CN116221611A

CN116221611A - Liquid nitrogen storage system

Info

Publication number: CN116221611A
Application number: CN202310303964.2A
Authority: CN
Inventors: 汪桢子; 李敏虹; 汤寿泉; 谢宏; 余鹏; 李重杭; 王哲; 张繁; 黄楷敏; 徐振华
Original assignee: Shenzhen Power Supply Co ltd
Current assignee: Shenzhen Power Supply Co ltd
Priority date: 2023-03-21
Filing date: 2023-03-21
Publication date: 2023-06-06

Abstract

The utility model relates to a liquid nitrogen storage system, including a jar body, heat exchanger and refrigerator, be equipped with the storage chamber that is used for storing liquid nitrogen in the jar body, and the one end is equipped with the opening of the other end intercommunication with the storage chamber in the storage chamber intercommunication, the heat exchanger shutoff is in the junction of keeping apart chamber and storage chamber, refrigerator detachably installs in the opening part, at least part of refrigerator penetrates the isolation intracavity through the opening, and be connected with the heat exchanger, and the refrigerator has the cold portion that leads that is used for being connected with the heat exchanger, wherein, cold portion that leads and storage chamber are configured to can carry out heat exchange with the help of the heat exchanger. Above-mentioned liquid nitrogen storage system sets up refrigerator and jar body detachably and is connected, makes the refrigerator be convenient for install and remove in the jar body to because the heat exchanger shutoff is in the junction in storage chamber and isolation chamber, and does not influence the normal work in storage chamber when installing and removing the refrigerator, it is more convenient to make the process of changing the refrigerator.

Description

Liquid nitrogen storage system

Technical Field

The application relates to the technical field of liquid nitrogen storage equipment, in particular to a liquid nitrogen storage system.

Background

At present, the temperature of liquid nitrogen is 77K, and liquid nitrogen is easy to evaporate when the liquid nitrogen is placed for a long time. For this reason, there is provided a liquid nitrogen storage system for reducing evaporation loss of liquid nitrogen by providing a refrigerator for refrigerating liquid nitrogen.

However, the liquid nitrogen storage system in the related art has a problem in that the replacement of the refrigerator is inconvenient.

Disclosure of Invention

Based on this, it is necessary to provide a liquid nitrogen storage system capable of more conveniently replacing a refrigerator in order to solve the problem of inconvenient replacement of the refrigerator in the liquid nitrogen storage system of the related art.

According to one aspect of the present application, there is provided a liquid nitrogen storage system comprising:

the liquid nitrogen storage tank comprises a tank body, wherein a storage cavity for storing liquid nitrogen and an isolation cavity with one end communicated with the storage cavity are arranged in the tank body, and an opening communicated with the other end of the isolation cavity is formed in the tank body;

the heat exchanger is plugged at the joint of the isolation cavity and the storage cavity; and

the refrigerator is detachably arranged at the opening, at least part of the refrigerator penetrates into the isolation cavity through the opening and is connected with the heat exchanger, and the refrigerator is provided with a cold guide part used for being connected with the heat exchanger;

wherein the cold guide and the storage chamber are configured to be capable of heat exchange by means of the heat exchanger.

Above-mentioned liquid nitrogen storage system sets up the storage chamber in order to store liquid nitrogen to set up the isolation chamber in order to install the refrigerator, the heat exchanger sets up in the junction in storage chamber and isolation chamber, so that the cold portion of leading of refrigerator carries out the heat exchange with the storage chamber with the help of the heat exchanger, thereby can utilize the refrigerator to reduce the temperature of storing the intracavity, reduces the evaporation loss of liquid nitrogen. And because the refrigerator is detachably connected with the tank body, the refrigerator is convenient to assemble and disassemble in the tank body, the heat exchanger is blocked at the joint of the storage cavity and the isolation cavity, and the normal work of the storage cavity is not affected when the refrigerator is assembled and disassembled, so that the process of replacing the refrigerator is more convenient.

In some embodiments, the refrigerator includes a first portion and a second portion;

at least part of the first part penetrates into the isolation cavity through the opening, and the part of the first part penetrating into the isolation cavity is provided with the cold guide part;

the second part is arranged outside the tank body and connected with the first part, and the second part is detachably connected with the outer wall of the tank body.

