Joule-Thomson Cryocooler Research Articles

The thermal performance model of a 105 mW@4.41 K 4He Joule-Thomson cryocooler designed for space applications

The 4He Joule-Thomson cryocooler (JTC) ensures the operation of space detectors working within the 4 K temperature range, such as the Block Impurity Band Infrared Detector (BIBID). In addition, the 4He JTC is one of the essential components of the 300 K to 50 mK space cryochain. It can precool sub-Kelvin refrigerators, such as the adiabatic demagnetization refrigerator (ADR) and the dilution refrigerator (DR). With the development of space science, the need for cooling power at the 4 K temperature range is growing. Thus, a thermal performance model of the 4He JTC precooled by a two-stage thermally coupled pulse tube cryocooler (PTC) is designed, manufactured, and tested with an eye toward space applications. A four-stage compression system with a high operating frequency and large pistons is designed and used to drive the JT cycle. This 4He JTC has a total mass of 55 kg and can provide a cooling capacity of 105 mW at 4.41 K with a total input electric power of 548 W.

Essential improvement of the JT cryocooler working at liquid helium temperature for space: Efficient and lightweight

Due to long lifetime, low level vibration and negligible electromagnetic interference, the Joule-Thomson (JT) cryocooler working at liquid helium temperature has been used in space. However, its cooling capacity and thermodynamic efficiency still need to be further improved under a certain mass limit, which is an essential improvement for space-efficient application of the JT cryocooler. Therefore, in this study, optimization design is carried out for a JT cryocooler working at liquid helium temperature. Based on the modification of Stirling cryocooler, pulse tube cryocooler and JT compressor, the developed JT cryocooler can provide a cooling capacity of 0.36 W at 4.18 K while the total input power and the total mass (without cryostat) are 1157 W and 26.8 kg, respectively. Compared with the literature research, it can be found that the developed JT cryocooler is suitable for space applications.

High-precision temperature control of helium Joule–Thomson cryocooler: Long-term temperature stability

To meet the refrigeration requirements of scientific instruments for mK-level temperature stability over a long-time range in the liquid helium temperature, the temperature characteristics and high-precision control strategies of the helium Joule-Thomson cryocooler (JTC) have been experimentally investigated for the first time. Based on the Ideal Gas Law, the influencing mechanism of pre-cooling temperature, gas reservoir volume, and liquid phase volume fraction on refrigeration temperature were qualitatively analyzed and experimentally verified. An active control studies of pre-cooling temperature, low-pressure and heat load were carried out to verify the feasibility of active temperature control of helium JTC. Finally, a long-term temperature stability of ±1 mK/h was successfully achieved when a multi-stage active control strategy was adopted, which is the optimal long-term temperature stability of helium JTC that have been reported to date.

Experimental study and infrared detector application research of micro miniature refrigerators

The MMR（Micro Miniature Refrigerator）is a novel Joule-Thomson cryocooler manufactured by micro-machining technologies, its axial length is significantly shorter than traditional Joule-Thomson cryocoolers commonly employed in infrared detectors. MMRs can greatly reduce the size of infrared detectors upon successful implementation. However, contemporary MMR products encounter challenges such as relatively low cool-down rates, cooling power, and structural strength. To address these issues and enhance the cool-down performance of the MMR for effective application in infrared detectors, a calculation model describing flow and heat transfer besides working characteristics of the MMR is proposed and verified. MMR prototypes are fabricated and experimentally studied. Building upon theoretical analysis and experimental findings cooling performance enhancement methods including transitioning the MMR material from glass to metal and modifying the structure and channel patterns of the MMR are introduced, the cooling performance of the MMR is thus greatly improved. Furthermore, an integrated design incorporating an MMR into an infrared detector is proposed, the axial length of this infrared detector is reduced by 65.3 % compared to conventional infrared detectors. And the MMR is further enhanced to adapt the working conditions in infrared detectors, 60.9 MPa working pressure and 38 s cool-down time is achieved, the cool-down requirements of infrared detectors is satisfied. Notably, the proposed MMR and infrared detector design in this paper exhibit technical advantages over similar products reported in the literature.

