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This paper will introduce our recent experimental results of cryogenic regenerator materials employed in Stirling-type one-stage pulse-tube refrigerator for the use at liquid hydrogen temperature. Thermal diffusion coefficient, according to which we choose the suitable regenerator materials, will prove to be a useful reference. We will also discuss...
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... in low-frequency refrigerator such as G-M PTR. Questions emerge when spheres materials are employed in STPTR, such as the choice of suitable size and larger flow resistance to be overcome. In this paper, we address these questions in our lab-made Stirling- type one-stage coaxial PTR used for 20 K temperature range. The Schematic is shown in Fig.1. (a). The pulse tube is driven by a home-made linear compressor through a long tube. The cold head flange can be opened up conveniently to replace the regenerator. The detailed structure, including components to adjust phase relationship can be found in the reference Chen et al. (2013). When the whole second-segment regenerator employs SS ...
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... where SS represents stainless steel wire-mesh and Pb, Er 3 Ni, HoCu 2 always appear in the form of spheres. Below 40 K, Pb, Er 3 Ni, HoCu 2 have an advantage over SS in higher specific heat capacity and thus are dominant in this temperature range. Here, we employed these three sphere materials in lab-made 20.4 K no-load temperature STPTR ( Fig. 1. (a)) and tested the performance. First, the principle to choose the suitable material will be introduced. Where T 1 is the amplitude of the temperature oscillating, ƒ is the oscillating frequency, we obtain the formula describing the internal temperature field after solving the energy ...
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Citations
... Magnetic materials such as Er 3 Ni and Gd 2 O 2 S(GOS) spheres replace Stainless steel and copper wire mesh screens for applications below the liquid hydrogen temperature range. 44,45 Yang et al. 46 measured the apparent thermal conductivities of regenerators¯lled with sphere-type (GOS, HoCu 2 , Er 3 Ni and lead) and mesh-type materials. They reported that the apparent thermal conductivities of these regenerators decrease with the decrease in the temperature. ...
Miniature Stirling coolers are preferred to provide cryogenic cooling for infra-red (IR) sensors used for communication, military, and space applications. They provide 0.25–1.5[Formula: see text]W of cooling effect at 60–80[Formula: see text]K. Miniature Stirling coolers used for space applications are time tested, reliable, and have the maximum COP compared to other types of coolers. Helium is used as the working fluid because of its low boiling point, high thermal conductivity, high ratio of specific heat, and inert gas properties. A regenerator is the primary heat exchanger in the system, which periodically exchanges heat with the cold and hot gases passing through the regenerator material. The effectiveness of the regenerator is the most important parameter influencing the cooling effect produced by the system. For the optimum performance of the cryocooler, the regenerator should have maximum heat transfer area, minimum void volume, minimum pressure drop, large heat capacity ratio between the matrix material and gas, and minimum longitudinal conduction. Since some of these requirements are conflicting in nature, the design of the regenerator becomes a challenge in the overall design of the cooler. A state-of-the-art review of regenerator materials, designs, and operation is presented in this study. The different sources of regenerator losses and the issues related to regenerator design and optimization are discussed in detail. Results of various experimental and numerical investigations conducted on a Stirling regenerator are discussed and the recent developments in material selection and design are highlighted.
... To a lesser degree, the focus was on the application studies for space electronics [66], free-piston refrigerators [67], split-types coolers [68], Vuilleumier coolers [69], and hybrid coolers [70]. Occasionally the research activities reported on the studies of regenerators [71], magnetic drives [72] and reliability questions [73]. The ...
