Study And Optimization Of Flat Lood Heat Pipe With Carbon Fiber Capillary Wicks

With the development of communication technology and electronic technology industry,the performance of electronic products is increasing faster and faster.The acceleration of the performance improvement of electronic products has put forward higher requirements for heat dissipation in the electronic field.The traditional single-phase fluid convection heat transfer method can no longer meet the new heat dissipation requirements.Although the application of the heat pipe solves the requirements of some new heat transfer scenarios to a certain extent,but its heat transfer distance is short,and it is seriously affected by the gravity direction.These shortcomings limit their application.Loop Heat Pipe(LHP)is a two-phase heat exchange device that separates the evaporator from the condenser.The capillary pressure generated by the capillary wick in the evaporator drives the working fluid to flow,effectively avoiding the shortcomings of the conventional heat pipe.Among them,the small flat loop heat pipe is an excellent solution for heat exchange of small electronic devices,and has attracted more and more scholars' attention.At present,small flat-plate loop heat pipes mostly use sintered porous wick.However,in the process of us:ing small flat-plate loop heat pipes,problems such as serious heat leakage and easy damage of wick have occurred due to too thin evaporator,which seriously affects The normal use of the small flat LHP.In view of these requirements of the application of small flat loop heat pipes,this paper proposes a method of using carbon fiber felt with flexibility and low thermal conductivity as the wick of small flat loop heat pipe.Carbon fiber exhibits significant hydrophobicity to water,but exhibits strong wettability to organic solvents such as ethanol and acetone.In this paper,the properties of carbon fiber wicks were studied by building a carbon fiber wicks performance test bench.Including the investigation of the wettability of carbon fiber wicks to various working fluids by high-speed camera;measuring the capillary suction characteristics of carbon fiber wicks to ethanol and acetone by infrared camera and electronic balance,and measuring the porosity of carbon fiber wicks;The Hot Disk Thermal Constant Analyzer measures the thermal conductivity of a carbon fiber capillary wick.It is verified by experiments that the performance of the carbon fiber wick meets the requirements of the loop heat pipe wick.At the same time,this paper also designed and manufactured a small flat loop heat pipe with carbon fiber wick,and achieved the operation of loop heat pipe by using ethanol as working fluid.In order to further improve the carbon fiber wick system,the crystallization precipitation method is used to control the porosity and pore structure of the carbon fiber wicks,improve the capillary suction performance of it,and provide a composite pore structure carbon fiber wick.The preparation method further improves the overall performance and application potential of the carbon fiber wicks.At the same time,the structure of the original loop heat pipe was optimized for the problems of reverse heat leakage and steam leakage during the operation of the loop heat pipe,and the heat transfer performance of the new loop heat pipe was verified by experiments.