Refrigerator mounting structure for low temperature system

Abstract

The present invention discloses a refrigerator installation structure for a low-temperature system, the refrigerator installation structure comprising a cold head cover (2) which is accommodated in a vacuum container in which a cooled object is placed and can be isolated from a vacuum area of ​​the vacuum container, the cold head cover (2) comprising a heat exchange installation cavity (8) for accommodating an insertion portion of a refrigerator (1), an open end of the heat exchange installation cavity (8) for inserting the insertion portion of the refrigerator (1), and a sealed cooling heat exchange cavity (9) for storing a low-temperature refrigerant at a closed end, a cooling heat exchanger (4c) on the cooling heat exchange cavity (9) for cooling the cooled object in the vacuum container; the cold head heat exchanger of the refrigerator (1) and the cold head cover heat exchanger of the cold head cover (2) are thermally connected and can be thermally disconnected along the axis direction of the refrigerator (1). The installation structure of the present invention avoids the use of a large amount of low-temperature refrigerant, and can better balance the rapid maintenance and heat transfer performance of the refrigerator.

Description

Technical Field

[0001] The invention belongs to the technical field of low-temperature refrigeration, and in particular to a refrigerator installation structure for a low-temperature system. Background Art

[0002] In cryogenic systems, to cool down a target object, such as a superconducting magnet, a GM (Gifford-McMahon) refrigerator is a common method. Traditional superconducting magnets are generally immersed in liquid helium. For example, a nuclear magnetic resonance system generally requires 1000 to 2000 L of liquid helium. A refrigerator is used to cool the helium vapor evaporated from the superconducting magnet dewar, liquefying it and then liquefying it again before flowing back into the dewar. Due to the high price of liquefaction, in order to reduce the use of liquid helium, current nuclear magnetic resonance systems at home and abroad have successively introduced liquid helium-free systems, that is, there is no liquid helium in the superconducting system, and a refrigerator is used to directly contact the superconducting magnet with a cold head to reach below the critical temperature of the superconductor to form superconductivity. This type of superconducting magnet will gradually replace the traditional immersion superconducting magnet.

[0003] Since the refrigerator needs regular maintenance, a method has been proposed for the liquid helium magnet-free refrigerator, in which the cylinder of the GM refrigerator is fixed in a vacuum container and the displacer is removed. However, in this method, since the cylinder is exposed to the atmosphere and the cylinder is continuously cooled by the vacuum container, the moisture in the air forms 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.

[0004] The Chinese patent with the patent name "Refrigerator Installation Structure" and patent number ZL201310042360.3 proposes to achieve refrigerator maintenance by forming a vacuum state between the cold head cover and the cylinder. In this structure, indium sheets are used between the refrigerator cold head heat exchanger and the cold head cover heat exchanger to reduce thermal resistance. However, the indium sheet is soft and will deform after one extrusion. If this solution is followed, the indium sheet cannot be replaced after the cylinder body and the cold head cover are separated. When the refrigerator contacts the cold head cover again, the deformation of the indium sheet cannot be guaranteed, which is very likely to greatly increase the contact thermal resistance and reduce the efficiency of cold transmission. If the indium sheet is to be replaced, the refrigerator must be completely pulled out of the cold head cover, and the inner surface of the cold head cover will condense and freeze, and hot gas must be used to heat the inner surface. If it is a liquid helium-free superconducting magnet, the heat exchanger of the cold head cover is directly connected to the superconducting magnet solid. Since the heat transfer components of the heat exchanger are made of oxygen-free copper with extremely high thermal conductivity, when the inner surface of the cold head cover is heated, the heat will be transferred to the superconducting magnet. First, it will affect the performance of the superconducting magnet. Second, due to the huge heat capacity of the superconducting magnet, the inner surface of the cold head cover cannot be heated to above 80°C in a short time, causing the condensed water to vaporize, affecting the efficiency of the entire maintenance work.