The importance of developing competitive commercial energy systems for the economy cannot be overstated. Existing research in design literature indicates that the question of how to carry out technical development of commercial science-intensive energy conversion technologies is covered inadequately. To cover this gap, the present thesis proposes a novel design methodology, which was validated by a real commercial development process of an energy conversion system based on the thermodynamic Stirling cycle. The design methodology contains five new design methods, each concerned with how to choose among alternative design configurations at different design stages. The first method offers an approach to a literature review at the conceptual design stage for Stirling systems using big data technologies. The second method describes an approach to perform trade studies at the system design stage for commercial Stirling machine configurations. The third method applies game theory to improve interactions between designers during the detail design stage and reduce negative influence of designers' collaborative decision-making on the design process outcomes. The fourth method shows how to improve the critical performance characteristics of the Stirling machines experimentally during testing stage, based on the example of the piston-cylinder sealing mechanism in a Stirling refrigerator. And the fifth method focuses on the problem of scaling the Stirling machine at the stage of scale-up by developing an experimentally validated numerical model using the example of the Stirling refrigerator. The application of the proposed design methods provides several insightful results. For example, the literature review shows that many existing designs of commercial Stirling machines for on-Earth civil applications are disadvantageously based on the design configuration that was initially developed for space applications. The results of trade studies indicate that alpha-type engines are better suited for high-power applications and beta-type-for high-efficiency applications. Game theory analysis shows that inappropriate designers' decision-making can lead to design outcomes with key perforce metrics 20% worse than the global optimum design. Experimental optimization shows that the choice of the sealing mechanism can significantly limit the commercial applications of the Stirling refrigerator due to its high-stress operation and complex behavior. Finally, the scale modeling, in combination with experimental data for the Stirling refrigerator, shows that its cooling performance demonstrates an exponential dependence from the cooling temperature. This relation is critical for accurate technology scaling. The results of this work show the possibility to apply the proposed design methodology to the development process of other energy conversion technologies. The work formulates a simple visual model that integrates key aspects of developed design methods and is named the Pentagon Model. This model can be used in the commercial development process of other science-intensive energy conversion systems, apart from Stirling machines.
... Introduction HFPTC has been proved to be a widely applicable cooling technology which guarantees the high reliability, low noise and long life [1] . A lowest temperature of 13.9 K has been reached by a single stage HFPTC [2] . However, in order to get a lower temperature a multi-stage configuration should be adopted. ...
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.
... In comparison with the traditional regenerative coolers such as G-M and Stirling coolers, the pulse tube cooler with no moving parts in low temperature region has the advantages of simple structure, high reliability, low mechanical vibration and low cost [1]. In retrospect, the quick development of Stirling type pulse tube coolers in the past two decades mainly benefited from the improvements of phase shifters [2][3][4] and regenerators [5][6][7]. On the other hand, the heat exchangers are also important. Insufficient heat transfer inside both ambient heat exchangers and cold end heat exchangers will influence the system performance seriously. ...
Improving the performance of the pulse tube cooler is one of the important objectives of the current studies. Besides the phase shifters and regenerators, heat exchangers also play an important role in determining the system efficiency and cooling capacity. A series of experiments on a 10 W @ 77 K class co-axial type pulse tube cooler with different cold heat exchanger geometries are presented in this paper. The cold heat exchangers are made from a copper block with radial slots, cut through using electrical discharge machining. Different slot widths varying from 0.12 mm to 0.4 mm and different slot numbers varying from around 20–60 are investigated, while the length of cold heat exchangers are kept the same. The cold heat exchanger geometry is classified into three groups, namely, constant heat transfer area, constant porosity and constant slot width. The study reveals that a large channel width of 0.4 mm (about ten times the thermal penetration depth of helium gas at 77 K, 100 Hz and 3.5 MPa) shows poor performance, the other results show complicated interaction effects between slot width and slot number. These systematic comparison experiments provide a useful reference for selecting a cold heat exchanger geometry in a practical cooler.
Magnetic properties, thermal expansion, heat capacity, and electrical resistivity of the cluster-glass compound Er4.8Pd2 and its paramagnetic isostructural counterpart Lu4.8Pd2 have been studied in the temperature range 2–300 K and in applied magnetic fields up to 140 kOe. Short-range antiferromagnetic (AFM) correlations of localized magnetic moments of Er³⁺ ions were found to develop in Er4.8Pd2 on cooling below T* ≈ 40 K. A cluster-glass magnetic state was observed below freezing temperature Tf ≈ 13.3 K, while Lu4.8Pd2 showed paramagnetic behavior. The crystal electric field (CEF) was found to substantially affect both the heat capacity and the thermal expansion of Er4.8Pd2. The CEF splitting of the Er³⁺ ion multiplet ⁴I15/2 was estimated to be as high as 280 K with a doublet ground state. Both the Schottky-type anomaly and short-range antiferromagnetic order contributions were found to give rise to a large volumetric heat capacity of Er4.8Pd2 at low temperatures. High direct magnetocaloric effect with −ΔSM(T)60kOe = 18.8 J mole⁻¹ K⁻¹ was confirmed to exist in Er4.8Pd2 while no inverse magnetocaloric effect was observed at low temperatures. Electrical resistivity of Er4.8Pd2 revealed a non-metallic behavior at low temperatures which was ascribed to an inhomogeneous electronic state due to the formation of clusters with the AFM short-range correlations.