Fast cooling miniature Joule-Thomson cryocooler with improvement of energy recovery and thermal mass distribution

Open-cycle conical miniature J-T cryocoolers are favored for applications in the infrared detection field, due to their fast cooling and compact lightweight features. In this type of cryocooler, the regenerative heat exchanger for energy recovery plays a vital role in both its miniaturization and fast cool-down, because its geometry greatly determines the distribution of its heat transfer area and thermal mass. To examine and optimize the effects of the geometry on its fast-cooling performance, a validated transient analysis model, being capable of simulating the entire operating process of an open-cycle miniature J-T cryocooler, was applied to analyze and compared the transient heat transfer and flow characteristics, and then the cooling performance under different operating conditions for one cylindrical and three different cone-angle J-T cryocoolers in this study. Researches show that in terms of geometry, it is advisable to increase the heat transfer area near the cold end of heat exchanger while ensuring a relatively small thermal mass for the entire cryocooler. By analysis, a novel structure of heat exchanger with reduced volume and mass was proposed to enhance the fast-cooling performance and miniaturize cryocooler. Studied results indicate that the performance of this novel cryocooler is improved in terms of reducing the cool-down time by 28% and the volume by 50%. Additionally, this optimized structure exhibits excellent fast-cooling performance under broader operating conditions.

Experimental investigation of the structure effects on the energy recovery and jet impinging process in a fast cooling Joule-Thomson cryocooler

Compared to other Joule-Thomson (J-T) refrigeration systems, open-cycle miniature J-T cryocoolers offer exceptional rapid cooling capabilities, making them ideal for applications such as infrared guidance in missiles. The energy recovery in the heat exchanger enables the refrigerant reach saturation temperature quickly and improve the jet liquefaction rate. The heat transfer intensity of the impinging jet determines the cooling rate of the target. Hence, heat recovery and the impact jet process are the primary factors behind this rapid cooling, with distinct roles that require separate consideration. The structural differences will directly affect the energy recovery and jet impact process. To investigate these affects, an experimental system for rapid cooling J-T cryocoolers was established and three distinct cryocoolers with substantial structural variations were designed. The important structures, including jet height, orifice diameter, enhanced heat transfer treatment of the cold plate, heat exchanger height, and heat exchanger cone angle, were closely studied. In the range of our experiments, it was found that larger heat exchanger cone angle leading better energy recovery performance, while the length of the heat exchanger is limited by the type of refrigerant. Longer heat exchanger actually introduce too much thermal mass for the refrigerant with better energy recovery performance. In the aspect of jet impingement, enhanced heat transfer treatment and larger jet height will improve the jet heat transfer intensity.

Investigation of refrigerant-dependency on the performance of conical double helix tube Joule-Thomson cryocooler

Miniature Joule-Thomson (J-T) cryocoolers are widely used in the cryogenic field due to their advantages of small size, and fast cooling. Selecting the appropriate refrigerant is a crucial task in designing a J-T cryocooler, as it significantly affects its cooling performance. To study the refrigerant-dependent influencing on the cryocooler's performance, an improved one-dimensional model for a conical double layer J-T cryocooler was developed. The model has been verified to have higher accuracy, faster computing speed, and applicability across a wider range of operating conditions. Nitrogen and argon, commonly used refrigerants with similar saturation temperatures, were investigated. Both simulation and experimental results indicate that argon exhibits a faster cooling rate, while nitrogen achieves a lower cooling temperature under the working conditions. The numerical studies suggest that argon's higher density and lower J-T coefficient contribute to its faster cooling characteristic, resulting in a higher heat transfer quantity in the double layer heat exchanger. However, increasing the vessel pressure can quickly reduce the difference in cooling rates between nitrogen and argon, and it may even make nitrogen more optimal. Moreover, it was observed that a significant portion of the cooling capacity is utilized to cool the cryocooler itself for both nitrogen and argon.

Effect of impinging jet on rapid cooling of a miniature Joule-Thomson cryocooler: Experimental study of operating conditions

