DE2349550A1 - REFRIGERANT TRANSPORT LINE - Google Patents

Description

PHN. 6590 Dr. Herbert Seh »left Patendawaft

Registration: RV- Flips' GbnUamp ^ nfas

AkfNo ,; PHH- 6590 2349550

Announcement from October 1, 1973

"Kaitetransportleitung"

The invention relates to a cold transport line with two cold transport means extending next to each other · !? ears, a radiation shield that covers the two pipes for the transport of cold surrounds and is kept at a distance from the tubes, two extending next to the radiation shield Coolant pipes on the outside of the radiation shield. lie and thus in thermal contact stand, and a vacuum jacket covering the radiation shield as well as surrounding the two coolant tubes and at a distance held by them.

A cold transport line of the kind that the The present invention is apparent from Figure 2 of U.S. Pat. Patent 3,364,687 known.

A09818 / 0794

-2- PHN. 6590

Flows through in the known Kaltetransportleitnng the refrigerant pipes high pressure helium, the one hand is in heat exchange with a liquid helium bath and on the other hand with an object to be cooled while through the coolant pipes liquid nitrogen to cool the refrigerant pipes with lower Temperature surrounding radiation shield is performed.

Instead of a liquid helium bath as a source of cold For example, a single or multi-stage gas refrigeration machine can also be used, as described in U.S. Pat. Patent 3. ^ 73.3 ^ 1 described, in which then also helium can flow through the coolant pipes under pressure.

In known cold transport lines of the present type, the cold transport pipes, the radiation shield, the coolant pipes and the vacuum jacket are rigid Components that are held apart by spacers. Such cold transport lines are usually made from metal tubing, mostly steel or copper. For the refrigerant pipes is also called Invar because of its low coefficient of expansion used.

These rigid cold transport lines have different ones Disadvantages on.

Though quite a bit for certain laboratory arrangements Can easily be made on site, if the overall arrangement is known, they are for factory production less suitable. Production of rigid cold trans-

409818/0794

jxtungen

port lines in a factory, which transport lines in practice, lengths of about 5 to 15 m ^ must be done in parts because of the transport. Assembling the parts is a time consuming, complicated and expensive matter and therefore undesirable.

The rigid cold transport lines are in use difficult to handle and your freedom of movement is extremely limited.

In addition, there is a great risk of vibrations, that come from the cold source (e.g. a cooling machine), as well as light impacts via the rigid cold transport line on the object to be cooled (e.g. a measuring instrument like an infrared cell) are transmitted and have a disruptive influence;

Now there are other types of cold transport lines in cryogenic technology for simple applications and therefore with a simpler structure with an inner and an outer tube known, which consist of flexible bellows (U.S. Patent 3

Use of flexible bellows for the entirety of the two refrigerant pipes, the radiation shield, the two coolant pipes and the vacuum jacket of the present cold transport line would be of great length however, too large structural complications, too large diametrical dimensions and too large a loss of cold to lead. High mean pressures in the quay transporting ttel- and coolant bellows in the vacuum jacket would be too

409818/0794

structural measures due to the expansion of these Bellows due to the large pressure differences above them to force.

The present invention aims to provide a cold To create a transport line of the type indicated, which, while maintaining the structural simplicity, is perfect is flexible, consequently in great lengths in the Factory production can be established and in the cryogenic applications a particularly great freedom of Provides a setup that eliminates the small diametrical dimensions and is relatively light in weight Has minimal cold losses and high mean pressures in the refrigerant and coolant pipes without additional Withstands measures.

The cold transport line according to the invention is characterized in that the refrigerant pipes, the radiation shield and coolant tubes in the vacuum jacket, designed as a flexible bellows, is made of a plastic, whereby ^ the refrigerant pipes Suspended locally on the radiation shield via flexible wires or bands made of poorly thermally conductive material are and wherein the radiation shield with the coolant tubes Via flexible wires or bands made of poorly thermally conductive material on locally in the flexible bellows are suspended coaxially erected support rings, the outer diameter of which is at least almost equal to the inner diameter of the bellows is.

