High Frequency Pulse Tube Research Articles

Thermal Performance of a 4 K High-frequency Pulse Tube Cryocooler with Different Working Fluids

Thermal Performance of a 4 K High-frequency Pulse Tube Cryocooler with Different Working Fluids

2 K J-T cooler for quantum detection: emphasis on the Stirling-type pulse tube pre-cooler

Quantum detection of single photon achieves its highest sensitivity for temperature below 2 K. The cooling requirements for such application are very low, a few milliwatts for current harness heat intercept and radiation shielding. For that purpose, we are developing a compact cryocooler based on a 4He JT cooler. A high frequency pulse tube will provide the pre-cooling of two intermediate stages on the JT. The pulse tube is the key component for miniaturization and energy consumption. With low cooling power goals, a miniaturization work has been done on the pulse tube with the aim of reducing the size and power of compressor units. The pulse tube configuration is using two cold fingers, connected together by a heat intercept providing precooling for the lowest temperature stage. Cooling power at the cold tip as well as intercept heat flow have been measured. Numerical simulations have been conducted in parallel to study the impact of the size of the pulsation tube and of the regenerator on the pulse tube performances. Three cold units pulse tubes have been tested in similar conditions. Net cooling power, power at the intercept and impact of the tube and regenerator size on performances will be discussed.

Manifestation of improvement in regenerator performance of a low and high-frequency pulse tube cryocooler using layered pattern

Pulse tube cryocoolers (PTCs) have wide applications such as space and military equipment, cooling superconducting coils, magnetic resonance imaging, cryopumps, etc. In a cryocooler, the regenerator plays a vital role to achieve low temperature by periodically storing and discharging refrigeration produced at the pulse tube cold end. This paper presents the optimization of the regenerator as a layered pattern using open-source software, REGEN 3.3 wherein multiple sizes of Stainless Steel (SS) mesh are used as regenerator material. A rigorous parametric study is conducted having uniform regenerator mesh size throughout the regenerator space as well as with layered configuration of different sizes of SS wire mesh as regenerator material. Parameters such as operating frequency, mass flow rate, and phase angle are also varied to analyze the Coefficient of Performance (COP) of the PTC. To optimize the multi-layer regenerator, an algorithm is provided, and based on the outcome of the optimization process, it is recommended to use the multi-layer configuration of SS wire mesh that provided significantly better performance as compared to the use of a uniform regenerator matrix material throughout the regenerator space. Additionally, it is also found through this study that there exists an optimum multi-layer combination of the regenerator for any configuration of the PTC that can be identified using the algorithmic procedure followed in this paper. The optimized layer patterns for the PTC are also reported in the paper. By the use of a 2-layer regenerator, COP increased by up to 10% over the single material regenerator. Whereas with a multi-layer regenerator, COP has increased by 9.86% to 5.21%. The algorithmic procedure followed in this paper can be conveniently used to optimize the layered pattern of the regenerator of a low-frequency as well as high-frequency PTC.

First high-frequency pulse tube cryocooler down to 2.5 K and its promising application in China’s deep space exploration

First high-frequency pulse tube cryocooler down to 2.5 K and its promising application in China’s deep space exploration

A 3.27 K High-Frequency Pulse Tube Cryocooler Using Adsorbed 4He as Part of the Regenerator Material

A 3.27 K High-Frequency Pulse Tube Cryocooler Using Adsorbed 4He as Part of the Regenerator Material

Optimization and sensitivity analysis of high frequency pulse tube cryocooler for aerospace application

The demand for cryogenic cooling systems has been on the rise ever since the development of long-range infrared imaging systems, especially high-frequency stirling-type cryocoolers which have a vast array of applications in the aerospace sector. While there have been many studies reporting analysis of the pulse tube cryocoolers, these lack an optimization approach with a further sensitivity analysis from computational fluid dynamic (CFD) data to obtain better cold end temperatures. Presently, a response surface method (RSM), has been utilized to characterize the influence of the affecting parameters and a global sensitivity analysis has been conducted to put forward the critical parameters that influence the performance of the device. It is observed that an increase in frequency for lower pressure ratios with higher mean pressure results in better cooling performance in smaller pulse tube diameter models. The sensitivity analysis indicates the operating parameters such as frequency and pressure ratios to be more influential than the geometric parameters with an impact of over 80%.