In some embodiments, the second portion is spaced from the can body along an axial direction of the opening;

the liquid nitrogen storage system further comprises a connecting pipe, the connecting pipe is sleeved on the part, extending out of the tank body, of the first part, one end of the connecting pipe is connected with the outer wall of the tank body, and the other end of the connecting pipe is detachably connected with the second part.

In some embodiments, a channel penetrating the connecting pipe is arranged in the connecting pipe, and a part of the first part extending out of the tank body penetrates through the channel;

the liquid nitrogen storage system further includes an evacuation valve connected to the outer peripheral wall of the connecting tube for evacuating the inside of the passage and the isolation chamber.

In some embodiments, along the axial direction of the opening, a heat exchange surface for connecting with the cold guide part is arranged on one side of the heat exchanger close to the isolation cavity, and a plurality of fins are arranged on the other side of the heat exchanger.

In some embodiments, the cooling guide portion is pressed against the heat exchange surface along the axial direction of the opening.

In some embodiments, the liquid nitrogen storage system further comprises a thermally conductive member disposed between the cold conducting portion and the heat exchanging surface.

In some embodiments, the liquid nitrogen storage system further comprises a heater coupled to the heat exchanger, the heater configured to heat the heat exchanger.

In some embodiments, the liquid nitrogen storage system further comprises a temperature sensing member disposed on the heat exchanger, the temperature sensing member for sensing the temperature of the heat exchanger.

In some embodiments, an inner shell is provided within the tank, the inner shell having the storage cavity and the isolation cavity therein;

a vacuum cavity is defined between the outer wall of the inner shell and the inner wall of the tank body.

Drawings

FIG. 1 is a schematic diagram of a liquid nitrogen storage system according to an embodiment of the present application.

FIG. 2 is a schematic partial view of the liquid nitrogen storage system of the embodiment of FIG. 1.

Reference numerals illustrate:

100. a liquid nitrogen storage system;

10. a tank body; 11. a storage chamber; 12. an isolation chamber; 13. an opening; 14. an inner case; 15. a vacuum chamber;

20. a heat exchanger; 21. a heat exchange surface; 22. a fin;

30. a refrigerating machine; 31. a cold guide part; 32. a first portion; 33. a second portion; 331. a second flange;

40. a connecting pipe; 41. a channel; 42. a first flange;

50. an evacuation valve;

60. a heater;

70. a temperature measuring member;

80. a first pipeline; 81. adding a liquid discharge valve;

90. a second pipeline; 91. an evacuation valve; 92. a pressure gauge; 93. a safety valve.

Detailed Description

In order to make the above objects, features and advantages of the present application more comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is, however, susceptible of embodiment in many other forms than those described herein and similar modifications can be made by those skilled in the art without departing from the spirit of the application, and therefore the application is not to be limited to the specific embodiments disclosed below.

In the description of the present application, it should be understood that, if there are terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., these terms refer to the orientation or positional relationship based on the drawings, which are merely for convenience of description and simplification of description, and do not indicate or imply that the apparatus or element referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present application.

Furthermore, the terms "first," "second," and the like, if any, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the terms "plurality" and "a plurality" if any, mean at least two, such as two, three, etc., unless specifically defined otherwise.

In this application, unless explicitly stated and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly. For example, the two parts can be fixedly connected, detachably connected or integrated; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art as the case may be.

In this application, unless expressly stated or limited otherwise, the meaning of a first feature being "on" or "off" a second feature, and the like, is that the first and second features are either in direct contact or in indirect contact through an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that if an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. If an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein, if any, are for descriptive purposes only and do not represent a unique embodiment.

The temperature of the liquid nitrogen at normal pressure is 77K (-196 ℃), and the liquid nitrogen is easy to gasify due to the lower temperature, so that the pressure in a liquid nitrogen storage system for storing the liquid nitrogen is increased, and further the discharge loss of the liquid nitrogen in the liquid nitrogen storage system is caused. Therefore, in the related art, a liquid nitrogen storage system is provided, and the system uses the cold energy of a refrigerant to re-condense the nitrogen evaporated in the liquid nitrogen storage system into liquid by additionally arranging a refrigerator as a cold source so as to reduce liquid nitrogen discharge caused by pressure rise in the system.