[0005] The Chinese patent application, entitled "Superconducting magnet low temperature heat exchange device" and with application number 202011264001.9, uses the method of adding low temperature refrigerant into the cold head cover to achieve rapid maintenance of liquid helium-free superconducting magnets. However, since the cold head cover is full of low temperature refrigerant, gas heat conduction is formed from the room temperature end to the liquid helium end, which increases the heat load of the system, reduces the surplus cold capacity of the superconducting magnet, and is not conducive to the stability of the superconducting magnet. Summary of the invention

[0006] The purpose of the present invention is to provide a refrigerator installation structure for a low-temperature system, which can avoid the use of a large amount of low-temperature refrigerant and can better balance the rapid maintenance and heat transfer performance of the refrigerator, in order to solve the maintenance problem of a liquid helium-free superconducting magnet refrigerator in the prior art.

[0007] The purpose of the present invention is to be solved by the following technical solutions:

[0008] A refrigerator installation structure for a low-temperature system, the refrigerator installation structure includes a cold head cover accommodated in a vacuum container for placing a cooled object and capable of being isolated from a vacuum area of ​​the vacuum container, characterized in that: the cold head cover includes a mounting heat exchange cavity for accommodating an insertion part of the refrigerator, the opening end of the mounting heat exchange cavity is used to insert the insertion part of the refrigerator, and the closed end is provided with a sealed cooling heat exchange cavity for storing a low-temperature refrigerant, and the cooling heat exchanger on the cooling heat exchange cavity is used to cool the cooled object in the vacuum container; the cold head heat exchanger of the refrigerator and the cold head cover heat exchanger of the cold head cover are thermally connected and can be thermally disconnected along the axis direction of the refrigerator.

[0009] The cooling heat exchange cavity is composed of a heat exchanger sleeve and cold head heat exchangers at both ends thereof, and the cooling heat exchanger is airtightly connected. The closed end where the heat exchange cavity is installed and the cooling heat exchange cavity share the same cold head heat exchanger. The heat exchanger sleeve is made of a metal with a thermal conductivity not exceeding 10W / (m•K) in the working temperature range of 4K to 77K.

[0010] The aspect ratio of the cooling and heat exchange cavity is greater than 1 and / or the pressure resistance of the cooling and heat exchange cavity is set to 2-3 MPa.

[0011] The cold head heat exchangers at both ends of the cooling heat exchange cavity and the contact surface between the inner side of the cooling heat exchanger 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.

[0012] The cold head heat exchanger and the cooling heat exchanger are both made of high-purity oxygen-free copper.

[0013] An indium sheet or indium wire with a thickness of 0.5 to 2.0 mm is placed between the thermal connection surfaces of the cold head heat exchanger of the refrigerator and the cold head cover heat exchanger of the cold head cover.

[0014] When the refrigerator is a two-stage refrigerator, the cold head cover includes a cold head cover flange, a first-level sleeve, a first-level cold head cover heat exchanger with a central through hole, a second-level sleeve, and a second-level cold head cover heat exchanger that are coaxially connected in sequence. The thin-walled cylindrical first-level sleeve and the second-level sleeve are air-tightly connected to the cold head cover flange, the first-level cold head cover heat exchanger, and the second-level cold head cover heat exchanger to form an integral structure with an installed heat exchange cavity; the cold head cover flange located at the open end of the installed heat exchange cavity is used for fixed connection with the flange of the refrigerator, and the first-level heat contact surface of the refrigerator protruding from the first-level cold head heat exchanger and the second-level heat contact surface of the refrigerator protruding from the second-level cold head heat exchanger of the refrigerator are respectively in thermal contact with the first-level cold head cover heat contact surface of the first-level cold head cover heat exchanger and the second-level cold head cover heat contact surface of the second-level cold head cover heat exchanger in the cold head cover; the second-level cold head cover heat exchanger, the heat exchanger sleeve, and the cooling heat exchanger are air-tightly connected to form a cooling heat exchange cavity.

[0015] The secondary sleeve and the heat exchanger sleeve are an integrated sleeve, and the secondary cold head sleeve heat exchanger is airtightly fixed in the inner cavity of the integrated sleeve by vacuum brazing and the integrated sleeve is divided into two parts that are not connected to each other.

