JPS5839919A - Gas liquifaction and cooling apparatus - Google Patents

Abstract

PURPOSE:To prevent the occurrence of clogging caused by ambient air flowed into a Dewar vessel, by sealing up the discharge side of a gas liquefier with a drier enclosed with a drying agent and sealing material. CONSTITUTION:A Dewar vessel 5, in which an infrared rays detector 4 is built in, is stuck to a Dewar vessel holder 8 and is held on the holder 8 and also, a drier 9 is provided at one end of the holder 8. A sealing material 11 performs duties to keep airtightness between a mandrel 7 fitted to the holder 8 and the holder 8. Discharged gas from the vessel 5 and ambient air flowing into the vessel 5 are flowed through the drier 9. Accordingly, humidity is removed by the action of the drier 9 even when the air current flowing into the vessel 5 contains moisture in a high humidity, and the inner part of the vessel 5 is kept under dry condition.

Description

[Detailed description of the invention] This invention is used as a cooling hand gong for an infrared detector.

Joule-Thomson effect
The present invention relates to a small-sized gas liquefaction cooling device that utilizes Eftset.

Infrared detectors have been used for the past several decades for military purposes such as guidance of flying objects, fuses, and various surveillance devices. For example, means for passively detecting infrared rays from a target as the first target of a projectile is subject to interference from the ROM from the target.

Moreover, it is generally well known that detection is possible even at night.

Since the atmosphere exists as a transmission medium for the infrared rays from the target object, this type of infrared detection avoids wavelength bands that are absorbed by the atmosphere.9 Normal atmospheric window (Atmospheric window).

The operation is performed in the far infrared wavelength region of 8 to 5 μm and 8 to 13 μm, called the mosphere's window.

Infrared detectors are physically classified as photon type (photon type).
n tape) and Thermal type
(e) Generally, infrared detectors used for purposes such as guidance and monitoring are of the photon type because high sensitivity and high-speed response are required.

Materials for photon type infrared detectors include Pb8e, In8b, and Pb8nTe in the 8 to spm band.

Ge: Hg, *Hg0dTe *Also 8 ~ 1
In the 3 μm band, Pb8nTe + Ge:Hg *
Possible materials include Hg0dTe and Ge:Ou.

However, the thermal noise of the materials used in such Photonya infrared detectors has a negative effect on the sensitivity (Ssns).
It is necessary to cool down below 10 G' to significantly affect the ifivtty.

Generally, in cryogenics, 100° is defined as the following low temperature (cr
Cooling methods in the yogenic temperature range include superconducting, maser, and rosette7)
It is also well known in the field of IJ hook width devices and the like.

Helium, nitrogen, or argon are used as refrigerants, and the equipment ranges from large-scale systems using diffusion engines to laboratory systems that simply inject liquefied gas.

Among these, the equipment used for the above-mentioned guidance and monitoring purposes must be able to operate outdoors) and be easily transported, and therefore the cooling system for the infrared detector incorporated in such equipment is required. It is clear that it must be able to be stored for a long time, its cooling action can be activated in any emergency, and it must also be small and lightweight. As a cooling device that meets this purpose, a small gas liquefaction cooling device that utilizes the Joule-Thomson effect has conventionally been used. Its schematic configuration is shown in FIG.

In Figure 1, (1) is a gas supply source, (2) is a filter, and (3) is a cryostat.
) is a gas liquefier.

As the gas supply source (1), if the cooling action time is short, a gas container filled with gas such as nitrogen or argon at high pressure is used; if the action time is long, a small gas circulation pump is used. used. In any case, the high pressure gas from the gas supply source tt) is purified of impurities by the filter (2) and flows into the gas liquefier (3). The gas liquefier (3) uses the Joule-Thomson effect, that is, the temperature drop of the refrigerant gas due to the pressure drop, to liquefy the incoming gas, and the latent heat of vaporization of the liquefied gas causes an infrared detector (not shown) Cooling.

FIG. 2 shows a more detailed structural diagram of the above-mentioned gas liquefier. (4) is an infrared detector, (5) is a dua, (6
) is Cheve, and (7) is ÷Ndrel.

