阅读说明：本技术 用于低温系统的制冷机安装结构 (Refrigerator mounting structure for cryogenic system ) 是由 李奥 周志坡 何韩军 朱良友 于 2021-09-15 设计创作，主要内容包括：本发明公开了一种用于低温系统的制冷机安装结构,该制冷机安装结构包括容纳于放置被冷却物体的真空容器中且能与真空容器的真空区域隔绝的冷头套(2),该冷头套(2)包括用于容纳制冷机(1)的插入部分的安装换热腔体(8),安装换热腔体(8)的开口端用于插入制冷机(1)的插入部分、封闭端设置用于存储低温制冷剂的密封的冷却换热腔体(9),冷却换热腔体(9)上的冷却换热器(4c)用于冷却真空容器中的被冷却物体；所述制冷机(1)的冷头换热器和冷头套(2)的冷头套换热器热连接且能够沿着制冷机(1)轴线方向解除热连接。本发明的安装结构避免使用大量的低温制冷剂,又能较好的兼顾制冷机快速维护和传热性能。(The invention discloses a refrigerator mounting structure for a low-temperature system, which comprises a cold head sleeve (2) accommodated in a vacuum container for accommodating a cooled object and capable of being isolated from a vacuum area of the vacuum container, wherein the cold head sleeve (2) comprises a mounting heat exchange cavity (8) for accommodating an insertion part of a refrigerator (1), the opening end of the mounting heat exchange cavity (8) is used for inserting the insertion part of the refrigerator (1), the closed end of the mounting heat exchange cavity is provided with a sealed cooling heat exchange cavity (9) for storing a low-temperature refrigerant, and a cooling heat exchanger (4 c) on the cooling heat exchange cavity (9) is used for cooling the cooled object in the vacuum container; the cold head heat exchanger of the refrigerator (1) is in thermal connection with the cold head sleeve heat exchanger of the cold head sleeve (2) and can be disconnected along the axial direction of the refrigerator (1). The mounting structure of the invention avoids using a large amount of low-temperature refrigerant and can better give consideration to the quick maintenance and heat transfer performance of the refrigerator.)

1. A refrigerator mounting structure for a cryogenic system, the refrigerator mounting structure comprising a coldhead sleeve (2) accommodated in a vacuum vessel in which an object to be cooled is placed and isolatable from a vacuum region of the vacuum vessel, characterized in that: the cold head sleeve (2) comprises a mounting heat exchange cavity (8) for accommodating an insertion part of the refrigerator (1), an opening end of the mounting heat exchange cavity (8) is used for being inserted into the insertion part of the refrigerator (1), a sealed cooling heat exchange cavity (9) for storing low-temperature refrigerant is arranged at a closed end of the mounting heat exchange cavity, and a cooling heat exchanger (4 c) on the cooling heat exchange cavity (9) is used for cooling a cooled object in a vacuum container; the cold head heat exchanger of the refrigerator (1) is in thermal connection with the cold head sleeve heat exchanger of the cold head sleeve (2) and can be disconnected along the axial direction of the refrigerator (1).

2. The refrigerator mounting structure for a cryogenic system according to claim 1, wherein: the cooling heat exchange cavity (9) is formed by hermetically connecting a heat exchanger sleeve (2 c) with a cold head sleeve heat exchanger and a cooling heat exchanger (4 c) at two ends of the heat exchanger sleeve, and the closed end of the heat exchange cavity (8) and the cooling heat exchange cavity (9) share the same cold head sleeve heat exchanger; the heat exchanger sleeve (2 c) is made of metal with the thermal conductivity not more than 10W/(m.K) at a working temperature range of 4K-77K.

3. The refrigerator mounting structure for a cryogenic system according to claim 1 or 2, wherein: the length-diameter ratio of the cooling heat exchange cavity (9) is larger than 1 and/or the pressure resistance of the cooling heat exchange cavity (9) is set to be 2-3 MPa.

4. The refrigerator mounting structure for a cryogenic system according to claim 1 or 2, wherein: the contact surfaces of the inner sides of the cold head sleeve heat exchangers and the cooling heat exchangers (4 c) at the two ends of the cooling heat exchange cavity (9) and the low-temperature refrigerant are provided with fin structures; the cooling heat exchanger (4 c) is in thermal contact with the cooled object through a cooling heat exchange surface (4 c 1).

5. The refrigerator mounting structure for a cryogenic system according to claim 1 or 2, wherein: the cold head sleeve heat exchanger and the cooling heat exchanger (4 c) are both made of high-purity oxygen-free copper.

