Performance Of Cryocooler Research Articles

Development of miniature Stirling cryocooler technology for Infrared Focal Plane array

A reliable miniature cryocooler is one of the basic and foremost requirements for successful operation of high performance cooled infrared focal plane array (IRFPA) used for defence applications. Technological complexity and requirement of long duration fail-safe operation of the cryocooler demands robust design, fabrication and assembly with tolerances and, perfection of an array of sub-technologies. The paper presents the progress of the development activities in Stirling cryocooler technology at SSPL, which evolved through essential milestones like the development of single and dual piston linear motor driven split coolers to the state-of-the-art integral Brushless DC (BLDC) motor crank-driven type highly miniaturized coolers of capacities ranging from 0.25 to 0.5W at 80K. The theoretical investigations in the design of Stirling cycle cryocooler have been reported and the issues related to the design aspects are discussed in sufficient details. Experimental results of cryocooler performance tests are also presented. The paper also focuses on regenerator design optimization. The results of optimizations have been shown at the end considering a sample data. Defence Science Journal, 2013, 63(6), pp. 571-580 , DOI:http://dx.doi.org/10.14429/dsj. 63.5756

Numerical analysis on performance and contaminated failures of the miniature split Stirling cryocooler

A mathematical model based on thermodynamic theory of variable mass is developed for the split Stirling refrigerator, in which, the whole machine is considered by one-dimensional approach while the processes in the regenerator are simulated by two-dimensional approach. First, the influence of the ideal frost layer distributions on the flow and heat transfer in the regenerator and the performance of the Stirling cryocooler are simulated. Then, the distribution of the contaminated water vapor and its coagulated and deposited process is qualitatively analyzed. Finally, the lifetime of the refrigerator is evaluated based on the calculated data. The results show that when the refrigerator is operated at uniform distribution of the water vapor partial pressure in the regenerator, the cooling capacity is reduced over 10% at about 631h, and the power consumption of compressor is increased over 20% at about 1168h. However, for the linear distribution of water vapor partial pressure, the refrigerator can work properly because the frost never reaches the criterion of failure. Also, it is found that when the Stirling cryocooler restarts after a shutdown, the cooling capacity is reduced by 10% once the frost mass is over 7.05mg, and there is no cooling capacity once the frost mass reaches 41.2mg.

LBM numerical study on oscillating flow and heat transfer in porous media

Oscillating flow and heat transfer in regenerative cryocoolers, are very important for the optimization of cryocooler's performance. A numerical study was conducted in such a system by Lattice Boltzmann Method (LBM), which is an efficiently new way compared to that of the traditional continuum Navier–Stokes method. The simulation work was firstly developed in a two-dimensional empty planar channel, and then followed by porous media. The oscillating flow is driven by a periodic pressure wave, with the isothermal or adiabatic planar wall. A coupled double distribution function model, which is one of the typical thermal LBMs, is used to investigate the thermo-hydrodynamics problem. As a key step, the extrapolation and bounce back schemes are used to treat the boundaries. The simulation results have shown a great effectiveness of the implementation of the LBM in the present study. LBM would serve as a promising method for predicting flow and heat transfer characteristics in regenerative cryocoolers, such as pulse tube cryocoolers. In this work, the effects of the characteristic system parameters on the fluid flow and the heat transfer are investigated. Detailed information for system behavior, especially in porous media, are also included in this paper.

Investigation of synchronous effects of multi-mesh regenerator and double-inlet on performance of a Stirling pulse tube cryocooler

In this paper synchronous effects of multi-mesh regenerator and double-inlet on performance of a Stirling pulse tube cryocooler (SPTC) have been considered. In this respect, a finite volume code was developed to simulate the SPTC. Set of governing equations were written in a general form such that all porous and non-porous sections of the system could be modeled. Results showed that synchronous application of double inlet and multi-mesh regenerator optimizes the phase shift between velocity and pressure at the warm end of the pulse tube, increases the regenerator’s outlet pressure amplitude, decreases inertial and viscous losses in the hot end of the regenerator and consequently increases the COP of the system. Furthermore, it was observed that a minimum temperature of 60.3K and COP of 0.03996 @ 80K is attainable using optimum multi-mesh regenerator and double inlet; whereas, for a simple SPTC with a uniform mesh regenerator, a minimum temperature of 71.3K and maximum COP of 0.0227 @ 80K are concluded.

