Design,Fabrication And Performance Study Of Fiber Wick Evaporator And Microchannel Condenser In Loop Heat Pipe

With the rapid development of microelectronics technology,the frequency and speed of electronic devices have increased dramatically resulting in high heat flux.Traditional heat dissipation technologies,such as fan heat dissipation technology,have been unable to meet the heat dissipation requirements.The loop heat pipe is a high-efficiency heat dissipation device with the principle of phase change heat transfer.The capillary force of the porous wick provides the driving force to drive the working fluid circulation,so the loop heat pipe has the advantages of strong heat transfer capability,long heat transfer distance,convenient installation,no entrainment limit,no external energy input,and has been widely used in the fields of microelectronics and aerospace.In this thesis,the wick structure of the evaporator and the microchannel structure of the condenser are optimized,and the optimized wick and microchannel are applied to the loop heat pipe.Through the experimental research and theoretical research,combined with numerical simulation,the heat and mass transfer performance of loop heat pipes are discussed.Optimization design and performance study of porous wick.The wick is the most important part of the evaporator,which provide capillary force to drive working fluid flow,and has the function of "liquid and steam barrier".Based on the rough surface copper fiber obtained by multi-tooth tool turning,a single porosity,composite porosity and graded porosity wicks are fabricated based on the low-temperature solid-phase sintering technology.The capillary pumping performance and adsorption performance test system were built,and the capillary pumping model was established.The effects of parameters such as porosity,pore size distribution and fiber surface morphology on the capillary pumping and adsorption performance were studied.Heat transfer performance study of loop heat pipe with copper fiber sintered wicks.The loop heat pipe with copper fiber sintered wick copper was designed,and the heat transfer test platform loop heat pipe was set up.The novel copper fiber sintered wick was firstly applied to the evaporator of loop heat pipe.By changing the porosity,pore size distribution and surface morphology of the wick,the influence of copper fiber sintered wick on the heat transfer of the loop heat pipe under different external conditions was studied.The feasibility of the application of copper fiber sintered wick in loop heat pipe was verified.Optimization design and performance study of microchannel structure.A novel interlaced microchannel with two kinds of fluid channels is designed,which can be used as the condenser of the loop heat pipe.The two side walls served as the main heat transfer area a is realized to improve the heat transfer performance.The microchannel heat transfer test platform was set up.The effects of microchannel structure on heat transfer performance were studied by comparing with the traditional parallel and spiral microchannels.The heat and mass transfer mechanism inside the microchannel was studied.The fluid-solid coupling numerical simulation method is used to optimize the parameters of the microchannel,such as depth,width and spacing.Heat transfer performance study of loop heat pipe with microchannel condenser.Based on the interlaced microchannel condenser,a special water-cooling loop heat pipe performance test platform was setup.The influence of structure and operating parameters of the microchannel on the heat transfer performance of the loop heat pipe were studied,and compared with the traditional finned air-cooling condenser.Compared to the conventional finned air-cooling condensers,the heat transfer capacity of the loop heat pipe was increased by 4 times and the thermal resistance was decreased by 4.4 times with interlaced microchannel condenser,demonstrating the feasibility of the application of interlaced microchannels in the loop heat pipe.In this thesis,the design and performance of key components such as the wick and microchannel of loop heat pipe are studied and applied in the loop heat pipe to improve the heat transfer performance.The results of thesis provide guidance for the design and practice application of loop heat pipe.