JP4975554B2 - Portable sensor cooler using liquid nitrogen - Google Patents

Description

The present invention relates to a portable sensor cooler using liquid nitrogen, and particularly to a portable container requiring liquid nitrogen cooling, particularly a small electronic device such as a SQUID nondestructive inspection device using a high-temperature superconductor, or an infrared sensor. The present invention relates to a portable sensor cooler using liquid nitrogen, which is characterized by a configuration for making a cooler used for cooling such as portable.

  In recent years, SQUID has come to be used for non-destructive inspection of superconducting wires, nuclear power plants, plants, aircraft, elevators, or playground equipment. A method using liquid nitrogen stored in a vacuum heat insulating container or a method using a refrigerator has been selected (for example, see Patent Document 1 or Patent Document 2).

  In addition, a high-sensitivity infrared sensor for astronomical observation and a high-sensitivity infrared sensor for reconnaissance that observe one photon at a time use a cooling mechanism using liquid nitrogen in order to operate at a liquid nitrogen temperature.

In recent years, electronic devices that require cooling at such a liquid nitrogen temperature, especially small electronic devices such as SQUID non-destructive inspection devices, have become handy type small electronic devices so that they can be easily inspected when necessary. There are many requests.
JP 05-333125 A JP-T-2006-527548

  However, in the case of liquid nitrogen cooling stored in a vacuum heat insulating container, the liquid is leaked during transportation and measurement, which causes a risk of liquid leakage and bumping, and is not suitable for cooling a handy measuring machine.

  In addition, refrigerators are expensive, difficult to drive, vibration noise becomes a problem, temperature stability is not sufficient, and there are many problems for handy measuring instrument applications. There is.

  For example, in the case of a large-sized or medium-sized low-vibration refrigerator, there is a restriction on movement even in the case of a stationary type or a mobile type, for example, non-destructive when an accident or the like occurs at a nuclear power plant. There is a problem that the configuration for the inspection becomes large and the inspection is very difficult when the portion requiring measurement is a narrow portion or a complicated portion.

  In particular, it is desirable to be cordless when measuring narrow or complicated places, but in the case of large or medium-sized low-vibration refrigerators, battery drive is not possible and cordless is not possible. There is a problem.

  Moreover, the medium-sized low-vibration refrigerator has a weight of 5 to 10 kg, the large-sized low-vibration refrigerator has a weight as high as 20 kg or more, and the price is very expensive as 2 to 3 million yen. There is.

  Under such circumstances, a small cooler that can be carried, is cordless, has a weight of about 1 kg, and has a price of about 10,000 yen is desired. Currently does not exist.

  Accordingly, an object of the present invention is to realize a liquid nitrogen cooler that can be carried at low cost.

FIG. 1 is a diagram illustrating the basic configuration of the present invention. Means for solving the problems in the present invention will be described with reference to FIG.
In addition, the codes | symbols 5 and 6 in a figure are a heat insulating material and a pressure release valve, respectively.
See FIG. 1 In order to solve the above-mentioned problem, the present invention is a portable sensor cooler using liquid nitrogen 4, which is accommodated in the heat insulating container 1 and the heat insulating container 1 and absorbs liquid nitrogen 4. And a plurality of hollow tubular containers 2 inserted into the fiber assemblies 3 having open cells having a holding structure, and only the fiber assemblies 3 except for the liquid nitrogen 4 in the hollow tubular containers 2. It is characterized by being filled with .

Thus, by absorbing and holding the liquid nitrogen 4 by the fiber assembly 3 having open cells, it is possible to prevent the liquid nitrogen 4 from being exposed during transportation and measurement, thereby preventing liquid leakage or bumping.
In addition, by providing a plurality of such hollow tubular containers 2, as shown in the lower diagram of FIG. 1, heat transfer is improved as compared with the case where a single large-diameter hollow tubular container 2 is used. The leakage of the liquid nitrogen 4 when the container is tilted can be effectively suppressed.

  In addition, it is desirable that the hollow tubular container 2 in this case is a circular tubular container, thereby facilitating the manufacture and being able to be accommodated in the heat insulating container 1 having a generally cylindrical interior with high density. The fiber assembly 3 can be easily inserted.