Performance improvement of multi-stage pulse tube cryocoolers with a self-precooled pulse tube

Reducing the pulse tube losses is significant for improving the cooling performance of pulse tube cryocoolers (PTCs) in particular for multi-stage ones, although ignored to a certain extent. A simple method called self-precooled pulse tube for multi-stage PTCs is comprehensively studied in order to reduce the entropy flow inside the pulse tube. Different from the complex multi-bypass or extra cryocooler or cryogens for precooling, the key of the idea is to directly precool some part of the lower stage pulse tube by using a small amount of cooling power from the upper stage through a thermal bridge. A two-stage separate Stirling PTC was chosen to demonstrate the effects of self-precooled pulse tube. Theoretical calculation showed that both the precooling temperature and position of the pulse tube affected the performance of the cryocooler. The experiment results showed that the cooling performance of the second stage with self-precooled pulse tube was remarkably improved as the bottom temperature decreased from 26.60K to 18.02K. The cooling power was notably increased with minor performance reduction of the first stage. By further optimizing the operation parameters, a no-load temperature of 15.87K was achieved, which is the lowest temperature ever obtained by a two-stage Stirling PTC with only an inertance shifter. The study proves that the precooled pulse tube can help hot end heat exchanger reject the heat inside pulse tube, reduce the heat losses of the cold end and consequently improve the cooling performance of the cryocooler.

Effect of Regenerator Entrance Shape on Performance of Compact Pulse Tube Cryocooler

Pulse tube cryocoolers are more attractive than other small cryocoolers because they have no moving parts in the expander and thus have higher reliability. However, Stirling type pulse tube cryocooler needs further improvement on regenerator. The entrance areas at the regenerator ends of the typical pulse tube cryocooler are smaller than the cross-sectional area of the regenerator matrix. So, the working gas flow in the regenerator has non-uniform velocity distribution with the expansion and contraction flow. They cause the excessive pressure loss and reheat loss. In this study, the effect of the regenerator entrance shape on the performance of compact pulse tube cryocooler was examined experimentally. Additionally, the analytical method for losses in the regenerator using experimental data is suggested. Experimentally and analytically, the effect of after-cooler end at the regenrator has been bigger than that of cold-head end.

Finite heat-capacity effects in regenerators

This paper deals with the influence the finite heat capacity of the matrix of regenerators on the performance of cryocoolers. The dynamics of the various parameters is treated in the harmonic approximation focussing on the finite heat-capacity effects, real-gas effects, and heat conduction. It is assumed that the flow resistance is zero, that the heat contact between the gas and the matrix is perfect, and that there is no mass storage in the matrix. Based on an energy-flow analysis, the limiting temperature, temperature profiles in the regenerator, and cooling powers are calculated. The discussion refers to pulse-tube refrigerators, but it is equally relevant for Stirling coolers and GM-coolers.

A three-stage Stirling pulse tube cryocooler operating below the critical point of helium-4

Precooled phase shifters can significantly enhance the phase shift effect and further improve the performance of pulse tube cryocoolers. A separate three-stage Stirling pulse tube cryocooler (SPTC) with a cold inertance tube was designed and fabricated. Helium-4 instead of the rare helium-3 was used as the working fluid. The cryocooler reached a bottom temperature of 4.97 K with a net cooling power of 25 mW at 6.0 K. The operating frequency was 29.9 Hz and the charging pressure was 0.91 MPa. It is the first time a refrigeration temperature below the critical point of helium-4 was obtained in a three-stage Stirling pulse tube cryocooler.

Performance of cryogenic regenerator with 3He as working fluid

Almost all experimental and theoretical studies on regenerative cryocoolers at temperatures below 20 K mention the use of 4He as working fluid. A preliminary qualitative evaluation indicates that because of the superfluid phase transition, a working fluid of 3He would overcome the cooling temperature limitation set by 4He. Starting with a comparison of the thermophysical properties of 3He and 4He, cryogenic regenerator simulations applied to the third/last stage of a pulse tube refrigerator, with 3He and 4He separately, were implemented to quantitatively analyze performance differences of the regenerator with respect to regenerator loss, cooling power and COP. Results conclude that 3He could significantly improve the performance of a regenerative cryocooler.

Optimal performance of regenerative cryocoolers

The key component of a regenerative cryocooler is its regenerative heat exchanger. This device is subject to losses due to imperfect heat transfer between the regenerator material and the gas, as well as due to viscous dissipation. The relative magnitudes of these losses can be characterized by the ratio of the Stanton number St to the Fanning friction factor f. Using available data for the ratio St/ f, results are developed for the optimal cooling rate and Carnot efficiency. The variations of pressure and temperature are taken to be sinusoidal in time, and to have small amplitudes. The results are applied to the case of the Stirling cryocooler, with flow being generated by pistons at both sides of the regenerator. The performance is found to be close to optimal at large ratio of the warm space volume to the regenerator void volume. The results are also applied to the Orifice Pulse Tube Refrigerator. In this case, optimal performance additionally requires a large ratio of the regenerator void volume to the cold space volume.

