Development And Characterization Of Capillaly Wicks For Flat Plate Loop Heat Pipes

Recently, the aerospace industry of our country has developed rapidly. Because of the special circumstances of the vacuum, low temperature, micro-gravity, and the thermal radiation of the sun and other planets, the thermal control of the space equipments becomes more difficult and complex. Moreover, miniaturization and high integration of electronic devices correspond to the permanent trend of electronic market. High heat flux due to increasing dissipated power and decreasing volume has made a great limitation to the development of electronic industry. Loop heat pipe (LHP) is a passive and stable two-phase heat transfer device. The high stability and efficiency of LHP make them ideal candidates to meet the thermal control requirements of the space equipment. Apart from the cylindrical design, the flat shape offers another design option for the LHP evaporator. Flat evaporators can be considered as the optimum design from the point of view that they do not need any special thermal interface (saddle),which can decrease the thermal resistance and the total mass of the system. Also, flat evaporators can be easily integrated into the compact space to be cooled. So the flat plate loop heat pipe will have a very broad application prospect in ground based electronic cooling.The paper focused on the porous wick of the LHP with flat evaporator. A series of flat porous wicks were fabricated in different parameters including material, sintering temperature and porosity. And the influence of their parameters on the performance were investigated.The main work of this research is as follows:1) A series of capillary wicks for flat loop heat pipes (FLHPs) were fabricated in two different methods, the cold-pressing sintering and direct loose sintering. The fabricating process, parameter control and cautions etc. are introduced to provide a standard method for the manufacturing of capillary wicks.2) Structure parameters of capillary wicks were measured by use of different methods. Permeability and pore radius were measured accurately by the comprehensive test platform.3) The effective thermal conductivity of the wick was studied using Steady-State method and Transient plane source method, respectively. The influence of the copper content on the effective thermal conductivity was analyzed. 4) The capillary force of the porous structure was measured to analyze the influence of the sintering parameters and working fluid on it, which provided the theoretical basis for optimizing sintering parameters and choosing working fluid of the loop heat pipe.