A regenerator material for use in a cryocooler and a regenerator and cryocooler incorporating the same

Abstract

The present invention relates to the field of cryogenic refrigeration technology, and particularly to a cold storage material for a cryogenic refrigerator, its cold storage device and refrigerator. The cold storage material is composed of Er a Pr b alloy, where a and b are atomic percentages, and 40 < a < 80, and the alloy does not contain lead. The cold storage device is filled with the above-mentioned Er a Pr b alloy as its entire cold storage material. The cryogenic refrigerator is equipped with the above-mentioned cold storage device. The purpose of the present invention is to solve the environmental and human health hazard problems caused by the use of lead in the existing cold storage materials for cryogenic refrigerators, and to achieve the technical effects of meeting the requirements of ROHS regulations and improving the refrigeration power.

Description

Technical Field

[0001] The present invention relates to the technical field of cryogenic refrigeration, and particularly to a cold storage material for a cryogenic refrigerator, a cold storage device thereof, and a refrigerator. Background Art

[0002] A cryogenic refrigerator is a device capable of generating extremely low temperatures and is widely used in fields such as superconducting technology, space technology, and medical equipment. In a cryogenic refrigerator, the cold storage material is one of the key components, and its performance directly affects the efficiency of the refrigerator and the lowest achievable temperature.

[0003] However, the main problem in the prior art is that below 50K, lead has a higher specific heat capacity than other materials and is therefore widely used as a cold storage material for cryogenic refrigerators. Especially in the temperature range of 10 - 20K, spherical lead is mainly used. However, due to the restrictions of the ROHS regulations on harmful substances and the harm of lead to the environment and human body, the use of lead is being restricted or even prohibited. Although some alternative materials have been proposed, such as nickel erbium compound (Er3Ni), as an intermetallic compound, nickel erbium compound is usually brittle in nature and difficult to be plastically deformed into an ideal shape (such as spherical), and may break and crack into powder. Moreover, its specific heat capacity in the 30K temperature range is not significantly superior to that of lead.

[0004] Therefore, there is an urgent need to develop a material with good ductility and toughness and a specific heat capacity higher than that of lead below 30K to replace traditional lead as a cold storage material. Summary of the Invention

[0005] The purpose of the present invention is to solve the environmental and human health hazard problems caused by the use of lead in the existing cold storage materials for cryogenic refrigerators, and to achieve the technical effects of meeting the requirements of the ROHS regulations and improving the refrigeration power.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] Provide a cold storage material for a cryogenic refrigerator, the cold storage material is composed of Er a Pr b alloy, where a and b are atomic percentages, and 40 < a < 80, and the alloy does not contain lead.

[0008] Optionally, in the Er a Pr b alloy, a satisfies 60 < a < 80.

[0009] Optionally, the Er a Pr b alloy is Er 73 Pr 27 .

[0010] Optionally, the alloy is a spherical powder with a particle size of 300-500 μm.

[0011] A cryogenic accumulator for an ultra-low temperature refrigerator is provided, wherein the cryogenic accumulator is filled with the aforementioned Er a Pr b Alloys are used as the entire cold storage material.

[0012] A cryogenic accumulator for an ultra-low temperature refrigerator is provided, the accumulator being filled with a composite cryogenic storage material, the composite cryogenic storage material comprising: a first cryogenic storage material, which is the aforementioned Er... a Pr b The alloy; and the second cold storage material; wherein the first cold storage material and the second cold storage material are arranged in sections along the axial direction of the cold storage device.

[0013] Alternatively, the second cold storage material may be a magnetic cold storage material other than lead.

[0014] Alternatively, the second cold storage material may be lead.

[0015] Alternatively, the second cold storage material may be composed of lead and other magnetic cold storage materials.

[0016] An ultra-low temperature refrigerator is provided, wherein the ultra-low temperature refrigerator is equipped with the above-mentioned cold accumulator.

[0017] The advantages of implementing this invention are:

[0018] 1. The Er provided by this invention a Pr b Alloy cold storage materials comply with RoHS regulations and can effectively replace traditional lead cold storage materials, avoiding the harm of lead to the environment and human body.

[0019] 2. The Er of the present invention a Pr b Alloy cold storage materials possess excellent thermophysical properties, when using all Er a Pr b When used as a secondary cold storage material, the alloy can achieve a cooling power of 5W at 20K, which is 0.5W higher than that of traditional lead cold storage materials; and it can achieve a cooling power of 2.2W at 15K, which is 1.1W higher than that of traditional lead cold storage materials.

