| With the miniaturization of electronic devices,higher requirements for heat dissipation are put forward.At present,mechanical fans are often used to strengthen heat dissipation,but they will produce noise and vibration that cannot be eliminated in the process of work,so it is urgent to find a new solution to heat dissipation technology.Therefore,researchers at home and abroad have turned to the research of ionic wind enhanced heat dissipation technology.In this thesis,the multistage needle-mesh ionic wind cooling system was studied.The electrical properties,flow law and heat transfer characteristics of multistage needle-mesh ionic wind cooling system were studied.The influence of the structural parameters of the ionic wind cooling system on the flow and heat transfer of the ionic wind is summarized.For this reason,the numerical simulation of ionic wind cooling system was studied.The theories of ionic wind electric field,flow field and temperature field are summarized.The ionic wind cooling system is improved to provide reliable theoretical guidance for the ionic wind heat dissipation technology.The specific work is as follows:The characteristics of ionic wind speed and heat dissipation performance of single-stage needlenet ionic wind cooling system were analyzed experimentally,and the influence mechanism of structural parameters of single-stage needle-mesh ionic wind cooling system on its performance was studied.In terms of heat dissipation performance,the needle-mesh ionic wind cooling system with single-stage structure has good heat dissipation performance and energy saving.Because the corresponding working voltage range is very narrow when the electrode spacing is 5mm,it does not have practical application value.The optimal needle-mesh spacing is 10 mm.When the electrode spacing is 5mm,the outlet air of the single-stage needle-mesh ionic wind cooling system is unstable.The air outlet effect at the ultimate operating voltage can be regarded as the ultimate heat dissipation performance of ionic wind cooling system.The corresponding limit performance is almost the same when the electrode spacing is 10 mm and 15 mm,but to achieve the same maximum velocity of ionic wind,the working voltage with electrode spacing of 15 mm is about 5k V higher than that with electrode spacing of 10 mm,which is not conducive to practical application.Among them,the ionic wind cooling system can reduce the heat source temperature from 70℃ to 37.9℃.The heat source temperature decreases significantly before the voltage is 6k V.After 6k V,the increase of power consumption leads to more joule heat and increase of friction loss in the ionic wind cooling system,which limits the heat dissipation performance of the ionic wind cooling system.The ionic wind cooling system only needs 2.6W to make the temperature of heat source drop from 70℃ to 37.9℃,and only needs 0.45 W to make the temperature of heat source drop from 70℃ to 43.5℃,and the cooling range is as high as 37.8%.A two-dimensional numerical simulation model of the ionic wind generating device using the needle-mesh electrode was established by taking the ionic wind generating device using the needlemesh electrode as the research object.The electric field and flow field characteristics of the ionic wind generating device using the needle-mesh electrode were studied,and the parameters of the ionic wind generating device using the needle-mesh electrode were studied through the simulation model.The effects of the number of needle electrodes,the spacing of needle electrodes,and the ratio of the spacing and thickness of mesh electrodes on the performance of the ionic wind generator using needle-mesh electrodes were investigated.In the electric field,the maximum potential and space charge density on the surface of the needle electrode are uniformly reduced to the mesh electrode,and there is obvious mutual interference between the needle electrodes,which weakens the air outlet effect of the ionic wind generator.In the flow field,due to the acceleration of the electric field force,the maximum velocity of ionic wind is found in the ionic drift region.In addition,the flow field of the ionic wind behind the mesh electrode is complex,and the area with high wind velocity is limited to a small area below the needle electrode,which makes it difficult to measure the velocity of ionic wind in practical experiments.The number of needle electrodes directly affects the size of the air flow area.Multiple needle electrodes can effectively increase the air output of the ionic wind,but the flow field distribution is relatively complex.With the increase of the distance between the needle electrodes,the interference between adjacent needle electrodes is significantly reduced,and the air outlet is significantly enhanced.When the distance between the needle electrodes is greater than20 mm,there is almost no interference between adjacent needle electrodes.The ratio of the distance to the thickness of the mesh electrodes is used to reflect the density of the mesh electrodes.The sparser the mesh electrode,the smaller the hindering effect on the ionic wind,which is more conducive to the full development of the ionic wind.The ionic wind speed characteristics and cooling performance of the multistage ionic wind cooling system using needle-mesh electrode and the single-stage heat dissipation system using needle-mesh electrode were compared through experiments.The influence of the structural parameters of the ionic wind generator on its performance was studied.An empirical correlation formula for calculating the relationship between the working voltage and the working current of the multistage ionic wind cooling system is established.The experimental data show that there is a linear relationship between the operating voltage and the square root of the operating current of the multistage needle-mesh ionic wind cooling system.The scale coefficient k in the U-I relation is mainly affected by the number of needles x and the number of stage n.The optimal number of stages of the multistage ionic wind cooling system using needle-mesh electrode is 2,and the optimal stage spacing is 25 mm.Increasing the number of stages can improve the average velocity of the ionic wind and the uniformity of the distribution of the velocity of ionic wind.The maximum enhancement factor of multistage ionic wind cooling system using needle-mesh electrode can reach 3.705.When the heat source temperature is around 38°C,the power consumption of the multistage ionic wind cooling system using needle-mesh electrode is only 0.8W,which is 1.2W lower than that of the single stage ionic wind cooling system using needle-mesh electrodes,which proves that energy saving of multistage ionic wind cooling system.The ionic wind speed characteristics and heat dissipation performance of the ionic wind cooling system using needle-mesh electrodes with integrated structure,traditional multistage structure and single-stage structure were compared and analyzed through experiments.The influence mechanism of the structural parameters of the integrated multi-stage ionic wind heat dissipation system with needle-mesh electrodes on its performance was studied.The results show that the integrated multistage ionic wind heat dissipation system using the needle-mesh electrode has the same electric field characteristics as the multistage ionic wind cooling system using the traditional structure of needlemesh electrode,but it has a smaller operating current and narrower operating voltage range.The optimal number of stages of the multistage ionic wind cooling system with the integrated structure of the needle-mesh electrode is 2.Increasing the number of stages cannot effectively enhance the ionic wind,but leads to a decrease in the efficiency of the ionic wind and an excessive increase in power consumption.Compared with the single-stage structure,the integrated multistage ionic wind cooling system using the needle-mesh electrode can effectively reduce the temperature of the heat source.It only needs 1.5W power consumption to achieve a temperature drop of about 35℃ for the heat source. |
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