A miniature open-cycle Joule-Thomson (J-T) cryocooler possesses excellent potential for rapid cooling from ambient temperature to about 100 K within seconds. In this rapid cooling process, the interplay of the heat transfer process between the cryogenic fluid and the cold plate plays a crucial role, in addition to the J-T effect and the energy recovery within the heat exchanger of the cryocooler. The phase state of the impinging jet is determined by the jet temperature and has different heat transfer mechanism. To investigate this impinging jet behavior separately, an experimental system for the rapid cooling J-T cryocooler was set up and the jet temperature was measured besides other important parameters. The operating conditions, including the cylinder pressure, cylinder volume, ambient temperature, and the refrigerant, were studied orthogonal. It was observed that argon, compared to nitrogen, can be more rapidly throttled into its two-phase region within a second. However, nitrogen will perform better than argon in terms of cool-down time. This is attributed to the temperature difference between the jet and the cold plate, which significantly influences the boiling mode of the two-phase jet, and in turn affects the cryocooler's cooling rate. Nevertheless, due to the smaller heat transfer intensity of single-phase jet, the cool-down time of nitrogen deteriorates quickly at high ambient temperatures. Experimental results also revealed that the cooling rate of the cryocooler still can be enhanced even if cylinder pressure beyond its saturation curve, caused by the dynamic cooling process and the pressure drop within the finned tube.

Further experimental work in mixed gas Joule-Thomson cryocooling

Miniature Joule-Thomson (JT) cryocoolers are attractive for many applications due to their small size and resulting fast cool-down time. Finned-tube heat exchangers are one of the most widely used heat exchanger for miniature JT cryocoolers. The basic configuration, known as a Giauque-Hampson (GH) or coiled tube heat exchanger, involves the high-pressure stream flowing through a finned-tube that is helically coiled upon a cylindrical core while the low-pressure return stream flows over the fins in the annular space created by the core and the inner diameter of a shell. The experimental work in this study aimed to gain insight into thermal characteristics of the shell-side of a GH heat exchanger by developing a test facility capable of measuring the two-phase heat transfer coefficient (htc) for this flow at operating conditions of interest to mixed-gas JT (MGJT) cryocooling. The capabilities of the test facility were demonstrated and measurements of the two-phase htc of the mixed gas on the shell-side of the GH heat exchanger prototype revealed that the shell side is the dominant thermal resistance for these operating conditions, even though the fins provide a larger surface area.

Performance of a single-stage mixed refrigerant miniature Joule Thomson cryocooler operating at 90-100 K for space applications

The performance of a closed-cycle miniature Joule Thomson (J-T) cryocooler operating with zeotropic mixtures is presented in this work. The system can provide refrigeration between 90-100 K and meet a heat load of 1 to 3 W. A miniature variable-speed rotary piston compressor is used in the present version. A coiled tubes-in-tube heat exchanger with an effectiveness greater than 95% is used. The details of the system and its performance are presented in this paper.

Design and performance analysis of a Joule-Thomson cryocooler systems

The aim of the work is to develop a mathematical model which has capability to analyses the design parameters as a function of operations conditions for single and multi-stage Joule Thomson Cryocooler System JTCS. The operations conditions are inlet and outlet pressure, precooling temperature, and mass flow rate. The design parameters are expansion device (length, diameter, and Joule Thomson coefficient), heat exchanger (length, diameter, and effectiveness) and gas type (nitrogen, oxygen, and argon). Theoretical results for nitrogen, oxygen, and argon at initial pressure of 25 MPa, initial temperature of 20ºC, indicate that the final temperature equal to (-16.46ºC, −37.34ºC and −56.75ºC) respectively at single stage JTCS. It also shows the possibility of decreasing the final temperature to (-194ºC, −180.9ºC and −183.8ºC) respectively at multistage JTCS. The experimental rig has been constructed for satisfying mathematical model. The experimental results for nitrogen gas show a temperature drop of 6.5ºC when the initial pressure and temperature were 3 MPa and 20ºC respectively. Theoretical results were validated using experimental measurements on the other hand. The computer program has been built to carry out the analysis required for solving the parameters of JTCS under different operations conditions with good agreement compared to recent published researchers.

A micromachined Joule-Thomson cryocooler for ice lithography

A micromachined Joule-Thomson cryocooler has been designed as a cryostage for ice lithography, which allows high-pressure nitrogen throttling to liquefy and fast cool samples with low vibration. The sample can be cooled down to 99.5 K in 30 min and then heated up to room temperature in 10 min. Compared with previous cooling systems based on liquid nitrogen, the Joule-Thomson cryostage has resulted in a significant 90% reduction in cooling time and a decrease in operating temperature by 30 K. Besides, the nitrogen mass-flow rate beneath the sample remains <20 mg/s to minimize vibration. The measured peak-to-peak amplitude at the minimum temperature is about 5.6 nm. As the first cooler integration within an ice lithography system, this Joule-Thomson cryostage not only enables the exploration of a wider range of ice resists, but also can be applied in kinds of microscopes for helping characterize materials at cryogenic temperatures.

