FLUID CONDUIT WALL INHIBITING HEAT TRANSFER AND METHOD FOR MAKING

• US 20040261875A1
• Filed: 06/26/2003
• Published: 12/30/2004
• Est. Priority Date: 06/26/2003
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Glover, Jeffrey, Witemyre, James Jay, Meek, Robert J.
• Granted Patent: US 6,854,487 B2
• Time in Patent Office: Days
• US Class Current: 138/114
• CPC Class Codes: F16L 59/143 Pre-insulated pipes
• CPC Class Codes: F16L 9/147 comprising only layers of metal and plastics with or without reinforcement
• CPC Class Codes: F16L 9/18 Double-walled pipes; Multi-channel pipes or pipe assemblies

Abstract

A fluid conduit wall enclosing a hollow interior for the flow of fluid includes an outer surface provided with a low emissivity coating having a coating emissivity of less than 0.2 and a thickness at least sufficient to provide the coating emissivity. One embodiment provides a fluid conduit with multiple spaced-apart walls. An outer surface of an inner wall of a first member and an inner surface of an outer wall of a second member define a gap therebetween. At least one of such surfaces includes the low emissivity coating. A method for providing such coating deposits the coating, for example by reactive vaporization, concurrently on both surfaces from within the gap after assembly of the members.

Claims

1. A multiple spaced-apart wall fluid conduit enclosing a hollow interior for the flow of a fluid therein, comprising:

a metal first conduit wall having a radially inner first surface enclosing the hollow interior and a radially outer second surface; and

,

a metal second conduit wall spaced apart radially outwardly from the first conduit wall and having a radially inner third surface spaced apart radially in juxtaposition with the outer second surface of the first wall to define a gap therebetween, wherein;

the first conduit wall includes on the outer second surface a single layer first low emissivity metal coating, and the second conduit wall includes on the inner third surface a single layer second low emissivity metal coating;

the first and second low emissivity coatings each having a coating emissivity of less than 0.2 and a coating thickness at least sufficient to provide the coating emissivity.

2. The fluid conduit of claim 1 in which the coating thickness is no greater than 5000 angstroms.

3. The fluid conduit of claim 2 in which each of the first and second coatings has:

a coating emissivity in the range of about 0.05-0.1; and

,

a coating thickness in the range of about 1000-2000 angstroms.

4. The fluid conduit of claim 1 in which:

the first conduit wall defines an inner first member of substantially circular cross section and having a first member outside diameter;

the second conduit wall defines an outer second member of substantially circular cross section disposed radially outwardly about the first member and spaced apart from the first member across the gap;

the gap having a radial gap length of no greater than about 30% of the first member outside diameter.

5. The fluid conduit of claim 4 in which the gap has a radial length of less than 0.3 inches.

6. The fluid conduit of claim 5 in which the gap has a radial length in the range of about 0.1-0.25 inches.

7. The fluid conduit of claim 4 in the form of an aircraft gas turbine engine anti-ice conduit segment, in which:

the first conduit wall and the second conduit wall each has an emissivity of at least about 0.4 prior to use and is made of a metal alloy based on at least one element selected from the group consisting of Fe, Co, and Ni and capable of withstanding the flow of the fluid at a temperature of at least about 800°

F.; and

,

the first and second low emissivity coatings each is based on an element selected from the group consisting of Pt, Au, and their combinations.

8. The fluid conduit of claim 7 in which:

the coating emissivity of each of the first and second coatings is in the range of about 0.05-0.1;

the gap radial length is in the range of about 0.1-0.25 inches; and

,

the thickness of each of the first and second coatings is in the range of about 1000-2000 angstroms.

9. A multiple spaced-apart wall fluid conduit enclosing a hollow interior for the flow of fluid therein, comprising:

a metal first conduit wall having a radially inner first surface enclosing the hollow interior and a radially outer second surface; and

,

a metal second conduit wall conduit wall spaced apart radially outwardly from the first conduit wall and having a radially inner third surface spaced apart radially in juxtaposition with the outer second surface of the first wall to define a gap therebetween, wherein;

the first conduit wall includes on the outer second surface a single layer low emissivity metal coating;

the low emissivity coating having a coating emissivity of less than 0.2 and a coating thickness at least sufficient to provide the coating emissivity.

10. The fluid conduit of claim 9 in which the coating thickness is no greater than 5000 angstroms.

11. The fluid conduit of claim 10 in which the low emissivity coating has:

a coating emissivity in the range of about 0.05-0.1; and

,

a coating thickness in the range of about 1000-2000 angstroms.

12. The fluid conduit of claim 9 in which:

the first conduit wall defines an inner first member of substantially circular cross section and having a first member outside diameter;

the second conduit wall defines an outer second member of substantially circular cross section disposed radially outwardly about the first member and spaced apart from the first member across the gap;

the gap having a radial gap length of no greater than about 30% of the first member outside diameter.

13. The fluid conduit of claim 12 in which the gap has a radial length of less than 0.3 inches.

14. The fluid conduit of claim 13 in which the gap has a radial length in the range of about 0.1-0.25 inches.

15. The fluid conduit of claim 9 in which:

the first and second conduit walls each is made of metal alloy based on at least one element selected from the group consisting of Fe, Co, and Ni; and

,

the low emissivity coating is based on an element selected from the group consisting of Pt, Au, and their combinations.

16. The fluid conduit of claim 15 in which:

the coating emissivity is in the range of about 0.05-0.1;

the gap radial length is in the range of about 0.1-0.25 inches; and

,

the coating thickness is in the range of about 1000-2000 angstroms.

17-20. -20. (canceled)

21. A method for making a multiple spaced-apart wall fluid conduit enclosing a hollow interior for the flow of fluid therein, comprising:

providing a first conduit member having a metal first wall including a radially inner first surface defining the hollow interior and a radially outer second surface of a first radial diameter, and a second conduit member having a metal second wall including a radially inner third surface of a second radial diameter greater than the first radial diameter;

assembling the first conduit member co-axially with and radially within the second conduit member to provide an assembly with the outer first surface of the first member maintained radially spaced-apart from the inner third surface of the second member to define a gap therebetween; and

then,

depositing a low emissivity coating concurrently on each of the radially outer first surface of the first member and the radially inner third surface of the second member from within the gap.

22. The method of claim 21 in which, after providing the assembly of the first and second conduit members and before depositing the coating, the assembly is shaped with bends for assembly about associated apparatus.

23. The method of claim 21 in which the low emissivity coating is deposited by reactive vaporization to a thickness of no greater than 5000 angstroms.

24. The method of claim 23 in which the coating is deposited from a metal compound based on an element selected from the group consisting of Pt, Au, and their combinations.