[0020] 3. When using 30% Er a Pr bWhen the alloy is combined with 70% lead (volume percentage), it can achieve a cooling power of 4.6W at 20K, which is 0.1W higher than that of traditional lead-based cold storage materials; and it can achieve a cooling power of 1.8W at 15K, which is 0.7W higher than that of traditional lead-based cold storage materials. This shows that the EraPrb alloy cold storage material of the present invention can still maintain a high cooling efficiency when partially replacing lead.

[0021] 4. The Er of this invention a Pr b Alloy cold storage materials can be flexibly applied in the cold storage units of ultra-low temperature refrigerators. They can be used alone or in combination with other materials, showing strong adaptability and broad application prospects. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 For Er a Pr b Schematic diagram of a refrigeration unit using alloys as the sole cold storage material;

[0024] Figure 2 To include Er a Pr b A schematic diagram of a refrigeration unit using composite cold storage materials made of alloys;

[0025] Figure 3 This is a graph showing the specific heat capacity of each material in this invention.

[0026] 1. Er a Pr b 1. Alloy; 2. First cold storage material; 3. Second cold storage material; 4. Cold accumulator; 5. Refrigeration machine. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] like Figure 1As shown, this embodiment provides a cold storage material for a cryogenic refrigerator. This cold storage material is composed of Er a Pr b Alloy 1, where a and b are atomic percentages, and 40 < a < 80. This alloy does not contain lead.

[0030] In this embodiment, the value range of a in the Er a Pr b alloy is 60 < a < 80, that is, the atomic percentage of the erbium element is between 60% and 80%. In a specific implementation, Er 73 Pr 27 alloy is selected as the cold storage material, that is, the atomic percentage of the erbium element is 73% and the atomic percentage of the praseodymium element is 27%.

[0031] During the preparation process, first, high-purity erbium metal and praseodymium metal are proportioned according to an atomic ratio of 73:27, and then melted in an environment protected by an inert gas. After melting, the molten alloy is prepared into spherical powder by gas atomization.

[0032] During the gas atomization process, the gas pressure is controlled at 5 MPa, the melt temperature is 1550 °C, and the cooling gas is high-purity argon. By adjusting the atomization parameters, spherical powder with a particle size in the range of 300 - 500 μm is obtained. After the prepared powder is screened, cleaned, and dried, the required Er 73 Pr 27 cold storage material is obtained.

[0033] This Er 73 Pr 27 alloy cold storage material has excellent magnetocaloric effect and heat capacity characteristics. The design of the spherical powder form makes the material have a large specific surface area and good hydrodynamic characteristics, which is conducive to the heat exchange between the refrigerant and the cold storage material. The particle size is controlled in the range of 300 - 500 μm, which not only ensures sufficient heat exchange area but also avoids the problem of excessive fluid resistance that may be caused by too small particles.

[0034] As Figure 3 shown, performance tests show that the specific heat capacity of the Er 73 Pr 27 cold storage material in the temperature range of 10 K - 30 K is much higher than that of traditional lead cold storage materials and also much higher than that of Er3Ni. The specific heat capacity of this Er 73 Pr 27 cold storage material is 0.5 J / (K·cm 3 ) in the 15 K temperature range and 0.8 J / (K·cm 3 ) in the 20 K temperature range; it is higher than that of traditional lead cold storage materials at 15 K, which is 0.4 J / (K·cm 3) and 0.6 J / (K·cm at 20K 3 ). And since it does not contain lead elements, this material is environmentally friendly and non-toxic, meeting the requirements of modern industry for green materials.

[0035] Figure 3 As shown, (As-Cast) Er 73 Pr 27 represents the specific heat capacity curve of Er in the as-cast state 73 Pr 27 ; (PREP+SPS) Er 73 Pr 27 represents the specific heat capacity curve of Er 73 Pr 27 prepared into spherical powder. The Er 73 Pr 27 in this embodiment is spherical powder, so it is the (PREP+SPS) Er 73 Pr 27 specific heat capacity curve.

[0036] Example Two

[0037] As Figure 1 shown, this embodiment provides a regenerator for a cryogenic refrigerator. The regenerator 4 is filled with Er a Pr b alloy 1 as its entire regenerative material.