However, the liquid nitrogen storage system in the related art has a problem in that the refrigerator is inconvenient to replace when the refrigerator is damaged and needs to be maintained or replaced.

Accordingly, it is desirable to provide a liquid nitrogen storage system that allows for more convenient replacement of the refrigerator.

FIG. 1 is a schematic diagram of a liquid nitrogen storage system according to an embodiment of the present application; FIG. 2 is a schematic partial view of the liquid nitrogen storage system of the embodiment of FIG. 1.

Referring to fig. 1-2, a liquid nitrogen storage system 100 according to an embodiment of the present application includes a tank 10, a heat exchanger 20, and a refrigerator 30.

The tank body 10 is internally provided with a storage cavity 11 for storing liquid nitrogen and an isolation cavity 12 with one end communicated with the storage cavity 11, the tank body 10 is provided with an opening 13 communicated with the other end of the isolation cavity 12, and the heat exchanger 20 is plugged at the joint of the isolation cavity 12 and the storage cavity 11. The refrigerator 30 is detachably installed at the opening 13, at least part of the refrigerator 30 penetrates into the isolation chamber 12 through the opening 13 and is connected with the heat exchanger 20, and the refrigerator 30 has a cold guide 31 for connection with the heat exchanger 20. Wherein the cold guide 31 and the storage chamber 11 are configured to be capable of heat exchange by means of the heat exchanger 20.

In the liquid nitrogen storage system 100, the storage cavity 11 is provided in the tank 10 to store liquid nitrogen, the isolation cavity 12 is provided to install the refrigerator 30, and the heat exchanger 20 is provided at the junction of the storage cavity 11 and the isolation cavity 12, so that the cold-conducting portion 31 of the refrigerator 30 exchanges heat with the storage cavity 11 by means of the heat exchanger 20, thereby reducing the temperature in the storage cavity 11 by using the refrigerator 30 and reducing the evaporation loss of liquid nitrogen. And because refrigerator 30 is connected with jar body 10 detachably, make refrigerator 30 be convenient for install and remove in jar body 10, heat exchanger 20 shutoff is in the junction of bin 11 and isolation chamber 12, and bin 11 and external each other do not influence when making install and remove refrigerator 30, do not influence bin 11's normal work promptly to reduce the risk of causing the accident by the low temperature, improve the security of changing refrigerator 30 and the safety in utilization of liquid nitrogen storage system 100, and make the process of changing refrigerator 30 more convenient, reduce the time that changes refrigerator 30 required.

In the actual use process, when the liquid nitrogen in the storage cavity 11 is evaporated, the cold energy of the refrigerator 30 is utilized to realize the reliquefaction of the evaporated nitrogen in the storage cavity 11, so that the nitrogen emission is avoided. In addition, by utilizing the redundant cold energy of the refrigerator 30, the pressure of the nitrogen can be further reduced to a negative pressure state, namely a supercooled state (< 77K), so as to meet various test requirements.

In some embodiments, as shown in fig. 1-2, the refrigerator 30 includes a first portion 32 and a second portion 33. At least part of the first part 32 penetrates into the isolation cavity 12 through the opening 13, a cold guide part 31 is arranged on the part of the first part 32 penetrating into the isolation cavity 12, the second part 33 is arranged outside the tank body 10 and connected with the first part 32, and the second part 33 is detachably connected with the outer wall of the tank body 10. In this way, the refrigerator 30 includes the first portion 32 and the second portion 33, the first portion 32 is used for penetrating into the isolation cavity 12, and the cold conducting portion 31 arranged on the first portion 32 is used for refrigerating the storage cavity 11 by means of the heat exchanger 20, and the second portion 33 is used for being detachably connected with the outer wall of the tank body 10, so that when the refrigerator 30 is replaced, only the refrigerator 30 and the tank body 10 need to be disassembled and assembled outside the tank body 10, and the operation convenience of replacing the refrigerator 30 is further improved.

