Research On Heat Transfer Characteristic Of Flat Plate Heat Pipe Cooling System For High-power LED

The development of electronic packaging technology has led high performance chips to more high power and miniaturized, which has resulted in the increase of heat flux and chip temperature, and the decrease of reliability and stability, so the heat dissipation and temperature uniformity problems have been a bottleneck for LED development. In order to solve question of heat accumulation and temperature uniformity, a novel micro-nano structure flat plate heat pipe have been designed, which had a hydrophilic and a hydrophobic surface characteristics, for enhanced axial and radial heat transfer capability. An experimental system was built to test factors to influence performance, and filling ratio and initial pressure, which affect to performance of flat plate heat pipe. Then three different cooling systems, includes natural convection cooling system, force convection cooling system and flat plate heat pipe compound system were tested. Specific contents are as follows:1. Oxide layers were built in the base material, copper. Oxidation-dehydration and molecular self-assembly were used to modified the surface to hydrophilic and hydrophobic. Scanning electron microscope and contact angle meter were used to characterized the surfaces, and the contact angle were 9.3°and 151°2. A flat plate heat pipe test system was designed to test the two important parameters, filling ratio and initial pressure, and the conclusions were as follow:with the increase of the ratio of filling, the axial thermal resistance was increased slightly, while the radial thermal resistance was almost unaffected; And with the decrease of the vapor chamber initial pressure, the axial and radial thermal resistance has declined, respectively, and the lower pressure, the lower starting and limit input power.3. Three type different cooling systems, included natural convection cooling system, force convection cooling system and flat plate heat pipe compound system were designed and tested, and the limit cooling capacity were got. The thermo-profile and thermal resistance network analysis methods were used to evaluation of heat transfer performance. The result were as follows:the cooling performance of flat plate heat pipe compound system s were better than another two cooling systems, and the flat plate heat pipe-force convection compound system had the best cooling performance, and the limit cooling system is 55W, while the force convection cooling system is 47W, and the natural convection cooling system is 21W, and the flat plate heat pipe-natural convection compound cooling system is 31W.The research on surface modification on evaporation surface and condensation surface have provided new idea for flat plate heat pipe design and optimization, and the research on heat transfer characteristics and cooling performances of heat pipe cooling system have enriched thermal design for the micro-electronic chip such as LED.