6. The refrigerator mounting structure for a cryogenic system according to claim 1, wherein: indium sheets or indium wires with the thickness of 0.5-2.0 mm are placed between the hot connecting surfaces of the cold head heat exchanger of the refrigerating machine (1) and the cold head sleeve heat exchanger of the cold head sleeve (2).

7. The refrigerator mounting structure for a cryogenic system according to claim 1, 2 or 6, wherein: when the refrigerator (1) is a two-stage refrigerator, the cold head sleeve (2) comprises a cold head sleeve flange (2-1), a first-stage sleeve (2 a), a first-stage cold head sleeve heat exchanger (4 a) with a central through hole, a second-stage sleeve (2 b) and a second-stage cold head sleeve heat exchanger (4 b) which are coaxially connected in sequence, wherein the thin-wall cylindrical first-stage sleeve (2 a) and second-stage sleeve (2 b) are connected with the cold head sleeve flange (2-1), the first-stage cold head sleeve heat exchanger (4 a) and the second-stage cold head sleeve heat exchanger (4 b) in an airtight mode to form an integral structure with an installation heat exchange cavity (8); the cold head sleeve flange (2-1) positioned at the opening end of the heat exchange cavity (8) is used for being fixedly connected with a flange of the refrigerator (1), and a refrigerator primary thermal contact surface (3 a) protruding from a primary cold head heat exchanger (H1) of the refrigerator (1) and a refrigerator secondary thermal contact surface (3 b) protruding from a secondary cold head heat exchanger (H2) are respectively in contact thermal connection with a primary cold head sleeve thermal contact surface (4 a 1) of a primary cold head sleeve heat exchanger (4 a) in the cold head sleeve (2) and a secondary cold head sleeve thermal contact surface (4 b 1) of a secondary cold head sleeve heat exchanger (4 b); the secondary cold head sleeve heat exchanger (4 b), the heat exchanger sleeve (2 c) and the cooling heat exchanger (4 c) are connected in an airtight mode to form a cooling heat exchange cavity (9).

8. The refrigerator mounting structure for a cryogenic system according to claim 7, wherein: the secondary sleeve (2 b) and the heat exchanger sleeve (2 c) are integrated sleeves, and the secondary cold head sleeve heat exchanger (4 b) is hermetically fixed in the inner cavity of the integrated sleeve in a vacuum brazing mode and divides the integrated sleeve into two parts which are not communicated with each other.

9. The refrigerator mounting structure for a cryogenic system according to claim 1, wherein: when the refrigerator (1) is a single-stage refrigerator, the cold head sleeve (2) comprises a cold head sleeve flange (2-1), a cold head sleeve and a cold head sleeve heat exchanger which are coaxially and sequentially connected, and the thin-wall cylindrical cold head sleeve, the cold head sleeve flange (2-1) and the cold head sleeve heat exchanger are hermetically connected to form an integral structure with an installation heat exchange cavity (8); the cold head sleeve flange (2-1) positioned at the opening end of the heat exchange cavity (8) is used for being fixedly connected with the flange of the refrigerator (1), and the refrigerator thermal contact surface protruded from the cold head heat exchanger of the refrigerator (1) is in contact thermal connection with the cold head sleeve thermal contact surface of the cold head sleeve heat exchanger in the cold head sleeve (2); the cold head sleeve heat exchanger is connected with the heat exchanger sleeve (2 c) and the cooling heat exchanger (4 c) in an airtight manner to form a cooling heat exchange cavity (9).

10. The refrigerator mounting structure for a cryogenic system according to claim 1, wherein: an installation cavity pipeline (7) which is in airtight communication with the installation heat exchange cavity (8) is connected with external pressure reduction equipment through an installation cavity connector (62) arranged on the atmosphere side; and a cooling cavity pipeline (5) which is in airtight communication with the cooling heat exchange cavity (9) is connected with external low-temperature refrigerant supply equipment and pressure regulation and control equipment through a cooling cavity connector (62) arranged on the atmosphere side.

Technical Field

The invention belongs to the technical field of low-temperature refrigeration, and particularly relates to a refrigerator mounting structure for a low-temperature system.

