Coaxial Pulse Tube Cryocooler Research Articles

Numerical and experimental investigation of 12 W/60 K high-efficiency coaxial pulse tube cryocooler

Maintaining a low-temperature environment is paramount in pursuing reliable operation for infrared detectors. To address the rising demand for long-wave infrared detectors functioning in low-temperature environments around 60 K, this study investigates the enhanced efficiency of a 60 K coaxial pulse tube cryocooler (PTC) through both simulation analysis and experimental methods. A PTC model was developed using Sage software to optimize parameters such as cold finger size. Analysis of the internal flow field highlighted that variations in cold head temperature, frequency, and input power significantly impact phase angle distribution within the regenerator. Experimental results yielded the same conclusion and confirmed how these critical factors affect the PTC’s performance. Through systematic optimization of simulations and experiments, a cooling performance of 12.7 W/60 K was achieved with an input power of 300 W. Furthermore, when the input power of the PTC was 200 W, a cooling capacity of 9.2 W/60 K was achieved, demonstrating a relative Carnot efficiency of 18.3 %.

Design and Optimization of a High Frequency Miniature Pulse Tube Cryocooler

A micro coaxial pulse tube cryocooler has been developed for infrared detection. This paper presents the experimental data of performance and describes the optimization process of a pulse tube cryocooler in detail. With a tiny size and high frequency, this cryocooler is driven by the linear compressor. The combination of inertance tube and buffer is adopted as phase shifter. The effect of the structure and operating parameters on cooling performance are investigated through experiments. As a result, the regenerator has a dimension of 40 mm length, and the optimal frequency is 175 Hz. It can provide a cooling power of 0.5 W at 80 K with a 30 W input electric power and 0.8 W at 150 K with a 10 W input electric power.

“Investigation Variable Parameters in Cryocooler Design: CFD simulation of Coaxial Pulse tube Cryocooler”

“Investigation Variable Parameters in Cryocooler Design: CFD simulation of Coaxial Pulse tube Cryocooler”

Numerical investigation on non-linear streaming effects in a two-stage coaxial pulse tube cryocooler

Stirling pulse tube cryocoolers (PTC) are widely used in aerospace applications for the cooling of infrared sensors and for filtering background thermal noise in the astro-imaging devices, etc. Present investigation aims to use numerical methods to demonstrate the nonlinear fluid flow, heat transfer, and vortex generation phenomena in a two-stage coaxial type inertance pulse tube cryocooler. The numerical simulation is conducted using commercially available Fluent® code for both single-stage and multi-stage configurations to show nonlinear processes with varying heat load conditions. It has been noticed that the width of the vortex produced inside the pulse tube grows with an increase in heat load capacity. This undesirable flow conditions yields an adverse effect in the cooling behavior and reduces overall performance of cryocooler with higher heat load. Additionally, streamlines, stream function, pressure and temperature variation plots are given for both stages with different heat load capacity to substantiate our results.

Effect of thermal dispersion and turbulent conduction on the heat transfer behavior of coaxial pulse tube cryocooler

In this article, a numerical analysis is conducted for a miniature coaxial pulse tube cryocooler including the effect of an axial conduction enhanced term. This term is a representative of supplementary energy loss, which happens because of turbulent conduction, mixing, and thermal dispersion. The complex physical domain of cryocooler is modeled intelligently in one-dimensional model by splitting the total computational domain into two subsections. The individual subsections of the cryocooler have been discretized into a number of small control volumes. Both subsections are merged together to make a complete computational domain for the cryocooler. The conservative form of the nonlinear, coupled partial differential equations demonstrating its heat and fluid flow aspects have been discretized into algebraic equations by utilizing the finite volume technique. Final discretized algebraic equations have been solved iteratively to predict its heat and fluid flow behaviors. Suitable relaxation factors have been incorporated to accelerate the convergence of the simulation. Moreover, the variation of mean cyclic energy, enthalpy, and exergy flow have been visualized along its physical domain with and without fluid axial conduction enhancement loss processes. Influences of different length of inertance tube, outer to inner radius ratio of annular passage, and length to radius ratio of pulse tube on no-load temperature is studied for with and without fluid axial conduction heat loss.

