Progress on a novel VM-type pulse tube cryocooler for 4 K

VM type pulse tube cryocooler is a new type pulse tube cryocooler driven by the thermal-compressor. This paper presented the recent experimental results on a novel single-stage VM type pulse tube cryocooler with multi-bypass. The low temperature double-inlet, orifice and gas reservoir, and multi-bypass were used as phase shifters. With the optimal operating frequency of 1.6 Hz and optimal average pressure of 1.4 MPa, a no-load temperature of 4.9 K has been obtained and 30 mW@5.6 K cooling power has been achieved. It was the first time for the single-stage VM-PTC obtaining liquid helium temperature reported so far. Moreover, it was also the first time for the multi-bypass being used in the low-frequency Stirling type pulse tube cryocooler.     

A cryogen-free Vuilleumier type pulse tube cryocooler operating below 10 K

Vuilleumier (VM) type pulse tube cryocooler (PTC) utilizes the thermal compressor to drive the low temperature stage PTC. This paper presents the latest experimental results of a cryogen-free VM type PTC that operates in the temperature range below 10 K. Stirling type pre-coolers instead of liquid nitrogen provide the cooling power for the thermal compressor. Compared with previous configuration, the thermal compressor was improved with a higher output pressure ratio, and lead and HoCu₂ spheres were packed within the regenerator for the low temperature stage PTC for a better match with targeted cold end temperature. A lowest no-load temperature of 7.58 K was obtained with a pressure ratio of 1.23, a working frequency of 3 Hz and an average pressure of 1.63 MPa. The experimental results show good consistency in terms of lowest temperature with the simulation under the same working condition.     

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.     

High-efficiency 3 W/40 K single-stage pulse tube cryocooler for space application

Temperature is an extremely important parameter for space-borne infrared detectors. To develop a quantum-well infrared photodetector (QWIP), a high-efficiency Stirling-type pulse tube cryocooler (PTC) has been designed, manufactured and experimentally investigated for providing a large cooling power at 40 K cold temperature. Simulated and experimental studies were carried out to analyse the effects of low temperature on different energy flows and losses, and the performance of the PTC was improved by optimizing components and parameters such as regenerator and operating frequency. A no-load lowest temperature of 26.2 K could be reached at a frequency of 51 Hz, and the PTC could efficiently offer cooling power of 3 W at 40 K cold temperature when the input power was 225 W. The efficiency relative to the Carnot efficiency was approximately 8.4%.     

Experimental study on the coupling characteristics of 100 Hz inertance tube pulse tube cryocooler working under optimal frequcency

Miniature pulse tube cryocooler is one of the main developing trends of pulse tube cryocooler. Four pulse tube cold fingers, two compressors and a series of inerance tube assemblies are employed to carry out the experimental investigation of coupling characteristic of miniature pulse tube cryocooler. It is concluded that the cooling performance of miniature pulse tube cryocooler is determined by the match conditions among its compressor, cold finger and inertance tube. If the three parts of cooler match well, the cold finger can achieve nearly same cooling performance under two totally different working conditions.     

Investigation on phase shifter of a 10 W/70 K inertance pulse tube refrigerator

A 10 W/70 K inertance pulse tube refrigerator (IPTR) has been developed for cooling infrared focal-plane array in a space mission. To investigate the influences of the phase shifter (inertance tube and reservoir) on the cooling performance, simulation models of the IPTR were built and experimental studies were conducted. The effects of reservoir volume and the surface roughness inside the inertance tube on cooling performance of the IPTR were investigated in detail. The optimized parameters of the phase shifter were developed to improve the cooling performance of the IPTR. The results show that a large reservoir volume reduces the optimal operating frequency, decreases the losses in the regenerator and improves the cooling performance of the IPTR. Because of the small surface roughness inside the stainless steel inertance tube, the input electric power of the IPTR is decreased, with a cooling power of 10 W at 70 K. The IPTR achieves 14.75% of the relative Carnot efficiency at 70 K by optimizing the inertance tube and reservoir.     

Development of a 30–50 K dual-stage pulse tube space cooler

There has been a trend towards increasing heat loads for cryogenically cooled Earth Observation instruments in recent years.This is the case at both the current operational temperature levels (∼50K), as well as at lower operational temperature levels (30–50 K). One solution to meet this trend is to use existing pulse tube technology in a double stage configuration. With such technology increased cooling power at a lower temperature can be achieved at the payload detector. Another advantage of such a system is the possibility to increase overall system efficiency by cooling an intermediate shield to avoid parasitic heat losses towards the detector.Therefore a consortium consisting of Thales Cryogenics B.V. (TCBV), Alternative Energies and Atomic Energy Commission (CEA) and Absolut System (AS) is working on the development of a space cryostat actively cooled by a 2-stage high reliability pulse tube cryocooler. This work is being performed in the frame of an European Space Agency (ESA) Technical Research Program (TRP) (refer 4000109933/14/NL/RA) with a target TRL of 6.This paper presents the design of the overall equipped cryostat and cryostat itself but is mainly focused on the 2-stage cryocooler. Design, manufacturing and test aspects of cryocooler and its the lower level components such as the compressor and cold finger are discussed in detail in this paper. The cryocooler test campaign is meanwhile in final stages of completion and the obtained test results are in line with program objectives.     