Background

In a cryogenic system, a GM (Gifford-McMahon) refrigerator is used as a common method for cooling an object such as a superconducting magnet. The traditional superconducting magnet is generally soaked in liquid helium, for example, a nuclear magnetic resonance system generally needs 1000-2000L of liquid helium, and a refrigerator is adopted to cool helium vapor evaporated from a dewar of the superconducting magnet, so that the helium vapor is liquefied again and then flows back to the dewar. Because the liquefaction price is high, in order to reduce the use of liquid helium, the current domestic and foreign nuclear magnetic resonance systems successively release a liquid helium-free system, namely, a superconducting system has no liquid helium, and a refrigerator is adopted to directly contact a cold head with a superconducting magnet to reach the temperature below the critical temperature of the superconductor so as to form superconductivity. The superconducting magnet gradually replaces the traditional immersion superconducting magnet.

Since the refrigerator requires regular maintenance, a method of pulling out the displacer in a state where the cylinder of the GM refrigerator is fixed to the vacuum vessel has been proposed for a liquid-free helium magnet. However, in this method, since the cylinder is exposed to the atmosphere and the cylinder is continuously cooled by the vacuum vessel, moisture in the air becomes an ice film and adheres to the inner surface of the cylinder. Therefore, the displacer cannot be inserted into the cylinder again, and as a result, maintenance work cannot be performed.

Chinese patent No. ZL201310042360.3, entitled refrigerator mounting structure, proposes a method of forming a vacuum state between a coldhead sleeve and a cylinder to maintain the refrigerator. In the structure, an indium sheet is adopted between the refrigerating machine cold head heat exchanger and the cold head sleeve heat exchanger to reduce the thermal resistance. However, the indium sheet is soft in texture and will deform after being extruded once, if according to the scheme, the indium sheet cannot be replaced after the cylinder body is separated from the cold head sleeve, and when the refrigerator contacts with the cold head sleeve again, the deformation of the indium sheet cannot be guaranteed, so that the contact thermal resistance is greatly increased, and the cold transmission efficiency is reduced. If the indium sheet needs to be replaced, the refrigerating machine needs to be completely pulled out of the cold head sleeve, the inner surface of the cold head sleeve is condensed and frozen, and the inner surface needs to be heated by hot gas. If the superconducting magnet is a liquid helium-free superconducting magnet, the heat exchanger of the cold head sleeve is directly connected with the superconducting magnet solid, and because the heat transfer parts of the heat exchanger are all made of oxygen-free copper with extremely high heat conductivity, when the inner surface of the cold head sleeve is heated, heat is transferred to the superconducting magnet, so that the performance of the superconducting magnet is influenced, and because the heat capacity of the superconducting magnet is huge, the inner surface of the cold head sleeve cannot be heated to more than 80 ℃ in a short time, condensed water is vaporized, and the working efficiency of the whole maintenance is influenced.

The Chinese patent application with the patent number of 202011264001.9, named as a superconducting magnet low-temperature heat exchange device, adopts a method of filling low-temperature refrigerant into a cold head sleeve to realize the quick maintenance of the liquid-helium-free superconducting magnet. However, because the inside of the cold head sleeve is completely provided with the low-temperature refrigerant, gas heat conduction from a room temperature end to a liquid helium end is formed, the heat load of the system is increased, the abundant cold quantity of the superconducting magnet is reduced, and the stability of the superconducting magnet is not facilitated.

Disclosure of Invention

The invention aims to solve the problem of maintenance of a liquid helium-free superconducting magnet refrigerator in the prior art, and provides a refrigerator installation structure for a cryogenic system, which can avoid using a large amount of cryogenic refrigerant and can better give consideration to the fast maintenance and heat transfer performance of the refrigerator.

The invention aims to solve the problems by the following technical scheme:

a refrigerator mounting structure for a cryogenic system, the refrigerator mounting structure comprising a coldhead sleeve accommodated in a vacuum vessel in which an object to be cooled is placed and isolatable from a vacuum region of the vacuum vessel, characterized in that: the cold head sleeve comprises an installation heat exchange cavity for accommodating an insertion part of a refrigerator, wherein the opening end of the installation heat exchange cavity is used for inserting the insertion part of the refrigerator, the closed end of the installation heat exchange cavity is provided with a sealed cooling heat exchange cavity for storing a low-temperature refrigerant, and a cooling heat exchanger on the cooling heat exchange cavity is used for cooling a cooled object in a vacuum container; the cold head heat exchanger of the refrigerator is thermally connected with the cold head sleeve heat exchanger of the cold head sleeve, and the thermal connection can be released along the axis direction of the refrigerator.

The cooling heat exchange cavity is formed by hermetically connecting a heat exchanger sleeve, a cold head sleeve heat exchanger and a cooling heat exchanger at two ends of the heat exchanger sleeve, and the closed end of the heat exchange cavity and the cooling heat exchange cavity share the same cold head sleeve heat exchanger; the heat exchanger sleeve is made of metal with the thermal conductivity not more than 10W/(m.K) at a working temperature range of 4K-77K.