409818/0794

Although it is often claimed in the literature that plastics are generally quite brittle at low temperature, it has surprisingly been found pointed out that good quality cold transport lines "can be realized.

In an advantageous embodiment of the cold transport line According to the invention, there are the refrigerant pipes, the coolant pipes and the flexible ones Wires or bands of nylon.

Nylon has great mechanical strength. On the one hand, there can be great pressure forces that result Withstand high pressure media exerted in the refrigerant transport and refrigerant pipes. on the other hand It may be the tensile forces acting on the nylon wires or nylon straps be exercised according to the suspension, catch easily.

Another advantageous embodiment of the invention Cold transport line is characterized in that the radiation shield is made of polytetrafluoroethylene consists. Polytetrafluoroethylene has the advantage that it is mechanically strong and gives off little gas, so that when the quay transport line cools down, the Vacuum jacket is evacuated, no gaseous impurities can escape from the radiation shield, which could cause the Impair vacuum and favor heat radiation.

In a further advantageous embodiment of the inventive cold transport line consists of

409818/0794

-G- PHN. 6590

Radiation screen made of polyethylene.

Polyethylene is also mechanically strong and also gives little gas a "b.

The plastic radiation shield is through the two plastic coolant pipes.

Plastic has a relatively poor quality Conduction.

To ensure a good exchange of air between the coolant pipes and to ensure the radiation shield, according to the invention, the radiation shield stands with everyone of the two coolant pipes via at least one connection made of a material that conducts heat well.

This can be done, for example, by attaching the two coolant tubes with the help of a highly thermally conductive contact paste (e.g. a paste containing aluminum powder) on the radiation shield and / or through. Wrapping the pipes and the Radiation shield with metal strips (e.g. copper or aluminum foil).

Wrapping with metal strips seems expedient due to its simplicity. The nylon coolant tubes will shrink by the cooling of the cold transport line at the Commissioning, however, more than the metal strip. There is then a great risk that the nylon pipes will separate from the Loosen the metal foil cover so that good thermal contact is no longer guaranteed.

In order to avoid this disadvantage, according to the invention around the structure of the radiation shield and an adjacent

409818/0794

-7- ■ ΡΗΝΓ. 659Ο

A metal strip is wound around the coolant tube and exercises the coolant tube lying outside the strip envelope at the transition point from the radiation shield to the adjacent coolant tube on the strip cover Pressure force.

The pressure force can be adjusted with the help of the nylon suspension wires, the locally around the whole of radiation screen and both coolant tubes are wound.

In this way it is achieved that, regardless of the relatively strong shrinkage of the nylon coolant tubes the metal strip cover is always stretched and in good thermal contact with the two coolant tubes.

According to a further advantageous embodiment the inventive cold transport line is around Structure of the metal strip cover and the coolant tube lying outside the cover is a band of radiation-reflecting Wrapped material, e.g. one on the surface facing the flexible bellows or aluminized on both sides Plastic tape.

This reduces cold losses through radiation.

According to the invention, it is advantageous between the Metal strip cover and the radiant reflective Tape material to attach a protective layer. The metal— ■ For example, strips made of copper or aluminum foil with their sharp edges can easily do that due to the cutting effect Damage radiation reflective tape. The ■ protective layer ensures that · the radiation reflective

409818/0794

-8- PHN. 6590

This will not damage the tape. The material from which If the protective layer exists, it should preferably not become hard at the low operating temperature. As cheap Materials such as medical bandage gauze and nylon film come into consideration.

In a further advantageous embodiment the inventive cold transport line is around Refrigerant pipes wound a band of radiation-reflecting material, e.g. again made of plastic, of which the surface facing the radiation shield or both surfaces are aluminized »This means a further one Reduction of cold losses through radiation. One further advantageous embodiment of the invention Cold transport line is characterized in that at one end of the line the cold transport medium and coolant pipe ends pushed onto a rigid-walled connecting pipe each and into one another with the help of two pushed conical bushings are clamped thereon, of which the inner one is cut lengthwise, with the connecting pipes are guided to the outside through a rigid end wall of the flexible bellows.