Development and experimental investigation of Stirling-type pulse tube refrigerator (PTR) below 20 K; cold compressor and colder expander

This research paper focuses on the experimental investigation of the Stirling-type pulse tube refrigerator with cold compression concept. Due to this innovative feature, the pulse tube refrigerator can reach lower temperature effectively other typical single-stage Stirling-type pulse tube refrigerators. The experiment as a proof of concept is carried out to demonstrate the capability of the pulse tube refrigerator operating between 80 K and 20 K. The cold linear compressor, which is submerged in a liquid nitrogen bath, produces cold mass flow with the efficiency of 85% for all the frequencies. At the lowest temperature part of the pulse tube refrigerator, the no-load temperature of 18.7 K is recorded and the cooling power of 0.4 W is measured at 20 K. The experimental results are analyzed in dynamic and thermal aspects by using the numerical model. The model can well explain how much losses are distributed in the system.     

Study of 4, 4′-methylenebis-cyclohexanamine as a high temperature-resistant shale inhibitor

In order to develop high-performance water-based drilling fluid with the aim of meeting the increasing requirement of drilling industry, highly inhibitive and high-temperature-resistant shale inhibitors are essential. In this study, 4, 4′-methylenebis-cyclohexanamine was introduced as a potential shale inhibitor. The inhibitive properties of the amine compound in comparison with currently available polyether diamine inhibitor were evaluated using bentonite inhibition test, shale cuttings hot-rolling dispersion test, linear swelling test, and pressure transmission test. The inhibitive mechanism was investigated with zeta potential measurement, X-ray diffraction analysis, and contact angle measurement. The results indicated that 4, 4′-methylenebis-cyclohexanamine can inhibit shale hydration and dispersion effectively, and prevent pressure transmission to a certain extent, performing better than that of polyether diamine. Furthermore, the new diamine provides reliable thermal stability as high as 220 °C, preserving the benefits of high-temperature wells application. This novel diamine inhibits shale hydration and dispersion with the combination of chemical inhibition and physical plugging. The intercalation into the interlayer of clay with monolayer collapses the hydrated clay structure and expels the water molecules. After adsorption, clay surface became more hydrophobic, which prevents the imbibition of water. The variation of solubility separates the compound from the solution, which can plug the micro-pores of shale and prevent fluid invasion.     

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.     

Microstructure and mechanical properties of high purity nanostructured titanium processed by high pressure torsion at temperatures 300 and 77 K

Several structural states of nanostructured high purity Ti with average grain size down to 100 nm were achieved by high pressure torsion (HPT) at temperatures 300 and 77 K. As a result of HPT processing, changes of crystallographic texture, of grain and crystallite size, and of the dislocation density have been measured and analyzed. Mechanical properties of the nanostructured Ti were studied by uniaxial compression at temperatures 300, 77, and 4.2 K. The texture components indicate simple shear deformation arising from HPT. With subsequent compression, the yield strength appears to be governed by the grain size rather than by crystallite size, dislocation density, and/or impurity content. Considerable changes of texture were observed after low temperature compressive deformation indicating that twinning markedly contributes to plasticity.     

Study on Cure Behavior of a Model Epoxy System by Means of TTT Diagram

Duetotheirhighstrength,modulusandfracture toughnessaswellasgoodadhesionandthermalre sistance[1],epoxyresinsasmatricesarewidelyused inaeronautics,astronautics,transportation,sports andotherindustry.Standardepoxyresinsareusually basedonDGEBA(diglycidyletherofbisphenolA),whichneedsactivehydrogenorotheractivegroupsto opentwoepoxyrings.Four functionalepoxylike TGMDA(tetraglycidylmethylenedianiline)isoften usedforhigh performanceepoxymatrixcomposites becauseofitsrelativelyhighercross linkingdens…     

CFD modeling and experimental verification of a single-stage coaxial Stirling-type pulse tube cryocooler without either double-inlet or multi-bypass operating at 30–35 K using mixed stainless steel mesh regenerator matrices

This paper presents the CFD modeling and experimental verifications of a single-stage inertance tube coaxial Stirling-type pulse tube cryocooler operating at 30–35 K using mixed stainless steel mesh regenerator matrices without either double-inlet or multi-bypass. A two-dimensional axis-symmetric CFD model with the thermal non-equilibrium mode is developed to simulate the internal process, and the underlying mechanism of significantly reducing the regenerator losses with mixed matrices is discussed in detail based on the given six cases. The modeling also indicates that the combination of the given different mesh segments can be optimized to achieve the highest cooling efficiency or the largest exergy ratio, and then the verification experiments are conducted in which the satisfactory agreements between simulated and tested results are observed. The experiments achieve a no-load temperature of 27.2 K and the cooling power of 0.78 W at 35 K, or 0.29 W at 30 K, with an input electric power of 220 W and a reject temperature of 300 K.     