[0016] When the refrigerator is a single-stage refrigerator, the cold head cover includes a cold head cover flange, a cold head cover sleeve, and a cold head cover heat exchanger that are coaxially connected in sequence. The thin-walled cylindrical cold head cover sleeve is airtightly connected to the cold head cover flange and the cold head cover heat exchanger to form an integral structure with an installed heat exchange cavity; the cold head cover flange located at the open end of the installed heat exchange cavity is used for fixed connection with the flange of the refrigerator, and the protruding refrigerator thermal contact surface of the cold head heat exchanger of the refrigerator is in contact and thermally connected with the cold head cover thermal contact surface of the cold head cover heat exchanger in the cold head cover; the cold head cover heat exchanger and the heat exchanger sleeve and the cooling heat exchanger are airtightly connected to form a cooling heat exchange cavity.

[0017] The installation cavity pipeline which is in airtight communication with the installation heat exchange cavity is connected to the external pressure reducing equipment through the installation cavity connector arranged on the atmosphere side; the cooling cavity pipeline which is in airtight communication with the cooling heat exchange cavity is connected to the external low-temperature refrigerant supply equipment and pressure control equipment through the cooling cavity connector arranged on the atmosphere side.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The mounting structure of the present invention is provided with a relatively independent mounting heat exchange cavity and a cooling heat exchange cavity. The cold head cover provided with the mounting heat exchange cavity is used for mounting and disassembling the refrigerator. The sealed cooling heat exchange cavity storing the low-temperature refrigerant is used for cooling the cooled object in the vacuum container. The refrigerator and the cooled object are separated by the cooling heat exchange cavity, so that the disassembly of the refrigerator will not affect the cooled object in the vacuum container. The cooling heat exchange cavity and the mounting heat exchange cavity sharing the same cold head cover heat exchanger can improve the heat exchange efficiency. The mounting structure can avoid the use of a large amount of low-temperature refrigerant and can better balance the rapid maintenance and heat transfer performance of the refrigerator. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1 It is a schematic diagram of the refrigerator installation structure for a low-temperature system of the present invention when the refrigerator is normally assembled;

[0021] Attached Figure 2 It is a schematic diagram of the refrigerator installation structure for a low-temperature system and the refrigerator separation state of the present invention.

[0022] Among them: 1—refrigerator; 2—cold head cover; 2-1—cold head cover flange; 2a—primary sleeve; 2b—secondary sleeve; 2c—heat exchanger sleeve; 3a—primary thermal contact surface of refrigerator; 3b—secondary thermal contact surface of refrigerator; 4a—primary cold head cover heat exchanger; 4a1—primary cold head cover thermal contact surface; 4a2—primary cold head cover heat exchange surface; 4b—secondary cold head cover heat exchanger; 4b1—secondary cold head cover thermal contact surface; 4b2—cold head cover fin contact surface; 4c—cooling heat exchanger; 4c1—cooling heat exchange surface; 4c2—heat exchanger fin contact surface; 5—cooling cavity pipeline; 61—cooling cavity connector; 62—installation cavity connector; 7—installation cavity pipeline; 8—installation heat exchange cavity; 9—cooling heat exchange cavity; 10—sealing ring; H1—primary cold head heat exchanger; H2—secondary cold head heat exchanger; C1—primary cylinder; C2—secondary cylinder. DETAILED DESCRIPTION

[0023] In combination with the technical background, the traditional refrigerator structure will not be described in detail.

[0024] The following is combined with Figure 1-2 The present invention is further described with examples.

[0025] The refrigerator 1 comprises a primary cylinder body C1 and a secondary cylinder body C2, and a primary cold head H1 and a secondary cold head H2 at the lower end, the primary cold head H1 and the secondary cold head H2 can cool the object to be cooled to 100~40K and 20~4K respectively; a sealing ring 10 is installed on the circumferential side of the hot end of the cylinder body to seal laterally in the cold head cover flange 2-1 of the cold head cover 2. The installation structure of the refrigerator comprises a cold head cover 2 capable of accommodating the refrigerator 1, and the cold head cover 2 is accommodated in a vacuum container ( Figure 1-2 The vacuum container and the object to be cooled are not shown in the figure), and the cold head cover 2 is isolated from the vacuum area of ​​the vacuum container.