It has been shown that such a coupling of flexible plastic pipes to rigid pipes is highly vacuum-tight even at low temperatures and can withstand pressures of at least hO ata. The rigid connecting pipes that open outside the line can easily be connected to a circuit or to a source with cold

409818/0794

-9- PHN ". 6590

means of transport or coolant can be connected.

The invention is explained in more detail below with reference to the drawing, which is schematic and not to scale. It shows

Fig. 1 shows an embodiment of the inventive Cold transport line in cross section,

2a shows, in longitudinal section, the coupling of a flexible plastic pipe to a rigid-walled connecting pipe,

FIG. 2b shows a cross section at the location of the line IXb-IXb according to FIG. 2a.

In Fig. 1, the reference number 1 indicates a cold transport line - which is constructed as follows. Two refrigerant pipes' 2 made of nylon are surrounded at a distance by a radiation shield 3 made of polytetrafluoroethylene. On the outside of the radiation shield 3 are two coolant pipes h made of nylon, which are in thermal contact with the radiation shield 3. The radiation shield 3 with the two coolant tubes 4 are surrounded at a distance by the flexible bellows 5 made of stainless steel as a vacuum jacket, which means that the space in the flexible bellows 5 can be evacuated.

The nylon refrigerant pipes 2 made of nylon are with the help of nylon wires 6, which over part of their length are wound around these tubes, locally on the radiation shield 3 hung. The suspension is such that the central The position of the two refrigerant pipes 2 with respect to the radiation shield 3 remains unchanged.

409818/0

-1O- PHN. 6590

The radiation shield 3 is suspended together with the coolant pipes k via nylon straps 7 on aluminum support rings 8, a number of which are distributed over the length of the cold transport line 1 in the flexible bellows and are arranged coaxially thereto. The outside diameter of the support ring 8 is almost the same as the inside diameter of the flexible bellows 5. As a result, there is a tight fit of the support ring in the bellows and further fastening means are superfluous.

One of the two Eöhlmittelrohre 4 is over one Contact layer 9 made of thermally conductive material or made of a paste containing aluminum powder is firmly attached to the radiation shield 3. Around the structure of the mentioned coolant pipe and the radiation shield is a strip 10 made of copper foil wrapped. The other coolant pipe is at one of the two places where the strip cover from the radiation shield passes over to the tightly fitting coolant pipe and presses against the strip cover there.

The heat-conducting layer 9 and the copper foil strip ensure good thermal contact between the coolant pipes h and the radiation shield 3 to be cooled. When the temperature drops from room temperature to the low operating temperature, the nylon coolant pipes h shrink more than the copper foil 10. The good contact between the The coolant pipes and the radiation shield are still retained. The coolant pipe lying outside the cover made of copper foil strips then pushes the cover further inwards, so that it is still attached to both the radiation shield 3 and the cooling

409818/0794

-Ir- 'PHN. 659O

middle tube fits well in the envelope.

To avoid cold losses. To reduce radiation, a strahlungsreflektierend.es tape 11 is wrapped around the structure of copper foil strip envelope 10 and the coolant tube h located outside) this envelope, which consists of foil made of the plastic Mylar, the outer surface of which is aluminized.

Between the aluminized mylar and the copper foil Located, a layer of bandage gauze 12 that prevents the mylar from getting through the sharp edges of the Copper foil is damaged. A further reduction in cold losses due to radiation is achieved by that also, the two refrigerant tubes 2 with a radiation-reflecting tape 13 made of aluminized Mylar wrapped.

The cold transport line described is implemented and has been successfully tested.