Errata to “The effect of an axial temperature gradient on the steady motion of a large droplet in a tube” by S. K. Wilson

Errata to The effect of an axial temperature gradient on the steady motion of a large droplet in a tube by S. K. Wilson J. Eng. Maths 29 (1995) 205–217     

Microstructure and mechanical properties of biocompatible high density Ti–6Al–4V/W produced by high frequency induction heating sintering

High frequency induction heating sintering method is used for sintering of the metal and ceramics powder. This technique has been used to produce high density compacts, containing as small grains as possible of powders. The alloy of Ti–6Al–4V was modified by addition of 2.5, 5, and 10 wt.% tungsten through powder metallurgy. Ti–6Al–4V/W was prepared by high-energy mechanical milling. The use of the high frequency induction heating sintering technique allows sintering to nearly full density at comparatively low temperatures and short holding times, and therefore suppressing grain growth. Different process parameters such as sintering temperature, and applied pressure have been investigated. The obtained compacts are characterized with respect to their densities, grain morphologies and pore distributions as well as hardness. Ti–6Al–4V/W powder precursors have been successfully compacted and consolidated to densities exceeding 98.8%. The maximum compressive strengths were obtained at sintering temperature 1000 °C for the samples containing 5% W, and at 1100 °C for the samples with 10% W. Maximum hardness was obtained 45 HRC at 1100 °C for 10% W.     

Specific heat capacity and electrical resistivity of a carbon-carbon composite in the range 1500–3000 K by a pulse heating method

Measurements are described of specific heat capacity and electrical resistivity of a 2-2-3 T-50 carbon-carbon composite in the temperature range 1500–3000 K by a subsecond duration pulse heating technique. The results are represented by the relations 1 $$C\rho = 1.691 + 2.598{\text{x10}}^{{\text{ - 4}}} T - 2.691{\text{x10}}^{{\text{ - 8}}} T^2 $$ 2 $$\rho = 733.0 + 6.594{\text{x10}}^{{\text{ - 2}}} T$$ where c _p is in J · g^?1 · K^?1, ρ is in ΜΩ · cm, and T is in K. Inaccuracy of specific heat capacity and electrical resistivity measurements is estimated to be not more than ±3%.     

Effect of frequency on very high cycle fatigue behavior of a low strength Cr–Ni–Mo–V steel welded joint

Axially fully-reversed fatigue test of a low strength Cr–Ni–Mo–V steel welded joint was conducted up to the very high cycle fatigue regime under the frequency of 110 Hz and 20 kHz. The S–N curve shows a duplex shape at low frequency while decreases continuously at high frequency. Sites of crack initiation and fracture of the welds depend on stress level and loading frequency, hence leading to changed fatigue strength. In addition, frequency effect varies among different parts of the welded joint and fatigue lifetime.     

SiO2 film deposition on the inner wall of a narrow polymer tube by a capacitively coupled μplasma

SiO₂ thin films were deposited on the inner wall of a narrow commercial poly(propylene) tube with inner/outer diameters of 1.0 mm/3.0 mm by plasma-enhanced chemical vapor deposition using He or Ar carrier gases and tetraethoxysilane (TEOS)/O₂ feedstock gases at high pressures from 30 kPa to atmospheric pressure and at room temperature. A glow μplasma was generated inside the tube by a radio frequency (RF 13.56 MHz) capacitively coupled discharge. X-ray photoelectron spectra and infrared spectra revealed that the inner surface of the plasma-treated tube was covered by a SiO₂ film. Scanning electron microscopy images indicated that the film produced by He/TEOS/O₂ μplasma had a smooth surface whereas the surface of the film produced by Ar/TEOS/O₂ μplasma appeared granulated. Typical deposition rates of approximately 300 nm/min were obtained by He/TEOS/O₂ μplasma at atmospheric pressure and a RF power of 11 W.     

Cu7.2S4 nanosheets decorated on the {3 3 2} high index facets of Cu2O with controllable oxygen defects and enhanced photocatalytic activity

The heterostructure of Cu_7.2S₄ nanosheets/trisoctahedron Cu₂O were successfully constructed on the {3 3 2} high-index facets of Cu₂O. The results show that oxygen defects amount of the Cu_7.2S₄/Cu₂O samples are closely related to the thickness of Cu_7.2S₄ nanosheets. Compared with the unmodified cuprous oxide and the Cu_7.2S₄/Cu₂O modified with thick Cu_7.2S₄ nanosheets, the Cu_7.2S₄/Cu₂O grafted with 10 nm thickness of Cu_7.2S₄ show higher oxygen defects content and photocatalytic performance for MO decoloration. UV–VIS DRS and PL detection show that the Cu_7.2S₄ nanosheets grafting on Cu₂O with high-index facets accelerates the charge carrier separation, which results in an elevated degradation properties for MO.