Design and optimization of heat exchanger in coaxial pulse tube cryocooler working above 100 K

The coaxial pulse tube cryocooler (PTC) has the advantages of without moving parts at the cold end, compactness and high-efficiency, it shows great application potential in many fields. The present work numerically and experimentally investigated a coaxial PTC working at temperature range from 90 K to 260 K. To improve its efficiency, the exergy analysis method was used to study the distribution of available energy loss in the coaxial PTC. To reduce one of the main available energy losses coming from the heat exchanger, three types of heat exchanger, slit, circular hole (CH) and copper mesh (CM), were analyzed and optimized based on the law of conservation of energy. Finally, two different cold end and hot end heat exchangers are designed respectively in the experiment. The results show the optimized pulse tube cooler can supply 50 W cooling power at 185.3 K with 200 W input power. To the best of our knowledge, its relative Carnot efficiency (16% at 165 K) lies one of the best results in the world. The experimental results also show that the refrigeration efficiency of the present PTC could be much improved by optimizing its operating parameter. In summary, the present PTC can work efficiently at a wide temperature range from 90 K to 260 K, which shows great potential candidate for small refrigerators such as vaccine preservation, organ freezing transportation and outdoor preservation of wildlife samples.

Investigation of intermediate cooling capacity from a single-stage coaxial pulse tube cryocooler

Pulse tube cryocoolers (PTCs) are suitable for cooling infrared detectors in space. With the development of multi-spectral detection, multi-temperature cooling of PTCs is essential. Multi-stage and two cold finger coolers are commonly used, which are not compact and difficult to control. To further compactness, we investigate the intermediate cooling capacity of a single-stage coaxial PTC in this paper. The single-stage PTC achieves dual temperature cooling by obtaining cooling power simultaneously from the cold end and the middle of its cold finger. Based on theoretical and simulation analysis, the effects of inter-cooling power on the temperature variation, loss, and phase angle, and the cooling performance at the dual-temperature zone with different input power are derived. Additionally, some experiments are carried out to demonstrate the accuracy of the theory and simulation, and the reasons for the difference between the simulation and the experiment are explained. The experiment shows that the cooling temperature of the cold end can increase from 70.7 K to 87.4 K when the inter-cooling capacity increase from 1 W to 4 W with an input power of 150 W and a cooling capacity of 4 W.

Investigation of Intermediate Cooling Capacity from Single-Stage Coaxial Pulse Tube Cryocooler

Investigation of Intermediate Cooling Capacity from Single-Stage Coaxial Pulse Tube Cryocooler

A High Efficiency Coaxial Pulse Tube Cryocooler for Cooling Medium-Wave Infrared Detectors

In order to meet the cooling demand of a medium-wave infrared detector, a coaxial pulse tube cryocooler (PTC) working at temperature around 90 K has been designed. The cooling capacity is requested to exceed 7 W at 90 K with an input electric power of 100 W. The compressor is made based on an engineering prototype which has been successfully applied in space. Experimental studies have been carried out to improve the performance of the cold finger from the aspects of inertance tube, cold-side heat exchange, hot-side flow straightener. By carrying out these optimizations the PTC can achieve a 7.64 W cooling capacity at 90 K when the input electric power is 100 W, and its relative Carnot efficiency is higher than 15% at temperature between 80 and 100 K.

Coaxial Stirling pulse tube cryocooler with active displacer

Coaxial pulse tube cryocoolers are the configuration of choice as they allow better access to the cold head. Hence, a previously built and tested in-line pulse tube cryocooler which uses an active displacer for phase control has been modified into a coaxial configuration. The active displacer allows the mass flow and the pressure pulse at the cold end of the pulse tube to be easily adjusted for optimum performance. The displacer also allows the expansion power at the warm end of the pulse tube to be recovered in order to operate more efficiently. A numerical Sage model is used to demonstrate this by examining the work flows throughout the cryocooler and it is shown that more than 6% of the power required to drive the cryocooler comes from the warm end of the pulse tube via the displacer. When using an inertance tube or orifice, this expansion power is dissipated as heat which is why using a displacer can lead to a more efficient cryocooler. Moreover, the effect of changing the displacer phase and stroke on cryocooler performance and pressure characteristics is examined both experimentally and numerically.

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.