[0038] The regenerator 4 uses the Er a Pr b alloy 1 described in Example One as the regenerative material, where a and b are atomic percentages, and 40 < a < 80. This alloy does not contain lead. In a preferred embodiment, the value range of a for the Er a Pr b alloy is 60 < a < 80. In a more preferred embodiment, the regenerative material filled in the regenerator 4 is Er 73 Pr 27 alloy, that is, the atomic percentage of erbium element is 73% and the atomic percentage of praseodymium element is 27%.

[0039] The structure of the regenerator 4 includes a cylindrical stainless steel outer shell with evenly distributed metal grids inside, which are used to fix the regenerative material and ensure that the refrigeration working medium can fully contact the regenerative material. The two ends of the regenerator are respectively connected with an air inlet and an air outlet for the circulating flow of the refrigeration working medium. The outer shell of the regenerator is made of stainless steel, having good mechanical strength and corrosion resistance.

[0040] Inside the regenerator 4, spherical Er with a particle size range of 300 - 500 μm is filled a Pr bAlloy 1 powder. This spherical powder morphology gives the cold storage material a large specific surface area and good hydrodynamic characteristics, which is conducive to the heat exchange efficiency between the refrigerant and the cold storage material. The packing density is controlled at about 65%, which not only ensures sufficient amount of the cold storage material but also retains an appropriate porosity to reduce the fluid resistance.

[0041] The regenerator 4 is installed at the cold head part of the cryogenic refrigerator and works in cooperation with components such as the compressor and the heat exchanger. When the high-pressure helium gas generated by the compressor passes through the regenerator, the Er a Pr b alloy absorbs the heat of the helium gas and stores it; when the low-pressure helium gas flows back, the Er a Pr b alloy releases the heat to the helium gas, forming an effective heat cycle to achieve cryogenic refrigeration.

[0042] The regenerator 4 filled with the Er 73 Pr 27 alloy exhibits excellent performance in practical applications. At the same time, since it does not contain lead elements, the regenerator 4 is environmentally friendly and non-toxic, meeting the requirements of modern industry for green refrigeration equipment.

[0043] Example 3

[0044] As Figure 2 shown, this example provides a regenerator for a cryogenic refrigerator, and the regenerator 4 is filled with a composite cold storage material.

[0045] The composite cold storage material of the regenerator includes a first cold storage material 2 and a second cold storage material 3, and these two materials are arranged in zones along the axial direction of the regenerator. The first cold storage material 2 is the Er a Pr <00000�6>alloy, which does not contain lead, a and b are atomic percentages, and 40 < a < 80. For the detailed composition, preparation method and performance characteristics of the Er a Pr b alloy, reference can be made to the relevant descriptions in Example 1.

[0046] In this example, the second cold storage material 3 can take various forms. In a preferred example, the second cold storage material 3 is other magnetic cold storage materials except lead, such as GdEr alloy, HoCu alloy or ErNi alloy, etc. These magnetic cold storage materials have good magnetocaloric effects in a specific temperature range and can form a complement with the first cold storage material 2 to expand the effective working temperature range of the regenerator.

[0047] In another preferred example, the second cold storage material 3 is lead. As a traditional cold storage material, lead forms a good complement with the excellent performance of the Er a Pr b alloy.

[0048] In yet another preferred embodiment, the second cold storage material 3 is composed of lead and other magnetic cold storage materials. This composite design can simultaneously utilize the stable heat capacity of lead and the magnetocaloric effect of other magnetic materials, further optimizing the performance of the cold storage device over a wide temperature range.

[0049] The cryogenic refrigerator 5 has a two-stage structure, including a primary accumulator and a secondary accumulator. Composite cryogenic storage material is filled in the secondary accumulator. In the structural design of this accumulator 4, the primary and secondary cryogenic storage materials are arranged in axial sections to form a gradient cryogenic storage structure. Typically, Er... a Pr b The alloy is filled at the low-temperature end to fully utilize its excellent cold storage performance in the ultra-low temperature region; while the second cold storage material is placed near the high-temperature end, responsible for heat storage and transfer in the medium- and high-temperature regions. This partitioned configuration design enables the cold accumulator to maintain efficient heat exchange performance in different temperature ranges, significantly improving the overall efficiency of the ultra-low temperature refrigerator.

[0050] In practical applications, the ratio and partition length of the first cold storage material 2 and the second cold storage material 3 can be adjusted according to specific temperature requirements and working environment to achieve the best cooling effect. For example, for applications requiring extremely low temperatures, Er can be increased. a Pr b The proportion of the alloy; however, for applications where stability is a priority, the proportion of the second cold storage material can be appropriately increased.