The length of the line was 10 meters and the outside diameter 75 mm

The nylon refrigerant tube had an inside diameter of 5 mm and an outside diameter of 7 mm. For the polytetrafluoroethylene radiation shield ¹ R ^e ~ _s , the outer diameter 28 mm and the wall thickness 2 mm. The outside diameter of the nylon coolant tubes was 8 mm; the wall thickness was also 2 mm.

Suspended, the two refrigerant pipes on the radiation shield took place at intervals of 20 cm,

4098.18 / 0794

-12- PHN. 6590

while the mutual distance between the aluminum rings , on which the structure of the radiation shield and coolant pipes had been suspended, was kO cm.

Fig. 2 shows how one end 20 of one of the four nylon tubes (refrigerant and coolant tubes) a steel connecting pipe 21 is coupled. To this end, the end 20 is pushed onto the connecting pipe 21 and onto it clamped by conical sleeves 22 and 23 pushed into one another. The inner sleeve 22 is lengthwise cut open to achieve a better clamping effect.

The connecting pipe 21, like the three other pipes not shown, is guided to the outside through the rigid end wall 2k of the flexible bellows 5.

Although only one embodiment in the drawing the cold transport line is reproduced in All kinds of other embodiments are of course possible within the scope of the invention.

40 98 18/0794

Claims (1)

-13- PHN. 6590 PATENT CLAIMS ; (i.i cold transport line with two side by side extending refrigerant transport pipes, one Radiation shield covering the two refrigerant pipes surrounds and is kept at a distance from the tubes, two coolant tubes extending next to the radiation shield, the one on the outside of the radiation shield and are therefore in thermal contact, and a vacuum jacket that covers the radiation shield and the two coolant pipes surrounds and is kept at a distance from them, characterized in that the refrigerant pipes, the radiation shield and the coolant tubes in the as flexible bellows made vacuum jacket made of a plastic, with the refrigerant pipes over flexible wires or tapes made of poorly thermally conductive Material are locally suspended on the radiation shield and wherein the radiation shield with the coolant tubes over flexible wires or bands made of poorly thermally conductive material is suspended from locally coaxially arranged support rings in the flexible bellows, the outer diameter of which is at least almost equal to the inner diameter of the bellows. 2 »Cold transport line according to claim 1, characterized in that that the cold transport pipes that The coolant tube and the flexible wires or bands are made of nylon. 409S 187OTS4 -14- PHN. 6590 3. Cold transport line according to claim 1 or 2, characterized in that the radiation shield made of polytetrafluoroethylene consists. k. Cold transport line according to Claim 1 or 2, characterized in that the radiation shield consists of polyethylene. 5. Cold transport line according to claim 1, 2, 3 or h, characterized in that the radiation shield is in contact with each of the two coolant tubes via at least one connection made of a material with good thermal conductivity. 6. Cold transport line according to claim 1, 2, 3, ^ or 5 » characterized in that there is a metal strip around the structure of the radiation shield and an adjacent coolant pipe is wrapped, the outside of the strip envelope lying coolant pipe at the transition point from the radiation shield to the adjacent coolant pipe on the Strip shell exerts a compressive force. 7 · Cold transport line according to claim 6, characterized in that around the structure of the metal strip casing and a band of radiation-reflecting material is wound around the coolant tube lying outside the envelope. 8. cold transport line according to claim 7 »characterized in that between the metal strip cover and the Radiation-reflecting tape material is provided with a protective layer that protects the tape material from damage protects the metal strip. 409818/0794 -15- PHN. 6590 9 · Cold transport line to one or more of the Claims 1 to 8, characterized in that a band of radiation-reflecting material around the refrigerant pipes Material is wrapped. 10. Cold transport line according to one or more of claims 1 to 9 »characterized in that on at one end of the line the quay transport and the coolant pipe ends are pushed onto a rigid-walled connecting pipe each and then with two conical sleeves pushed into one another are clamped, the inner one of which is cut open lengthways, wherein the connecting pipes are guided to the outside through a rigid end wall of the flexible bellows. 4098 18/0794 Blank page