Drawn-polymer microchannel heat exchangers with application to recuperative cryocoolers

Polymer microchannel heat exchangers for use in cryocooler applications have been developed. These heat exchangers are manufactured using a thermal drawing process where a bulk polymer preform is heated and stretched. The thermal drawing process results in microchannels with a characteristic dimension of 50–100 µm with an overall length of many meters. The drawn heat exchangers are lightweight, flexible, and have a large surface-area-to-volume ratio. Proof of concept design and testing of a nitrogen and hydrogen Joule-Thomson cryocooler utilizing a Polyetherimide (PEI) drawn-polymer recuperative heat exchanger is presented. These heat exchangers operated leak free at cryogenic temperatures under pressures up to 11 MPa. With a 95 % effective drawn polymer recuperator, the hydrogen cryocooler reached a saturation temperature of 20.5 K and demonstrated a cooling power of 28 mW. Mass flow maldistribution has been identified as a barrier to higher effectiveness performance. Suggestions for improvements and future development are discussed.

Multi-objective optimization of precooled JT cryocooler working at liquid hydrogen temperature

With the advantages of no moving parts at low temperature, flexibility and simple structure, the precooled Joule-Thomson (JT) cryocooler working at liquid hydrogen temperature has the potential to be applied in the liquid hydrogen zero boil-off (ZBO) storage system in space. For JT cryocooler used in aerospace, cooling capacity, efficiency and mass are key parameters which should be considered simultaneously. For this reason, in this study, a theoretical model of the precooled JT cryocooler working at liquid hydrogen temperature which is composed of the heat exchangers, the JT compressor and the precooler is established. The target cooling capacity of the cryocooler is 10 W at liquid hydrogen temperature. Multi-objective optimization method is introduced to comprehensively optimize input power and mass. The Pareto frontier consisting of a series of non-dominated solutions is obtained. The linear programming technology of multidimensional analysis preference (LINMAP) method is used to select the final optimal solution from the Pareto frontier. The multi-objective optimization results of input power and mass of the cryocooler are 3484.72 W and 40.92 kg, respectively.

Experimental study on a closed-cycle Joule-Thomson cryocooler working at liquid hydrogen temperature

Because of high reliability, simplicity and no moving parts in the cold end, the Joule-Thomson (JT) cryocooler working at liquid hydrogen temperature has the potential to be used in the field of hydrogen liquefaction, liquid hydrogen storage and electronic devices cooling. However, studies on JT cryocoolers with cooling capacities above 10 W at liquid hydrogen temperature are rare. Therefore, in order to study cooling characteristics of a closed-cycle JT cryocooler working at liquid hydrogen temperature with a cooling capacity above 10 W, a laboratory prototype of a simplified JT cryocooler driven by an oil-lubricated scroll-type compressor has been built and tested. Pure hydrogen gas is used as the working fluid. The cool-down process of this closed-cycle JT cryocooler is illustrated and analyzed. The cooling temperature of 20.7 K is approached at the end of the cool-down process. Using the heat balance method, a stable cooling capacity of 10.9 W at 20.8 K is measured. The stability of temperature, pressure and mass flow rate is analyzed. Over a period of 0.5 h, the maximum differences in cooling temperature and pressure are lower than 0.1 K and 0.001 MPa, respectively. Mass flow rate fluctuation which is 0.44 mg/s has little influence on the cooling temperature.

Experimental and dynamic simulation study of the Joule-Thomson cryocooler working at liquid hydrogen temperature

With advantages of long-life time, low level vibration and continuous refrigeration, precooling Joule-Thomson cryocooler (PJTC) working at liquid hydrogen temperature has the potential to be applied to liquid hydrogen storage system in space. For the large-cooling-power PJTC working at liquid hydrogen temperature, its dynamic response characteristic to heat load has a great importance on liquid hydrogen storage system, especially in aerospace applications. In order to study dynamic characteristics of PJTC working at liquid hydrogen temperature, an experimental setup for an open-cycle PJTC is built and its dynamic model is established by MATLAB software. Cool-down process and temperature variation characteristic with a heat load of 10.19 W are simulated and verified with experimental results. Meanwhile, the effect of precooling power on the performance of JT cryocooler is analyzed. It is found that if the precooling power is lower than 50% of the original precooling power, the recovery time of JT cryocooler will increase significantly.