  In this case, since a gap is formed between adjacent cylindrical containers, it is desirable to fill the fiber assembly 3, thereby increasing the amount of liquid nitrogen 4 retained.

  Alternatively, the hollow tubular container 2 may be a hollow tubular container 2 having a polygonal cross section. In particular, in the case of a hollow tubular container 2 having a hexagonal cross section, a plurality of hollow tubular containers 2 are in close contact with each other to form a close-packed structure. Thus, the honeycomb structure can be configured, and the amount of liquid nitrogen 4 that can be held in the heat insulating container 1 having the same volume can be maximized.

  Further, the fiber assembly 3 holding container into which the fiber assembly 3 is inserted may be a lotus root container having a plurality of through holes into which the fiber assembly 3 is inserted, and the heat insulating container 1 of the fiber assembly holding container. Storage inside becomes easy.

  The rising height of the liquid surface due to the capillary phenomenon is proportional to cos θ when the contact angle of the fiber assembly 3 with the liquid nitrogen 4 is θ, so the contact angle θ of the fiber assembly 3 with the liquid nitrogen 4 It is desirable to use a fiber assembly 3 made of a material having an angle of 90 degrees or less, so that the ability to hold liquid nitrogen 4 by the fiber assembly 3 can be increased.

  Further, the rising height of the liquid surface due to the capillary phenomenon is inversely proportional to the diameter of the capillary, that is, the diameter of the tube constituted by open cells, so that the fiber assembly 3 is compressed into the hollow tubular container 2 or the through hole. By inserting, it is possible to reduce the effective diameter of the capillary tube, thereby increasing the retention capacity of the liquid nitrogen 4 by the fiber assembly 3.

  In addition, a breathable partition may be provided at the top of each hollow tubular container 2 or through-hole, whereby the leakage of liquid nitrogen 4 can be effectively suppressed even when the container is inclined.

  In addition, carbon nanotubes may be filled around the portion to be cooled by the liquid nitrogen 4, and since the carbon nanotube has a high thermal conductivity, the portion to be cooled can be efficiently cooled.

  Further, a partition wall may be provided in the heat insulating container 1 and at the upper part of the assembly of the hollow tubular containers 2 or the lotus root container, so that the liquid nitrogen 4 leaks even when the container is inclined. It can be effectively suppressed.

According to the present invention, cooling using liquid nitrogen becomes safer and easier, and an inspection device such as a handy SQUID can be realized. Higher sensitivity measurement such as non-destructive inspection can be easily performed, which can contribute to improvement of safety of power plants, aircrafts, plants and the like.

Here, an embodiment of the present invention will be described with reference to FIGS.
See Figure 2
FIG. 2 is a basic configuration diagram of the liquid nitrogen cooler according to the present invention. The envelope 11 holds the vacuum heat insulation container 12, the plurality of hollow tubular containers 13 accommodated in the vacuum heat insulation container 12, and the inside of the hollow tubular container 13. Fiber aggregate 14 that absorbs and holds liquid nitrogen, carbon nanotubes 15 that transmit the temperature of liquid nitrogen, sapphire rod 16 that compresses and incorporates carbon nanotubes, and SQUID attached to the tip of the sapphire rod. A cooling material 17, a heat insulating material 18 provided at the upper part of the hollow tubular container 13, a pressure release valve 19 for releasing vaporized nitrogen gas, a handle 20 attached to the upper part of the envelope 11 and containing an electrical system 21; And it is comprised from the portable information terminal 22 attached to the side part of the envelope.

See Figure 3
FIG. 3 is an explanatory view of the circular tubular container and the fiber assembly according to the embodiment of the present invention. The hollow tubular container 13 is made of, for example, a metal such as Cu or Al or an insulator such as glass epoxy or acrylic. The
Note that when the object to be cooled 17 is an infrared sensor or the like, the material of the hollow tubular container 13 is preferably a metal such as Cu or Al. However, the object to be cooled 17 has a current applied to the hollow tubular container 13 by a magnetic field like SQUID. When it is not desirable to produce, it is desirable to comprise with insulators, such as glass epoxy.

