Research On Condensation And Heat Transfer Performance Of Nanosecond Laser Micro-textured Copper Superhydrophobic Surface

In the industrial field,steam condensation is widely applied to energy,chemical,refrigeration,microelectronics,and batteries.With the highest heat transfer efficiency,droplet condensation is the best approach among all of the phase change heat transfer modes,and the preparation of superhydrophobic surfaces is a important factor for the realization of droplet condensation.The post-treatment method for common metal super-hydrophobic surface is commonly modified by organic matter,which has problems as environmental pollution,high thermal resistance,low processing efficiency,easy to fall off,etc.,It is aimed to the application requirements of steam condensation heat transfer of copper components,and the laser micro-nano texturing assisted with green post-processing is introduced.The nano-laser was used to micro-nano texture the surface of H62 brass,and combined with the subsequent heat treatment process to prepare a super-hydrophobic surface.Firstly,the effects of laser parameters on the structure and properties of textured H62 brass were studied.The surface topography of the laser micro-textured copper plate was analyzed by means of optical microscopy,surface profilometer,scanning electron microscope(EDS),X-ray photoelectron spectroscopy(XPS),etc.,.The results found that surface of textured copper plate can form a micro-nano periodic structure,and the laser parameters affect the microstructure on copper plate surface,furthermore,affect the wetting property.The micro-nano secondary structure was formed by the "well"-shaped weaving,which played a role in superhydrophobic performances.Then through the experimental study by condensing heat transfer test platform,it was found that the condensing heat transfer performance is better as the laser single pulse energy increases under the condition of the same pulse width.Based on this,a condensation heat transfer model was established to analyzing the surface free energy.And it was found that the heat treatment process can effectively reduce the surface energy of the condensation surface.After EDS and XPS analysis,it was revealed that heat treatment promote stable oxidation of copper surface,the surface energy decreases rapidly,and facilitates the formation of a full nano-cluster structure.Since the nano-cluster structure promoted the condensation of droplets,the condensation heat transfer coefficient of laser textured copper surface after heat treatment was 4.16 times that of the original surface,which was 1.06 times higher than the only textured surface.It provides a green and non-chemical surface treatment method for heat exchange applications of copper parts.