具有独立气路的液氦温区G-M型二级脉管制冷机性能研究

研究了一台具有独立气体回路的液氦温区G-M型二级脉管制冷机的制冷性能.目前的实验装置由两套独立的单级双向进气型脉管系统构成,第一级冷头对第二级进气的预冷通过安装在第二级回热器中部的换热器与一级冷头之间的热联接来实现.研究表明,该制冷机采用4He为工质,分别以Leybold CP4000和RW2氦压缩机来驱动第一级和第二级,可以获得2.18 K的最低无负荷制冷温度,4.2 K提供的最大制冷量为595 mW.     

深冷文献消息(国内部分)

20 0 5 110 1　 1 2 7K 3 He二级脉管制冷机性能研究蒋　宁等　《低温工程》　 2 0 0 4　№ 5　 1～ 7在一台具有独立气体回路的液氦温区G M型二级脉管制冷机上 ,采用3He为第二级制冷工质 ,获得了 1 2 7K的最低无负荷制冷温度。与两级均采用4 He工质的情况相比 ,在相同的条件下 (相同压缩机耗功 :4 3kW 1 3kW) ,第二级采用3He为工质 ,使得该二级脉管制冷机在 4 2K的制冷量提高了 4 0 5 %。2 0 0 5 110 2　斯特林型高频脉冲管制冷机的实验研究王国平等　《低温工程》　 2 0 0 4　№ 5　 8～ 12介绍了一台单级U型高频脉冲管制冷机的…     

分离型二级脉管制冷机的实验研究--Ⅱ:液氦温区二级脉管制冷机

研制1台新型液氦温区分离型二级脉管制冷机,该制冷机由2台独立的脉管制冷机组成,一级回热器冷端和二级回热器中部通过热桥相连,从根本上弥补了传统直接耦合型多级脉管制冷机级间干扰的不足.采用双压缩机双旋转阀驱动该二级脉管制冷机,第二级最低温度达到了2.5 K,在4.2 K下有508 mW制冷量,同时一级在37.5 K有15 W制冷量.第二级充气压力由1.7 MPa增大到1.85 MPa,制冷机在4.2 K下的制冷量可以达到590 mW.为了能简化结构、扩大应用,提出采用单压缩机单旋转阀驱动该分离型脉管制冷机,达到了相同的制冷性能.     

4.2 K温区1瓦级脉管制冷机的实验研究

小型回热式低温制冷机中的冷端换热器在制冷量高效传输过程中起着至关重要的作用,而这一作用往往被忽视.研究发现,通过脉管冷端换热器的结构改进,液氦温区脉管制冷机在4.2 K温区的制冷量可以得到显著提高.实验结果表明,在压缩机输入功率分别为4.8 kW和6.0 kW的条件下,双向进气型二级脉管制冷机在4.2 K获得了760 mW和900 mW的制冷量,相应的制冷系数(COP)为1.58×10-4和1.50×10-4.该脉管制冷机在4.2 K获得的最大制冷量达960 mW.     

4 K以下温区脉管制冷性能的改进

最新研究表明，采用陶瓷磁性回热材料GdAlO3（GAP）可以大大提高4K以下温区脉管制冷机的制冷量和制冷系数（COP）。在压缩机输入功率约为4.8kW的条件下，采用GAP的二级双向进气型脉管制冷机在2.8K，3.13K,3.70K分别获得了200mW，300mW和400mW制冷量，与采用HoCu2及ErNi的二级脉管制冷机相比，该制冷机在3.0K附近的制冷量增幅高达150%。     

液氦温区脉管制冷机的优化实验

研制了一台用作德国国家标准局 (PTB)约瑟夫森效应 (JosephsonEf fect) 1V电压标准冷却系统的二级脉管制冷机。其设计要求在 4 2K提供 1 0 0mW左右制冷量 ,并同时冷却 70K左右的冷屏。采用额定功率为 1 8kW的氦压缩机驱动脉管制冷机 ,在不同制冷量负荷条件下分别对其进行了优化。初步实验结果表明 ,在输入功率 1 8kW的情况下 ,该制冷机最低制冷温度达 2 8K ,4 2K制冷量最大达 1 90mW ,制冷系数达 1 0 6× 1 0 4,火用效率最高达 1 1 3% ,可以充分满足冷却电压标准芯片的需要。此外 ,还与用 6kW压缩机驱动同一制冷机的实验结果进行了比较。     

分离型二级脉管制冷机的实验研究第一部分20～40 K温区单级大功率脉管制冷机

为了满足液氦温区分离型二级脉管制冷机第二级预冷的需要,设计制作了1台20～40K温区单级大功率脉管制冷机.采用额定功率为6 kW的压缩机驱动该制冷机,最低制冷温度达13.8K,刷新了单级脉管制冷机最低制冷温度纪录.该制冷机在40 K可获得高达55.9 W的制冷量,基本可以满足15～40 K温区超导磁体等冷却的需要.着重分析了频率、充气压力和不同压缩机对系统制冷性能的影响,测试了长时间运行中系统性能的变化情况.     

氦氢混合工质G-M单级脉管制冷机性能研究

对G-M型单级脉管制冷机采用氦氢混合工质在30 K温区进行实验研究,从制冷量、COP、压降特性、压缩机耗功、制冷温度的稳定性等方面进行了讨论和分析,同时给出了在最优状态下加载热负荷的温度变化情况.实验结果表明,采用适当配比的氦氢混合工质有助于提高脉管制冷性能.     

