The Groove Composite Structure Design Of Micro-heat Pipe And Heat Transfer Performance Study

In recent years,the rapid development of electronic technology,high-frequency and high-speed of electronic devices and integrated-miniature circuit-intensive make the unit volume of electronic devices can increase rapidly in heat.In this way,in the limited volume range,the power consumption of electronic products continues to increase,the heat flux rapidly increase,resulting in rapid increase in the temperature of electronic equipment,thus these can result in more and more electronic products problems.Heat dissipation has become a major problem which can restrict the development of electronic technology.The heat dissipation surface of flat heat pipe can be well contact with heat source;good thermal conductivity;heat flux density,for e above and other reasons the heat pipes are widely used.Therefore,this paper introduced design and manufacture of a new compound groove structure flat micro-heat pipe.The main research contents are as follows:1.Through analyzing the working principle and relevant heat transfer limit of the plate heat pipe,it can find the microstructure of the liquid-absorbent core which promotes the heat transfer of the working fluid in the tube is proposed.That is,the design of the evaporating section promotes the boiling and evaporating structure of the liquid working fluid and suppresses the generation of large bubbles and even the vapor film.This promotes the cooling and condensation of the steam and the flow a nd uniform distribution of the condensate.The groove structure and the groove array structure are designed respectively for the evaporation section and the condensation section o f the plate micro-heat pipe.The boiling heat transfer performance and steam cooling condensation of different surface morphology copper plates were tested.The results show that the design of the evaporative segment structure not only makes the bubble break away and prevents the small bubbles from being merged into large bubbles,the temperature difference is obviously reduced,the average temperature differe nce is 4.3℃.The structure of the condensate section provides more effective nucleation sites while maintaining a large heat transfer area,and has the effect of thinning the l iquid film and the current distribution.2.On the basis of determining the structure of the evaporation section and the condensation section,using the laser equipments produce liquid-absorbent core structure and finally,the method of preparing the structure of the liquid-absorbent core was determined,then a set of flat micro-heat pipe was designed.After the processes of laser processing of the liquid-absorbent core structure,the super-hydrophobic modification of the upper cover plate,the cutting of the middle copper frame,the low-temperature solder paste welding assembly and leak detection,injection of vacuum the flat micro heat pipes are successfully produced.3.Design and build the experimental platform for the test plate micro-heat pipe and other experimental pieces of heat transfer performance.The heat transfer performance of pure copper plate,empty tube and flat micro heat pipe was analyzed.The results showed that the heat transfer performance of flat micro-heat pipe is the best,the temperature difference is the smallest and the thermal resistance is the lowest.With the heating time continues,flat micro heat pipe first began to slow down the temperature rise,the same first to achieve a stable state.With the increase of heating power,both ends of the temperature are rising,flat micro-heat pipe will soon slow down the trend,the thermal resistance increases with the increase in heating power.4.Analyzing the heat transfer performance of the plate micro heat pipe with different filling rate and pressure in the tube.The main factors are as follows: the temperature and the thermal resistance changes with the heating power increases.The experimental results show that the heating power is increasing and the increase of the filling fluid increases the thermal resistance as a whole,but the trend of decreasing is becoming more and more slowly.When it increases to 61.4%,it increases wit h the increase of heating power.The thermal resistance of the micro heat pipe is 0.125℃/W.With the increase of heating power,the temperature of the heat pipe has been increasing at both ends,but the rising trend is gradually slowing down with the increase of the liquid filling rate.The temperature difference is shrinking,In the liquid filling rate is 61.4% when the temperature difference is 10.077℃,so we speculate the best liquid filling rate is about 60%.In the pipe pressure is 4.5kpa,the final temperature difference is 13.774 ℃,the thermal resistance is 0.172℃/W.When the pipe pressure is 7.3kpa,the final thermal resistance is 0.201℃/W,temperature difference is 16.123℃,above all we can indicate that the smaller pressure the better the heat transfer performance of the pipe.