Research On Controllable Heat Dissipation Performance Of Electronic Components Under Magnetic Field

In recent years,the heat dissipation of electronic components has attracted extensive attention from all social circles.On the one hand,with the development of science and technology,electronic components tend to be miniaturized and intensive.On the other hand,the performance of electronic components is getting better and better,and the speed of updating is also getting faster and faster.All these lead to the high heat flux of electronic components.The high heat flux will directly cause the temperature rise of electronic components.Too high temperature and too fast temperature rise are the direct causes of thermal failure and damage of electronic components.In order to solve the problem of high heat flux of electronic components,in this paper,the magnetic field was used to control the magnetic nanofluids to realize the research of controllable cooling of electronic components.That is: Fe3O4-H2 O nanofluids were used as the working fluid for cooling electronic components,and the temperature of electronic components was controlled by adjusting the magnetic field.The flow and heat transfer characteristics of magnetic nanofluids under different magnetic field intensities(?=0.000 T,0.005 T,0.010 T,0.015T)and different magnetic field angles(?=0°,30°,60°)were discussed,mainly including: Flow and heat transfer mechanism of magnetic nanofluids when the heat exchange surface is a flat plate;Flow and heat transfer mechanism of magnetic nanofluids when the heat exchange surface is stepped structure;Flow and heat transfer mechanism of magnetic nanofluids when the the heat transfer model is filled with foam metal;Flow and heat transfer mechanism of magnetic nanofluids when the heat transfer surface is drag reduction enhanced surface.The details are as follows:(1)Study on preparation,stability and thermophysical properties of nanofluids.The experimental results showed that the prepared magnetic nanofluids keep good stability.(2)Study on cooling characteristics of electronic components by magnetic field.Based on magnetic field intensity and magnetic field angle,the temperature of electronic components was controlled,in order to comprehensively evaluate and study the thermal and hydraulic performance of the system,the thermal efficiency was introduced as the evaluation standard.The results are as follows: The maximum increase ratio of heat transfer is 61.5%;the hot surface temperature of electronic components can be reduced by up to 19.7?(34.0%);Enhancement of magnetic field intensity and the adjustment of magnetic field angle can enhance the heat transfer and increase the flow resistance.The comprehensive evaluation of flow and heat transfer was carried out,and the maximum comprehensive evaluation index is 1.27,indicating that the improvement of heat transfer is more dominant than the increase of resistance.(4)Enhanced heat transfer mechanism under the coupling of magnetic field and foam metal: The flow and heat transfer mechanism of magnetic nanofluids in cavities filled with and without foam metal under different magnetic field intensity and magnetic field angles was studied.In order to comprehensively evaluate and study the thermal and hydraulic performance of the system,the exergy efficiency was introduced as the evaluation standard.The results are as follows: the magnetic field enhances the cooling performance of electronic components,and the surface temperature can be reduced by 14.64?(31.7%)at most.The existence of foam metal increases the flow loss during fluid flow.It is found that when the magnetic field is not applied,the efficiency of the heat exchanger filled with foam metal begins to be smaller than that of the heat exchanger without filling the foam metal.After increasing the magnetic field intensity and the inclination of the magnetic field,the efficiency of the heat exchanger filled with foam metal is greater than that of the heat exchanger without filling the foam metal.(5)Enhanced heat transfer mechanism under the coupling of magnetic field and enhanced drag reduction surface: In order to reduce the increase of resistance in the process of flow,the heat transfer surface were changed into convex and grooved structure surface,and the thermal and hydraulic performance of these two kinds of surface drag reduction structures(convex and grooved)under different magnetic field intensities and magnetic field angles was studied,and the exergy efficiency and entropy generation were introduced as evaluation criterias.The results are as follows:Compared with the smooth surface,the drag reduction effect of the two drag reduction surfaces is more obvious,and the the maximum drag reduction effect can reach 37.4% and 35.4% respectively.Based on the convex structure surface,the surface temperature of electronic components is reduced by 9.5? at most,and the heat transfer performance can be enhanced by 136.2%;Increasing the magnetic intensity and rotation angle can improve exergy efficiency and reduce entropy production,of which the entropy production of nanofluids with ?=0.3% is the smallest.Based on the grooved surface,the surface temperature of electronic components is reduced by 14.96%;The Nusselt number can be increased by 163.12% by nanofluids;When the nanofluids concentration is ?=0.1%,the Reynolds number is 712,the rotation angle is ?=60° and the magnetic field intensity is ?=0.015 T,the thermal and hydraulic performance is the best.There are 59 figures,5 tables and 80 references in this paper.