Biocomposites or green composites are mainly defined as mixture of two or more components in which any building raw materials possess large quantity as matrix and natural fibers possess in smaller quantity as reinforcement. Due to the increase in greenhouse gas emissions and the global energy crisis, the demand for composites with natural fibers and biodegradable resins is increasing due to its low cost, renewable nature, and biodegradability. This paper presents the most comprehensive review on recent studies and development of natural fibers which includes animal-based fibers and various types of plant-based fibers and their potential applications in building materials and construction.KeywordsBiocompositesMatrixNatural fibersReinforcementBiodegradable resins
This paper presents a comparison and solution of the regenerator’s material of stirling-type pulse tube cryocooler. Here, a method of precisely controlling temperatures using different materials for regenerator in stirling-type pulse tube cryocooler (SPTC) has been studied and compared to a conventional cryosystem. The main aim is to focus on the cooling performance and to suggest best the optimal filling proportion for regenerator of SPTC. The main contribution of this work lies in the comparative study of different regenerator’s material for SPTC. The study shows that the system uses meshes of stainless steel along with Pb for the first stage regenerator and HoCu2, Er3Ni, Pb, and SS meshes in the volume percentage ratio 27:27:27:19 for the second stage regenerator give a good specific heat. This study shall help the policymakers to choose the best criteria, while formulating a newer edition of SPTC.KeywordsRegeneratorSPTCRegenerator’s materialCryocooler
The axial heat leakage between the cold and hot ends of the regenerator caused by the huge temperature difference is an important part of the cryocooler loss, where the apparent thermal conductivity of regenerator materials is the key parameter that determines the heat leakage. At present, only the apparent thermal conductivity of stainless steel wire mesh, lead and copper sphere above 80 K can be obtained, while measurement results for lower temperatures or other materials are currently not available. A low-temperature apparent thermal conductivity measurement apparatus for regenerator materials has been developed, and the apparent thermal conductivities of sphere-type material (GOS, HoCu2, Er3Ni, and lead), mesh-type material (stainless steel wire mesh), and helium-4 under various pressures have been measured. When the regenerator is in a vacuum state (below 10⁻⁴ Pa), the experimental results show that the thermal conduction factors (the ratio of the apparent thermal conductivity of the filled regenerator to that of the material itself) are 0.02 for GOS in 4-10 K temperature range, 0.28 for HoCu2, 0.43 for Er3Ni in 4-20 K temperature range, 0.005 for lead sphere and 0.13 for stainless steel wire mesh in 10-40 K temperature range, respectively. However, when the regenerator is filled with helium-4, the thermal conduction factor values increase by one order of magnitude.
this paper investigates the performance of a gamma-type Stirling refrigerator. The proposed refrigerator has a shell and tube condenser and evaporator. In the proposed refrigerator, a wire net regenerator is suggested. The working fluid is selected to be Helium. A drive mechanism controls the synchrony of the reciprocation of both the displacer and the piston. A computer program in the form of a spreadsheet is prepared to solve the refrigerator cycle numerically. The results get the more suitable dimensions of the evaporator, the condenser, the regenerator, the more suitable piston diameter to bore ratio, and the cooling capacity increases continuously with the rotational speed where the COP has a maximum value. The refrigerator develops 0.011596 TR/cc, COP = 0.5597, at 600 rpm and p = 2 bar. The comparison among the present work and previous ones shows that; the present refrigerator explores an enhancement in COP up to 100%, especially at low-speed levels.