混合工质脉管制冷的热力学性能预测

提出了用于预测混合工质脉管制冷热力学性能的改进型Brayton制冷循环,建立了制冷系统制冷量和制冷系数COP的理论表达式。在对多种低温流体的预测计算的基础上,提出了具有应用潜力的混合工质对。计算结果表明,如果用10%氮与90%氦的混合工质对代替纯氦,脉管制冷机在80K温度下的制冷系数和制冷量分别可以提高9.5%和6.7%。此外还讨论了其它可能用于80K温区脉管制冷的混合工质对,如氢-氦、氩-氦、氖-氦混合物等。     

低于11 K的单级脉管制冷机性能研究

研究了回热器长度以及80 K以下温区不同回热材料布置形式对单级G-M型脉管制冷机性能的影响.试验研究表明,适当增加回热器长度,制冷机性能可显著提高.在此基础上对低温区回热材料进行优化,采用Er3Ni、铅丸和不锈钢丝网3层复合回热材料获得了最佳的制冷性能.采用额定输入功率为7.5 kW的压缩机驱动,脉管制冷机最低制冷温度达10.9 K,这是目前单级脉管制冷机达到的最低制冷温度.该制冷机在21 K可获得20 W制冷量.     

A He pulse tube cooler operating down to 1.3 K

Regenerative cryocoolers that employ ⁴He as working fluid can only reach a lowest temperature of about 2 K. This limitation can be overcome by the use of ³He as working fluid. Here we report on the performance of a two-stage pulse tube cooler that consists of two parallel stages with independent gas circuits. The pressure oscillation in each stage is generated by means of a separate compressor in combination with a rotary valve. With ⁴He in both stages, the minimum no-load temperature of the 2nd stage was 2.23 K, and cooling powers of 50 W at 53 K and 380 mW at 4.2 K were simultaneously available at electrical input powers of 4.54 and 1.45 kW to the 1st and 2nd stage, respectively. Using ³He as working fluid in the 2nd stage, a minimum stationary temperature of 1.27 K has been achieved, which is, up to now, the lowest temperature obtained by regenerative cryocoolers. At an electrical input power of 1.3 kW, the 2nd stage provides a cooling power of 42 mW at 2.0 K and 518 mW at 4.2 K. With ³He, at the same operating condition, the cooling power at 4.2 K was found to be larger than with ⁴He.     

Two-stage pulse tube refrigerator in an entire coaxial configuration

In this paper, we introduce a new kind of two-stage pulse tube refrigerators. The chosen entire coaxial configuration combines the advantages of the coaxial design with the two-stage pulse tube concept. Lead coated screens build the inhomogeneous regenerator matrix of the second stage. Without any rare earth compounds the refrigerator reaches a no load temperature of 6.6 K at the second stage cold tip. The active type of phase shifting is generated by a rotary valve combined with two needle valves at the hot end of each pulse tube (compressor Leybold RW 6000, 6 kW input power). This paper focuses on the design parameters and first performance measurements.     

Experimental study of staging method for two-stage pulse tube refrigerators for liquid He temperatures

The first two-stage pulse tube refrigerator, providing a lowest temperature of 2.23 K and a cooling power of 370 mW at 4.2 K, employed a parallel arrangement of the two pulse tubes with phase shifters located at room temperature¹. With the aim of increasing the COP at liquid ⁴He temperatures, three modified staging methods were tested in this paper. All refrigerator versions operate with the same two regenerators as already used in the first two-stage setup¹ and also the same 6 kW He-compressor combined with a redesigned G-M rotary valve. The best performance is achieved with a parallel arrangement two-stage refrigerator by introducing proper negative DC flow and impedance tubes. So far the highest cooling power achieved on the second stage at 4.2 K was 0.5 W. With a heat load of 20 W at 67 K on the first stage, the second stage can provide a cooling power of 0.42 W at 4.2 K. Details of the design of the different refrigerators and a comparison of their performance are presented.     

20K温区两级脉冲管制冷机的研究

脉冲管制冷机的实用化是目前脉冲管制冷机的一个主要研究方向。介绍了作者为提高脉冲管效率而研究的一种分离结构的两级脉冲管制冷机。实验获得了１１．７Ｋ的最低温度,制冷量３Ｗ／２０Ｋ。采用名义功率２．２ｋＷＧ－Ｍ压缩机驱动得到了１２．４Ｋ的最低温度,制冷量２Ｗ／１８．５Ｋ,４Ｋ／２４．６Ｋ,实际输入功率约１．５ｋＷ。这一效果已基本达到了实用化应用的要求。该研究表明脉冲管制冷机的效率在２０Ｋ温区已接近类似的     

Characteristics of a 4 K Gifford–McMahon cryocooler using the Gd2O2S regenerator material

In order to improve the cooling power at 4.2 K, performance of a Gifford–McMahon cryocooler was investigated. We focus on regenerator materials and structure of 2nd stage regenerator. A ceramics regenerator of Gd₂O₂S (GOS) was used in the cold part of the 2nd stage regenerator. To utilize the GOS effectively, we applied a layered structure to the 2nd stage regenerator. It was divided into three parts along the length for the temperature distribution, to which lead (Pb), HoCu₂ and GOS spheres were filled. The cooling power improved to 0.22 W at 4.2 K. The electric power consumption is 1.3 kW. When only Pb and HoCu₂ (without the GOS) are filled, the cooling power is 0.15 W at 4.2 K. The experimental results show that GOS is very effective to increase the cooling power at 4.2 K.