The length-diameter ratio of the cooling heat exchange cavity is larger than 1 and/or the pressure resistance of the cooling heat exchange cavity is set to be 2-3 MPa.

The contact surfaces of the inner sides of the cold head sleeve heat exchanger and the cooling heat exchanger at the two ends of the cooling heat exchange cavity and the low-temperature refrigerant are provided with fin structures; the cooling heat exchanger is in thermal contact with the cooled object through the cooling heat exchange surface.

The cold head sleeve heat exchanger and the cooling heat exchanger are both made of high-purity oxygen-free copper.

Indium sheets or indium wires with the thickness of 0.5-2.0 mm are placed between the hot connecting surfaces of the cold head heat exchanger of the refrigerating machine and the cold head sleeve heat exchanger of the cold head sleeve.

When the refrigerator is a two-stage refrigerator, the cold head sleeve comprises a cold head sleeve flange, a primary sleeve, a primary cold head sleeve heat exchanger with a central through hole, a secondary sleeve and a secondary cold head sleeve heat exchanger which are coaxially and sequentially connected, and the thin-wall cylindrical primary sleeve and the thin-wall cylindrical secondary sleeve are hermetically connected with the cold head sleeve flange, the primary cold head sleeve heat exchanger and the secondary cold head sleeve heat exchanger to form an integral structure with an installation heat exchange cavity; the cold head sleeve flange positioned at the opening end of the heat exchange cavity is used for being fixedly connected with a flange of a refrigerator, and a primary refrigerator thermal contact surface projected by a primary cold head heat exchanger of the refrigerator and a secondary refrigerator thermal contact surface projected by a secondary cold head heat exchanger of the refrigerator are respectively in contact thermal connection with a primary cold head sleeve thermal contact surface of the primary cold head sleeve heat exchanger in the cold head sleeve and a secondary cold head sleeve thermal contact surface of the secondary cold head sleeve heat exchanger; the second-stage cold head sleeve heat exchanger, the heat exchanger sleeve and the cooling heat exchanger are connected in an airtight mode to form a cooling heat exchange cavity.

The second-stage sleeve and the heat exchanger sleeve are integrated sleeves, and the second-stage cold head sleeve heat exchanger is hermetically fixed in an inner cavity of the integrated sleeve in a vacuum brazing mode and divides the integrated sleeve into two parts which are not communicated with each other.

When the refrigerator is a single-stage refrigerator, the cold head sleeve comprises a cold head sleeve flange, a cold head sleeve and a cold head sleeve heat exchanger which are coaxially and sequentially connected, and the thin-wall cylindrical cold head sleeve, the cold head sleeve flange and the cold head sleeve heat exchanger are hermetically connected to form an integral structure with an installation heat exchange cavity; the cold head sleeve flange positioned at the opening end of the heat exchange cavity is used for being fixedly connected with a flange of a refrigerator, and a refrigerator thermal contact surface projected by a cold head heat exchanger of the refrigerator is in contact thermal connection with a cold head sleeve thermal contact surface of a cold head sleeve heat exchanger in a cold head sleeve; the cold head sleeve heat exchanger, the heat exchanger sleeve and the cooling heat exchanger are connected in an airtight mode to form a cooling heat exchange cavity.

The installation cavity pipeline which is in airtight communication with the installation heat exchange cavity is connected with external pressure reduction equipment through an installation cavity connector arranged on the atmosphere side; and a cooling cavity pipeline which is in airtight communication with the cooling heat exchange cavity is connected with external low-temperature refrigerant supply equipment and pressure regulation and control equipment through a cooling cavity connector arranged on the atmosphere side.

Compared with the prior art, the invention has the following advantages:

the installation structure is provided with the relatively independent installation heat exchange cavity and the cooling heat exchange cavity, the cold head sleeve with the installation heat exchange cavity is used for installing and disassembling the refrigerator, the sealed cooling heat exchange cavity for storing the low-temperature refrigerant is used for cooling the cooled object in the vacuum container, and the refrigerator and the cooled object are separated by the cooling heat exchange cavity, so that the disassembly of the refrigerator cannot influence the cooled object in the vacuum container; the cooling heat exchange cavity and the installation heat exchange cavity of the same cold head sleeve heat exchanger are shared, so that the heat exchange efficiency can be improved; the mounting structure can avoid using a large amount of low-temperature refrigerants and can better give consideration to the quick maintenance and heat transfer performance of the refrigerating machine.

