Figure 1 - uploaded by P. E. Bradley
Content may be subject to copyright.
Source publication
Presently we are in the development process for a 4 K Stirling-type pulse tube cryocooler to support cooling requirements for a mobile THz detector system. In this paper we discuss the status of this development and the optimization methods for achieving 4 K with a three-stage hybrid design employing separate He-4 first and second stages that preco...
Contexts in source publication
Context 1
... we are undertaking an effort to develop a 4 K pulse tube cryocooler that supports a program to develop a mobile THz detection system (known as a mobile demonstrator). Figure 1 shows a schematic of the laboratory-based system upon which the mobile system is based 1,2 . The present laboratory system relies on a GM cryocooler for the 4 to 5 K needed. ...
Context 2
... Fig. 10 we compare estimated acoustic power delivered by the compressor with electrical power input. As stated previously the cold head is not instrumented to obtain the acoustic power at the cold head. Therefore we are left only with the input power or perhaps in this case the estimated acoustic power determined from scaling laws for pressure ...
Context 3
... discussed the importance of this impedance matching between cold head and compressor and the significance to overall efficiency of both compressor and cold head performance. Due to poor 1 st stage performance of considerably lower cooling of ~ 8 W at 80 K compared to desired values of ~ 18 W a background heat leak test was performed as shown in Fig. 11. It resulted in a background load of 1.87 W which compared quite favorably with calculations estimating ~ 1.9 W. Thus we must explore other sources for losses in the stage to explain this poor performance. One likely candidate is the cold end heat exchanger which was shortened to 3 mm in length as a compromise to achieve adequate ...
Similar publications
This paper presents the improvement of a large GM cryocooler, Cryomech model AL600, based on redesigning a cold head stem seal, regenerator, heat exchanger and displacer bumper as well as optimizing operating parameters. The no-load temperature is reduced from 26.6 K to 23.4 K. The cooling capacity is improved from 615 W to 701W at 80 K with a powe...
Citations
... In order to cool the terahertz detector, NIST designed a threestage HPTC. They proposed a new phase shifter named secondary pulse tube and regenerator, which finally obtained a no-load temperature of 5.4 K using 3 He as the working gas [82,83]. In 2002, Sunpower was supported by NASA to develop a 10 K-class HPTC [84]. ...
Liquid-helium temperature is a widely used working temperature in low-temperature physics. At present, liquid-helium or low-frequency cryocoolers, including Gifford Mahon (GM) cryocoolers or GM pulse tube cryocoolers, are usually employed to obtain a cooling temperature of about 4 K. The use of closed-cycle mechanical cryocoolers to replace liquid helium and the development of mechanical cryocoolers toward lightweight are advantageous development directions for refrigeration technology, and certain progress has been made in recent years. This paper summarizes the development status of lightweight cryocoolers, including Joule–Thomson cryocoolers, high-frequency pulse tube cryocoolers, and Vuilleumier cryocoolers, which have the advantages of small size and low power consumption compared with GM-type cryocoolers. The evolutionary ideas of miniaturization, the research advances, the characteristics of different types of cryocoolers, and the future development directions are also systematically introduced.
... There are two main types of HPTC configurations which have been shown to be capable of achieving the liquid helium temperature: one is a hybrid structure using a HPTC (or Stirling cryocooler) as a pre-cooling stage to reach 10-20 K and a Joule-Thomson (J-T) cryocooler as the second stage to further cool down to around 4 K, as reported by Narasaki et al. [11], Kotsubo et al. [5], Quan et al. [12] and others [13]. The other configuration consists of a HPTC with multiple thermal-coupled stages, that is, the hot end of a HPTC is pre-cooled by the cold head of another, as reported by researchers from NIST, Zhejiang University, SECT/TIPC, etc. [14][15][16][17]. However, J-T cryocoolers require at least an additional compressor and suffer from the problem of cryogenic throttle valve blockage [18][19][20] while the thermal-coupled HPTCs also require additional compressors and thermal bridges which inevitably cause cooling power losses and thus reduce the efficiency of the whole system. ...
Recent breakthroughs in space science have motivated space exploration programs in many countries including China. Cryocoolers, which provide the mandatory low-temperature environment for many sensitive yet delicate space detectors, are crucial for the proper functioning of various systems. One benchmark for the cryocooler performance is attaining the liquid helium temperature. However, even with complex configurations and multiple driving sources, only a few cryocoolers to date can achieve this goal. Here we report a high-frequency pulse tube cryocooler (HPTC) driven by a single non-oil-lubrication compressor which is capable of reaching the liquid helium temperature while offering other advantages such as high compactness, excellent reliability and high efficiency. The HPTC obtains a no-load temperature of 4.4 K, which is the first realization of cooling below the ⁴He critical point with a gas-coupled two-stage arrangement. The prototype can provide a cooling power of 87 mW at 8 K, and 5.2 mW at 5 K with a 425 W input electric power, showing leading-level efficiency. Moreover, we demonstrate the ability of the cryocooler to simultaneously provide cooling power at different temperature levels to meet different requirements. Therefore, the prototype developed here could be a promising cryocooler for space applications and beyond.
