METHOD AND APPARATUS FOR COOLING A CRYOGENIC STORAGE CONTAINER

• US 3,705,498 A
• Filed: 11/03/1969
• Issued: 12/12/1972
• Est. Priority Date: 11/03/1969
• Status: Expired due to Term

• Current Assignee: Helix Technology Corporation (Azenta, Inc.)
• Original Assignee: James R. Dehaan
• Inventors: DeHaan, James R.
• Primary Examiner(s): Davis, Jr., Albert W.
• Application Number:
  US04/873,313
• Time in Patent Office: 1,135 Days
• Field of Search: 62/45,54 220/9,14 165/179,181
• US Class Current: 62/47.1
• CPC Class Codes: F17C 2203/018 by attachment at the neck
• CPC Class Codes: F17C 3/08 by vacuum spaces, e.g. Dewar flask for household use A47J41/02
• CPC Class Codes: Y10S 220/901 Liquified gas content, cryogenic

Abstract

A method of conserving the refrigeration value of a dewar by increasing the thermal conductivity of a selected portion of an otherwise low thermal conductivity conduit and restricting the effective cross sectional area along at least as much as the conduit as the higher conductivity portion so as to increase the velocity of the boil-off gases and permit more of the refrigeration value of the boil-off gas to pass through the conduit'"'"''"'"'s high conductivity portion from which the refrigeration is directed into the dewar'"'"''"'"'s vacuum space. A preferred structure for performing the above method includes a high thermal conductivity collar about the conduit and a high conductivity shield extending from the collar into and through the dewar'"'"''"'"'s vacuum space. A second tube is placed within the conduit to form an annular space therebetween. One end of the second tube is closed so that the boil-off gases are forced through the annular space which is filled with a fine fibrous relatively non-conductive packing material in an area that extends for a distance at least as long as the collar. In this manner, the boil-off gas velocity is increased as it passes through the packing material and results in an increase in the transfer of the boil-off gas'"'"''"'"' refrigeration value to the collar, shield, and vacuum space.

Claims

1. In a double walled cryogenic storage vessel having a cold storage container wall separated from a warm outer wall by a vacuum space in which at lEast one radiation shield is located, and being of the type in which a low thermal conductivity conduit of a given cross sectional area extends from said container wall through said vacuum space to said outer wall, the method of conserving the refrigeration value of the boil-off gases from said container comprising the steps of:

increasing the effective thermal conductivity between the low thermal conductivity conduit and the radiation shield for at least about one inch along the length of said conduit at a selected portion intermediate the ends thereof;

directing said boil-off gases through said conduit; and

, restricting the effective cross sectional area of said conduit at said selected portion along at least the same length as that for which the thermal conductivity is increased to increase the velocity of said gas as it flows through the restricted portion of said conduit to thereby increase the transfer of cold from said boil-off gas to said selected portion of said conduit.

2. The method of claim 1 including the step of increasing the turbulence of said boil-off gas as it flows through the restricted portion of said conduit.

3. The method of claim 2 wherein said turbulence is increased by directing said boil-off gas through a fibrous packing material.

4. The method of claim 1 including the step of increasing the turbulence of said boil-off gas as it flows through said restricted portion of said conduit.

5. In a double walled cryogenic storage vessel having a cold storage container wall separated from a warm outer wall by a vacuum space, the combination comprising:

a low thermal conductivity conduit extending from said container wall through said vacuum space to said outer wall for carrying cold boil-off gas out of said storage container;

a collar of highly thermally conductive material located in said vacuum space and surrounding a selected portion of the outer surface of said conduit so as to be in heat transfer relationship with said outer surface for at least about one inch along the length thereof;

a highly thermally conductive shield affixed to said collar and extending into said vacuum space; and

, restriction means in said conduit for restricting the cross sectional area of said conduit along at least the same length as that for which said collar extends, said restriction means being operative to increase the velocity of said boil-off gas as it passes through said selected portion.

6. The apparatus according to claim 5 wherein the restriction means is comprised of a packing material in said conduit in heat transfer relationship with the portion of the inner surface of said conduit adjacent said selected portion of said outer surface.

7. The apparatus of claim 6 wherein said restriction means has an effective thermal conductivity of about that of terephthalic ester polymer fibers.