The refrigerator 30 may be of different types according to the use requirements, and for example, a GM refrigerator, a pulse tube refrigerator, a stirling refrigerator, or the like may be used.

Optionally, the first portion 32 comprises a refrigerator body and the second portion 33 comprises a refrigerator cylinder.

In some embodiments, as shown in fig. 1-2, the second portion 33 is spaced from the can 10 along the axis of the opening 13. The liquid nitrogen storage system 100 further includes a connection pipe 40, wherein the connection pipe 40 is sleeved on the portion of the first portion 32 extending out of the tank body 10, one end of the connection pipe 40 is connected with the outer wall of the tank body 10, and the other end of the connection pipe 40 is detachably connected with the second portion 33. In this way, the second portion 33 is connected to the tank 10 by means of the connecting pipe 40, and the second portion 33 is detachably connected to the end of the connecting pipe 40 away from the tank 10, so that when the refrigerator 30 is replaced, the connection between the connecting pipe 40 and the second portion 33 is operated, and the convenience in assembling and disassembling the refrigerator 30 is further improved. And since both ends of the connection pipe 40 are respectively connected to the second portion 33 and the outer wall of the tank body 10, thereby isolating the isolation chamber 12 from the outside, the heat exchange amount of the first portion 32 of the refrigerator 30 with the outside is reduced during the normal operation of the liquid nitrogen storage system 100.

Alternatively, the connection tube 40 may employ a bellows.

Specifically, the material of the bellows may be metal or rubber. It should be noted that, when the material of the bellows is rubber, the rubber needs to have higher strength and lower air release rate.

In some embodiments, as shown in fig. 2, the end of the connection pipe 40 away from the can body 10 is provided with a first flange 42, and the side of the second portion 33 adjacent to the can body 10 in the axial direction of the opening 13 is provided with a second flange 331, and the second flange 331 is connected to the first flange 42.

In some embodiments, as shown in fig. 1-2, a passage 41 is provided through the connecting tube 40, and the portion of the first portion 32 extending out of the tank 10 extends through the passage 41. Liquid nitrogen storage system 100 further includes an evacuation valve 50 connected to the outer peripheral wall of connecting tube 40, evacuation valve 50 being used to evacuate the interior of passageway 41 and isolation chamber 12. In this way, during the operation of the liquid nitrogen storage system 100, the evacuation valve 50 may be used to evacuate the channel 41 and the isolation chamber 12, so as to further reduce the heat exchange amount between the second portion 33 of the refrigerator 30 and the outside, and thus improve the refrigerating effect of the refrigerator 30 on the storage chamber 11. And by providing the evacuation valve 50, the connection between the cold guide 31 of the refrigerator 30 and the heat exchanger 20 can be made more firm by using the vacuum suction force in the passage 41 and the isolation chamber 12.

Optionally, the liquid nitrogen storage system 100 further includes a sealing ring (not shown) sealingly connected between the first flange 42 and the second flange 331 to improve the gas tightness of the isolation chamber 12.

In some embodiments, as shown in fig. 1-2, along the axial direction of the opening 13, a side of the heat exchanger 20 adjacent to the isolation chamber 12 has a heat exchange surface 21 for connection with the cold guide 31, and the other side of the heat exchanger 20 is provided with a plurality of fins 22. In this way, by arranging the fins 22, the heat conducting performance of the heat exchanger 20 is improved, and the heat exchange between the heat exchanger 20 and the storage cavity 11 is enhanced.

Specifically, the heat exchange surface 21 is in surface contact with the cold guide 31.

In some embodiments, the cold guide 31 is pressed against the heat exchange surface 21 along the axial direction of the opening 13. In this way, the cold guide part 31 is contacted with the heat exchange surface 21 under a certain pressure, so that the thermal contact between the cold guide part 31 and the heat exchange surface 21 is better.

In some embodiments, liquid nitrogen storage system 100 further includes a thermally conductive member disposed between cold-conducting portion 31 and heat exchange surface 21 to further enhance thermal contact between cold-conducting portion 31 and heat exchange surface 21.

It is understood that the heat conductive member has a high heat conductivity. Alternatively, the heat conductive member may be made of a soft metal such as an indium sheet.