A thermal-coupled/gas-coupled hybrid high-frequency pulse tube cryocooler attaining the liquid-helium temperature

High-frequency pulse tube cryocooler (HPTC) has become an attractive method for space cooling in the liquid-helium temperature range, due to its advantages of potential high efficiency, no moving parts at the cold end, small size, and light weight. However, key problems such as large regenerator losses and insufficient phase-shifting ability challenge it to obtain the liquid-helium temperature. A thermal-coupled/gas-coupled hybrid refrigeration process of HPTC has been designed to obtain the liquid-helium temperature. One HPTC working in the liquid-nitrogen temperature range is used as a pre-cooling stage, and another two-stage gas-coupled structure is employed to obtain liquid-helium temperature. The simulation results show that the lowest no-load temperature is 3.6 K and a cooling power of 84 mW can be provided at 6 K with a total input PV power of 128 W and 10.9 W/77 K pre-cooling power when Helium-4 is chosen as the working gas. An experimental prototype was designed, built, and tested. The simulation and experiment results will be introduced in detail in this paper.

Performance improvement of a pulse tube cryocooler with a single compressor through cascade utilization of cold energy

The high-frequency pulse tube cryocooler (HPTC) has been attracting increasing and widespread attention in the field of cryogenic technology because of its compact structure, low vibration, and reliable operation. The gas-coupled HPTC, driven by a single compressor, is currently the simplest and most compact structure. For HPTCs operating below 20 K, in order to obtain the mW cooling capacity, hundreds or even thousands of watts of electrical power are consumed, where radiation heat leakage accounts for a large proportion of their cooling capacity. In this paper, based on SAGE10, a HPTC heat radiation calculation model was first established to study the effects of radiation heat leakage on apparent performance parameters (such as temperature and cooling capacity), and internal parameters (such as enthalpy flow and gas distribution) of the gas-coupled HPTC. An active thermal insulation method of cascade utilization of the cold energy of the system was proposed for the gas-coupled HPTC. Numerical simulations indicate that the reduction of external radiation heat leakage cannot only directly increase the net cooling power, but also decrease the internal gross losses and increase the mass and acoustic power in the lower-temperature section, which further enhances the refrigeration performance. The numerical calculation results were verified by experiments, and the test results showed that the no-load temperature of the developed cryocooler prototype decreased from 15.1 K to 6.4 K, and the relative Carnot efficiency at 15.5 K increased from 0.029% to 0.996% when substituting the proposed active method for the traditional passive method with multi-layer thermal insulation materials.

Experimental study on a 20W/80K high frequency pulse tube cryocooler

The cryocoolers working around the liquid nitrogen temperature have important applications in high temperature superconducting, infrared detectors and gas liquefaction. A cryocooler sometimes needs to work in different temperatures. For the high-frequency pulse tube cryocooler operating around the liquid hydrogen temperature, due to the limitation of the length of the regenerator, it is often impossible to simultaneously have higher performance around the liquid nitrogen temperature. Therefore, this paper enhances its performance around the liquid nitrogen temperature based on a high-frequency pulse tube cryocooler working around the liquid hydrogen temperature, by changing the effective length of the regenerator with filling different lengths of copper mesh. Firstly, the effect of filling different lengths and meshes of copper mesh on its 80 K refrigeration performance is simulated. Finally, the experimental verification is also carried out. Moreover, by further optimizing the phase modulation mechanism and operating parameters including working frequency and charge pressure, the cryocooler can provide 20 W cooling capacity at 78 K under the input electric power of 420 W. The relative Carnot efficiency is increased from the initial 9.8 % to 13.56 %.

Design of a two-stage gas-coupled high-frequency pulse tube cryocooler working around 4 K

High-frequency pulse tube cryocooler have unique advantages for aerospace and ground applications. However, it is difficult to obtain lower cooling temperature: to obtain the liquid helium temperature, three-stage or four-stage structure by thermal coupling are currently used. In order to further improve the compactness, a two-stage gas-coupled high-frequency multi-bypass coaxial pulse tube cryocooler has been designed. The simulation results indicate that the designed cryocooler can provide a cooling capacity of 25 mW@4.2 K with 416 W input electrical work. The interaction between structural parameters and operating conditions, as well as some preliminary test results will be presented in this paper.