... The past over three decades have seen a worldwide quest for the space-qualified SPTCs and also witnessed their successful in-orbit applications [5][6][7][8][9][10][11]. Up till now, single-and two-stage SPTCs which cover the temperatures ranging from 20 K to 140 K have already been widely used in a variety of space missions, and the three-stage SPTCs developed for space applications with the cooling capacity at around 10 K are also becoming mature [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. In the authors' laboratory, a four-stage SPTC is being developed for the following three purposes. ...
This paper conducts systematic theoretical analyses of a four-stage SPTC aimed at directly reaching a temperature of around 3 K and also simultaneously achieving the cooling capacities at four temperatures varying from 3.3 K to 80 K for multiple uses. The fourth stage cold finger is focused on and a 2-D axis-symmetric CFD model is set up to study the irreversible losses and phase characteristics. The operating mechanisms in the fourth stage are modelled, in which the distributions of the losses along the whole regenerator are analysed quantitatively and the phase characteristics simulated as well. The interactions among the four stages are studied, in which the effect of parameters at each stage on the cooling performances of the other three stages is elaborated, respectively. The systematic optimization for the four-stage SPTC is then conducted. The detailed experimental verifications are presented in Part B.
... temperatures at different locations. Recently, multistage pulse tube refrigerators are used to meet the cooling demand ( Bradley et al., 2011;Gan et al., 2010;Yan et al., 2009 ), but it is difficult to control the cooling temperatures and cooling capacities at the same time in multistage pulse tube refrigerator. The multi-cold-finger PTR driven by single compressor can provide different cooling temperatures and cooling capacities at different locations, which could also reduce the number of compressor. ...
... Raab et al. [3] built a three-stage SPTC to precool a J-T cryocooler to 6 K, and Jaco et al. [4] summarized the performance data of the 10 K Engineering Model (EM) three-stage SPTC. Wilson and Gedeon [5] developed a three-stage gas-coupled SPTC with a predicted no-load temperature of 5.5 K. Bradley et al. [6] designed a hybrid three-stage SPTC employing He-4 at both the first and the second stages to precool a He-3 third stage to 4 K. Duval et al. [7] developed a three-stage SPTC as the precooler for a J-T cryocooler at 15 K. ...
... Stirling-type PTR (STPTR) is driven by no-valve compressor with a relatively high frequency. Nowadays, Stirling-type PTR can reach a temperature below liquid helium and distinguish itself in many fields such as optical detection for its superiority in small size, light weight, and high stability Olson et al. (2003), Olson et al. (2006), Nguyen et al. (2007), Nast et al. (2007), Qiu et al. (2011), Bradley et al. (2011). ...
This paper will introduce our recent experimental results of cryogenic regenerator materials employed in Stirling-type one-stage pulse-tube refrigerator for the use at liquid hydrogen temperature. Thermal diffusion coefficient, according to which we choose the suitable regenerator materials, will prove to be a useful reference. We will also discuss the impact of resistance of sphere regenerator materials on the performance of the refrigerator and the method to improve it. Take an overall consideration, suitable-size Er3Ni will be applied as the regenerator materials at the cold head and we achieve a remarkable 14.7 K no-load temperature.
... Compared with the relatively matured 80 K SPTCs, the efficiency of 4 K SPTCs is still rather low (about 0.5%-1% Carnot efficiency) (Olson et al., 2006;Nast et al., 2007;Bradley et al., 2008;Radebaugh et al., 2008;Qiu et al., 2011) due to regenerator losses with both the 4 K low temperature region (van Sciver, 1986) and high operating frequencies (Tanaeva et al., 2006). At temperatures below about 15 K, the specific heat capacity of regenerator materials significantly decreases with the cube of the temperature, while the specific heat capacity of helium-4 (He-4) increases remarkably, which leads to large regenerator heat transfer loss. ...
The efficiency of 4 K Stirling type pulse tube cryocoolers (SPTCs) is rather low due to significant regenerator losses associated with the unique properties of helium around 4 K and the high operating frequencies. In this paper, regenerator performance at liquid helium temperature regions under high frequencies is investigated based on a single-stage SPTC precooled by a two-stage Gifford-McMahon type pulse tube cryocooler (GMPTC). The 4 K SPTC used a 10 K cold inertance tube as phase shifters for better phase relationship between pressure and mass flow. The effect of the operating parameters, including frequency and average pressure on the performance of the 4 K SPTC, was investigated and the first and second precooling powers provided by the GMPTC were obtained. To reduce the regenerator heat transfer losses, a multi-layer regenerator matrix, including Gd2O2S (GOS) and HoCu2, was used instead of a single-layer HoCu2 around 4 K. A theoretical and experimental comparison between the two types of regenerator materials was made and the precooling requirements for a regenerator operating at high frequencies to reach liquid helium temperatures were given, which provided guidance for the design of a three-stage SPTC.
