Experimental Investigation On A Pulsating Heat Pipe With Hydrogen At Different Filling Ratios

In recent decades, the rapid development of cryocoolers makes its applications wider, such as for cooling down the superconductor, cells, cryogenic liquid storage tank, etc. However, its applications are usually limited by the volume and the requirement of temperature distribution of the object, the distance between the cryocooler and the object, the requirement of vibration, etc. Therefore, a high-efficiency heat transfer method is eagerly needed to match with the cryocoolers. Since invented in 1990, pulsating heat pipe (PHP) has attracted the attention of researchers from all over the world because of its simple and flexible structure, heat transfer efficiency and quick response. But the PHP has been mainly studied in room temperature range. In recent years, the PHP has been being applied in cryogenic field. Especially, the superconductor material MgB2 was discovered in 2001, which makes the study and application of the PHP with hydrogen more significantly. In view of this, the following work has carried out in this paper:Firstly, the progress on PHP is summarized, and the differences due to the working fluid at cryogenic and room temperature are proposed. Then, the difficulties of the research on cryogenic PHP are analyzed, and the concerns of the investigation on hydrogen PHP are put forward. Besides, the theoretical basis of PHP is introduced briefly.Secondly, the existing experimental device of PHP with hydrogen is improved on the data collection system, and the connection between cryocooler and PHP, to make the heat transfer performance under high heating power be obtained.Finally, the experimental investigation on the PHP with hydrogen is performed. The effects of filling ratio and heating power on the heat transfer characteristics of PHP are provided. Under our experimental conditions, when filling ratio is 51.0%, with the increasing of the heating power, there are 5 periods in the PHP:start-up, pulsation, a mixed of pulsation and annular, annular, and dry out. The results show that during the start-up and the mixed of pulsation and annular period, the fluctuation of PHP’s temperature difference is large, and the heat transfer performance of PHP is not stable. But during pulsation process, the fluctuation of PHP’s temperature difference is very small, and the heat transfer performance of PHP is stable. When filling ratio is 35.0%, the PHP achieves the highest effective thermal conductivity 18.7 kW/m-K at the heating power of 5.0 W. At this moment, the temperature difference between the condenser and the evaporator is 1.0 K, which verifies the efficient heat transfer performance of this PHP.