The fiber assembly 14 inserted into the hollow tubular container 13 is preferably a fiber assembly having open cells such as glass fiber or melamine foam. These materials have open cells and a liquid nitrogen temperature. It will not freeze and shrink.
By the way, since the foamed polystyrene which is typical as a foam is not an open cell but an isolated bubble, the foamed polystyrene is frozen and contracted at the liquid nitrogen temperature.

Liquid nitrogen increases stability even if it is simply absorbed by the fiber assembly 14, but if the fiber assembly 14 absorbs water so that water penetrates into the towel under the conditions of capillary action as described below, the holding force is increased. Further improve.
Water is the same as being easily transported while being absorbed in a towel.
In this case, the rising height h [m] of the liquid level due to capillary action is
h = 2T cos θ / ρgr
It is represented by here,
T: Surface tension [N / m]
θ: Contact angle [degree]
ρ: Density of liquid [kg / m ³ ]
g: Gravity acceleration [m / s ² ]
r: radius of the pipe [m]

In this case, since the radius r of the tube corresponds to the radius of the open cells of the fiber assembly 14, the capillary phenomenon becomes more remarkable as the radius of the open cells becomes smaller, and the contact angle θ with respect to the liquid nitrogen of the fiber assembly 14 becomes larger. The smaller the value, the more pronounced capillary action.
When θ> 90 °, cos θ <0, so h <0 and the capillary phenomenon does not act. Therefore, the contact angle θ needs to be θ ≦ 90 °.

  In addition, the rising height h of the liquid level due to capillary action is proportional to the surface tension T, whereas the surface tension of liquid nitrogen is 0.007 N / m at 77K and 1 of 0.07 N / m at 20 ° C. water. / 10, but 100 times that of liquid helium (4.2K), and if a material with sufficiently small open cells (corresponding to a small radius r of the tube) is selected, the adsorption effect by capillary action is sufficiently high. It can be demonstrated.

  In this way, by causing the fiber assembly 14 to absorb and hold liquid nitrogen, it is possible to prevent liquid nitrogen from spilling and causing liquid leakage or bumping when liquid nitrogen is conveyed or measured.

In addition, when the fiber assembly 14 absorbs and holds liquid nitrogen, it is possible to limit the movement of liquid nitrogen by directly putting the fiber assembly 14 into the heat insulating container, and to have a holding force. By inserting and storing in the hollow tubular container 13, the movement of liquid nitrogen can be further restricted by separating into a cylindrical shape.
For example, when the container is largely inclined, there is a risk that the absorbed liquid nitrogen leaks according to the inclination angle when the whole is composed of a large fiber assembly 14, but when separated into a cylinder, Since the tube side wall of the hollow tubular container 13 serves as a barrier for movement of liquid nitrogen, leakage of liquid nitrogen can be suppressed.

Based on the above, the liquid nitrogen cooler according to the first embodiment of the present invention will now be described with reference to FIG. 4. Here, only the basic configuration inside the envelope will be described.
See Figure 4
FIG. 4 is a conceptual configuration diagram of the liquid nitrogen cooler according to the first embodiment of the present invention. The vacuum heat insulating container 31, a plurality of copper circular tubular containers 32 accommodated in the vacuum heat insulating container 31, and the circular tubular container 32 are illustrated. It consists of a fiber assembly 33 made of melamine foam, a heat insulating material 34 also made of melamine foam, and a pressure release valve 35 for releasing vaporized nitrogen gas.

The circular tubular container 32 in this case is constituted by, for example, a circular tube having an inner diameter φ of 15 mm, a thickness of 0.5 mm, and a length of 80 mm.
Since the melamine foam as the fiber assembly 33 inserted into the tubular container 32 has a contact angle with liquid nitrogen of 90 degrees or less, a capillary phenomenon can be used as a holding force.

Incidentally, glass wool, which is widely used as a heat insulating material, can also absorb liquid nitrogen with the same effect by compressing and narrowing the fiber spacing, but melamine foam with a bubble size of 0.2 μm is approximately 1 in the same volume. Experiments have shown that it has 6 times the absorption power.
In addition, since the heat insulation capability is high, it effectively works as a heat insulating material for holding liquid nitrogen when it becomes low.