概要
研究目的 研究新型磁性回热填料Gd2O2S 对液氦温区高频脉管制冷机多级回热器损失特性的影响。 创新要点 确定了不同回热填料以及运行参数 (频率、 平均压力) 下液氦温区多级脉管制冷机的制冷温度和各级预冷量, 进一步明确了4 K 高频回热损失机理。 研究方法 采用理论研究与实验验证相结合的方法, 基于一台两级G-M 型低频脉管制冷机预冷的单极斯特林型高频脉管制冷机, 研究多级回热器在高频以及4 K 温区下的损失特性。 选取新型回热填料Gd2O2S 替代部分回热填料HoCu2, 比较回热器采用两种填料时在不同运行频率及平均压力下的冷端制冷温度 (图10) 、 各级预冷量和预冷温度 (图11-12) 。 重要结论 采用孔隙率较小的新型磁性回热填料Gd2O2S 可显著改善第一级回热器内压力波与质量流的相位关系, 从而减小该级回热损失。 减小平均压力可以降低制冷机无负荷制冷温度并减小第二级预冷量, 但制冷工质氦的体积比热容会急剧增大, 从而使低温级回热器的换热对频率非常敏感。 此外, 频率对高温级回热器的回热特性影响不明显。 该方法可以为三级斯特林型4 K 多级脉管制冷机提供设计依据。
... SPTCs operating between 20 K and 50 K, usually as two-stage coolers, have now been integrated into space applications [2,3]. However, multi-stage SPTCs working below 10 K, are still under investigation [4,5]. ...
... The performance of a precooled SPTC was reported by this same group in 2011. A no-load temperature of 5.4 K [4] was measured using He-3 as the working fluid, with a precooling temperature of around 30 K. A warm expander was used to enhance the required phase shift, thereby increasing the complexity. The present authors have conducted experimental investigations on precooled 4 K systems [5] since 2007. ...
Gas-coupled Stirling-type pulse tube cryocooler (SPTC) is currently the most compact and simplest configuration among all types of cryocoolers, but it is challenging to achieve a very low temperature. This paper investigates a gas-coupled SPTC which is capable of directly achieving a temperature of around 4 K. Theoretical analyses were performed based on SAGE to study the effects of employing one or more multi-bypass structures on apparent cooling performance, and internal working parameters. The simulation results indicate that the function of the multi-bypass is similar to that of a multi-stage gas-coupled structure, producing a pre-cooling effect on the lower-temperature section by increasing the acoustic power and the enthalpy flow in the pulse tube of the higher-temperature section. The cooperation of two multi-bypass structures can promote a higher enhancement of the cooling performance, but it is difficult to achieve the same cooling performance of a completely multi-stage gas-coupled SPTC due to weak phase-shifting capability and excessive reduction of the mass flow. Based on the model, the developed prototype has achieved a no-load temperature of 4.4 K, which shows the great potential of using a gas-coupled SPTC to obtain a cooling temperature below 4 K.
Stirling type pulse tube refrigerators have great application potentials in terahertz detection, deep space mid/long infrared detection and so on. It is still hard for Stirling type pulse tube refrigerators to work at liquid helium temperatures efficiently. One of the reasons is the large regenerative heat loss under such low temperatures. In this paper, the cooling performance of the regenerative materials HoCu2 and Gd2O2S at liquid helium temperatures are investigated. Focused on the heat exchange between gas and matrix and the axial heat conduction, Sage simulations indicate that with high specific heat capacity and high thermal conductivity, Gd2O2S is able to improve the regenerator performance when the temperature is below 5.6 K since the Gd2O2S’s specific heat capacity is higher than that of HoCu2 at these temperatures. As the refrigeration temperature increases, the optimal length of Gd2O2S decreases and too much Gd2O2S may deteriorate the performance, even causing the temperature to rise slightly at the cold end. This is because heat is released from matrix to gas and the axial heat conduction decreases even to negative value, which causes an increase in temperature gradient in the Gd2O2S part. Experimental results verify that the no-load refrigeration temperature can decrease from 4.75 to 4.57 K with 5 mm Gd2O2S instead of pure HoCu2 at the cold end, and the refrigeration temperatures at the cooling powers of 20 mW and 40 mW also decrease. Experiments show that Gd2O2S is capable of improving the performance when the refrigeration temperature is below 6.1 K, which agrees well with the findings from the simulations.