Numerical modelling of a coaxial Stirling pulse tube cryocooler with an active displacer for space applications

A numerical model for a coaxial Stirling pulse tube cryocooler with an active displacer has been developed. An active displacer, in place of an inertance tube, has already demonstrated good efficiency in an in-line pulse tube, but incorporating this design into a coaxial configuration permits better access to the cold head. A model of the coaxial cold head was developed to include the radial flow and cooling in this region. The sub-assembly models were validated with flow testing of the physical sub-units of the cryocooler. The performance has been predicted for the cryocooler as a function of: fill pressure, operating frequency, and phase angle between the position of the linear compressor and displacer. The projected difference in performance and efficiency of the coaxial configuration was compared to the in-line design. The coaxial cryocooler numerically simulates 6 W of cooling at 80 K with an input power of 85 W, at a fill pressure of 28 bar, an operating frequency of 60 Hz, and a compressor-displacer phase angle of 41°. Overall, the coaxial cryocooler outperforms the in-line design in terms of cooling power, but not in terms of efficiency.

Investigation of a coaxial Stirling-type pulse tube cryocooler with the cooling capacity of 600 W at 77 K

This paper conducts the investigation of a coaxial Stirling-type pulse tube cryocooler (SPTC) with the cooling capacity of 600 W at 77 K, in which a two-dimensional CFD model is established and the effects of the flow are studied. With the aimed high cooling capacity, the flow straighteners at both inlet and outlet of the pulse tube become crucial to ensure the cooling performance by minimizing the turbulence flows in it. The interaction of the pulse tube cold finger and the linear compressor is investigated in view of that the match between them plays an important role in improving the cooling performance. In the experiment, the SPTC has a cooling capacity of 580 W at 77 K with the relative Carnot efficiency of 12%.

Modelling and experimental study of a 700 g micro coaxial Stirling-type pulse tube cryocooler operating at 100-190 Hz

This paper presents the modelling and experimental study of a 700 g micro coaxial Stirling-type pulse tube cryocooler (SPTC) operating at 100-190 Hz. Neither double-inlet nor multi-bypass is used while the inertance tube with a gas reservoir becomes the only phase-shifter. A two-dimensional axis-symmetric CFD model of the micro SPTC is developed, in which the effect of frequency on the thermal process and cooling performance is studied in detail. Mixed regenerator matrices are used to decrease the irreversible loss, and a variety of approaches to minimize the overall cooler mass are attempted. The experimental results show that the SPTC could produce cooling power of 1.1 W at 77 K with an input power of 60 W.

A 15K two-stage gas-coupled Stirling-type pulse tube cryocooler

A gas-coupled two-stage Stirling-type coaxial pulse tube cryocooler (SPTC) driven by a dual opposed-piston configuration linear compressor was designed and experimental test. Both of the two stages adopted coaxial structure for compactness. At the cold end of first stage, a part of working gas was introduced to the regenerator of second stage, while the others were returned to the pulse tube of the first stage. A lowest temperature of 7.3 K and 0.3 W/15 K cooling capacity can be achieved with 250 W PV power by simulation. At present, a lowest temperature of 8.1 K and 0.56 W/15 K cooling capacity can be achieved with 600 W the input power. The influence of the frequency, amplitude of the positon and the hot end temperature were studied. This paper presents the simulation results and primary test results of the designed cryocoolers.

A high efficiency coaxial pulse tube cryocooler operating at 60 K

In recent years, improved efficiency of pulse tube cryocoolers has been required by some space infrared detectors and special military applications. Based on this, a high efficiency single-stage coaxial pulse tube cryocooler which operates at 60 K is introduced in this paper. The cryocooler is numerically designed using SAGE, and details of the analysis are presented. The performance of the cryocooler at different input powers ranging from 100 W to 200 W is experimentally tested. Experimental results show that this cryocooler typically provides a cooling power of 7.7 W at 60 K with an input power of 200 W, and achieves a relative Carnot efficiency of around 15%. When the cooling power is around 6 W, the cryocooler achieves the best relative Carnot efficiency of around 15.9% at 60 K, which is the highest efficiency ever reported for a coaxial pulse tube cryocooler.

