KR890002867B1 - Vacuum insulated conduit - Google Patents

Abstract

The vacuum insulated conduit reduces a heat leakage at joint. A round plate (22) coorperates with bellows (27) and reduces heat leakage through a territory adjacent the portion working as a half section of the conduit joint section. The insulator (29) is formed by fiber- glass compact in a hollow space between the bellows (27) and a first pipe (10). The fiber-glass encloses the bellows (27) and obstructs convection beat transfer for the bellows or a length of bellows.

Description

Vacuum Insulated Pipe

1 is a partial cutaway cross-sectional view of a vacuum insulated conduit of the present invention connected to another conduit.

2 is a cross-sectional view of one embodiment of a vacuum insulated conduit of the present invention.

3 is a side view of a vacuum insulated conduit of another embodiment of the present invention.

4 is a graph comparing the thermal performance characteristics of the vacuum insulated conduit and the conventional conduit of the present invention.

* Explanation of symbols for main parts of the drawings

10: first pipe 12, 16, 17, 29: heat insulation

14: second pipe 18: sleeve

19, 20: compression band 22: metal disc

25: insulation color 27: bellows

30: flange 31: fiberglass disk

34: adsorbent 35: valve

36, 37: relief valve

The present invention relates to thermally insulated conduits, and more particularly to conduits in which at least a portion is insulated by vacuum. Insulated conduits are used extensively to maintain their temperature characteristics as far as possible while transporting fluids at temperatures significantly different from the ambient temperature. Specific examples of such uses include liquefied gas transport and melt transport. A commonly used terminal insulated conduit is a conduit at least partially insulated by vacuum. In general, such conduits are composed of concentric inner pipes and outer pipes, fluid flows into the inner pipes, and the space between the two pipes is vacuumed to insulate the external state. As an example of the double-walled conduit used industrially, radiation shielding made of multilayer thin plates is often provided between two conduits.

Couplings are connected at intervals of approximately 30 feet of the fluid transport conduit to facilitate the construction and handling of the conduit with axial stretch.

This coupling is the source of heat leakage to the vacuum insulated conduit, which intensifies the vacuum loss of the connection portion. Therefore, there is a need to manufacture a complicated construction method and an expensive material such as the configuration of the bayonet joint.

Accordingly, an object of the present invention is firstly to provide an improved vacuum insulated conduit, and secondly, to provide a vacuum insulated conduit in which heat leakage is reduced compared to a conventional vacuum insulated conduit when the degree of vacuum drops. To provide a vacuum insulated conduit having an end region that can be easily joined to a similar end region to form a joint having heat resistance characteristics. Fourth, a vacuum insulated conduit that can be manufactured using a relatively inexpensive material. To provide, and, fifth, to provide a vacuum insulation conduit that can be manufactured with relatively little effort than conventional ones.

When explaining the specific content of the present invention for achieving the above object and other objects as follows.

The vacuum insulated conduit of the present invention for reducing heat leakage at the joint is (1) a first pipe having one end; (2) The diameter of the first pipe is larger than that of the first pipe and is located along the axial direction around the first pipe, and terminates at the point just in front of the end of the first pipe, thereby reducing the axial distance from the point to the first pipe. Defining a second pipe; (3) its axial end is attached to the first pipe, the diameter of which is larger than the first pipe and smaller than the second pipe, at least a portion of the axial distance along its axial direction around the first pipe; Bellows located along the; (4) a plate having a continuous radial dimension from the radially outermost extension of the bellows to the second pipe, generally perpendicular to both pipes and connecting the bellows with the second pipe at its other axial end; Is done. The term "vacuum" is used herein to define a space having a pressure lower than atmospheric pressure. In addition, the term "bellows" means a metal cylinder with a thin corrugated wall, which allows the cylinder to expand and contract along its axial direction.