C02 パルス管冷凍機性能に及ぼす蓄冷器出入口形状の影響(パルス管冷凍機,熱音響機器及び関連要素と応用システム(1))

Pulse tube cryocoolers are more attractive than other small cryocoolers because they have no moving parts in the expander and thus have higher reliability. Stirling type pulse tube cryocooler need further improvement, on especially, regenerator. The working gas flow in the regenerator becomes a flow field with non-uniform velocity distribution accompanying the expansion and contraction flow. They cause the excessice pressure loss and reheat loss. We examined the effect of the regenerator entrance shape on the performance of pulse tube cryocooler experimentally. The effect of after-cooler end was bigger than that of cold-head end.

Cryocoolers: the state of the art and recent developments**Contribution of NIST; not subject to copyright in the US.

Cryocooler performance and reliability are continually improving. Consequently,they are more and more frequently implemented by physicists in their laboratoryexperiments or for commercial and space applications. The five kinds of cryocoolersmost commonly used to provide cryogenic temperatures for various applicationsare the Joule–Thomson, Brayton, Stirling, Gifford–McMahon, and pulse tubecryocoolers. Many advances in all types have occurred in the past 20 years that haveallowed all of them to be used for a wide variety of applications. The present stateof the art and on-going developments of these cryocoolers are reviewed in thispaper. In the past five years new research on these cryocoolers has offered thepotential to significantly improve them and make them suitable for even moreapplications. The general trend of this new cryocooler research is also presented.

Study on the phase shift characteristic of the pneumatic Stirling cryocooler

Due to entire pneumatic connection between free piston and free displacer, the motion parameters of them including amplitude and phase shift can actually impact the cooling capacity and overall performance of cryocooler obviously. In this study, the procedure of design and manufacture pneumatic free piston and free displacer (FPFD) Stirling cryocooler had firstly been described in details. Then in order to accomplish study, the experimental bench has been set up based on 80 K@1 W Stirling cryocooler. The effect of the thermodynamic and pneumatic parameters including charging pressure, natural frequency of displacer, damping coefficient of displacer, working frequency on the pressure, displacement and displacer phase shift has been investigated, respectively by means of experimental and theoretical method. In particular, the variation of damping is realized by adjusting the width of clearance cut on the additional damping component, which is screwed on the displacer rod. Similarly, natural frequency of displacer is changed by the extra mass connected on the displacer. Due to the results of experimental study, the optimum working conditions of this Stirling cryocooler for 80 K cold tip temperature are as follows: charge pressure 15 bar, natural frequency of displacer 46 Hz, width of clearance 300 μm and working frequency 43 Hz. In agreement with the optimum working conditions, neighborhood interval of 90° is the ideal working domain for displacement phase shift. Meanwhile, the displacer phase shift should approach to 0°as near as possible and pressure phase shift should also be as small as possible, which have linear relation with non-dimensional damping characteristic of compressor. In view of theoretical study, the expressions of three phase shifts deduced from thermodynamic equation of piston and displacer respectively are expressed as the functions of working parameters, which are verified by the experimental data and consequently can be used as the powerful guidance to optimum seeking.

Second law based modeling to optimum design of high capacity pulse tube refrigerators

The optimum design of a high capacity double inlet pulse tube refrigerator based on second law of thermodynamics has been presented in this paper. Second law is applied to calculate the work loss in the regenerator and to optimize the cryocooler performance. To investigate the behavior of the pulse tube refrigerator, mass and energy balance equations are applied to several control volumes of the cryocooler cycle. A complete system of conservation equations is employed to solve the regenerator analytically. The proposed model reports the cooling capacity of 110 W at 80 K cold end temperature at frequency of 50 Hz, orifice conductance of 0.4 and double inlet coefficient of 0.6, with 2.4 kW net power delivered to the gas. In this case, the entropy generation in the gas phase is dominant which is contributing more than 85% of the total lost work in the regenerator. The optimum thermal efficiency of 99.1% was achieved at a proper mesh number. However, the second law efficiency is reported to have an inverse behavior at this mesh number.