[0026] The cold head cover 2 includes a cold head cover flange 2-1, and the lower part of the cold head cover flange 2-1 is coaxially connected to the primary sleeve 2a and the secondary sleeve 2b in sequence, and the primary sleeve 2a and the secondary sleeve 2b are connected by the primary cold head cover heat exchanger 4a of the cold head cover 2, and the lower end of the secondary sleeve 2b is connected to the secondary cold head cover heat exchanger 4b. In this way, a cold head cover 2 with a semi-closed cylindrical structure in an inverted "convex" shape is formed, with one side of the cold head cover flange 2-1 open, one side of the secondary cold head cover heat exchanger 4b closed, and an inverted "convex" shape. In addition, a heat exchanger 4c is arranged on the side of the secondary cold head cover heat exchanger 4b 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 a 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, forming a cooling heat exchange cavity 9. The cold head cover flange 2-1 is fixed on the vacuum container to form a whole.

[0027] The flange 2-1 of the cold head cover 2 has a mounting cavity pipe 7 which is in airtight communication with the mounting heat exchange cavity 8 and a mounting cavity connector 62 which is in airtight communication with the mounting cavity pipe 7 and arranged on the atmosphere side; the mounting cavity connector 62 can be connected to an external decompression device (not shown). The cooling cavity pipe 5 is in airtight communication with the cooling heat exchange cavity 9 and a cooling cavity connector 61 at one end of the flange 2-1 of the cold head cover 2 on the atmosphere side; the cooling cavity connector 61 can be connected to an external low-temperature refrigerant supply device and a pressure control device (not shown)

[0028] The primary cold head cover heat exchanger 4a, the secondary cold head cover heat exchanger 4b, and the cooling heat exchanger 4c are all made of high-purity oxygen-free copper with high thermal conductivity; and the primary cold head cover heat exchanger 4a and the secondary cold head cover heat exchanger 4b are perpendicular to the axial direction of the refrigerator 1, and the primary cold head cover heat contact surface 4a1 and the secondary cold head cover heat contact surface 4b1 accommodated in the heat exchange cavity 8 are used to exchange cold with the cold head of the refrigerator 1. The cooling heat exchanger 4c has a cooling heat exchange surface 4c1 for solid heat transfer with the cooled object.

[0029] like Figure 1 When the refrigerator 1 is inserted into the cold head cover 2, the first-stage heat contact surface 3a of the refrigerator protruding from the first-stage cold head heat exchanger H1 and the second-stage heat contact surface 3b of the refrigerator protruding from the second-stage cold head heat exchanger H2 are in contact with the first-stage heat contact surface 4a1 of the first-stage heat exchanger 4a of the cold head cover 2 and the second-stage heat contact surface 4b1 of the second-stage heat exchanger 4b of the cold head cover 2, and in order to improve the heat transfer performance of their contact surfaces, indium sheets with a thickness of 0.5 to 2.0 mm are respectively provided.

[0030] The cold head cover 2 and the part of the refrigerator 1 inserted into the heat exchange cavity 8 form an annular cavity. The annular cavity area can be evacuated by installing the cavity connector 62.

[0031] In addition, the secondary cold head heat exchanger 4b and the cooling heat exchanger 4c are provided with a cold head fin contact surface 4b2 and a heat exchanger fin contact surface 4c2 contained in the cooling heat exchange cavity 9, and low-temperature refrigerant is added into the cooling heat exchange cavity 9 through the cooling cavity connector 61. The added low-temperature refrigerant can be filled with a gas medium at room temperature according to the site conditions, and enter the cooling heat exchange cavity 9 through the cooling cavity pipe 5, and the gaseous refrigerant gas in the cooling heat exchange cavity 9 is gradually liquefied through the conduction cooling of the refrigerator 1; liquid refrigerant can also be directly added into the cooling heat exchange cavity 9 through the cooling cavity pipe 5.

[0032] Combination Figure 1 and Figure 2 The characteristics of the refrigerator installation structure are further explained.

