Effects Of Hydrophilic/hydrophobic Segmented Modification On The Performance Of Gravity Heat Pipe

Gravity heat pipe is one of many types of heat pipe which is characterized by simple structure and no internal capillary core structure,only composed of shell and end cover.Easy to manufacture and efficient heat exchange performance make the gravity heat pipe popular in the industry.With the development of automation and intelligence in the industrial field,more and more attention has been paid to the efficient and reliable operation of heat exchanger which plays an important role in the industrial process.Because of this,many researchers pay more attention to the widely used gravity heat pipe and its heat transfer performance.In the industrial application field,the demand for the gravity heat pipe with stronger heat transfer capacity and more stable operation is increasing,which makes many researchers pay attention to the heat transfer performance enhancement of the gravity heat pipe from the perspective of efficient heat transfer medium and new wall surface and has achieved remarkable results.In this paper,the influence of hydrophilic and hydrophobic segmented treatment on the heat transfer performance of gravity heat pipe is discussed by experimental method.The hydrophilic or hydrophobic surface is segmented on the inner surface of gravity heat pipe by chemical etching.The heat transfer performance of hydrophilic and hydrophobic segmented treatment is studied and compared.The main research contents include:(1)The gravity heat pipe is designed and developed independently,the wettability modification technology of copper base surface is determined,the heat pipe performance test-bed is built,and the wettability section layout scheme and experimental research scheme of the inner wall of the heat pipe are defined.(2)The effects of hydrophilic and hydrophobic segmented modification on the performance of heat pipe were studied which compared with the common heat pipe without surface modification,it is found that hydrophilic and hydrophobic segmented modification can effectively reduce the overall thermal resistance of the heat pipe.Hydrophilic segmented modification can also improve the evaporation heat transfer coefficient of the heat pipe,but the condensation heat transfer coefficient of the heat pipe is not significantly increased,or even worsened.The heat transfer of evaporation and condensation can be enhanced by the segmented modification.(3)Based on the heat pipe comparative experiment of hydrophobic and hydrophilic segmented modification,the heat pipe of hydrophilic hydrophobic composite modification was designed and prepared,and the comparative experimental study was carried out.It is found that the heat transfer performance of the gravity heat pipe treated by two kinds of combined hydrophilic and hydrophobic modification is further enhanced than that of the gravity heat pipe treated by single hydrophilic and hydrophobic modification on the whole,especially in the reduction of the heat resistance of the heat pipe and the improvement of the total heat transfer coefficient and the equivalent thermal conductivity.(4)In addition,0.15wt%n-heptanol aqueous solution was used in the gravity heat pipe.It was found that the self wetting fluid can effectively reduce the evaporation temperature of the heat pipe and raise the drying limit of the heat pipe when it is placed horizontally.When it is placed vertically,it can improve the heat transfer performance of the common heat pipe and the hydrophilic heat pipe,but it does not decrease the performance of the hydrophobic surface heat pipe.