Effect of Low Temperature on a 4 W/60 K Pulse-Tube Cryocooler for Cooling HgCdTe Detector

Temperature is an extremely important parameter for the material of the space-borne infrared detector. To cool an HgCdTe-infrared detector, a Stirling-type pulse-tube cryocooler (PTC) has been developed based on a great deal of numerical simulations, which are performed to investigate the thermodynamic behaviors of the PTC. The effects of different low temperatures are presented to analyze different energy flows, losses, phase shifts, and impedance matching of the PTC at a temperature range of 40–120 K, where woven wire screens are used. Finally, a high-efficiency coaxial PTC has been designed, built, and tested, operating around 60 K after a number of theoretical and experimental studies. The PTC can offer a no-load refrigeration temperature of 40 K with an input electric power of 150 W, and a cooling power of 4 W at 60 K is obtained with Carnot efficiency of 12%. In addition, a comparative study of simulation and experiment has been carried out, and some studies on reject temperatures have been presented for a thorough understanding of the PTC system.

CFD modeling and experimental verification of oscillating flow and heat transfer processes in the micro coaxial Stirling-type pulse tube cryocooler operating at 90–170 Hz

This paper presents the CFD modeling and experimental verifications of oscillating flow and heat transfer processes in the micro coaxial Stirling-type pulse tube cryocooler (MCSPTC) operating at 90–170 Hz. It uses neither double-inlet nor multi-bypass while the inertance tube with a gas reservoir becomes the only phase-shifter. The effects of the frequency on flow and heat transfer processes in the pulse tube are investigated, which indicates that a low enough frequency would lead to a strong mixing between warm and cold fluids, thereby significantly deteriorating the cooling performance, whereas a high enough frequency would produce the downward sloping streams flowing from the warm end to the axis and almost puncturing the gas displacer from the warm end, thereby creating larger temperature gradients in radial directions and thus undermining the cooling performance. The influence of the pulse tube length on the temperature and velocity when the frequencies are much higher than the optimal one are also discussed. A MCSPTC with an overall mass of 1.1 kg is worked out and tested. With an input electric power of 59 W and operating at 144 Hz, it achieves a no-load temperature of 61.4 K and a cooling capacity of 1.0 W at 77 K. The changing tendencies of tested results are in good agreement with the simulations. The above studies will help to thoroughly understand the underlying mechanism of the inertance MCSPTC operating at very high frequencies.

Numerical analysis of miniature coaxial Stirling type pulse tube cryocooler with a modified reservoir

A Numerical model of a compact coaxial Stirling pulse tube cryocooler with a cooling capacity not less than 2W at 80K is done. The performance characteristics with varying geometrical parameters are simulated. The Inertance Pulse Tube Cryocooler (IPTC) with a modified reservoir is suggested, where the reverse fluctuation of pressure in the compressor case is used instead of the steady pressure in the reservoir to shift the phase of the flow velocity the hot end of the pulse tube. Therefore, the large reservoir volume of the cryocooler could be reduced, to make the cryocooler compact. The performance of the cryocooler was investigated and compared with the IPTC. The simulation results show that the cryocooler with modified reservoir can work as efficient as inertance type pulse tube cryocooler.

Numerical analysis of inertance pulse tube cryocooler with a modified reservoir

Pulse tube cryocoolers are used for cooling applications, where very high reliability is required as in space applications. These cryocoolers require a buffer volume depending on the temperature to be maintained and cooling load. A miniature single stage coaxial Inertance Pulse Tube Cryocooler is proposed which operates at 80 K to provide a cooling effect of at least 2 W. In this paper a pulse tube cryocooler, with modified reservoir is suggested, where the reverse fluctuation in compressor case is used instead of a steady pressure in the reservoir to bring about the desired phase shift between the pressure and the mass flow rate in the cold heat exchanger. Therefore, the large reservoir of the cryocooler is replaced by the crank volume of the hermetically sealed linear compressor, and hence the cryocooler is simplified and compact in size. The components of the cryocooler consist of a connecting tube, aftercooler, regenerator, cold heat exchanger, flow straightener, pulse tube, warm heat exchanger, inertance tube and the modified reservoir along with the losses were designed and analyzed. Each part of the cryocooler was analysed using SAGE v11 and verified with ANSYS Fluent. The simulation results clearly show that there is 50% reduction in the reservoir volume for the modified Inertance pulse tube cryocooler.