Trapezoidal Axial Grooved Heat Pipe Heat Source Heat Sink Heat Transfer Characteristics

The trapezoidal axially grooved heat pipes (AGHP) are widely used in the thermal controlling system of the international cooperative project AMS-02 in which Shandong University participates. As the main heat transfer devices, their heat transfer performance is very important for the normal running of the thermal controlling system. Therefore, experimental study of this kind of heat pipe's performance with multiple heat sources and heat sinks is performed in this paper to provide information for properly and effectively locating the electronic devices and controlling their startup sequences, so as to offer instructions for the ground vacuum tests of the thermal controlling system.The axial temperature distribution, maximum temperature difference, working temperature and equivalent heat transfer coefficients of the heat pipe with single heat source in both horizontal mode and vertical mode are given in this paper, considering different heat source locations and different heat loads. In the vertical mode, as a result of the existence of gravity, the working temperature and equivalent heat transfer coefficients decreased slightly, while the heat transfer limitation increased obviously compared with those of the horizontal mode.In the horizontal mode, an analysis of the impact of heating and condensing conditions on working temperature is made. Meanwhile, the transient temperature distribution characteristic when heat transfer limitation has been reached is given, as well as an analysis of the location where dry-out phenomena occurred originally together with the temperature increasing rate. Capillary limitation in different locations with different efficient distances were measured in single heat source and two heat sink mode, as well as those in the single heat source and single heat sink mode while changes like reducing heat sinks and adding more heat sources were made to get more measure points along the axial direction. Moreover, a theoretical arithmetic is made for the two modes, and the results differ slightly with the experimental results in the double heat sink mode, while they have an excellent agreement in the single heat sink mode. In the multiple heat source and two heat sink mode, the summations of heat loads of all heat sources when heat transfer limitation had been reached are studied for different heat source combinations according to the relations of capillary limitation and the corresponding efficient distances measured in the single heat source and two heat sinks mode, and an equivalent coefficient and an equivalent heat load are introduced to convert heat loads from all other heat sources to one heat source. Comparing the summation of equivalent heat loads with the capillary limitation of the corresponding heat source in the single heat source mode, it is able to judge whether heat transfer limitation will be reached.In the vertical mode, an experimental study of the startup characteristics in the single heat source mode is presented. Heat sources below the surface of the liquid pool could startup alone, while heat sources above it could not, and situations became worse as the distance between the heat source and the surface of the liquid pool increased. With the aid of an assistant heat source, the heat source above the surface could startup normally, but a special requirement of the ratio of the power of the primary heat source to that of the assistant heat source must be met. After the startup, the assistant heat source must be kept on, otherwise, the heat pipe could not work normally, but there was no need to satisfy the ratio mentioned above.