Mechanism Study On The Influencing Factors Of The Melting Process Of Frozen Sessile Droplets

Droplets exist widely in plasma storage,aerospace and other technical fields,and their mechanism research is mainly concentrated in the freezing stage,while the research on the melting stage is relatively small.The application of the melting process of frozen droplets is concentrated in the field of industrial deicing and defrosting.,For example,the melting reaction mechanism of frost crystals needs to be considered in the defrosting technology.The purpose of this study is to change the droplet shape by regulating the influence of the frozen droplet,to detect the contact surface and interface morphology characteristics of the droplet on the material surface,and to study many characteristics of the droplet during the melting process.The influencing factors and dynamic evolution modes of the droplet melting process on different substrates provide theoretical basis and technical reference for improving production and life in the field of defrosting and deicing.The main research contents and achievements include:(1)The DSA-30 droplet surface analyzer was used to visualize the freezing process and melting process of droplets on the cold surface,and to analyze the change rules of droplet volume,height and solid-liquid interface during the phase transition of droplets.Under different freezing conditions,the wetting process of frozen droplets mainly occurs in the initial stage of melting.The freezing condition(low temperature initial condition)has a significant effect on the initial wetting process,while the effect is slower in the middle stage of the phase transition of the droplet.(2)The dynamic surface and interface evolution modes of the melting process of frozen droplets on different material surfaces and at different substrate temperatures are found and summarized,and the morphological evolution parameters such as the droplet surface diffusion coefficient,height coefficient,and phase interface deviation are summarized.The change law between the phase transition times and the analysis are carried out.There are three different surface and interface evolution modes of frozen droplets;in the middle and later stages of melting,the ice phase region of frozen droplets on the surface of metal materials(pure copper,galvanized sheet)melts in a particle group distribution state,and the degree of ice crystal bonding is low.On the other hand,the ice phase region of the frozen droplets on the surface of polymer materials(plexiglass(PMMA)and polyvinyl chloride(PVC)test plate)melts in a block-like distribution state,and the degree of ice crystal bonding is high;The phase transition rate is faster than that of frozen droplets on the surface of polymer materials.(3)The liquid under different freezing conditions(substrate temperature-4,-6,-8,-10and-16 ?)and different heating conditions(substrate temperature 6,11,16,20,24 ?)on the surface of the substrate The droplet phase transition process and the wetting characteristics of the melting stage were visualized,and the phase transition laws of droplets under different conditions were sorted out.Combined with the surface wetting parameters,the mechanical analysis system of the droplet surface wetting process was carried out.The study found that in the melting stage,the wettability of droplets is mainly affected by gravity,surface tension,and thermocapillary force.Gravity promotes the lateral diffusion of droplets,and the effect of surface tension is related to the contact angle.,the thermocapillary force is affected by the temperature of the bottom plate,and also has the effect of inhibiting the wetting process of droplets.