Development of an in-situ analysis instrument for microstructure of materials with low temperature

The development of instruments capable of dynamically observing the microstructure at different temperatures is of great significance for the study of materials. The liquid nitrogen and a self-developed high-frequency pulse tube cryocooler were used as the cold source to develop the cryogenic system of scanning electron microscope (SEM) in this paper. The vibration and temperature control problems and solutions involved in using these two cold sources as SEM cryogenic systems were described and discussed in detail. It was found that it is necessary to fully achieve the heat balance at a certain temperature and adjust the image displacement to overcome the adverse effects caused by the thermal expansion and contraction of the low temperature components, and the cryocooler needs to use an intermittent operation mode to avoid distortion of the material microstructure image caused by vibrations of the cryocooler. Whether it is for liquid nitrogen or cryocooler, a thermal switch between the cold source and the thermal bridge is helpful for temperature control of the sample and reduced heat leakage of the system.

Attaining the liquid helium temperature with a compact pulse tube cryocooler for space applications

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.

An 80 mW/8 K high-frequency pulse tube refrigerator driven by only one linear compressor

High-frequency pulse tube refrigerator (HPTR) has significant advantages in terms of compactness and high reliability, but it is difficult to obtain very low cooling temperatures. To obtain temperatures below 10 K, multi-stage structures driven by more than one compressor are currently used. This paper reports a two-stage gas-coupled HPTR driven by a single compressor that is extremely compact and even comparable to a single-stage structure. The pre-cooling temperature influences and gas distribution characteristics, which are two important issues in the research of gas-coupled structure refrigerator, were first numerically calculated and analyzed. Then the calculation results were verified by experiments and the cooling performance was tested. Before gas-coupling with the lower stage, the pre-cooling stage can obtain 4.3 W/40 K cooling capacity with 330 W electric input power, which belongs to a high-efficiency 40 K refrigerator that has been reported so far. With an electric power of 400 W, the gas-coupled HPTR taking the developed 40 K refrigerator as the pre-cooling stage achieves a no-load temperature as low as 5.7 K, which is the lowest record of the current two-stage gas-coupled structure in HPTCs. The developed two-stage HPTR can obtain a cooling capacity as high as 80 mW/8 K, and the two stages can also output the cooling capacity of 100 mW/9.3 K and 1000 mW/40 K simultaneously.

Optimization of an 8K Level High Frequency Pulse Tube Cryocooler

As very low temperature high frequency pulse tube cryocooler is the precondition of many space detection researches, it has been a hot topic in the field of pulse tube cryocooler. Improving the cryocooler’s performance is a common goal of researchers. In this paper, the regenerator material and the compressor of the second-stage pulse tube cryocooler as well as the first-stage pulse tube cryocooler are experimentally optimized using a new thermally coupled high frequency pulse tube cryocooler. Finally, more than 20mW of cooling power is achieved at 8K and the electric power decreases from 450W to 300W. The results increase the reliability of the space application of NbN terahertz detectors.

Study on a high frequency pulse tube cryocooler capable of achieving temperatures below 4 K by helium-4

High-frequency pulse tube cryocooler (HPTC) has advantages of compact structure, low vibration, high reliability and long operation time. In this study, Theoretical analysis and experimental tests have been conducted in four aspects based on a developed 4 K HPTC. Firstly, a compressor with larger power output capability was employed and the impedance match between the cold head and the compressor was discussed. Secondly, simply using inertance tube configuration to replace the traditional inertance tube-gas reservoir structure. Then, the type and the size of the regenerator materials working at 4–20 K have been experimentally optimized. Finally, the performance of double-inlet working at as low as 20 K has also been tested for the first time for the HPTC. The present prototype achieved a no-load temperature of 3.6 K, which is the lowest temperature record ever reported for HPTC using helium-4 as working gas. A cooling power of 6 mW/4.2 K was also obtained with 250 W input power and a precooling power of 12.1 W/77 K.

Influence of Regenerator Material on Performance of a 6K High Frequency Pulse Tube Cryocooler

As very low temperature high frequency pulse tube cryocooler has been a hot topic in the field of pulse tube cryocooler, improving the cryocooler’s performance is a common goal of researchers. By integrating the former results, we found that regenerator material is a key factor for the improvement of pulse tube cryocooler’s efficiency. In this paper, methods of simulation and experiment were used to investigate the influence of stacking style on performance of 6K high frequency pulse tube cryocooler. Finally, the lowest temperature has dropped from 8.8K to 6.7K and more than 10mW of cooling power is achieved at 8K with a two-stage thermally coupled high frequency pulse tube cryocooler. The results make the space application of NbN terahertz detectors possible.