Drawings

FIG. 1 is a schematic view of a chiller mounting structure for a cryogenic system of the present invention during normal assembly of the chiller;

fig. 2 is a schematic view of a refrigerator installation structure and a refrigerator separated state for a cryogenic system according to the present invention.

Wherein: 1-a refrigerator; 2-a cold head sleeve; 2-1-a cold head sleeve flange; 2 a-first-stage sleeve; 2 b-a secondary sleeve; 2 c-heat exchanger sleeve; 3 a-refrigerator primary thermal contact surface; 3 b-refrigerator secondary thermal contact surface; 4 a-first-stage cold head sleeve heat exchanger; 4a 1-primary coldhead sleeve thermal contact surface; 4a 2-first-stage cold head sleeve heat exchange surface; 4 b-a secondary cold head sleeve heat exchanger; 4b 1-secondary coldhead sleeve thermal interface; 4b 2-cold head sleeve fin contact surface; 4 c-cooling heat exchanger; 4c1 — cooling the heat exchange surface; 4c 2-heat exchanger fin contact surface; 5-cooling the cavity pipeline; 61-cooling chamber connector; 62-mounting a cavity connector; 7, installing a cavity pipeline; 8, installing a heat exchange cavity; 9-cooling the heat exchange cavity; 10, sealing rings; h1-first stage cold head heat exchanger; h2-two-stage cold head heat exchanger; c1-first stage cylinder; c2 — secondary cylinder.

Detailed Description

In connection with the background, a detailed description of the conventional refrigerator structure will not be provided.

The invention will be further described with reference to the following examples and figures 1-2.

The refrigerator 1 comprises a primary cylinder C1, a secondary cylinder C2, a primary cold head H1 and a secondary cold head H2, wherein the primary cold head H1 and the secondary cold head H2 can respectively cool a cooled object to 100-40K and 20-4K; the hot end of the cylinder body is provided with a sealing ring 10 at the circumferential side and is laterally sealed in a cold head sleeve flange 2-1 of the cold head sleeve 2. The mounting structure of the refrigerator comprises a cold head sleeve 2 capable of accommodating the refrigerator 1, wherein the cold head sleeve 2 is accommodated in a vacuum container for placing a cooled object (the vacuum container and the cooled object are not shown in figures 1-2), and the cold head sleeve 2 is isolated from the vacuum area of the vacuum container.

The cold head sleeve 2 comprises a cold head sleeve flange 2-1, the lower part of the cold head sleeve flange 2-1 is coaxially and sequentially connected with a first-stage sleeve 2a and a second-stage sleeve 2b, the first-stage sleeve 2a and the second-stage sleeve 2b are connected through a first-stage cold head sleeve heat exchanger 4a of the cold head sleeve 2, and the lower end of the second-stage sleeve 2b is connected with a second-stage cold head sleeve heat exchanger 4 b. Thereby forming the cold head sleeve 2 with an opening at one side of the cold head sleeve flange 2-1, a closed and inverted convex semi-closed cylinder structure at one side of the secondary cold head sleeve heat exchanger 4 b. And, a heat exchanger 4c is arranged on the side of the secondary cold head cover heat exchanger 4b far away from the refrigerator 1, and the secondary cold head cover heat exchanger 4b and the cooling heat exchanger 4c are connected together in an airtight manner through a heat exchanger cylinder 2c made of low-thermal-conductivity metal (such as 304 stainless steel or TC4 titanium alloy) between the secondary cold head cover heat exchanger 4b and the cooling heat exchanger 4c to form a cooling heat exchange cavity 9. The cold head sleeve flange 2-1 is fixed on the vacuum container to form a whole.

A flange 2-1 of the cold head sleeve 2 is provided with an installation cavity pipeline 7 which is in airtight communication with the installation heat exchange cavity 8 and an installation cavity connector 62 which is communicated with the installation cavity pipeline 7 and is arranged at the atmosphere side; through which the chamber connector 62 may communicate with an external pressure relief device (not shown). The cooling cavity pipeline 5 is hermetically communicated with the cooling heat exchange cavity 9 and a cooling cavity connector 61 at one end of the flange 2-1 atmosphere side of the cold head sleeve 2; through which the cooling chamber connector 61 can communicate with an external cryogenic refrigerant supply device, a pressure regulating device (not shown)

The first-stage cold head sleeve heat exchanger 4a, the second-stage cold head sleeve heat exchanger 4b and the cooling heat exchanger 4c are all made of high-purity oxygen-free copper with high heat conductivity; the first-stage coldhead jacket heat exchanger 4a and the second-stage coldhead jacket heat exchanger 4b are perpendicular to the axial direction of the refrigerator 1, and are accommodated in the first-stage coldhead jacket thermal contact surface 4a1 and the second-stage coldhead jacket thermal contact surface 4b1 on which the heat exchange chamber 8 is mounted, for exchanging cooling energy with the coldhead of the refrigerator 1. The cooling heat exchanger 4c includes a cooling heat exchange surface 4c1 that transfers heat to the cooling target object solid.