[0051] Example 4

[0052] An ultra-low temperature refrigerator is a refrigeration device capable of achieving extremely low temperature environments. This refrigerator 5 is equipped with a special cold accumulator 4 to improve refrigeration efficiency and reduce the final achieved temperature. The ultra-low temperature refrigerator provided in this embodiment is equipped with a special cold accumulator 4 filled with Er... a Pr b Alloy 1 is used as a cold storage material.

[0053] This cryogenic refrigerator mainly consists of five parts: a compressor, a heat exchanger, an expansion mechanism, a cold accumulator, and a control system. The compressor is responsible for compressing the working gas and providing the pressure difference required for the refrigeration cycle; the heat exchanger is responsible for heat exchange during the refrigeration process; the expansion mechanism causes the high-pressure gas to expand and do work, producing a refrigeration effect; the cold accumulator plays a key role in storing and releasing heat in the refrigeration cycle; and the control system is responsible for the operation control and parameter adjustment of the entire refrigerator.

[0054] In a preferred embodiment, the accumulator 4 is filled with Er a Pr bAlloy 1 is used as the sole cold storage material. This single-material filling method simplifies the structural design of the cold accumulator, facilitates processing and assembly, and ensures optimal cold storage performance in a specific temperature range.

[0055] In another preferred embodiment, the cold storage 4 is filled with a composite cold storage material, including a first cold storage material Er a Pr b The alloy and the second cold storage material are arranged in zones along the axial direction of the cold accumulator. This zoned design allows for the use of the most suitable cold storage material in different temperature zones, thus achieving good cooling performance over a wide temperature range. Typically, Er... a Pr b The alloy is placed at the low-temperature end of the cold storage, while the second cold storage material is located at the relatively high-temperature end.

[0056] In a further preferred embodiment, the second cold storage material 3 is a magnetic cold storage material other than lead, such as GdEr alloy, HoCu alloy, or ErNi alloy. These magnetic materials exhibit good magnetocaloric effects in the medium-low temperature region and are compatible with Er... a Pr b The alloys complement each other in the ultra-low temperature region, enabling the entire cold accumulator to maintain efficient cold storage capacity over a wide temperature range.

[0057] In yet another preferred embodiment, the second cold storage material 3 is lead. Lead, as a traditional cold storage material, possesses stable heat capacity characteristics and good thermal conductivity, and can react with Er... a Pr b The alloy forms an effective temperature gradient, improving overall cold storage efficiency. Lead materials are typically processed into small spheres or meshes to increase the contact area with the working gas.

[0058] In another preferred embodiment, the second cold storage material 3 is composed of lead and other magnetic cold storage materials. This composite configuration further refines the temperature gradient range within the cold storage unit, allowing each temperature zone to utilize the most suitable material. Typically, the materials are arranged sequentially from the high-temperature end to the low-temperature end: lead, magnetic cold storage material, and Er. a Pr b Alloys are used to form three- or multi-segment cold storage structures.

[0059] The working principle of this cryogenic refrigerator is based on a regenerative refrigeration cycle. When the high-pressure gas generated by the compressor passes through the accumulator, the gas exchanges heat with the accumulator material, and the temperature decreases. Subsequently, the gas expands and does work in the expansion mechanism, and the temperature decreases further. The returned low-temperature gas passes through the accumulator again, cooling the accumulator material to an even lower temperature, while being preheated itself.

[0060] This cryogenic refrigerator is suitable for fields such as superconducting material testing, quantum computer cooling, deep space probe thermal management, and fundamental physics research, meeting the stringent requirements of these fields for extremely low temperature environments.

[0061] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A cold accumulator for a cryogenic refrigerator, characterized by comprising: The cold accumulator is filled with a composite cold storage material, which comprises: a first cold accumulating material, the first cold accumulating material being Er 73 Pr 27 alloy, the alloy being a spherical powder with a particle size of 300-500 μm; and The second cold storage material is other magnetic cold storage material except lead, or the second cold storage material is lead, or the second cold storage material is composed of lead and other magnetic cold storage material. The first cold storage material and the second cold storage material are arranged in zones in the axial direction of the cold accumulator, wherein the first cold storage material is filled at the low-temperature end, and the second cold storage material is placed close to the high-temperature end.

2. A cryogenic refrigerator, characterized by comprising: The ultra-low temperature refrigerator is equipped with the cold accumulator of claim 1.

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