[0033] In order to reduce heat leakage, the primary sleeve 2a and the secondary sleeve 2b of the cold head cover 2 are processed into thin-walled cylindrical shapes using metal with low thermal conductivity, and the thermal conductivity of the metal used in the working temperature range of 4K~77K is less than 10W / (m·K). The primary sleeve 2a and the secondary sleeve 2b are connected to the hot end flange 2-1, the primary cold head cover heat exchanger 4a, and the secondary cold head cover heat exchanger 4b by welding to form an integral body. When the refrigerator 1 is inserted into the heat exchange cavity 8, The flange of the refrigerator 1 is fixed to the cold head sleeve flange 2-1 by forward bolts (not shown), and the first-stage cold head heat exchanger H1 and the second-stage cold head heat exchanger H2 are squeezed by axial preload force, so as to improve the contact performance between the first-stage heat contact surface 3a of the first-stage cold head heat exchanger H1 and the second-stage heat contact surface 3b of the second-stage cold head heat exchanger H2 and the first-stage heat contact surface 4a1 of the first-stage cold head sleeve heat exchanger 4a and the second-stage heat contact surface 4b1 of the second-stage cold head sleeve heat exchanger 4b, respectively. In order to improve the heat exchange effect, indium sheets or indium wires can be added between the heat contact surfaces, and the slight gaps or cracks between the contact surfaces can be filled and leveled by their deformation. The heat exchange cavity 8 is installed at the hot end to be airtightly isolated from the external atmospheric environment by a sealing ring 10.

[0034] Before starting, the atmosphere in the heat exchange cavity 8 is decompressed to a vacuum state, generally below 0.1 Pa, through the cavity connector 62. At the same time, a certain amount of low-temperature refrigerant is added to the cavity through the cooling cavity connector 61.

[0035] After starting up, the refrigerator 1 performs cooling, and the primary cold head heat exchanger H1 and the secondary cold head heat exchanger H2 gradually transfer the cold energy to the primary cold head jacket heat exchanger 4a and the secondary cold head jacket heat exchanger 4b at the corresponding cold heads.

[0036] The first-stage cold head cover heat exchanger 4a, whose heat exchange surface 4a2 is not contained in the heat exchange cavity 8, can be used to connect with a cold screen, especially a 4K low-temperature refrigerator, and finally cool to 60~40K to form a low-temperature radiation screen to prevent objects in the 4K temperature zone from directly exchanging heat with the room temperature.

[0037] In addition, the low-temperature refrigerant contained in the cooling heat exchange cavity 9 can be helium, neon or nitrogen, or a mixed gas of the above gases according to the requirements of the cooling temperature zone.

[0038] When the refrigerator 1 is further cooled, the low-temperature refrigerant in the cooling heat exchange cavity 9 is cooled and heat exchanged with the cold head cover fin contact surface 4b2 of the fin structure of the secondary cold head cover heat exchanger 4b, and is gradually cooled to the liquefaction point temperature, forming liquid deposited on the "bottom" of the cooling heat exchange cavity 9, that is, on the heat exchanger fin contact surface 4c2 of the cooling heat exchanger 4c with a fin structure, and is cooled to the refrigerant liquefaction temperature. For example, for a 4K refrigerator, helium is used as the refrigerant. Initially, the helium contained in the cooling heat exchange cavity 9 is at room temperature near 300K. As the secondary cold head heat exchanger H2 of the refrigerator 1 gradually cools to 4K, the helium is gradually cooled to the liquefaction point, forming liquid helium stored in the cooling heat exchange cavity 9. The cooling heat exchanger 4c is solidly connected to the cooled object through the cooling heat exchange surface 4c1, and also transfers heat to the liquid helium. At this moment, the liquid helium will evaporate and rise, and will be condensed again after contacting the cold head cover fin contact surface 4b2 of the secondary cold head cover heat exchanger 4b, forming droplets, which will drip into the liquid helium or onto the heat exchanger fin contact surface 4c2, forming a small zero evaporation system.

[0039] Further explanation.