As shown in fig. 1. When the refrigerator 1 is inserted into the cold head sleeve 2, the refrigerator primary thermal contact surface 3a protruding from the primary cold head heat exchanger H1 and the refrigerator secondary thermal contact surface 3b protruding from the secondary cold head heat exchanger H2 are respectively in contact with the primary cold head sleeve thermal contact surface 4a1 of the primary cold head sleeve heat exchanger 4a of the cold head sleeve 2 and the secondary cold head sleeve thermal contact surface 4b1 of the secondary cold head sleeve heat exchanger 4b, and in order to improve the heat transfer performance of the contact surfaces, indium sheets with the thickness of 0.5-2.0 mm are respectively arranged.

The cold head sleeve 2 and the part of the refrigerator 1 inserted into the heat exchange cavity 8 form an annular cavity, and the annular cavity area can be vacuumized through the installation cavity connector 62.

The secondary coldhead jacket heat exchanger 4b and the cooling heat exchanger 4c are provided with a coldhead jacket fin contact surface 4b2 and a heat exchanger fin contact surface 4c2 which are accommodated in the cooling heat exchange cavity 9, and the cooling heat exchange cavity 9 is filled with a low-temperature refrigerant via the cooling cavity connector 61. The filled low-temperature refrigerant can be filled with a normal-temperature gas medium according to field conditions, enters the cooling heat exchange cavity 9 through the cooling cavity pipeline 5, and is cooled through conduction of the refrigerator 1, so that the gaseous refrigerant gas in the cooling heat exchange cavity 9 is gradually liquefied; or the liquid refrigerant can be directly filled into the cooling heat exchange cavity 9 through the cooling cavity pipeline 5.

The features of the refrigerator mounting structure are further described in conjunction with fig. 1 and 2.

In order to reduce heat leakage, the first-stage sleeve 2a and the second-stage sleeve 2b of the cold head sleeve 2 are made into thin-walled cylinders by low-thermal-conductivity metal, the thermal conductivity of the adopted metal at a working temperature range of 4K-77K is less than 10W/(m.K), and the first-stage sleeve 2a and the second-stage sleeve 2b are connected with the hot end flange 2-1, the first-stage cold head sleeve heat exchanger 4a and the second-stage cold head sleeve heat exchanger 4b in an airtight mode into a whole in a welding mode. When the refrigerator 1 is inserted into the installation heat exchange chamber 8. The flange of the refrigerator 1 is fixed with the cold head sleeve flange 2-1 through a forward bolt (not shown), and the primary cold head heat exchanger H1 and the secondary cold head heat exchanger H2 are extruded through axial pretightening force, so that the contact performance of the refrigerator primary thermal contact surface 3a protruding from the primary cold head heat exchanger H1 and the refrigerator secondary thermal contact surface 3b protruding from the secondary cold head heat exchanger H2 and the primary cold head sleeve thermal contact surface 4a1 of the primary cold head sleeve heat exchanger 4a and the secondary cold head sleeve thermal contact surface 4b1 of the secondary cold head sleeve heat exchanger 4b is improved. In order to improve the heat exchange effect, indium sheets or indium wires can be added between the thermal contact surfaces, and weak gaps or cracks between the contact surfaces are filled and leveled through deformation of the indium sheets or the indium wires. And the heat exchange cavity 8 is hermetically isolated from the external atmospheric environment at the hot end by a sealing ring 10.

Before starting up, the atmosphere in the heat exchange chamber 8 is decompressed to a vacuum state through the installation chamber connector 62, and the pressure is generally below 0.1 Pa. While a quantity of cryogenic refrigerant is injected into the cavity through the cooling cavity connector 61.

After the refrigerator is started, the refrigerator 1 performs refrigeration, and the primary cold head heat exchanger H1 and the secondary cold head heat exchanger H2 gradually transmit the cold energy to the primary cold head heat exchanger 4a and the secondary cold head heat exchanger 4b at the corresponding positions of the cold heads.