The tube (6) is spirally wound around the mandrel (7), and high pressure gas flows inside it. A structure in which a spirally wound chain (6) and a mandrel (7) are combined is inserted into the dure so that the outermost diameter of the diagonal structure is in close contact with the inner surface of the dure (5). Dare (the group) is a kind of magic bottle, and in order to maintain the connection with the outside, the inside of the double-bottom is kept in a vacuum, and an infrared detector (4) is installed in the hollow wall inside. The high-pressure gas supplied in such a configuration passes through the inside of the chain (6) and is connected to the tube (6).
) is ejected from the tip toward the bottom of the Dua (5).

At that time, the high-temperature gas is diffused into the surrounding area, and the resulting pressure drop causes a temperature drop due to the so-called Joule-Thomson effect. However, at the normally used supply gas pressure of about 200 to 600 atm, the temperature drop is negligible, so Dua (5) and Chape (6) are used.
), and by repeating this action, the gas is finally ejected from the tip of the tube (6) to the bottom of the Dua (5). The gas is lowered to its liquefaction temperature, producing liquefied gas at the bottom of the dure (5). Since the liquefaction temperature of nitrogen and argon as refrigerants is 77° 87'K, the infrared detector (4) mounted on the internal hollow wall of the dure (5) is cooled to such a low temperature.

By the way, it goes without saying that in order to achieve good cooling in a gas liquefier like the one shown in Figure 2, it is necessary to smooth the flow of the supply gas in the tube.

The tube diameter is very thin with an inner diameter of 50 to 200 (μmφ), and the actual length of the tube is several meters in order to further improve the efficiency of heat exchange. Therefore, the purity of the refrigerant gas in the gas supply source shown in FIG. 1 and the performance of the filter become issues. When the impurities contained in the supply gas flow through the inside of the long and narrow tube as described above, there is a risk that they will accumulate in the tube and cause so-called clogging. child? When clogging occurs, the flow of the gas inside the tube stops and the cooling effect on the infrared detector is no longer performed. This can be easily inferred from the explanation of the principle of the gas liquefier described above.

Impurities contained in the supplied gas include solid particles such as dust,
Possible carbon, carbon dioxide, and moisture. It is natural for solid particles and carbon to clog the tube due to their particle size, but moisture in particular becomes water vapor and mixes in the supplied gas until it reaches the tube, where it is cooled to a low temperature, that is, the tube. Since the gas condenses inside the gas liquefier and becomes solid particles, causing clogging t and b, it is extremely difficult to remove the gas using a filter installed in front of the gas liquefier.

Therefore, it is required that such impurities be removed from the supply gas in advance. For example, the solid and moisture content of nitrogen, argon, etc. used is very strictly limited to 2 PPm or less.

Now, using the highly purified supply gas as described above, and using a filter for the purpose of removing impurities mixed in during the first maintenance inspection, a cooling system as shown in Fig. 1 is constructed and operated. However, in many tests, it was confirmed that clogging occurred. It was found that the cause of this was the influence of ambient air flowing in opposite to the flow of exhaust gas inside the gas liquefier. To explain in more detail, the gap between the outer surface of the spirally wound tube and the wire is extremely small, but in this gap.

It has been observed that the air around the gas liquefier flows in the opposite direction to the gas flow that is ejected from the tube and then discharged. Depending on the usage environment, the air around the gas liquefier is highly humid and contains moisture, so the moisture may be removed. The gas condenses as it cools inside the chamber, closing the gap between the outer surface of the chamber and the chamber or the tip of the chamber, and as a result, stopping the flow of gas.

This phenomenon depends on the operating environment of the cooling device, the temperature and humidity, and the amount of ambient air flowing into the unit, but as mentioned above, the moisture limit for the gas liquefier to function properly is +
Since the humidity is extremely low (less than 2 ppm), if even a small amount of ambient air enters the dua, even if the relative humidity of that air is only a few percent, it will cause problems, and guidance and monitoring systems using such cooling devices will be affected. can be a serious problem.