Improving the performance of small Joule–Thomson cryocooler

This paper presents a new cycle for improving the performance of small Joule–Thomson (JT) cryocooler by applying an additional ejector in cycle system. Based on the presented JT cycle with an additional ejector (JTE), the performance of small JT cryocooler operating with pure N 2 and the mixture N 2−CH 4 for cryogenic applications in a temperature range of 80–130 K is investigated by theoretical calculations. It can be found that the refrigeration efficiency of the JTE cryocooler operating with pure N 2 increase by 55.6–25.1%, and the refrigeration capacity increase by a factor of 4.9–1.5 compared to a conventional JT cryocooler. Similar performance improvements are also obtained when the mixture N 2−CH 4 is used as the working gas. The refrigeration efficiency increase by 46.6–17.7% and the refrigeration capacity increase by a factor of 3.8–1.3. It is concluded that the performance of small JT cryocooler can be significantly improved based on the presented JTE cycle.

Improvement in performance of cryocoolers as condensers

Modifications to the cold head of a Cryomech PT410 pulse tube cryocooler, being used as a helium condenser, have led to an increase in liquefaction rate from 12.8 to 21.4 L/day. These modifications are the first experimental results from attempts to enhance the use of natural convective heat transfer to precool the helium vapour prior to liquefaction.

Thermodynamic performance of a laser cryocooler

The quantum dynamic action of a laser cooling system is analyzed by means of a simplified luminescence center model with ground state and excited state in this paper. The thermodynamic performance of a laser cryocooler is described by solving quantum master equation. The cooling load and the coefficient of performance of the cooler are obtained by using finite time thermodynamics. Some features of the system under the weak coupling and under the intense coupling conditions are discussed.

Developments in reverse Brayton cycle cryocooler in China

As one of the primary methods of cryogenic refrigeration, reverse Brayton cycle cryocooler, which includes high-speed turbine using gas bearing and compact heat exchanger, has many advantages such as long-life, high reliability and efficiency. In this paper general aspects of reverse Brayton cycle cryocooler in China are introduced, such as its application in the space simulation program, mechanical cryocooler for lower temperature space applications. The main design parameters and operating performance of cryocoolers are presented in this paper.

Thermal performance of the CrIS passive cryocooler

The configuration, performance, and test validation of a passive radiant cooler for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Crosstrack Infrared Sounder (CrIS) Instrument are presented. The cooler is required to provide cryogenic operation of IR focal planes. The 11 kg device, based on prior ITT Industries Space Systems Division coolers, requires virtually no power. It uses multiple thermally isolated cooling stages, each with an independent cryoradiator, operating at successively colder temperatures. The coldest stage, with a controlled set point at 81 K, cools a longwave IR (LWIR) focal plane. An intermediate stage, with a 98 K control point, cools detectors operating in MWIR and SWIR spectral regions. The warmest stage includes a fixed, integral earth shield that limits the thermal load from the earth in the NPOESS Operational Low-earth Orbiting (LEO) orbit. A study of the thermal balance and loads analysis used to evaluate the predicted cooler performance is discussed. High performance margins have been retained throughout the cooler development, fabrication and test phases of the program. The achievable in-orbit temperatures for this cooler are anticipated to be 73 K for the LWIR cooling stage and 91 K for the midwave IR (MWIR)/shortwave IR (SWIR) stage. Test results from two iterations of thermal vacuum verification testing are presented. Lessons learned from the first test, which failed to produce the predicted performance are included. The thermal model of the cooler and test configuration was used to identify deficiencies in the test targets resulting in unexpected heat loads. Corrective action was implemented to remove the heat leaks and a second test verified both the cooler performance and the correlation of the detailed thermal model.

Development of parallel wire regenerator for cryocoolers

This paper describes development of a novel regenerator geometry for cryocoolers. Parallel wire type is a wire bundle stacked in parallel with the flow in the housing, which is similar to a conventional parallel plate or tube. Simple and unique fabrication procedure is developed and fully depicted in this paper. Hydrodynamic and thermal experiments are performed to demonstrate the feasibility of the parallel wire regenerator. First, pressure drop characteristic of the parallel wire regenerator is compared to that of the screen mesh regenerator. Experimental result shows that the steady flow friction factor of the parallel wire type is three to five times smaller than that of the screen mesh type. Second, thermal ineffectiveness is determined by measuring the instantaneous pressure, the flow rate and the gas temperature at the warm and cold ends of the regenerator. The measured ineffectiveness of the parallel wire regenerator is larger than that of the screen regenerator due to the excessive axial conduction loss. To alleviate the intrinsic axial conduction loss of the parallel wire regenerator, segmentation is introduced and the experimental results reveal the favorable effect of the segmentation. Entropy generation calculation is adopted to compare the total losses between the screen regenerator and the parallel wire regenerator for various operating ranges. Simulation results show that the parallel wire regenerator can be an attractive candidate to improve cryocooler performance especially for the case of smaller NTU and lower cold-end temperature.