Research On Fabrication And Thermal Performance Of Sublevel Composite Wick Micro Heat Pipe

Currently, electronic technology is continuously advancing toward high integration and miniaturization, which resulted in the rapid rise of heating power of electronic components. Effective cooling method is the key to solve cooling of electronic component. As a highly efficient cooling component, heat pipe has good thermal conductivity, Isothermal performance and adaptability. It is widely used in aerospace, electronics, solar energy field. Heat pipe realize heat transfer by phase change of working liquid. Working liquid cycles inside micro heat pipe by its wick structure. Therefore, the heat pipe wick structure and thermal performance have been the research focus and hot of domestic and foreign scholars.In order to improve thermal performance of micro heat pipe, this paper proposed a new wick structure which is sublevel composite wick. Evaporating section and adiabatic section adopted copper sintered wick, which will help improve the capillary suction force. Cooling section adopted groove wick, which can increase penetration. The sublevel composite wick of micro heat pipe used TP2 as its shell material and distilled water as working liquid.According to manufacturing process requirement of sublevel composite wick, cooling section adopted oil-filled spinning to machine axial groove and Evaporating section and adiabatic section adopted sintered process to machine copper sintered wick. Experiment results indicated equivalent diameter of the spinning balls and the relative position between the tool and spinning balls show much influences on the groove shape and dimension, such as the groove depth, the groove width and ratio of depth to width. While the relative position between the tool and spinning balls and drawing velocity decide whether heat pipe will be dragged off, and drawing velocity greatly influences the roughness of the outer pipe surface. The sublevel composite wick can be manufactured with 950°c sintering temperature and about 1 hour sintering time, and then get out of vacuum sintering furnace when temperature drop down to 200°c by air cooling. Through comparative analysis, the process will help to obtain good performance of heat pipe as follow working liquid perfusion, vacuum-pumping, secondary deaeration and then weld sealing.Based on virtual instrument technology, thermal performance test system of micro heat pipe was developed. The system owned test accuracy and test efficiency, good stability and adaptability. It was easy to be operated and suitable for industrial production. Thermal resistance model was established by thermal analysis. The thermal performances of micro heat pipe were tested by the test system. The results indicated: sublevel composite wick is helpful for improving thermal performance of micro heat pipe, the best working fluid infusion rate is about equal to the wick pore size and it should use copper sintered wick as evaporating section. The results also show that the length of sintered wick, copper particle size and sintered thickness significantly influenced the thermal performance.