Conceptual design of a sorption-based cryochain for the ETpathfinder

Next-generation gravitational wave detectors, including the Einstein Telescope [1][2], aim to achieve amplitude-spectral-density strain sensitivities on the order 10−24m/Hz[3]. In the low-frequency band such sensitivities can only be obtained when thermal noise, mainly stemming from the mirror coating, is reduced by employing cryogenic cooling techniques for the mirrors. The optical surface of the mirror should not vibrate with strain noise amplitude spectral densities above 10−20m/Hz for the cryogenic mirrors in the Einstein Telescope [3]. The ETpathfinder research facility [4][5], aims to facilitate the development and testing of critical new technologies required for the design and operation of future gravitational wave detectors. A key enabling technology for the design and operation of such advanced interferometers is the cryogenic system that cools the main optics to a temperature of approximately 10 K. Given the stringent requirements on vibrational noise for these optics, the cryogenic cooling under continuous operation should be essentially vibration free. Joule-Thomson cryocoolers using sorption compressors are known to generate an absolute minimum of vibrational noise during operation. We propose a modular cryochain design comprised of a system of sorption compressors and Joule-Thomson cold stages fitting the ETpathfinder project requirements. In this paper, we present the conceptual design of the cooler chain that is based on a parallel cascade arrangement of a 40 K neon stage, a 15 K hydrogen stage and a 8 K helium stage. The operating parameters of the sorption-based cooler chain are selected via a hybrid modeling workflow, aiming to optimize performance and other design considerations within an envelope of acceptable design parameters.

Temperature Fluctuation of a Closed-Cycle Helium Joule-Thomson Cryocooler with Two-Stage Precooling

Temperature Fluctuation of a Closed-Cycle Helium Joule-Thomson Cryocooler with Two-Stage Precooling

Experimental study on an open-cycle conical Hampson-type miniature Joule-Thomson cryocooler

Hampson-type miniature Joule–Thomson (J–T) cryocooler is widely used for the fast cooling of infrared detectors. In this work, a conical Hampson J-T cryocooler is designed and fabricated, and an experimental setup is built to test its performance. Accordingly, the cooling capacity, heat transfer coefficient, and efficiency of the cryocooler are analyzed based on the experimental cooling curves, the axial temperature distribution, the mass flow rate, and the pressure of the expansion chamber. The results showed that a minimum cooling temperature of 168 K with cooling capacity of 393.5mW can be attained by employing nitrogen gas as the working fluid at inlet pressure of 10 MPa. In addition, it was found that the axial temperature of the cold finger shell is distributed exponentially in the vertical direction. Also, the comprehensive heat transfer coefficient between the incoming flow and the backflow decreases gradually with the increase in the height. Due to the heat leakage, the heat transfer coefficient is less than 150 W/ (m2· K) and the efficiency of the cryocooler is around 80%. With the increase in the inlet pressure, the minimum stable operating temperature, cooling capacity, mass flow rate, and expansion chamber pressure of the cryocooler are found to increase. On the other hand, this will negatively affect the efficiency of the cryocooler.

Numerical and experimental study on a tube-in-tube heat exchanger working at liquid-hydrogen temperature with a large temperature span

With the advantages of no moving parts at low temperature and a flexible and simple structure, the precooled Joule–Thomson cryocooler working at liquid-hydrogen temperature has the potential to be used in the liquid-hydrogen zero-boil-off storage system. The recuperative heat exchanger is one of the key components of Joule–Thomson cryocoolers, and it is usually a tube-in-tube heat exchanger (T-THX). In this study, a numerical model of a T-THX working from room temperature to liquid-hydrogen temperature was developed. Based on the requirement that the heat-exchanger efficiency should be at least 97%, a T-THX was designed and tested. The performance of the T-THX with a temperature span of 280 K was obtained at pressure of 0.539–0.982 MPa and mass flow rate of 4.57–25.81 mg/s. The heat-exchanger efficiency varied from 95.83% to 97.50%, by which the feasibility of the numerical model was preliminarily verified. To improve the calculation accuracy, the T-THX model was modified. Compared with further experimental results, using the modified T-THX model, the relative deviation of the outlet temperature was within 0.3% and the deviation of the heat-exchanger efficiency was less than 0.05%.