【作者】 刘华钊；

【导师】 甘智华；

【作者基本信息】 浙江大学 ， 制冷及低温工程， 2005， 硕士

【摘要】 本文介绍了脉管制冷机的发展历史、研究热点以及最新研究进展,进行了单级脉管制冷机纯氦性能调试实验,在此基础上进行了氦氢混合工质单级脉管制冷机的实验研究。具体内容简述如下: 一、直流机理分析 脉管制冷机处于双向进气模式工作时,在流经脉管、回热器的闭合回路中会引起直流。其不仅增加了冷端换热器的负载,降低了脉管制冷机的性能,而且还是引起脉管制冷机制冷温度不稳定的一个重要原因。因此如何有效控制和调节直流,对于提高脉管制冷机性能具有重要的意义。本文介绍了两种有关直流产生机理的理论。 二、氦氢混合工质制冷与蓄冷填料的吸收特性理论分析 根据改进的Brayton循环,对氦氢混合工质在20～35K温度范围内的制冷性能做了理论预测分析,同时计算分析了回热器磁性蓄冷填料Er₃Ni的吸氢特性。理论分析结果表明,磁性蓄冷填料Er₃Ni在吸收氦氢混合工质中的氢组分后,其相应的比热容明显增加,有可能改善回热器的回热性能。 三、15K温区单级脉管制冷性能实验 对各个参数:小孔阀、并联双向进气阀、频率等进行了细致的调节,对蓄冷器填料进行了优化,并进行了压缩机气量对制冷性能以及压缩机匹配实验,得到了很有意义的结果。经过一系列的改进和优化,压缩机采用LEYBOLD COOLPAK 4000时达到了15.1K的无负荷最低制冷温度,在40.6K时有30W的制冷量,为后续氦氢混合工质实验顺利进行打下基础。在这个实验台上,首次突破了20K温区的限制,也为后来同组的二级分离型脉管制冷机实验顺利进行提供了可靠的依据和借鉴作用。 四、氦氢混合工质单级脉管制冷性能实验 本章介绍了氦氢混合工质单级脉管制冷机性能实验的情况。实验结果表明,30K温区采用含氢10%的混合工质得到的制冷量和COP相比纯氦提高最大,分别比纯氦提高了3.6%和4.7%,然而却远远小于二级机中的实验结果:30K温区含氢60%时分别比纯氦时提高33%和42%。对比分析了造成氦氢混合工质在单级机和二级机中性能如此差异的原因。更多还原

【Abstract】 The history and recent development of pulse tube cryocooler are introduced. After the performance optimization of single-stage pulse tube cryocooler with pure helium, experiments about gas mixture -helium and hydrogen in the same pulse tube cryocooler are carried out, as follows:1. The DC flow appears when the pulse tube cryocooler works as double-inlet mode, which results in the deterioration of cool capacity and temperature instability. It’s pretty meaningful for us to look for an efficient way to adjust DC flow. Two kinds of theories about DC flow are introduced here.2. The theoretical analysis on how He-Hi mixture to influence the performance of pulse tube cryocooler is done. The specific heat of Er₃Ni increases a lot after adsorbing hydrogen, which is one of possible reasons to improve the performance of pulse tube cryocooler.3. Two parallel-placed needle valves with opposite flow direction referred as two-valved configuration instead of traditional single-valved configuration as double-inlet are adopted in experiments to control DC flow and are proved to be a successful way to decrease the refrigeration temperature of a single-stage pulse tube below 20K. After the optimization of such parameters as orifice valve, two-valved double-inlet, frequency and so on, with the input power 4KW, no load temperature 15.1K has been reached, and the cooling power 30W at 40.6K could be obtained. It was the first time in our country to reach the temperature below 20K, which did great help to the experiment of two-stage split pulse tube cryocooler.4. The performance of single-stage pulse tube cryocooler with He-H₂ mixtures is experimentally studied. The results show that the performance of pulse tube cryocooler is improved while using He-H₂ mixtures as working fluids. The cooling power and COP increase by 3.6% and 4.7% respectively at 32.9K when hydrogen fraction is 10%. However, the results in a two- stage pulse tube cooler show that the performance could be greatly improved at 30K with He-H₂ mixture and its positive effect is much larger than that of the single-stage cooler.更多还原