The first-stage cold head sleeve heat exchange surface 4a2, which is not accommodated in the installation heat exchange cavity 8, of the first-stage cold head sleeve heat exchanger 4a can be used for being connected with a cold screen, particularly used for a 4K low-temperature refrigerator, and is finally cooled to 60-40K to form a low-temperature radiation screen, so that direct heat exchange between objects in a 4K temperature area and room temperature is prevented.

In addition, the low-temperature refrigerant contained in the cooling heat exchange cavity 9 may be helium, neon, nitrogen, or a mixture of these gases, depending on the requirements of the temperature zone to be cooled.

After the refrigerator 1 is further cooled, the low-temperature refrigerant in the cooling heat exchange cavity 9 is cooled and exchanged heat through the cold head sleeve fin contact surface 4b2 of the fin structure of the secondary cold head sleeve heat exchanger 4b, and is gradually cooled to the liquefaction point temperature, so that liquid is formed and deposited at the bottom of the cooling heat exchange cavity 9, namely on the heat exchanger fin contact surface 4c2 of the cooling heat exchanger 4c with the fin structure, and is cooled to the refrigerant liquefaction temperature. For example, helium is used as the refrigerant for a 4K refrigerator. Initially, the helium gas contained in the cooling heat exchange cavity 9 is at about 300K at room temperature. After the secondary cold head heat exchanger H2 of the refrigerator 1 is gradually cooled to 4K, the helium gas is gradually cooled to a liquefaction point, and liquid helium is formed and stored in the cooling heat exchange cavity 9. The cooling heat exchanger 4c is connected with the cooled object through the cooling heat exchange surface 4c1, and simultaneously transfers heat to the liquid helium, at the moment, the liquid helium can be evaporated and ascended, and is condensed again after being contacted with the cold head sleeve fin contact surface 4b2 of the secondary cold head sleeve heat exchanger 4b to form liquid drops, and the liquid drops fall into the liquid helium or onto the heat exchanger fin contact surface 4c2 to form a small-sized zero evaporation system.

Further explanation is provided.

When the refrigerator 1 needs to be maintained, the refrigerator 1 needs to be pulled out of the coldhead sleeve 2. At the moment, air enters the installation heat exchange cavity 8 of the cold head sleeve 2, ice or dew is solidified on the inner circumferential surfaces of the primary sleeve 2a and the secondary sleeve 2b, the primary cold head sleeve heat contact surface 4a1 of the primary cold head sleeve heat exchanger 4a and the secondary cold head sleeve heat contact surface 4b1 of the secondary cold head sleeve heat exchanger 4b, and hot nitrogen at the temperature of 60-100 ℃ can be adopted to heat the interior of the installation heat exchange cavity 8. At this moment, the liquid helium in the cooling heat exchange cavity 9 is vaporized, and is connected with an external vacuum pump set (not shown) through the cooling cavity connector 61, and the helium in the cooling heat exchange cavity 9 is pumped out through the cooling cavity pipeline 5, so that the inside of the cooling heat exchange cavity 9 is in a negative pressure or vacuum state.

For the cooling heat exchange cavity 9 containing the low-temperature refrigerant, the secondary cold head sleeve heat exchanger 4b and the cooling heat exchanger 4c are both made of high-purity oxygen-free copper, so when the thermal contact surface 4b1 of the secondary cold head sleeve is heated, the secondary cold head sleeve heat exchanger 4b can be quickly raised to 60-100 ℃. Because the cylinder of the heat exchanger sleeve 2c connecting the secondary cold head sleeve heat exchanger 4b and the cooling heat exchanger 4c is made of metal with low thermal conductivity, and the thermal conductivity at the working temperature range of 4K-77K is less than 10W/(m.K), the heat heated in the installation heat exchange cavity 8 is not easy to be transferred to the cooling heat exchanger 4c, and the cooled object is prevented from being heated. Therefore, when the coldhead sleeve 2 is heated, the object to be cooled is still at a lower temperature, and does not need to return to the room temperature environment together with the coldhead sleeve 2, so that the whole heating process takes less time.

In a specific implementation process, the cooling heat exchange cavity 9 can be made to be long and thin, for example, the length-diameter ratio is greater than 1, so that the heat leakage of the heat exchanger sleeve 2c is made smaller. In addition, the helium in the cooling heat exchange cavity 9 is not required to be directly decompressed to a negative pressure or vacuum state. In the heating process, the upper part is in a hot state, and the lower part is in a cold state, so that stable gas stratification is formed, and convective heat transfer cannot be caused. Because the thermal conductivity of the gas is small, the static heat leakage is small, and the liquid helium at the bottom cannot be volatilized too much.