In order to more reliably seal the heat exchanger 20 at the junction between the isolation chamber 12 and the storage chamber 11, in some embodiments, along the axial direction of the opening 13, one side of the heat exchanger 20, which is close to the isolation chamber 12, is welded to the chamber wall of the isolation chamber 12, and the other side of the heat exchanger 20 is welded to the chamber wall of the storage chamber 11, so that the heat exchanger 20 more reliably isolates the isolation chamber 12 and the storage chamber 11, and the air tightness of the storage chamber 11 is improved.

Optionally, the heat exchanger 20 is welded to the wall of the isolation cavity 12 by vacuum brazing, and the heat exchanger 20 is welded to the wall of the storage cavity 11 by vacuum brazing, so as to further improve the air tightness of the storage cavity 11.

In some embodiments, the heat exchanger 20 may be made of copper, so that the heat exchanger 20 has a high thermal conductivity coefficient, and the heat exchanger 20 is convenient to be welded with the cavity walls of the isolation cavity 12 and the plugging cavity. In other embodiments, heat exchanger 20 may be made of aluminum, or other materials having a higher thermal conductivity in the liquid nitrogen temperature region.

In some embodiments, liquid nitrogen storage system 100 further includes a heater 60 coupled to heat exchanger 20, heater 60 being configured to heat exchanger 20. In this way, the heater 60 is provided to balance the excess cooling capacity. For example, during normal operation of the liquid nitrogen storage system 100, the heat exchanger 20 can be heated by the heater 60 to adjust the temperature of the heat exchanger 20, thereby achieving temperature adjustment of supercooled liquid nitrogen or saturated liquid nitrogen in the storage chamber 11. In addition, when the refrigerator 30 needs to be replaced, the heater 60 can heat the heat exchanger 20, so that the refrigerator 30 is more convenient to detach.

In the actual replacement process, when the refrigerator 30 fails and needs maintenance, the heater 60 is used to heat the heat exchanger 20 to normal temperature, then the evacuation valve 50 is used to charge normal pressure nitrogen into the channel 41 and the isolation cavity 12, then the refrigerator 30 is separated from the connecting pipe 40, and the refrigerator 30 is pulled out for replacement. Since the isolation chamber 12 and the storage chamber 11 are isolated from each other, nitrogen gas of the storage chamber 11 is not discharged from the storage chamber 11 when the refrigerator 30 is replaced, thereby reducing liquid nitrogen loss when the refrigerator 30 is replaced.

Alternatively, the heater 60 may include a heating wire or a heating rod. When the heater 60 includes a heating wire, the heating wire may be wound outside the heat exchanger 20. When the heater 60 includes a heating rod, the heating rod may be inserted into the heat exchanger 20.

In some embodiments, as shown in fig. 1-2, the liquid nitrogen storage system 100 further includes a temperature sensing member 70 disposed on the heat exchanger 20, the temperature sensing member 70 being configured to sense the temperature of the heat exchanger 20. In this way, the temperature of the heat exchanger 20 is sensed by providing the temperature measuring member 70 so as to control the heater 60 to perform temperature adjustment of the heat exchanger 20 according to the temperature acquired by the temperature measuring member 70.

In some embodiments, as shown in fig. 1, the liquid nitrogen storage system 100 further includes a first pipeline 80 and a liquid adding and draining valve 81, the first pipeline 80 is penetrating through the tank body 10, one end of the first pipeline 80 extending into the tank body 10 is communicated with the storage cavity 11, and the liquid adding and draining valve 81 is disposed on one end of the first pipeline 80 extending out of the tank body 10. In this way, the liquid adding and discharging valve 81 is provided so as to charge the liquid nitrogen into the storage chamber 11 through the liquid adding and discharging valve 81 or to discharge the liquid nitrogen in the storage chamber 11 out of the tank 10 through the liquid adding and discharging valve 81.

For example, if liquid nitrogen is lost during replacement of the refrigerator 30 during actual use, the storage chamber 11 may be filled with nitrogen gas by the liquid adding/discharging valve 81 to perform liquefaction replenishment.