Two-stage high frequency pulse tube refrigerator with base temperature below 10 K

This paper introduces our recent experimental results of pulse tube refrigerator driven by linear compressor. The working frequency is 23-30 Hz, which is much higher than the G-M type cooler (the developed cryocooler will be called high frequency pulse tube refrigerator in this paper). To achieve a temperature below 10 K, two types of two-stage configuration, gas coupled and thermal coupled, have been designed, built and tested. At present, both types can achieve a no-load temperature below 10 K by using only one compressor. As to gas-coupled HPTR, the second stage can achieve a cooling power of 16 mW/10K when the first stage applied a 400 mW heat load at 60 K with a total input power of 400 W. As to thermal-coupled HPTR, the designed cooling power of the first stage is 10W/80K, and then the temperature of the second stage can get a temperature below 10 K with a total input power of 300 W. In the current preliminary experiment, liquid nitrogen is used to replace the first coaxial configuration as the precooling stage, and a no-load temperature 9.6 K can be achieved with a stainless steel mesh regenerator. Using Er3Ni sphere with a diameter about 50-60 micron, the simulation results show it is possible to achieve a temperature below 8 K. The configuration, the phase shifters and the regenerative materials of the developed two types of two-stage high frequency pulse tube refrigerator will be discussed, and some typical experimental results and considerations for achieving a better performance will also be presented in this paper.

Experimental research on a 12.1 K gas-coupled two-stage high frequency pulse tube cryocooler

High frequency pulse tube cryocoolers (HFPTC) have been widely used in many fields like physics experimental research and aerospace, for no moving part in cold region, low vibration and long life. A gas-coupled two-stage high frequency pulse tube cryocooler with single compressor is introduced in this paper. In the first stage of the cryocooler, double-inlet and multi-bypass has been adopted as phase shifters. To get a better performance in phase shifting the reservoir and the inertance tube of the second stage has been located on the cold head of the first stage. With SS mesh screen as the regenerator of both stage, no-load temperature of 13.5K has been achieved. To improve the heat capacity of the regenerator of the second stage magnetic material Er3Ni has been employed in the second stage as regenerator matrix. With the charge pressure of 1.8MPa, input power of 260W and operating frequency of 23.5 Hz, the no-load temperature of 12.1K has been achieved.

Design of High Frequency Pulse Tube Cryocooler for Onboard Space Applications

To meet the growing demands of on-board applications such as cooling meteorological payloads and the satellite operational constraints like power, lower mass, reduced size and redundancy; a Pulse Tube Cryocooler (PTC) is designed by arriving at an operating frequency of 100 Hz and Helium gas pressure of 35 bar based on insights obtained from combination of phasor diagram, pulse tube and regenerator geometries with overall system mass of ≤ 2.0 kg. High frequency operation would allow reducing the size and mass of pressure wave modulator for a given input power. High Frequency also helps in reducing the volume of regenerator for a given cooling power, which increases the power density and leads to faster cool down. A component level modelling of the regenerator for optimising length and diameter for maximum Coefficient of Performance (COP) is carried out using REGEN3.3. The overall system level modelling of PTC is carried out using 1-D software SAGE. The cold end mass flow rate of the optimised regenerator is taken as reference for the system modelling. The performance achieved in REGEN3.3 is 2.15 W of net heat lift against the performance of 1.02 W of net heat lift at 80 K in SAGE.

10 K high frequency pulse tube cryocooler with precooling

A high frequency pulse tube cryocooler with precooling (HPTCP) has been developed and tested to meet the requirement of weak magnetic signals measurement, and the performance characteristics are presented in this article. The HPTCP is a two-stage pulse tube cryocooler with the precooling-stage replaced by liquid nitrogen. Two regenerators completely filled with stainless steel (SS) meshes are used in the cooler. Together with cold inertance tubes and cold gas reservoir, a cold double-inlet configuration is used to control the phase relationship of the HPTCP. The experimental result shows that the cold double-inlet configuration has improved the performance of the cooler obviously. The effects of operation parameters on the performance of the cooler are also studied. With a precooling temperature of 78.5K, the maximum refrigeration capacity is 0.26W at 15K and 0.92W at 20K when the input electric power are 174W and 248W respectively, and the minimum no-load temperature obtained is 10.3K, which is a new record on refrigeration temperature for high frequency pulse tube cryocooler reported with SS completely used as regenerative matrix.