The present invention provides an insulated conduit that can be at least partially insulated by a vacuum space between the transport fluid and the ambient conditions. Ambient conditions refer to the external state of the outer concentric pipe, which does not necessarily have to be in the standby state.

The thermal insulation conduits of the present invention exhibit significantly improved thermal resistance over conventional ones when the degree of vacuum is reduced. This improved thermal resistance is achieved by means of constructing a novel interdigital circumferential region shape that reduces heat transfer around the end region when the end is joined to the other end to form a conduit or connector. Achieved by means of constructing the novel end region configuration. The novel end region shape can be easily manufactured, and the end regions can be easily joined to each other to form a connection quickly and conveniently. The end region shape also allows the use of inexpensive insulators normally used only for atmospheric insulation purposes to fill the exhaust area of the assembly. In particular, the end region makes it possible to achieve improved thermal insulation at a lower degree of vacuum, thereby further reducing costs.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

Referring to FIG. 2, there is shown an inner, ie first pipe 10, and an outer, ie second pipe 14, through which fluid is conveyed, the second pipe 14 being a first one. It extends axially around the pipe and terminates in the vicinity of the first pipe 10 to define the axial distance from (51) to (52). The bellows 27 is located around it along the axial distance between the point 51 and the end 52 and joined to the first pipe 10 at point 23 by eg butt welding at its axial end adjacent to the end 52. do. The circular plate 22 is positioned substantially perpendicular to the pipe and from the outermost radial extension 24 of the bellows 27 to the second pipe 14 the disc 22 is connected to the second pipe (23). 14, to bellows 27 at 24.

The space between the first pipe and the second pipe is exhausted. The space is preferably filled with a continuous foamed or fibrous insulation 12 which is used only at atmospheric pressure and is generally not considered suitable for vacuum insulation. The vacuum space may be at an appropriate pressure in the range of 1 μm Hg or less at atmospheric pressure. However, as will be explained in detail in the following, the advantages of the conduit according to the invention are more preferably obtained when the pressure in the space is at a pressure from 1 μm Hg to 1 atmosphere, preferably from 10 to 100,000 μm Hg. In addition, the vacuum space acts as a main means or an auxiliary means for obtaining a vacuum, and activated carbon, a molecular sieve, which serves as a means for maintaining a vacuum by absorbing a gas introduced into the space into a leak or material outflow gas. The same adsorbent 34 is received.

The disc 22 and the bellows 27 cooperate to greatly reduce heat leakage from the conduit to the region proximate the end serving as half of the conduit junction. The disc 22 and the bellows 27 serve to effectively reduce the exhaust volume near the junction such that the decrease in the degree of vacuum does not seriously affect the heat transfer resistance as in conventional vacuum insulated conduits. Further, the disc 22 and the bellows 27 are from the point where the bellows 278 is attached to the first pipe 10 at point 28 to the point at which the disc 22 is attached to the first pipe 14 at point 23. Heat transfer occurs only along the surface paths of the disc 22 and the bellows 27 to reduce heat leakage at the joint. For example, when liquefied gas is transported through the first pipe 10, the first pipe 10 is at a low temperature and the second pipe 14 is at a room temperature. Heat transfer to the low temperature liquid is generated only through the first pipe 10 from the point 23 to the point 28 along the curved surface of the disc 22 and the bellows 27 to the liquid. This heat transfer is significantly suppressed by the present invention, while convective heat transfer along the pipe length is suppressed by vacuum and insulation. In addition, the bellows 27 also serves to provide the axial elasticity required for the conduit when the temperature difference between the inner and outer pipe waves is severe.

