US 3565118 A
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United States Patent Thronton Stearns 5 Fernway St., Winchester, Mass. 01890 747,284
July 24, 1968 Feb. 23, 1971 Inventor Appl. No. Filed Patented THERMAL INSULATION FOR FLUID STORAGE CONTAINERS 9 Claims, 3 Drawing Figs.
11.8. CI. 138/112; 138/148; 138/149; 220/9 Int. Cl. F161 9/18 FieldolSearch .138/111, 112,113,114,148,149z220/l5;161/241,242
References Cited UNITED STATES PATENTS 229,620 7/1880 Lynch 138/148 675,447 6/1901 McMahon 138/148 903,316 11/1908 Reimann 138/1 49X 2,934,096 4/1960 Banks 138/111 3,332,446 7/1967 Mann.... 138/148X 3,383,875 5/1968 Haas l38/122X Primary Examiner-Herbert F. Ross Atmm'ey Rowland V. Patrick ABSTRACT: Insulation for fluid storage chambers includes a hollow vacuum-tight tube or sets of tubes surrounding the chamber and spaced from the chamber and from each other by thermal insulating spacer means, each tube, or set of tubes, being in contact with a heat-conductive layer extending circumferentially with or without helical windings and spaced convolutions, around the chamber, and separated from one another and from the chamber by thermal insulating spacer means.
PATENTEU FEB23 l97l SHEET 1 0F 2 PATENTED FEB23 I971 SHEET 2 OF 2 THERMAL INSULATION FOR FLUID STORAGE CONTAINERS This invention relates to thermal insulation of cryogenic fluid storage containers including transfer lines and has for an object the provision of insulating structures which diminish the heat leak rate from such containers, though the structures and operation herein described may also be applied to the reduction of heat leakage to or from any stored or flowing fluid.
To this end the invention contemplates surrounding an enclosure in the form of a chamber or conduit with insulation which, in the case of cryogenic fluids, includes one or more hollow cooling tubes which may, if the container is a semiflexible tube, be corrugated and spirally wound about'the container so as not to eliminate flexibility. The hollow cooling tube or tubes are formed of thermally conductive material and are in contact with thin thermally conductive and preferably radiation reflective sheet material which extends around the container with interposed spacer means for restricting radial heat conduction, thereby establishing a relatively stable temperature differential between the container and the surrounding thermally conductive sheet.
Further stages of hollow cooling tubes may lie radially outwardly, each insulated from the next innermost stage of hollow cooling tubes and each contacting a separate surrounding thermally conductive sheet.
One basic embodiment of the invention and a typical more complicated embodiment of the invention are shown in the accompanying drawings, wherein:
FIG. 1 is a perspective view of the basic embodiment of the invention with successive layers cut away for illustration purposes.
FIG. 2 is a cross-sectional view of the complete assembly shown in FIG. I; and
FIG. 3 is a cross-sectional view of a different embodiment of the invention.
FIG. 1 shows an inner corrugated vacuum-tight metal tube I around which is helically wrapped a spacer 12 which may be a plastic or metal ribbon or may be a ribbon of fibrous insulating material such as disclosed in an application filed simultaneously herewith, SER. No. 747,134. Helically wound around the inner tube and spaced therefrom by the spacer 12 is a hollow metallic vacuum-tight tube 14 which, though shown uncorrugated in the drawing, may be corrugated if desired. The pitch of the tube 14 is much greater than that of the spacer l2.
Wrapped around the spacer means 12 is also a 100 percent coverage of a heat radiation reflective material such as a metal foil 16 which is heat conductive and contacts the metallic tube 14.
Further spacer means 18 is wound in an opposite direction from the spacer l2 and may be of like material. Around the spacer means 18 are layers of insulation material 20, the whole being surrounded by a corrugated vacuum-tight outer tube 24.
The insulation material 20 may be of the type disclosed in U. S. Pat. Nos. 3,009,600; 3,265,236; and 3,236,406, comprising alternate layers of fibrous material and heat-reflective sheet material.
The annular space between the vacuum-tight tubes 10 and 24 is evacuated except for the volume occupied by the tube 14.
In use, it is contemplated that the inner tube 10 may, as in a transfer line, carry a cryogenic fluid such as helium at a temperature well below 80 K. with or without an electrical conductor, and the tube 14 may carry a cryogenic fluid such as nitrogen at a temperature between the temperatures of tube It) and of tube 24, the heat conductive layer 16 acting to stabilize the intermediate temperature circumferentially.
Alternatively, the tube 14 may have connections at the outflow end of tube 10 so as to carry cryogenic fluid bled from the inner tube 10 counter flow-wise back through the tube 14.
In the embodiment shown in cross section in FIG. 3, there are multiple sets of surrounding hollow tubes, each set of tubes being in contact with a circumferentially extending layer of heat conductive material, such as metal foil, thus providing a plurality of separate and insulated temperature stages radially of the coaxial tubing.
Thus an inner vacuum-tight tube 6 is surrounded by a hellcally wound spacer means 8, and the tube 10, like the tube 10 in FIG. 1, which may or may not be vacuum-tight, furnishes further mechanical support. Tube 10 is surrounded by a heat conductive layer 30 which encloses a single helically wound hollow vacuum-tight tube 32. A spacer means 34 is then spirally wound in one direction around the conductive layer 30 to space therefrom a circumferentially extending thermally conductive layer 36 which encloses and is in contact with a pair of vacuum-tight tubes 38. This is followed radially outward by a spacer ribbon 40 wound spirally in the opposite direction around the conductive layer 36 and spacing outwardly therefrom a third conductive layer 42 which encloses and is in contact with a set of three vacuum-tight tubes 44.
