| Microscopic droplet freezing is the root cause of macroscopic icing/frosting.The freezing of water phenomena on cold surfaces widely exists in the fields of production and life such as aviation,meteorology,power communication,and refrigeration.In order to reduce the damage in engineering caused by icing accretion,studies on the deformation properties of droplet freezing experiments are done in this research.As the main research goal,systematic experimental study and numerical study are carried out through the icestructured protein droplet series experiments and the acetic acid droplet freezing series experiments.The purposes of this work are to clarify the interface effects and the heat transport of the frozen phase transition process,providing theoretical basis and technical reference for improving the icing/anti-icing/de-icing applications in engineering.The freezing deformation properties,heat transfer properties,and kinetic properties of a single solute-like droplet are revealed.And combined with the practical application of anti-icing to explore the application prospect of solute-like droplet freezing with deformation characteristics in practical engineering.In terms of theoretical research,based on the basic model of the phase transition of sessile droplets freezing on the supercooled surface,the theoretical analysis of the phase transition process of nucleation/re-glowing and freezing is carried out.Based on the mass conservation to deduce the law of profile change during droplet freezing.Based on the density ratio of solid-liquid phase,contact radius,and initial contact angle,the contour of the droplet after freezing can be obtained by numerical solution through MATLAB.Based on the mass conservation to deduce the droplet freezing heat transfer model,which can derive the relationship between the variation law of the droplet freezing phase interface height with time and the completion time of droplet freezing.In terms of experimental research,the droplet freezing experiment platform builted to carry out ice-structured protein droplet freezing experiments with different concentrations and different cold surface temperatures.The results showed that with the increase of the ice-structural protein concentration,the droplet profile tended to be rounded.The volume expansion coefficient before and after freezing decreased gradually with the increase of concentration and tended to be stable.The tip angle after freezing increases with the increase of the ice structure protein concentration decreases,which linearly with the increase of the droplet volume expansion coefficient and not affected by the initial contact angle.The height ratio of droplets before and after freezing decreases logarithmically with the increase of concentration,and not affected by the temperature of the cold surface.The completion time of droplet freezing increases linearly with the increase of the ice-structural protein concentration,which increases exponentially with the increase of the cold surface temperature.The interfacial motion of the frozen phase of the droplet is slower with the increase of the concentration,indicating that the increase of the concentration has an enhanced effect on its ability to inhibit freezing.The freezing characteristics of acetic acid droplets were studied experimentally.The molecular motion mechanism in the phase transition process of multi-component solutions was revealed through the freezing experiments of acetic acid droplets with different concentrations and different cold surface temperatures.It was observed in the experiment that the acetic acid droplets had a pagoda-like morphology and a distinct layering after freezing.With the increase of the acetic acid concentration,the slower the volume expansion of the droplet,the higher the height of the droplet after freezing.Under the condition of the same cold surface temperature,the completion time of droplet freezing will be delayed with the increase of acetic acid concentration.The rising rate of the frozen phase interface of acetic acid droplets is inversely proportional to the temperature of the cold surface.The higher the concentration of acetic acid makes the inhibition of the freezing of acetic acid droplets.The heat transfer model of acetic acid droplet freezing was established,which explained the reason why the droplet contour appeared delamination after acetic acid freezing,which was mainly caused by the difference of acetic acid concentration,and revealed the molecular dynamics characteristics caused by the phase transition process of acetic acid freezing.In terms of numerical research,the axisymmetric Lattice Boltzmann(LB)physical model is established to simulate the freezing process of ice-structured protein droplets.The results show that the variation of the interface motion of the droplet experiment frozen phase is in good agreement with the variation of the height and contour of the simulated frozen phase interface,which verifies the correctness of the theoretical model. |