8. The apparatus of claim 6 wherein said packing material is fibrous and comprised of fibers having diameters of less than about 100 microns.

9. The apparatus of claim 8 wherein said fibers are comprised of terephthalic polymer fibers.

10. The apparatus according to claim 5 including a second low thermal conductivity conduit located inside of the first conduit to form a channel for the flow of said boil-off gas between the inner wall of said first conduit and the outer wall of said second conduit, said restriction means being located in said channel;

and, means for normally preventing the flow of boil-off gas through said second conduit.

11. The apparatus of claim 10 wherein said means for normally preventing the flow of boil-off gas through said second conduit is responsive to more than a predetermined amount of pressure in said storage container to permit said boil-off gas to pass through said second conduit so as to relieve said pressure.

12. The apparatus of claim 10 wherein the restriction is comprised of a packing material in heat transfer relationship with the outside surface of said second conduit and the inSide surface of said first conduit.

13. The apparatus of claim 10 wherein said restriction means has an effective thermal conductivity of about that of terephthalic ester polymer fibers.

14. The apparatus of claim 10 wherein said packing material is fibrous and comprised of fibers having diameters of less than about 100 microns.

15. The apparatus of claim 14 wherein said fibers are comprised of terephthalic ester polymer fibers.

16. The apparatus of claim 10 wherein said second conduit is spaced from said first conduit by no more than about one-eighth inch.

17. In a double walled cryogenic storage vessel having a cold storage container wall separated from a warm outer wall by a vacuum space, the combination comprising:

a low thermal conductivity conduit extending from said container wall through said vacuum space to said outer wall for carrying cold boil-off gas out of said storage container;

a collar of highly thermally conductive material located in said vacuum space and surrounding a selected portion of the outer surface of said conduit so as to be in heat transfer relationship with said outer surface for at least about one inch along the length thereof;

a highly thermally conductive shield affixed to said collar and extending into said vacuum space; and

, a fibrous packing material in said conduit in heat transfer relationship with the portion of the inner surface of said conduit adjacent said selected portion of said outer surface.

18. The apparatus of claim 17 wherein said packing material has an effective thermal conductivity of about that of terephthalic ester polymer fibers.

19. The apparatus of claim 18 wherein said fibers have a diameter of less than about 100 microns.

20. The apparatus of claim 17 wherein said packing material is comprised of terephthalic ester polymer fibers having diameters of less than about 100 microns.

21. The apparatus of claim 17 including a second low thermal conductivity conduit located inside of the first conduit to form a channel for the flow of said boil-off gas between the inner wall of said first conduit and the outer wall of said second conduit, said fibrous packing material being located in said channel;

and, means for normally preventing the flow of boil-off gas through said second conduit.

22. The apparatus of claim 21 wherein said second conduit is spaced from said first conduit by no more than about one-eighth inch.

23. The apparatus of claim 21 wherein said means for normally preventing the flow of boil-off gas through said second conduit is responsive to more than a predetermined amount of pressure in said storage container to permit said boil-off gas to pass through said second conduit so as to relieve said pressure.

24. The apparatus of claim 21 wherein said packing material has an effective thermal conductivity of about that of terephthalic ester polymer fibers.

25. The apparatus of claim 24 wherein said fibers have diameter of less than about 100 microns.

26. The apparatus of claim 21 wherein said packing material is comprised of terephthalic ester polymer fibers having diameters of less than about 100 microns.

27. The apparatus of claim 17 including at least a second highly thermally conductive collar located in said vacuum space and surrounding at least a second selected portion of the outer surface of said conduit so as to be in heat transfer relationship with said outer surface, the height of the collar closer to said cold storage container wall being less than the height of a collar being further from said storage container wall.

28. The apparatus of claim 27 including a highly thermally conductive shield affixed to each of said collars, each of said shields extending into said vacuum space.

29. The apparatus of claim 27 wherein said collar closer to said cold storage container is at least about one inch high.

30. The apparatus of claim 27 wherein said packing material has an effective thermal conductivity of about that of terephthalic ester polymer fibers.

31. The apparatus of claim 30 wherein said fibers have a diameter of less than about 100 microns.

32. The apparatus of claim 27 wherein said packing material is comprised of terephthalic ester polymer fibers having diameters of less than about 100 microns.