Next, the liquid nitrogen cooler according to the second embodiment of the present invention will be described with reference to FIG. 5. Here, only the basic configuration inside the envelope will be described.
See Figure 5
FIG. 5 is a conceptual configuration diagram of the liquid nitrogen cooler according to the second embodiment of the present invention. The vacuum heat insulating container 31, a plurality of glass epoxy circular tubular containers 40 accommodated in the vacuum heat insulating container 31, and a circular tubular shape are illustrated. A fiber assembly 33 made of melamine foam inserted into the container 40, a heat insulating material 34 made of melamine foam, a carbon nanotube 36 provided on the bottom side of the tubular container 40, and a sapphire rod that compresses and incorporates the carbon nanotube. 37, a SQUID chip 38 attached to the tip of the sapphire rod 37, and a pressure release valve 35 for releasing vaporized nitrogen gas.

  In the second embodiment, a carbon nanotube 36 having excellent thermal conductivity is used around the SQUID chip 38 in order to cool a SQUID element that requires temperature stability. The carbon nanotube 36 is a fine fiber. While being an aggregate and holding liquid nitrogen, it is also responsible for heat conduction and is an advantageous structure for constructing a handy SQUID device.

Next, the liquid nitrogen cooler according to the third embodiment of the present invention will be described with reference to FIG. 6. Here, only the basic configuration inside the envelope will be described.
See FIG.
FIG. 6 is a conceptual configuration diagram of the liquid nitrogen cooler according to the third embodiment of the present invention. The vacuum heat insulating container 31, a plurality of copper circular tubular containers 32 accommodated in the vacuum heat insulating container 31, and the circular tubular container 32 are illustrated. It consists of a fiber assembly 33 made of melamine foam, a heat insulating material 34 also made of melamine foam, and a pressure release valve 35 for releasing vaporized nitrogen gas.

However, here, the fiber assembly 33 made of melamine foam is compressed and inserted.
For example, as shown in the figure, a fiber assembly 33 made of melamine foam of φ34 × 65 mm is compressed and inserted into a circular tubular container 32 of φ15 × 50 mm.
In this case, when the melamine foam was inserted without compression and liquid nitrogen was retained, the absorption amount was 2.6 cc, but the absorption amount when the melamine foam was compressed and inserted was increased to 4.5 cc.
This is presumably because the open cell in the melamine foam contracts due to compression and the radius r of the open cell becomes small, thereby increasing the height h of the liquid level due to capillary action.

Next, a liquid nitrogen cooler according to a fourth embodiment of the present invention will be described with reference to FIG. 7. Here, only the configuration of the hollow tubular container will be described.
See FIG.
FIG. 7 is a conceptual configuration diagram of a hollow tubular container accommodated in the liquid nitrogen cooler of Example 4 of the present invention, and the hollow tubular container 41 has a hollow polygonal column shape with a regular hexagonal cross section. A container 41 is brought into close contact with each other to form a honeycomb structure.
Since such a honeycomb structure is a close-packed structure, the volume of melamine foam per unit volume in the vacuum heat insulating container 31 can be increased, and more liquid nitrogen can be held in a smaller container.

Next, the liquid nitrogen cooler according to the fifth embodiment of the present invention will be described with reference to FIG. 8. Here, only the filling configuration of the hollow tubular container will be described.
See FIG.
FIG. 8 is a diagram illustrating a filling configuration of a hollow tubular container housed in the liquid nitrogen cooler according to the fifth embodiment of the present invention. The cylindrical container 32 is brought into close contact with each other to form a close-packed filling structure. The gap formed between them is also filled with a fiber assembly 39 made of melamine foam.

  In this Example 5, since the melamine foam is also inserted into the gap formed between the tubular containers 32, the volume of the melamine foam per unit volume in the vacuum heat insulating container 31 can be increased. More liquid nitrogen can be held in a smaller container compared to Example 1.