[0040] When the refrigerator 1 needs to be maintained, the refrigerator 1 needs to be pulled out of the cold head cover 2. At this moment, air enters the installation heat exchange cavity 8 of the cold head cover 2, and freezes into ice or condenses on the inner circumference of the primary sleeve 2a, the secondary sleeve 2b, and the primary cold head cover heat contact surface 4a1 of the primary cold head cover heat exchanger 4a and the secondary cold head cover heat contact surface 4b1 of the secondary cold head cover heat exchanger 4b. Hot nitrogen at 60 to 100°C can be used to heat the installation heat exchange cavity 8. At this moment, the liquid helium in the cooling heat exchange cavity 9 will be vaporized, and at the same time, it will be connected to the external vacuum pump group (not shown) through the cooling cavity connector 61, and the helium in the cooling heat exchange cavity 9 will be extracted through the cooling cavity pipeline 5, so that the cooling heat exchange cavity 9 is in a negative pressure or vacuum state.

[0041] For the cooling heat exchange cavity 9 containing low-temperature refrigerant, the secondary cold head cover heat exchanger 4b and the cooling heat exchanger 4c are both made of high-purity oxygen-free copper. Therefore, when the secondary cold head cover heat contact surface 4b1 is heated, the secondary cold head cover heat exchanger 4b will quickly rise to 60~100°C. Because the barrel of the heat exchanger sleeve 2c connecting the secondary cold head cover heat exchanger 4b and the cooling heat exchanger 4c is made of metal with low thermal conductivity, and the thermal conductivity in the working temperature range of 4K~77K is less than 10W / (m·K), so that the heat heated in the installation heat exchange cavity 8 is not easily transferred to the cooling heat exchanger 4c, which avoids the object being cooled from being heated. Therefore, when the cold head cover 2 is heated, the object being cooled is still at a relatively low temperature and does not need to be restored to the room temperature environment together with the cold head cover 2, so the entire heating process takes less time.

[0042] In the specific implementation process, the cooling heat exchange cavity 9 can be made slender, for example, the aspect 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 does not need to be directly decompressed to a negative pressure or vacuum state. During the heating process, the upper part is hot and the lower part is cold, forming a stable gas stratification, which will not cause convective heat transfer. Since the thermal conductivity of the gas is small, the static heat leakage is small, and the liquid helium at the bottom will not volatilize too much.

[0043] The strength of the heat exchanger sleeve 2c on the periphery of the cooling heat exchange cavity 9 can also be appropriately strengthened to make the cooling heat exchange cavity 9 a pressure-resistant cavity. The helium evaporated during the heating process is contained therein to avoid helium loss. Since the volume of the cooling heat exchange cavity 9 is relatively small, it is recommended that it does not exceed 20L in this embodiment, and the pressure resistance of the cavity is set to 2-3MPa.

[0044] If the liquid helium at the bottom continues to evaporate and the internal pressure is too high, the evaporated helium can also be discharged into the atmosphere through the cooling chamber connector 61. The amount of liquid helium in the cooling heat exchange cavity 9 is greatly reduced compared to the traditional 1000L to 2000L liquid helium superconducting system. There are two modes for filling the cooling heat exchange cavity 9 with low-temperature refrigerant: one is to directly fill it with liquid low-temperature refrigerant through the cooling chamber connector 61; the other is to use gas high-pressure refrigerant gas to inject it through the cooling chamber connector 61, and through conduction cooling of the refrigerator 1, the low-temperature refrigerant is converted from gas to liquid. Therefore, during maintenance, it is not necessary to use a liquid Dewar system, and only a pressure cylinder can be used.

[0045] In order to reduce heat leakage, the cooling cavity pipe 5 is made of a thin-walled capillary tube. The secondary cold head heat exchanger 4b and the cooling heat exchanger 4c at both ends of the cooling heat exchange cavity 9 are basically in the same temperature zone, so there is no conduction heat leakage problem in this area; and because the heat leakage of the primary sleeve 2a is offset by the cold amount provided by the primary cold head heat exchanger H1, it will not be conducted to the secondary cylinder C2; the only heat transfer heat leakage is the heat leakage of the secondary sleeve 2b of the cold head 2.

