Design Of Flat Electrospray Atomizers And Its Heat Dissipation Performance Research

At present,electronic components are developing rapidly towards a high degree of integration,and their Thermal Design Power(TDP)is also increasing.How to solve the heat dissipation problem of components has become a key technical challenge.Compared with conventional air cooling technology,phase change cooling technology such as spray cooling has become a research hotspot at home and abroad in recent years because of its strong heat exchange capacity,small cooling temperature difference,and no contact thermal resistance.Compared with conventional air cooling,phase change cooling technologies such as spray cooling have stronger heat exchange capacity,smaller cooling temperature difference,and lower contact thermal resistance.However,the electrospray atomizer has a complicated process and high cost,which is not conducive to large-scale application and promotion;and scholars have not fully studied the electrospray cooling,and the mechanism and influence of various parameters on the heat transfer performance are not yet available clear.Therefore,this article starts from the numerical simulation of electrospray to provide guidance for the design of electrostatic atomizer,and then manufactures flat-plate electrostatic atomizer and test its heat dissipation performance.The research results provide guidance and basis for the engineering application of electrospray technology in the field of heat dissipation of electronic components.The main research contents and conclusions of this article are as follows:(1)Based on the Lagrangian method,a three-dimensional numerical model was established and the droplet trajectory of the electrostatic spray was calculated.The change trends of droplet impact velocity and deposition area with flow rate,electric field strength,array spacing and other parameters are summarized.It was found that the deposition area of the electrospray and the impact velocity of the droplets were positively correlated with the flow rate;when the electric field intensity was increased,the deposition area of the spray decreased and the droplet velocity was greater.In the electrospray array design,proper spacing helps to improve the uniformity of deposition.(2)The electrospray plume is equivalent to a space charge field by Gauss’s law,and then the force analysis of the droplets outside the plume is carried out,and the expansion radius of the spray plume at different positions is obtained,which is the deposition radius of the electrospray.The comparison shows that the model is in good agreement with the related results,and the maximum error is about 10%.Compared with the traditional Lagrangian method and experimental method,this model can quickly obtain the deposition area of the spray.(3)Some structural parameters are determined by means of numerical simulation,and a flat electrostatic atomizer is designed and manufactured.The atomizer adopts a dual-electrode structure,the array density is 57 sources/cm~2,and the size of the packaged atomizer is only 7cm~3,which ensures the stability of spray emission on the basis of miniaturization.(4)The heat transfer characteristics of the electrospray were tested.According to the difference of the main heat transfer methods,the heat transfer process can be divided into single-phase zone,transition zone,boiling zone and stable zone.Subsequently,the change trend of heat flux and heat transfer coefficient with the wall temperature under different working conditions was studied respectively.The flow rate has a huge influence on the heat transfer performance.When the total flow Q increases from 25m L/h to 100m L/h,the limit heat flux qmax increases from 7.601W/cm~2 to 21.42W/cm~2,Increased by 181.4%.In the experiment,the spray plume and surface liquid film flow patterns were obtained through visual means.It was found that the surface liquid film was thicker when the flow rate was low,and a large number of bubbles were generated in the liquid film when the heat exchange was in the boiling zone.When the heat exchange is in the boiling zone,the liquid film will continue to break and move until it evaporates.(5)The effects of spraying height and electric field intensity have been studied.The results show that spraying height has little effect on heat transfer performance,but if the spraying height is too large or too small,it will affect the safety and stability of the atomizer;Lifting promotes heat transfer,because a larger electric field intensity corresponds to a faster droplet impact speed,which has a very good strengthening effect on single-phase flow heat transfer,but when the electric field intensity is too large,it will cause the liquid film to sputter tiny The droplets pose a safety hazard.The research results provide new ideas for the design and optimization of electrostatic atomizers,and have certain guiding significance for the development of electrospray heat dissipation technology.