Research And Application Of Electronic Equipment Phase Change Thermal Dissipation Technology

In order to meet the high heat and high heat flux thermal control requirements of both military and civilian electronic equipment(e.g:high-power phased array antennas,Microsystem,RF components),this dissertation carries out the optimization design of a variety of traditional phase change cooling technologies and the integrated application reserch of a variety of thermal control technologies.Firstly,the concept of phase change heat dissipation is presented,and its technical characteristics and advantages for thermal management of aerospace electronic equipment are summarized.Then the optimal design and performance tests of three thermal management schemes are carried out,which are the VC(vapor chamber)thermal diffusion structures based on additive manufacturing,the loop heat pipe heat transfer structures based on R134a,and the enhanced phase change heat sink based on variable gradient fractal structures.Finally,a phase change heat dissipation device with extremely high heat flux is put forward,which integrates VC,array heat pipe,and high-density small channel liquid cooled heat exchanger.Furthermore,another phase change heat dissipation device for missile-borne seeker system is proposed,which integrates the high thermal conductivity cold plate,the heat pipe,and the enhanced phase change heat sink.These efforts lay the foundation for the successful application of phase change heat dissipation technology in next-generation aerospace electronic equipment.The main contributions are as follows:1.The design concept is proposed,which is based on additive manufacturing technology to generate capillary wick structures and integrate them into VC thermal diffusion cold plates.Firstly,by optimizing parameters such as laser power,scanning speed,scanning spacing,and layer thickness,the capillary liquid absorption core structure samples are produced.The key parameters such as porosity and permeability are tested to validate feasibility.Then,detailed design and manufacture of VC thermal diffusion structures based on additive manufacturing are conducted,and a testing system is established for the VC thermal diffusion performance testing.The integrated VC thermal diffusion structure based on additive manufacturing exhibits good temperature uniformity characteristics,with an equivalent thermal conductivity of 460 W/m·K,which is 2.29times that of aluminum plates.Its weight is only about 60%of the aluminum plates.Besides,it has advantages such as simple process,high efficiency,low cost,and easy to achieve integrated design of structural and function.2.A new loop heat pipe heat transfer structure is carried out by using R134a refrigerant instead of ammonia as the working fluid,which could meet the special requirements of safety and environmental friendliness in the civil aerospace industry.By optimizing the design process of loop heat pipes,engineering application requirements and design parameters are clarified.A mapping model is established to adress the relationship among the key parameters such as capillary core sintered particle diameter,capillary inner diameter,steam pipeline inner diameter,and the difference between the total power and total pressure drop of the heat pipe.The optimization design,verification,sample production,and performance testing of the new loop heat pipe are completed.By increasing the inner diameter of the evaporator core from 5 mm to 11 mm,the radius of the capillary hole is reduced from 1um to 0.47 um,and the inner diameter of the pipeline is increasing from 2 mm to 4mm,which effectively solve the problem of R134a refrigerant that owns lower surface tension and smaller evaporation latent heat than the ammonia working fluid.The experiment results show that the loop heat pipe heat transfer structures based on R134a has excellent start-up performance and operational stability under different thermal loads and heat exchange conditions.The maximum heat transfer capacity can reach 250 W in the horizontal direction,and it can also meet the design requirements of 200W at an anti-gravity height of 30 cm.3.A variable gradient fractal structure is proposed to improve the thermal performance of enhanced phase change heat sink.Based on the traditional rib effectiveness calculation method,the theoretical model is established for variable gradient fractal enhanced heat transfer structure.The numerical solution is obtained by using the central difference to discretize the second-order derivative.The results show that the heat transfer capacity of the tree-like fractal enhanced structure is 2.27 to 1.22 times higher than that of traditional cylindrical rib structure.By analysising the heat transfer performance,it is found that the temperature rise and phase change in the heat absorption process of phase change heat sink are more uniform,which can effectively improve the thermal management performance.Comparing with traditional columnar rib structures,the temperature of the heat surface is lower by 6?C under uniform heat source conditions,and it is lower by 16?C under concentrated heat source conditions.The thermal diffusivity is 2.5 times higher than that of traditional cylindrical structures.The experiment results demonstrate that the enhanced phase change heat sink based on variable gradient fractal structure could achieve an average temperature,which is 3-4?C lower than that of the traditional cylindrical enhanced structure under a uniform heat source of 80 W.It also has advantages such as simple process,high efficiency,low cost,and easy to achieve integrated design of structure and function.4.A novel design scheme for vapor chamber phase change heat dissipation device is proposed to deal with the challenge of RF Microsystem which always obtains extremely high thermal and heat flux density.The design scheme integrates the VC phase change heat diffusion structure,the array heat pipe phase change heat transfer structure,and the high-density small channel liquid cooled heat exchanger.The evaporation surface of the vapor chamber adopts a main channel porous structure to enhance the critical heat flux density,while the condensation surface utilizes a cylindrical cavity array heat pipe to increase the heat transfer area.On the outer side of the array heat pipe,high-density small channel liquid cooled heat exchangers are incorporated to achieve secondary heat transfer in a very limited space.This new Microsystem achieves a maximum heat transfer capacity of 850 W and a heat flux density of 260 W/cm~2 within a compact size of 30 mm×60mm×60 mm.It has good application prospects in the thermal management of electronic equipment and components with high heat load and heat flux.5.A new design scheme for the phase change heat dissipation device is proposed to fulfill the high-power short-duration thermal control requirement in missile-borne seeker system,which integrates high thermal conductivity diffusion plates,heat pipes,and enhanced phase change heat sinks.The hot side of the heat pipe is integrated with high thermal conductivity diffusion plates,and the cold side is integrated with enhanced phase change heat sinks.The heat diffusion plate is integrated with the structural substrate of the seeker’s T/R(Transmitter and Receiver)component,and the enhanced phase change heat sink is integrated with the missile body structure.This design includes the heat sources and heat diffusion plates design,optimization design of phase change heat sinks,and integration design of heat pipes with heat diffusion plates and phase change heat sinks.The prototypes are developed,and the thermal performance tests are carried out at the room temperature,the high temperature,the vibration,and the temperature cycling conditions.The phase change heat dissipation device developed in this study is analyzed with a total heat consumption of 600 W in a 80?C high-temperature environment,and a working duration for 150 seconds,the simulation results show that the average temperature of the heat source is 122.16?C,and the measured value deviates only 3.3%,which is significantly better than the requirement of 140?C.The phase change heat dissipation device manifests a promising potential for integrating electronic equipment and installation platform structures with thermal control,and has bright prospects.