[0046] In order to simplify the structure, the secondary sleeve 2b of the cold head sleeve 2 can be made into one piece with the heat exchanger sleeve 2c on the outer periphery of the cooling heat exchange cavity 9, and the entire secondary cold head sleeve heat exchanger 4b is inserted into the integrated sleeve, and the secondary cold head sleeve heat exchanger 4b is fixed in an appropriate axial position of the integrated sleeve in an airtight manner by vacuum brazing.

[0047] Further explanation.

[0048] For easy maintenance, indium sheets or indium wires can be fixed on the primary thermal contact surface 3a and the 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. When the refrigerator 1 is pulled out of the cold head cover 2, the indium sheets and indium wires are also taken out together.

[0049] During the specific operation, a new refrigerator 1 can be prepared in advance, and after the indium sheet or indium wire is properly arranged, the above operation can be performed. Once the water vapor in the cold head cover 2 is removed, the spare refrigerator 1 is quickly inserted into the cold head cover 2, and refrigeration is performed according to the method described above. Since the indium sheet and indium wire on the new refrigerator 1 have not been squeezed, when they are inserted into the cold head cover 2 again, the first-level thermal contact surface 3a of the refrigerator and the first-level thermal contact surface 4a1 of the cold head cover, and the second-level thermal contact surface 3b of the refrigerator and the second-level thermal contact surface 4b1 of the cold head cover can be better contacted, thereby improving the heat transfer performance between the contact surfaces.

[0050] Different from the traditional immersion cooling, the structure adopted in the present invention avoids the use of a large amount of low-temperature refrigerant, and can better balance the rapid maintenance and heat transfer performance of the refrigerator.

[0051] In the above embodiment, a two-stage refrigerator is taken as an example. This structure can also be used for the installation of a single-stage refrigerator.

[0052] Specifically, when designing the cold head cover 2, it is not necessary to process the primary sleeve 2a and the primary cold head cover heat exchanger 4a, and only the secondary sleeve 2b and the secondary cold head cover heat exchanger 4b at the low temperature end need to be retained.

[0053] The above embodiments are only for illustrating the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention; any technology not involved in the present invention can be realized by existing technologies.

Claims

1. A refrigerator installation structure for a low temperature system, the refrigerator installation structure comprising a cold head cover (2) accommodated in a vacuum container for placing a cooled object and capable of being isolated from a vacuum area of ​​the vacuum container, characterized in that: The cold head cover (2) comprises a heat exchange installation cavity (8) for accommodating an insertion portion of a refrigerator (1); the open end of the heat exchange installation cavity (8) is used to insert the insertion portion of the refrigerator (1); the closed end is provided with a sealed cooling heat exchange cavity (9) for storing a low-temperature refrigerant; the cooling heat exchanger (4c) on the cooling heat exchange cavity (9) is used to cool a cooled object in a vacuum container; the cold head heat exchanger of the refrigerator (1) and the cold head cover heat exchanger of the cold head cover (2) are thermally connected and can be thermally disconnected along the axis direction of the refrigerator (1); the cooling heat exchange cavity (9) is composed of a heat exchanger sleeve (2c) and the cold head cover heat exchangers and the cooling heat exchanger (4c) at both ends of the heat exchanger sleeve (2c) being airtightly connected; the closed end of the heat exchange installation cavity (8) and the cooling heat exchange cavity (9) share the same cold head cover heat exchanger.

2. The refrigerator installation structure for a low temperature system according to claim 1, characterized in that: The heat exchanger sleeve (2c) is made of a metal having a thermal conductivity not exceeding 10 W / (m•K) in a working temperature range of 4K to 77K.

3. The refrigerator installation structure for a low temperature system according to claim 1 or 2, characterized in that: The aspect ratio of the cooling heat exchange cavity (9) is greater than 1 and / or the pressure resistance of the cooling heat exchange cavity (9) is set to 2-3 MPa.

4. The refrigerator installation structure for a low temperature system according to claim 1 or 2, characterized in that: The cold head heat exchangers at both ends of the cooling heat exchange cavity (9) and the inner side of the cooling heat exchanger (4c) in contact with the low-temperature refrigerant have fin structures; the cooling heat exchanger (4c) is in thermal contact with the object to be cooled via the cooling heat exchange surface (4c1).