In order to improve the thermal insulation of the conduit according to the invention, it is preferable to fill the joint with a heat insulator. In FIG. 2, the heat insulating material 29 formed using the fiberglass occupies the empty space between the bellows 27 and the first pipe 10 to prevent radiant heat transfer. A mat enclosure 26, such as fiberglass, surrounds the bellows 27 to restrain convective heat transfer to or along the length of the bellows. The joint is surrounded by the heat insulating parts 16 and 17, and the heat insulating parts 16 and 17 are preferably rigid, independent foamed urethane foams. An insulating collar 25 made of a molded independent foam type flexible foam is disposed between the disc 22 and the heat insulating portion 17 to adhere to the disc 22 to provide axial flexibility. Alternatively, the enclosure 26 may be wound in layers to enclose the entire space occupied by the thermal insulations 16, 17. This structure is desirable when the liquid oxygen is a fluid that is transported to avoid problems with the adaptability of the material. A sleeve 18, preferably made of aluminum, is secured to the pipe 14 by means of a flexible, non-permeable seal 21, which surrounds the joint, which seal 21 is a rubbery elastomer to the compression mens 19, 20. Supported in place. 2 is a preferred embodiment of the present invention, the end of the first pipe 10 is provided with a flange 30 to facilitate the joining of one end and the other end to form a joint. Alternatively, the end of the pipe may be welded with the other end.

Fiberglass is a good insulator for insulation between pipes. Other types of insulation include phenol foams and pearlite.

The second pipe 14 is preferably made of aluminum having a moderate strength and low cost. Suitable materials thereof include carbon steel or other metal alloys or nonmetallic materials such as polyethylene.

The first pipe 10 is suitable for the fluid to be transported therethrough and may be of any conduit, but stainless steel is preferred. The bellows 27 uses metal, most preferably stainless steel. The disc 22 is preferably aluminum, bonded by welding in similar material parts, and by suitable adhesive to different material parts.

The axial length of the bellows 27 is a matter of design within the capabilities of those skilled in the art. The longer the axial length of the bellows, the greater the axial stretch of the conduit and the greater the heat transfer resistance in the axial direction. However, the radial convection or radiative heat transfer around the bellows increases with the axial length of the bellows. The radius of the bellows can be any suitable radius, but it is desirable to allow the insulation 29 between the bellows and the first pipe to be sufficiently larger than the radius of the first pipe. The distance between the first pipe and the bellows is preferably equal to or less than 25 sets of the distance between the inner shaft and the outer pipe, most preferably 5 to 20 percent. It is usually determined by the bellows specification.

The number of bellows wrinkles depends on the required degree of axial stretch. If greater axial stretch is required, then more wrinkles per unit length will be required.

The bellows length to minimize heat transfer through the conduit junction was found to be 1-12 inches, most preferably 1.5-6 inches.

3 shows another example of a vacuum insulated conduit according to the present invention. Parts like those in FIG. 2 are denoted using the same reference numerals. In this embodiment, the metal disc 22 is welded to the second pipe 14 and bonded to the bellows 27. The seal 21 is a heat-shrinkable plastic seal with an adhesive attached to the back, which does not require a compression band. A high density fiberglasssk 31 is provided to align the first pipe 10 into the second pipe 14. The valve 35 may be used to evacuate the junction or to fill its portion up to atmospheric pressure with a low conductivity gas such as CO ₂ , Ar.

1 shows a state in which the vacuum insulated conduit of the present invention is joined to other conduits in each region to form a conduit junction. Parts identical to those in FIGS. 1 to 2 are denoted by the same reference numerals. The relief valves 36 and 37 are for releasing excess pressure when an accident occurs in the first pipe 10 or the joint.

4 is a graph showing the thermal insulation performance of the vacuum insulation conduit of the present invention, curve A is for the conduit of the present invention, curve B is for the conventional vacuum insulation conduit using a multi-layer radiation shielding. The data is similar to that in FIG. 2 and is based on the performance evaluated for a vacuum insulated conduit with a first pipe of 2 inches in diameter and 30 feet in length and one junction.

As shown, both conduits work well in gouging holes below 10 μm Hg. However, as the degree of vacuum decreases, conventional conduits degrade significantly in performance, while the conduits of the present invention continue to maintain their performance at an acceptable level, including the overall vacuum loss.

