The Design And Performance Analysis Of Micro Heat Exchangers For High-power LED By Water Cooling

The new solid-state lighting LED（Light Emitting Diode）has many advantages, suchas energy saving, long life, which is recognized as the fourth-generation lighting. With therapid development of LED industry, LED light source becomes miniaturization,high-brightness and high-power. This increased the heat flux of single chip, resulting in therising of junction temperature, which seriously affecting the life and performance of LED.Therefore, the heat issue has been restricting the development of LED. The traditionalair-cooling has been unable to meet the requirements of heat dissipation, and looking fornew ways of heat dissipation to ensure the normal work of LED and extend its life hasfar-reaching significance. This paper puts forward a heat dissipation system for high-powerLED by water cooling. The miniature heat exchangers were designed and manufactured,and the performance of micro heat exchanger has been studied by building an experimentalplatform. The main researches are as follows:（1）A micro heat exchanger for high-power LED by water cooling was designed,which can be used as the heat dissipation by micro-channel water cooling and porousmaterial. To investigate the influence of micro-channel structure on performance of the heatexchanger, different structures of micro channel heat exchanger were designed. Meanwhile,the cavity also was designed, which can be used to fill the porous copper fiber felt.（2）Thermal performances of four different structures of micro-channel heatexchangers on the chip surface were simulated by using FLUENT. The effect of input power,inlet flow and the structure of micro-channel on the temperature field of high power LEDmodule was analyzed, and related parameters were selected. The mechanism between thedistribution of velocity in the micro-channel and the heat dissipation of high-power LEDwas analyzed. The results show that the greater aspect ratio micro channels of heatexchangers are, the better the performance of heat dissipation on the chip surface.（3）The performance of micro-channel heat exchangers was investigated by theexperimental system which based on Agilent data logger and pressure transmitters. Theexperimental results showed that the greater aspect ratio micro channels of heat exchangers, the better the performance of heat dissipation on the chip surfaces. And the pressure drop ofimport and export is greater. The experimental results and the simulation results arecompared and analyzed. The simulation results and experimental results are basicallyconsistent.（4）Continuous copper fibers were manufactured by multi-tooth cutting tool, andsintering crafts of copper fiber sintered felt were experimentally investigated by using solidphase sintering technology. The experimental results showed that the best temperature ofsintering process parameters for copper fiber felt is900℃and holding time is60minutes.The forming process of copper fiber felt was analyzed. The possibility of forming sinteredcopper fiber felt is analyzed from the theory.（5）The performance of single-type and complex-type porous heat exchanger werestudied. Depending on the different porosity and composite forms, the performance ofmicro heat exchangers is compared. The experimental results showed that the higher theporosity of the porous heat exchanger, the smaller the inlet and outlet pressure drop is.Among three different porosities, the preferable thermal performance of the heat exchangerson the chip surface is the porosity of80%. In the study of the performance of three differentforms of porous composite heat exchanger, The greater the integrated porosity is, the greaterthe pressure drop of import and export is, and the smaller the integrated porosity is, thebetter thermal performance of the chip surface is. Meanwhile, the experimental resultsobtained were compared with the micro-channel heat exchanger. The results show thatunder the same inlet flow, the pressure drop of the import and export of micro channel heatexchanger is less than the porous heat exchanger, but the performance of heat dissipation onthe chip surface is worse than the porous heat exchanger.