In some embodiments, as shown in fig. 1, the liquid nitrogen storage system 100 further includes a second pipeline 90 and an evacuation valve 91, the second pipeline 90 is disposed through the tank body 10, one end of the second pipeline 90 extending into the tank body 10 is communicated with the storage cavity 11, the evacuation valve 91 is disposed on one end of the second pipeline 90 extending out of the tank body 10, and the evacuation valve 91 is used for discharging nitrogen evaporated in the storage cavity 11.

In some embodiments, as shown in fig. 1, the liquid nitrogen storage system 100 further includes a pressure gauge 92 provided at an end of the second pipeline 90 extending out of the tank body 10, the pressure gauge 92 being used to detect the pressure in the storage chamber 11, and a safety valve 93 being used to prevent an explosion accident caused by an overpressure in the storage chamber 11.

In some embodiments, as shown in fig. 1, an inner shell 14 is provided in the tank 10, a storage chamber 11 and an isolation chamber 12 are provided in the inner shell 14, and a vacuum chamber 15 is defined between the outer wall of the inner shell 14 and the inner wall of the tank 10. In this way, the vacuum chamber 15 further isolates the storage chamber 11 from the outside, so as to reduce the heat exchange amount between the storage chamber 11 and the outside, and further reduce the evaporation loss of the liquid nitrogen in the storage chamber 11.

Therefore, the liquid nitrogen storage system 100 provided by the application is provided with the refrigerator 30 so as to utilize the cold energy of the refrigerator 30 to re-condense the evaporated nitrogen in the storage cavity 11 into liquid, thereby avoiding liquid nitrogen discharge caused by pressure rise in the storage cavity 11, and when the cold energy of the refrigerator 30 is larger than the cold energy required by the re-liquefaction of the nitrogen in the storage cavity 11, the pressure in the storage cavity 11 is reduced to below 1barA, so that the temperature of the liquid nitrogen in the storage cavity 11 is reduced to below 77K, thereby obtaining supercooled liquid nitrogen, and meeting some test requirements. In order to avoid the influence on the normal use of the storage cavity 11 when the refrigerator 30 is replaced, the isolation cavity 12 is arranged, and the heat exchanger 20 blocked at the joint of the isolation cavity 12 and the storage cavity 11 is arranged to isolate the isolation cavity 12 from the storage cavity 11, and heat exchange is performed between the cold conducting part 31 of the refrigerator 30 and the storage cavity 11 through the heat exchanger 20. The heater 60 and the temperature measuring piece 70 are arranged on the heat exchanger 20 so as to realize the temperature adjustment of the heat exchanger 20, thereby realizing the temperature adjustment of the liquid nitrogen in the storage cavity 11.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the claims. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.

Claims

1. A liquid nitrogen storage system, comprising:

2. The liquid nitrogen storage system of claim 1, wherein the refrigerator comprises a first portion and a second portion;

3. The liquid nitrogen storage system of claim 2, wherein said second portion is spaced from said tank along an axis of said opening;

4. A liquid nitrogen storage system according to claim 3 wherein a passageway is provided through said connecting tube, said first portion extending beyond said tank being disposed through said passageway;

5. The liquid nitrogen storage system according to claim 1, wherein a side of the heat exchanger, which is close to the isolation chamber, has a heat exchange surface for connection with the cold guide portion along an axial direction of the opening, and the other side of the heat exchanger is provided with a plurality of fins.

6. The liquid nitrogen storage system of claim 5, wherein said cold-conducting portion is pressed against said heat exchange surface in an axial direction of said opening.

7. The liquid nitrogen storage system of claim 6, further comprising a thermally conductive member disposed between the cold guide and the heat exchange surface.

8. The liquid nitrogen storage system of any one of claims 1 to 7, further comprising a heater coupled to the heat exchanger, the heater configured to heat the heat exchanger.

9. The liquid nitrogen storage system of claim 8, further comprising a temperature sensing member disposed on the heat exchanger, the temperature sensing member configured to sense a temperature of the heat exchanger.

10. The liquid nitrogen storage system of claim 1, wherein an inner housing is provided within said tank, said inner housing having said storage chamber and said isolation chamber therein;