As stated above, this invention provides a means for solving the major problem of clogging caused by ambient air flowing into the dure, which has been found in conventional small gas liquefaction cooling devices that utilize the Ziehl-Thomnon effect. It is something to do. In more detail, the discharge side of the welfare gas liquefier is sealed with a dryer containing a desiccant and a sealing material, and the exhaust gas from the gas liquefier and the air flow flowing into the gas liquefier from the surroundings flow through the dryer. The present invention provides a cooling device having such a structure.

An embodiment of the invention will be described below with reference to FIG.

FIG. 8 is a main sectional view of the gas liquefier according to the present invention. (8) is a dual holder, (9) is a dryer, member is a desiccant, and 1g is a sealing material. The duer (5) in which the infrared detector (4) is incorporated is adhered and held by the duer holder (8). A dryer (9) is provided at one end of the dual holder (8). The dryer (9) is made of, for example, two cylindrical metal meshes with different diameters, and a desiccant (1) such as silica gel is sealed inside the mesh. A possible solution would be to enclose a mesh-like desiccant agent in a deurea holder (6) that has holes at several locations on its circumference, thereby structurally separating the so-called deurea interior from its surroundings, and preventing the flow of gas between them. Various structures can be considered as long as they have the role of drying at the same time as allowing drying.The sealing material aO may be an O-ring or the like (not shown), but it may be a mandrel (7) attached to the air holder (8) with a fastener such as a screw. ) and the dual holder (8
) to maintain airtightness between the

When a gas liquefier with such a configuration is assembled in a clean and dry atmosphere and then incorporated into the small gas liquefaction cooling device shown in FIG. 1, the exhaust gas from the Dua (5) and the Dua (5) The ambient air flowing into the dryer (
9) flows through.

Therefore, even if the airflow flowing into the special KfS chamber (I) is highly humid and contains moisture, it is dehumidified by the action of the dryer (9), and the inside of the chamber (5) is maintained in an extremely dry condition. Even if the interior of the duure (5) approaches a low temperature state due to the Jeer-Thomson effect of high-pressure gas, which is its original purpose, the moisture contained in the ambient air flow flowing into the duure (5) as described above The phenomenon of condensation and adhesion to the slight gap between the chape and the dure or to the tip of the chape is avoided, making the operation of the cooling device highly reliable.

As described in detail above, the present invention has been developed to place the dryer on the discharge side of the gas liquefier in order to prevent the clogging phenomenon caused by moisture that occurs in the conventional small gas liquefaction cooling device that utilizes the Jehl-Thompson effect. This is a device that can guarantee good operation of small-sized gas liquefaction cooling equipment, and although its configuration is simple, it has a great effect on gas liquefaction cooling equipment for cabins where the amount of moisture that can be tolerated is strict. This will ultimately significantly increase the reliability of guidance and monitoring systems incorporating such cooling devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a gas liquefaction cooling device for a shed, FIG. 2 is a detailed diagram of a conventional gas liquefier, and FIG. 8 is a diagram showing the configuration of a gas liquefier according to the present invention. ``In the figure, (1) is the gas supply source, (2) is the filter, and (3) is the gas supply source.
) is a gas liquefier, (4) is an infrared detector, and (5) is a dua. (7) is a mandrel, (8) is a dual holder, (9)
is a dryer, mouse is a desiccant, and a9 is a sealing material. In the drawings, the same or corresponding parts are designated by the same reference numerals. Agent Shin Kuzuno −

Claims (1)

[Claims] Used as a cooling means for infrared detectors, gas supply source,
In a gas liquefaction cooling system consisting of a filter and a gas liquefier, there is a duure holder that holds the duure to which an infrared detector is attached, a dryer containing a desiccant, and airtightness when the duure holder and mandrel are connected. 1. A gas liquefaction cooling device comprising a gas liquefier having a sealing material for holding the dryer and a gas liquefier which structurally isolates the inside of the deurea from the surrounding environment by the dryer and the sealing material.