5. The refrigerator installation structure for a low temperature system according to claim 1 or 2, characterized in that: The cold head heat exchanger and the cooling heat exchanger (4c) are both made of high-purity oxygen-free copper.

6. The refrigerator installation structure for a low temperature system according to claim 1, characterized in that: An indium sheet or indium wire with a thickness of 0.5 to 2.0 mm is placed between the thermal connection surfaces of the cold head heat exchanger of the refrigerator (1) and the cold head cover heat exchanger of the cold head cover (2).

7. The refrigerator installation structure for a low temperature system according to claim 1, 2 or 6, characterized in that: When the refrigerator (1) is a two-stage refrigerator, the cold head cover (2) comprises a cold head cover flange (2-1), a primary sleeve (2a), a primary cold head cover heat exchanger (4a) having a central through hole, a secondary sleeve (2b), and a secondary cold head cover heat exchanger (4b) which are coaxially connected in sequence; the thin-walled cylindrical primary sleeve (2a) and the secondary sleeve (2b) are airtightly connected to the cold head cover flange (2-1), the primary cold head cover heat exchanger (4a), and the secondary cold head cover heat exchanger (4b) to form an integral structure having a heat exchange cavity (8) for mounting; the cold head cover flange (2-1) located at the open end of the heat exchange cavity (8) for mounting is ) is used for fixed connection with the flange of the refrigerator (1); the refrigerator's first-level thermal contact surface (3a) protruding from the first-level cold head heat exchanger (H1) and the refrigerator's second-level thermal contact surface (3b) protruding from the second-level cold head heat exchanger (H2) of the refrigerator (1) are respectively in contact and thermally connected with the first-level cold head cover thermal contact surface (4a1) of the first-level cold head cover heat exchanger (4a) and the second-level cold head cover thermal contact surface (4b1) of the second-level cold head cover heat exchanger (4b) in the cold head cover (2); the second-level cold head cover heat exchanger (4b) and the heat exchanger sleeve (2c) and the cooling heat exchanger (4c) are airtightly connected to form a cooling heat exchange cavity (9).

8. The refrigerator installation structure for a low temperature system according to claim 7, characterized in that: The secondary sleeve (2b) and the heat exchanger sleeve (2c) are integrated sleeves, and the secondary cold head sleeve heat exchanger (4b) is airtightly fixed in the inner cavity of the integrated sleeve by vacuum brazing, and the integrated sleeve is divided into two parts that are not connected to each other.

9. The refrigerator installation structure for a low temperature system according to claim 1, characterized in that: When the refrigerator (1) is a single-stage refrigerator, the cold head cover (2) comprises a cold head cover flange (2-1), a cold head cover sleeve, and a cold head cover heat exchanger that are coaxially connected in sequence; the thin-walled cylindrical cold head cover sleeve, the cold head cover flange (2-1), and the cold head cover heat exchanger are airtightly connected to form an integral structure having a heat exchange cavity (8) for mounting; the cold head cover flange (2-1) located at the open end of the heat exchange cavity (8) for mounting is used for fixed connection with the flange of the refrigerator (1); the protruding refrigerator thermal contact surface of the cold head heat exchanger of the refrigerator (1) is in contact with the cold head cover thermal contact surface of the cold head cover heat exchanger in the cold head cover (2); the cold head cover heat exchanger, the heat exchanger sleeve (2c), and the cooling heat exchanger (4c) are airtightly connected to form a cooling heat exchange cavity (9).

10. The refrigerator installation structure for a low temperature system according to claim 1, characterized in that: The installation cavity pipeline (7) which is in airtight communication with the installation heat exchange cavity (8) is connected to an external pressure reducing device via an installation cavity connector (62) arranged on the atmosphere side; the cooling cavity pipeline (5) which is in airtight communication with the cooling heat exchange cavity (9) is connected to an external low-temperature refrigerant supply device and a pressure control device via a cooling cavity connector (61) arranged on the atmosphere side.

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