The strength of the heat exchanger sleeve 2c at the periphery of the cooling heat exchange cavity 9 can be properly enhanced, and the cooling heat exchange cavity 9 is made into a pressure-resistant cavity. Helium gas evaporated during the heating process is contained therein, and helium gas loss is avoided. Because the cooling heat exchange cavity 9 is small in size, 20L is recommended in the embodiment, and the pressure resistance of the cavity is set to be 2-3 MPa.

If the liquid helium in the bottom continues to volatilize and the internal pressure becomes excessive, the volatilized helium gas can also be vented to the atmosphere through the cooling chamber connector 61. The liquid helium storage in the cooling heat exchange cavity 9 is greatly reduced compared with the traditional 1000L-2000L liquid helium superconducting system. The low-temperature refrigerant filled into the cooling heat exchange cavity 9 can adopt two modes: firstly, the liquid low-temperature refrigerant is filled into the cooling cavity connector 61 directly through the cooling cavity connector; the second is that the refrigerant gas with high pressure is injected into the cooling cavity connector 61 through the cooling cavity connector, and the low temperature refrigerant is converted into liquid state from gas through the conduction cooling of the refrigerator 1. Therefore, in the maintenance process, a liquid Dewar system is not needed, and only a pressure steel cylinder is used.

In order to reduce heat leakage, the cooling cavity pipeline 5 is made of thin-wall capillary tubes. The secondary cold head sleeve heat exchanger 4b and the cooling heat exchanger 4c at the two ends of the cooling heat exchange cavity 9 are basically in the same temperature zone, so that the problem of heat conduction and heat leakage does not exist in the zone; the cold energy provided by the first-stage cold head heat exchanger H1 is offset due to the heat leakage of the first-stage sleeve 2a, and the heat is not conducted to the second-stage cylinder C2; the only heat transfer leakage is the leakage of the secondary sleeve 2b of the coldhead sleeve 2.

In order to simplify the structure, the secondary sleeve 2b of the coldhead sleeve 2 can be integrated with the heat exchanger sleeve 2c on the periphery of the cooling heat exchange cavity 9, the whole secondary coldhead sleeve heat exchanger 4b is inserted into the integrated sleeve, and the secondary coldhead sleeve heat exchanger 4b is fixed on the appropriate position of the integrated sleeve in the axial direction in an airtight mode through vacuum brazing.

Further described.

For maintenance convenience, indium sheets or indium wires may be fixed to the refrigerator primary thermal contact surface 3a and the refrigerator secondary thermal contact surface 3b of the primary cold head heat exchanger H1 and the secondary cold head heat exchanger H2 of the refrigerator 1, and when the refrigerator 1 is pulled out from the cold head housing 2, the indium sheets and the indium wires are also brought out together.

Specifically, a new refrigerator 1 is prepared in advance, and the above operation is performed after the indium sheet or the indium wire is properly arranged. Once the water vapor in the coldhead sleeve 2 is removed, the spare refrigerator 1 is quickly inserted into the coldhead sleeve 2 and is refrigerated as described above. Because the indium sheet and the indium wire on the new refrigerator 1 are not extruded and inserted into the cold head sleeve 2 again, the primary thermal contact surface 3a of the refrigerator and the primary cold head sleeve thermal contact surface 4a1 can be well contacted, and the secondary thermal contact surface 3b of the refrigerator and the secondary cold head sleeve thermal contact surface 4b1 can be well contacted, so that the heat transfer performance between the contact surfaces is improved.

Different from the traditional immersion type cooling, the structure adopted in the invention avoids using a large amount of low-temperature refrigerant, and can better give consideration to the quick maintenance and heat transfer performance of the refrigerating machine.

In the above embodiment, the two-stage refrigerator is taken as an example, and this structure can be used for mounting a single-stage refrigerator.

Specifically, when the coldhead sleeve 2 is designed, the primary sleeve 2a and the primary coldhead sleeve heat exchanger 4a do not need to be processed, and only the secondary sleeve 2b and the secondary coldhead sleeve heat exchanger 4b at the low temperature end need to be reserved.

The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby, and any modification made on the basis of the technical scheme according to the technical idea proposed by the present invention falls within the protection scope of the present invention; the technology not related to the invention can be realized by the prior art.