Therefore, by using the vacuum insulated conduit of the present invention it is possible to better insulate in a lower vacuum than that required until now, it is possible to considerably reduce the cost. Since the degree of weaving is not desperate for some insulation performance, it is possible to maintain vacuum at a lower cost by using an adsorbent rather than an expensive getter package such as barium or palladium oxide in an empty space. In addition, inexpensive insulation, which is usually used for thermal insulation, is used instead of expensive radiation shielding material. By using the atmospheric insulation material, the center of the inner pipe can be effectively aligned, causing high heat leakage, and removing the spacer having high manufacturing cost. Moreover, the costly vacuum pump time is significantly reduced. Furthermore, depending on the low degree of vacuum that can be tolerated by the vacuum insulated conduit of the present invention, the cost and time required for fabrication and maintenance can be reduced or eliminated completely.

The foregoing description has been set forth to illustrate some preferred embodiments of the invention in order to facilitate understanding of the invention, and is not meant to be limited to the foregoing several examples of the invention. Therefore, various modifications within the spirit and scope of the invention may be made. Modifications and modifications are possible.

Claims (19)

A conduit for reducing heat leakage at a junction, comprising: a first pipe having an end portion; A second pipe having a larger diameter than the first pipe and positioned axially around the first pipe and terminating at a point near the end of the first pipe to define an axial distance from the point to the first pipe ; The axial end is attached to the first pipe, the diameter thereof is larger than the first pipe and smaller than the second pipe, and the axial distance around the first pipe and along the axial direction of the first pipe. A bellows located along at least a portion of the bellows, and a radial size from the radially outermost extension of the bellows to the second pipe, both perpendicular to both pappes, the other axial end of which is connected to the second pipe; Vacuum insulation conduit characterized in that consisting of a plate. The vacuum insulated conduit according to claim 1, wherein the space between the first pipe and the second pipe is filled with a heat insulating material. The vacuum insulated conduit according to claim 1, wherein an adsorbent capable of adsorbing gas is contained in the space between the first pipe and the second pipe. The vacuum insulated tube according to claim 1, wherein a heat insulating material is filled in the space between the first pipe and the bellows. The vacuum insulated tube according to claim 1, wherein a flange is provided at an end of the first pipe. The vacuum insulated conduit of claim 1, wherein the first pipe and bellows are made of stainless steel, the second pipe and plate are made of aluminum, and the plate is bonded to the bellows and welded to the second pipe. . The vacuum insulation of claim 1, wherein the first pape and the bellows and the plate are made of stainless steel, the second pape is made of aluminum, and the plate is bonded to the second pape and welded to the bellows. conduit. A conduit junction, wherein the conduit of claim 1 is attached separately to its same conduit at each end. The conduit junction according to claim 8, wherein the junction is surrounded by a sleeve. 10. The conduit junction according to claim 9, wherein the space enclosed by the sleeve is filled with insulation. 10. The conduit junction according to claim 9, wherein the sleeve is sealed to the second pipe by a soluble, impermeable seal. The vacuum insulated conduit according to claim 1, wherein the space between the first and second breaks is below atmospheric pressure. 13. The vacuum insulated conduit of claim 12, wherein said pressure is about 10 to 100,000 [mu] m Hg. The vacuum insulated conduit of claim 1, wherein the bellows has a diameter such that the distance between the first pipe and the bellows is less than 25 percent of the distance between the first pipe and the second pipe. The vacuum insulated conduit of claim 4, wherein said distance is between 5 and 20 percent. The vacuum insulated conduit of claim 1 wherein the bellows is between 1 and 12 inches in length. 17. The vacuum insulated conduit of claim 16 wherein said length is between 1.5 and 6 inches. 10. The conduit junction according to claim 9, wherein the space surrounded by the sleeve is empty. 10. The conduit junction according to claim 9, wherein the space surrounded by the sleeve is filled with a low conductive gas.

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