Next, although the liquid nitrogen cooler of Example 6 of this invention is demonstrated with reference to FIG. 9, only the structure of a hollow tubular container is demonstrated here.
See FIG.
FIG. 9 is a configuration diagram of a hollow tubular container accommodated in the liquid nitrogen cooler according to the sixth embodiment of the present invention, and a partition wall 42 having vent holes 43 is provided on the upper bottom surface and the lower bottom surface of the circular tubular container 32. Is.
In this case, the material of the partition walls may be a metal such as glass epoxy, acrylic, copper, or Al.

  In the sixth embodiment of the present invention, since the partition wall 42 having the vent holes 43 is provided on the upper bottom surface and the lower bottom surface of the tubular container 32, the leakage of liquid nitrogen with respect to the inclination of the container and the deviation in the heat insulating container are prevented. This can be prevented and is more advantageous when used in a handy measuring instrument.

Next, a liquid nitrogen cooler according to a seventh embodiment of the present invention will be described with reference to FIG. 10, but here only the basic configuration inside the envelope will be described.
See FIG.
FIG. 10 is a conceptual configuration diagram of the liquid nitrogen cooler according to the seventh embodiment of the present invention. The vacuum heat insulating container 31, a plurality of copper circular tubular containers 32 accommodated in the vacuum heat insulating container 31, and the circular tubular container 32 are illustrated. A fiber assembly 33 made of melamine foam, a heat insulating material 34 made of melamine foam, a glass epoxy shielding plate 44 embedded in the heat insulating material 34, and a pressure release valve 35 for releasing vaporized nitrogen gas. Consists of.

In the seventh embodiment, since the shielding plate 44 is provided on the upper part, the liquid nitrogen acts as a barrier in the unlikely event that liquid nitrogen leaks from the circular tubular container 32, so that safety can be further improved.
The shielding plate 44 is not limited to glass epoxy, and acrylic or metal material can also be used.

Next, a liquid nitrogen cooler according to an eighth embodiment of the present invention will be described with reference to FIG. 11. Here, only the configuration of the container that stores the fiber assembly will be described.
See FIG.
FIG. 11 is a conceptual configuration diagram of a fiber assembly storage container constituting the liquid nitrogen cooler according to the eighth embodiment of the present invention, for example, a copper lotus root having a plurality of through holes 46 for storing the fiber assembly. A cylindrical container 45.

  In the eighth embodiment, since the fiber assembly storage container is constituted by the integral lotus root container 45, the process for storing the storage container in the vacuum heat insulating container 31 is simplified.

The embodiments of the present invention have been described above. Since the cooling effect was confirmed by producing a prototype, the structure of the liquid nitrogen cooler according to the present invention, which was prototyped with reference to FIGS. The cooling effect will be described.
See FIG.
FIG. 12 is a conceptual configuration diagram of the prototype, which includes a vacuum heat insulating container 12, a plurality of brass hollow tubular containers 13 housed in the vacuum heat insulating container 12, and a melamine foam inserted into the hollow tubular container 13. A fiber assembly 14, an aluminum mesh 23 that holds the hollow tubular container 13, a fiber assembly 24 that is provided under the aluminum mesh 23 and is made of melamine foam that holds liquid nitrogen, and is provided above the hollow tubular container 13. It comprises a heat insulating material 18 made of melamine foam, a glass epoxy leak-proof shielding plate 25 inserted in the heat insulating material 18, and a pressure release valve 19 attached to the upper lid 26.

The hollow tubular container 13 in this case uses the hollow tubular container of the type shown in Example 6 above, and is provided with partition walls 27 having vent holes 28 on the upper and lower bottom surfaces of the hollow tubular container 13.
In this prototype, liquid nitrogen did not leak due to vibration, and there was no leakage even when tilted 90 degrees.

See FIG.
FIG. 13 is an explanatory diagram of the cooling effect of the prototype. In the prototype in the stationary state, as shown in the figure, the amount of liquid nitrogen decreases almost in proportion to the time, but it is 77 K for 3 hours. It was confirmed that

  The embodiments of the present invention have been described above. However, the present invention is not limited to the configurations and conditions described in the embodiments and can be variously modified. For example, the embodiments can be accommodated in a vacuum heat insulating container. The size of the hollow tubular container and the number of containers to be accommodated are arbitrary according to the size of the vacuum heat insulating container, and the size of the vacuum heat insulating container is appropriately set according to the size of the object to be cooled and the required cooling time. is there.

