Hermetic high temperature dielectric conduit assemblies
A conduit assembly for a fuel cell system includes a dielectric tube comprising a first end and a second end, a first metal tube including a first lip coupled to the first end of the dielectric tube, a first dielectric ring coupled to the first lip of the first metal tube, a second metal tube including a second lip coupled to the second end of the dielectric tube, and a second dielectric ring coupled to the second lip of the second metal tube.
1. A conduit assembly for a fuel cell system, comprising:
a dielectric tube comprising a first end and a second end;
a first metal tube comprising a first lip coupled to the first end of the dielectric tube;
a first dielectric ring coupled to the first lip of the first metal tube;
a second metal tube comprising a second lip coupled to the second end of the dielectric tube; and
a second dielectric ring coupled to the second lip of the second metal tube.
2. The conduit assembly of claim 1 , wherein the conduit assembly is incorporated into a fuel conduit of a fuel cell stack.
3. The conduit assembly of claim 2 , wherein the dielectric tube and the first and second dielectric ring each comprise a ceramic.
4. The conduit assembly of claim of 3 , wherein the ceramic comprises zirconia toughened alumina or silicon nitride.
5. The conduit of claim 3 , wherein the dielectric tube and first and second dielectric rings have coefficients of thermal expansion that differ by 10 −2 or less.
6. The conduit of claim 3 , wherein the dielectric tube and first and second dielectric rings have coefficients of thermal expansion that differ by more than 10 −2 .
7. The conduit assembly of claim 2 , wherein the first dielectric ring is located inside the first metal tube and the second dielectric ring is located inside the second metal tube.
8. The conduit assembly of claim 7 , wherein the first lip extends inward from a circumference of the first metal tube and the second lip extends inward from a circumference of the second metal tube.
9. The conduit assembly of claim 2 , wherein the first dielectric ring is located outside the first metal tube and the second dielectric ring is located outside the second metal tube.
10. The conduit assembly of claim 9 , wherein the first lip extends outward from a circumference of the first metal tube and the second lip extends outward from a circumference of the second metal tube.
11. The conduit assembly of claim 2 , wherein the first and second metal tubes comprise stainless steel or a nickel chromium alloy.
12. The conduit assembly of claim 2 , wherein the first and second metal tubes are metal bellows.
13. The conduit assembly of claim 2 , wherein the first and second metal tubes are coupled with metal bellows.
14. The conduit assembly of claim 13 , wherein the first and second metal tubes are coupled with metal bellows by brazed or welded joints.
15. The conduit assembly of claim 2 , wherein the dielectric tube and the first dielectric ring are coupled to the first lip by brazed joints, and wherein the dielectric tube and the second dielectric ring are coupled to the second lip by brazed joints.
16. The conduit assembly of claim 15 , wherein the brazed joints comprise a nickel based braze alloy.
17. The conduit assembly of claim 2 , wherein the first lip comprises a first surface coupled to the first end of the dielectric tube and a second surface opposite from the first surface and coupled to the first dielectric ring, and
wherein the second lip comprises a third surface coupled to the second end of the dielectric tube and a fourth surface opposite from the third surface and coupled to the second dielectric ring.
18. A fuel cell system, comprising:
a fuel cell stack comprising a fuel manifold;
and a fuel cell conduit assembly fluidly coupled to the fuel manifold, the fuel cell conduit assembly comprising:
a dielectric tube comprising a first end and a second end;
a first metal tube comprising a first lip coupled to the first end of the dielectric tube;
a first dielectric ring coupled to the first lip of the first metal tube;
a second metal tube comprising a second lip coupled to the second end of the dielectric tube; and
a second dielectric ring coupled to the second lip of the second metal tube.
19. A fuel cell system assembly method, comprising:
assembling a conduit assembly, comprising:
brazing or welding a first end of a dielectric tube to a first surface of a first lip of a first metal tube;
brazing or welding a first dielectric ring to a second surface of the first lip;
brazing or welding a second end of the dielectric tube to a third surface of a second lip of a second metal tube; and
brazing or welding a second dielectric ring to a fourth surface of the second lip; and
inserting the conduit assembly into the fuel cell system.
20. The method of claim 19 , wherein inserting the conduit assembly into the fuel cell system comprises attaching the conduit assembly to a fuel manifold of a fuel cell stack, and wherein the dielectric tube and the first and second dielectric ring each comprise a ceramic.