| The collision and freezing phenomenon of supercooled water droplets is widely used in many practical engineering fields such as refrigeration and low temperature,power communication,aerospace and so on.In view of the hazards caused by icing,a variety of anti-icing methods have been developed by researchers,However,the traditional anti-icing methods have problems such as high energy consumption,heavy weight and complex system structure.Inspired by the superhydrophobic phenomenon in nature,the excellent anti-icing performance of superhydrophobic surfaces have been discovered by people.Aiming at the problem of surface deicing,hydrophilic and superhydrophobic surfaces are used as research objects in this paper,and systematically studies the effects of surface inclination,surface wettability,surface temperature,water droplet diameter and velocity on the icing of water droplets colliding with the surface.The main research results are as follows:(1)The effects of surface temperature and tilt angle on the process of water droplets hitting the surface were investigated experimentally.The results show that for superhydrophobic surfaces,the contact time between water droplets and the surface decreases with the increase of the tilt angle and the increase of the surface temperature.It is worth noting that increasing the tilt angle reduces the retraction time of the droplet.The separation of the secondary droplet from the primary droplet on the superhydrophobic surface occurs at θ=0°.For θ≥30°,droplet separation is suppressed.The superhydrophobic surface has excellent anti-icing properties,which can ensure that the impact droplets can be completely bounced off without freezing at-25℃.The maximum spreading factor and spreading time of hydrophilic surfaces increase with the inclination angle.(2)The kinetic characteristics and heat transfer mechanism of supercooled droplets of different diameters colliding with superhydrophobic surfaces were simulated and studied.The results show that with the increase of the droplet diameter,the maximum spreading area of the droplet,the contact time between the droplet and the wall,the droplet retraction time,and the time required for the droplet to spread to the maximum value will increase.Large droplet diameter results in higher heat transfer.The simulated droplet morphology and wetting factor were compared with existing experiments and simulations to verify the accuracy of the simulation method.(3)The influence of different velocities of water droplets on the impact of superhydrophobic surfaces was investigated by simulation,and the icing process of water droplets impacted was quantitatively discussed based on water droplet impact dynamics and heat transfer theory,and the dynamic behavior characteristics of water droplets in this process were obtained.The results show that:when the velocity of v=0.5 m/s is small,the water droplets do not bounce off the water droplets;when the velocity of the water droplets is further increased to v=1.4 m/s and v=2.6 m/s,the water droplets appear secondary water droplets.Bounce off;when the water droplet velocity increases to 3.8 m/s,the water droplet spreads and breaks.As the speed of the water droplet decreases,the time it takes for the water droplet to spread to the maximum value gradually increases,and the time from the first time the water droplet bounces off to the contact with the surface again gradually shortens.In addition,the higher the velocity of the water droplet,the higher the heat exchange between it and the surface.Droplet diameter has a greater impact on heat transfer than droplet velocity.This article has a total of 44 figures,9 tables,and 108 references. |
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