  Further, in the above embodiment 8, the through hole has a circular cross section. However, it may be a square or a hexagon, and in the case of a hexagon, as in the above embodiment 4. A honeycomb structure is obtained.

Moreover, also in said Example 8, like the said Example 6, you may provide the partition which has a vent so that a through-hole may be covered.
In addition, the partition in this case may be provided for each through hole, or an integral partition having a vent according to the through hole may be used.

  As an application example of the present invention, a portable measuring device that requires cooling at a liquid nitrogen temperature, such as a SQUID or a high-sensitivity infrared sensor, is typical. However, the present invention is not limited to the portable measuring device, and vibration is involved. It is also used as a cooling device necessary for measurement at a place or the like.

It is explanatory drawing of the fundamental structure of this invention. It is a basic lineblock diagram of the liquid nitrogen cooler of the present invention. It is explanatory drawing of the hollow tubular container and fiber assembly of embodiment of this invention. It is a notional block diagram of the liquid nitrogen cooler of Example 1 of the present invention. It is a notional block diagram of the liquid nitrogen cooler of Example 2 of the present invention. It is a notional block diagram of the liquid nitrogen cooler of Example 3 of the present invention. It is a notional block diagram of the hollow tubular container accommodated in the liquid nitrogen cooler of Example 4 of this invention. It is a filling block diagram of the hollow tubular container accommodated in the liquid nitrogen cooler of Example 5 of this invention. It is a notional block diagram of the hollow tubular container accommodated in the liquid nitrogen cooler of Example 6 of this invention. It is a notional block diagram of the liquid nitrogen cooler of Example 7 of this invention. It is a notional block diagram of the storage container of the fiber assembly which comprises the liquid nitrogen cooler of Example 8 of this invention. It is a conceptual block diagram of a prototype. It is explanatory drawing of the cooling effect of a prototype.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat insulation container 2 Hollow tubular container 3 Fiber assembly 4 Liquid nitrogen 5 Heat insulation material 6 Pressure release valve 11 Envelope 12 Vacuum heat insulation container 13 Hollow tubular container 14 Fiber assembly 15 Carbon nanotube 16 Sapphire rod 17 Object to be cooled 18 Heat insulation material 19 Pressure release valve 20 Handle 21 Electrical system 22 Mobile information terminal 23 Aluminum mesh 24 Fiber assembly 25 Leakage prevention shielding plate 26 Upper lid 27 Partition 28 Vent 31 Vacuum insulation container 32 Circular tubular container 33 Fiber assembly 34 Insulation 35 Pressure release Valve 36 Carbon nanotube 37 Sapphire rod 38 SQUID chip 39 Fiber assembly 40 Circular tubular container 41 Hollow tubular container 42 Partition wall 43 Vent hole 44 Shielding plate 45 Lotus root container 46 Through hole

Claims (5)

Comprising at least a heat insulating container, and a plurality of hollow tubular container a fiber aggregate having open cells is inserted therein with a structure for absorbing and holding the liquid nitrogen while being accommodated in the heat insulating container, wherein the hollow tubular container A portable sensor cooler using liquid nitrogen, wherein the inside is filled only with the fiber assembly other than liquid nitrogen . Comprising a heat-insulating container and a lotus root-like container having a plurality of through holes for inserting the fiber aggregate having open cells having a structure for absorbing and holding the liquid nitrogen while being accommodated in the heat insulating container at least, the through hole A portable sensor cooler using liquid nitrogen, wherein the inside is filled only with the fiber assembly other than liquid nitrogen . The portable sensor cooler using liquid nitrogen according to claim 1 or 2, wherein the fiber assembly is compressed and inserted into the hollow tubular container or the through hole. The portable sensor cooler using liquid nitrogen according to any one of claims 1 to 3, wherein an air-permeable partition is provided on each of the hollow tubular containers or the through holes. The portable sensor cooler using liquid nitrogen according to any one of claims 1 to 4, wherein a carbon nanotube is filled around a portion to be cooled by liquid nitrogen.

Images