Further spacer means 46 then separate outwardly a last layer of conductive material48 which encloses a set of four spirally wound hollow vacuum-tight tubes 50 and the last layer is similar to the layer 20 in the embodiment of FIGS. 1 and 2; the entire assembly being enclosed in the outer vacuum-tight corrugated tube 24.
Any of the sets of tubes may be further supported by contacting rigid coaxial corrugated tubing similar to the arrangement of 10, 32 and 30 or other rigidifying structure at the greater radii of the other set of tubes.
It is contemplated that cooling fluid may be circulated in one direction down tube 32, back in the other direction through tubes 38 then in reverse flow through tubes 44, and finally back through the set of four tubes 50, the increased number of tubes taking care of expansion of the fluid as it heats. As in the case of FIG. 1, if desired, the input feed to inner tube 32 may be a bleed off from the fluid within the inner central container 6. Or, any of the sets of tubes may be supplied from a separate refrigeration source, alone or in combination, permitting use of different cryogenic fluid in different stages.
No matter how connected, the intention is to carry off heat longitudinally via the fluid flowing in each set of cooling tubes, thereby reducing the temperature of each conductive layer which in turn materially reduces the overall heat leakage to or from fluid in central tube 6.
The diameters and number of cooling tubes may vary in the same or different stages depending upon the temperature, the fluid used and the length, to give optimum performance.
It is contemplated that the annular spaces between vacuumtight coaxial tubes not occupied by cooling tubes will be evacuated separately; or, if any intermediate coaxial tube is not vacuum-tight may be evacuated together, in which case the intermediate coaxial tube or tubes may be perforated.
While the conductive layer 16 in FIGS. 1 and 2 gives I00 percent coverage, where there are multiple conductive layers as in FIG. 3, only the outer one needs to have I00 percent coverage and be beat reflective and the inner conductive layers may then be helically wound with spaced convolutions with only partial coverage. percent coverage can be attained either with a wrap or an abutting or overlapping helical winding.
While the container storage of this invention is particularly efficient in the case of cryogenic fluids, it can be used for controlling heat leakage to and from fluids having higher boiling points including methane and fluorocarbons.
1. An insulated container comprising:
a vacuum-tight inner enclosure;
a vacuum-tight outer enclosure;
a thermally conductive hollow tube extending axially of said container between said inner and outer enclosures;
said tube being in contact with an associated layer of thermally conductive material extending circumferentially about said inner enciosure;
circumferentially extending spacing means of thermal insulating material radially separating said layer of thermally conductive material from said inner enclosure; and
whereby fluid flowing in said hollow tube tends to establish a substantially stable equilibrium temperature for said conductive layer by absorbing and removing heat leakage via conduction through said conductive layer and tube.
2. A container as claimed in claim 1 having a plurality of said hollow tubes, each tube being in contact with an associated layer of thermally conductive material contacting that tube and each such tube and associated layer being separated from other tubes and their associated layers by thermal insulating material.
3. An insulated container for cryogenic fluids having:
a central enclosure;
an outer enclosure;
a series of circumferentially extending layers of thermally conductive material extending around said central enclosure;
spacing means between said thermally conductive layers for holding said layers in radially spaced relation; and
at least one hollow tube of thermally conductive material extending axially of said central enclosure in contact with one of said layers of thermally conductive material but radially spaced from said central enclosure.
4. A container as claimed in claim 3 wherein there are at least three of said hollow tubes and more of said tubes contact the outermost conductive layer than contact any other layer of conductive material inside of said outermost layer.
5. A container as claimed in claim 3 wherein there are a plurality of said hollowtubes and the number of said tubes contacting successive circumferentially extending layers increases in number progressively from the innermost layer to the outermost layer.
6. A container as claimed in claim 3 wherein at least some of said spacer means are constituted of thermal Insulating material.
7. A container as claimed in claim 3 wherein the innermost spacer means is a spirally wound ribbon.
8. Semiflexible cryogenic transfer tubing comprising:
inner and outer corrugated coaxial vacuum-tight tubes and successively overlying layers of the following materials in the following sequence between said inner and outer tubes; I
helically wound spacer means having spaced convolutions;
a helically wound hollow heat conductive tube;
a heat conductive film in heat conductive contact with said helically wound tube;
helically wound spacer means having spaced convolutions layed with a pitch opposite to that of said first named spacer means; and
a layer of fibrous insulation.
9. A transfer tubing as claimed in claim 8 also having heat reflective foil insulation adjacent to said layer of fibrous insulation.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 565 118 Dated 23 J91] lnventofls) Thornton Stearns It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
In the Caption:
Change "Thronton" to --'Ihornton--;
Add as assignee Vacuum Barrier Corporation of Woburn, Massachusetts, a corporation of Delaware Col. 2, line 75, after "enc1osure;" delete and insert Col. 3, line 3, after "enclosureg" delete and--.
Signed and sealed this 6th day of July 1971.
EDJARD M.FIETGHER,JR. WILLIAM E. SCHUYIER, JR. Attesting Officer Commissioner of Patents