about 32.4%, within an uncertainty of about 1%. However, the influence of gravity factor is important in determining the droplet deformation rate for different droplet volumes.