Insulation test cryostat with lift mechanism

Patent metadata

Field	Value
Publication number	US-9488607-B2
Application number	US-201314090193-A
Country	US
Kind code	B2
Filing date	Nov 26, 2013
Priority date	Jun 12, 2009
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

A multi-purpose, cylindrical thermal insulation test apparatus is used for testing insulation materials and systems of materials using a liquid boil-off calorimeter system for absolute measurement of the effective thermal conductivity (k-value) and heat flux of a specimen material at a fixed environmental condition (cold-side temperature, warm-side temperature, vacuum pressure level, and residual gas composition). An inner vessel receives liquid with a normal boiling point below ambient temperature, such as liquid nitrogen, enclosed within a vacuum chamber. A cold mass assembly, including upper and lower guard chambers and middle test vessel, is suspended from a lid of the vacuum canister. Each of the three chambers is filled and vented through a single feedthrough. All fluid and instrumentation feedthroughs are mounted and suspended from a top domed lid allowing easy removal of the cold mass. A lift mechanism allows manipulation of the cold mass assembly and insulation test article.

First claim

We claim:

1. A method for testing thermal conductivity, comprising:
positioning a cylindrical test specimen around a cylindrical cold mass comprised of a stacked upper vessel, an upper vapor pocket, test vessel, a lower vapor pocket, and a lower vessel, which in turn is within a vacuum chamber, wherein each vapor pocket comprises bulkhead plates welded together around respective circumferential surfaces with at least one bulkhead plate having a concave surface oriented toward the other bulkhead plate defining the respective vapor pocket that provides a thermal isolation for stratified liquid condition;
filling and venting each of the stacked upper vessel, test vessel, and lower vessel of the cylindrical cold mass with a liquid, which is atmospheric pressure saturated, via a respective single top fed feedthrough;
maintaining a warm or cold vacuum pressure within the vacuum chamber;
measuring a cold boundary temperature of an inner portion of the test specimen and a warm boundary temperature of an outer portion of the test specimen while the liquid maintains a set temperature of the cold mass; and
calculating an effective thermal conductivity for the test specimen based upon the fluid boil-off or evaporation flow rate, heat of vaporization of the liquid, cold boundary temperature, warm boundary temperature, effective heat transfer surface area of the cold mass, and thickness of the specimen.

2. The method of claim 1 , further comprising calculating a mean heat flux for the test specimen based upon the liquid boil-off or evaporation flow rate, heat of vaporization of the liquid, effective heat transfer surface area of the cold mass, and thickness of the test specimen.

3. The method of claim 1 , further comprising filling the cylindrical cold mass with liquid nitrogen.

4. The method of claim 1 , further comprising filling the cylindrical cold mass with liquid hydrogen.

5. The method of claim 1 , further comprising filling the cylindrical cold mass with liquid helium.

6. The method of claim 1 , further comprising filling the cylindrical cold mass with a selected one of a group consisting liquid carbon dioxide, Freon R134a, and ethyl alcohol.

7. The method of claim 1 , further comprising operating with a k-value range from approximately 0.01 mW/m-K to 100 mW/m-K.

8. The method of claim 1 , further comprising operating with a k-value range from 0.01 to 10 mW/m-K.

9. The method of claim 1 , further comprising operating with a range of mean heat flux from 0.1 W/m 2 to 500 W/m 2 .

10. The method of claim 1 , further comprising operating with a range of mean heat flux from 0.1 to 100 W/m 2 .

11. The method of claim 1 , further comprising operating with a Cold Boundary Temperature (CBT) between 77 K and 300 K and a Warm Boundary Temperature (WBT) between 100 K and 400 K.

12. The method of claim 1 , wherein the test specimen comprises at least one of a group consisting of a loose-fill powder, particle, blankets, multilayer insulations, foams, clam-shells, panels, and composites.

13. The method of claim 1 , further comprising confining a loose-fill powder or particle material within a sleeve assembly comprising a cylindrical side wall of diameter greater than the cold mass to create an annular space there between and evenly centered about the cold mass by top and bottom centering rings that respectively enclose a top opening and a bottom opening of the annular space to keep the loose-fill powder or particle materials in place and that center and space off the cylindrical side wall by circumferentially contacting an outer surface of the cold mass.

14. The apparatus of claim 13 , wherein the sleeve assembly comprises a cylindrical sleeve including a high-emissivity black coated external surface.

15. The apparatus of claim 13 , wherein the sleeve assembly is held in place inside an inner wall of the vacuum canister by plastic composite stand-offs comprising a stack of fiberglass rings.

16. The method of claim 1 , further comprising assembling the cylindrical cold mass into the vacuum chamber by raising and lowering a lid of the vacuum chamber on a carriage raised by a vertical machine screw jack.

17. The method of claim 1 , further comprising assembling the cylindrical cold mass into the vacuum chamber by raising and lowering a lid of the vacuum chamber on a carriage raised by an overhead hoist.

18. The method of claim 1 , further comprising:
directing vent gases from the top fed feedthroughs to a common reservoir surge vessel that is maintained at a slightly higher pressure above prevailing room pressure to offset daily cyclic variations in barometric pressure.

19. The method of claim 18 , further comprising maintaining the common reservoir surge vessel at a delta pressure of about 4 millibars.

20. An apparatus for measuring thermal conductivity or heat flux, comprising:
a vacuum canister having a lid attachable and sealable to a lower cylindrical portion;
a cold mass comprised of a vertical cylindrical stack of an upper vessel, an upper vapor pocket, a test vessel, a lower vapor pocket, and a lower vessel, wherein each vapor pocket comprises bulkhead plates welded together around respective circumferential surfaces with at least one bulkhead plate having a concave surface oriented toward the other bulkhead plate defining the respective vapor pocket that provides a thermal isolation for stratified liquid condition;
three top feedthrough conduits that pass through the lid of the vacuum canister, each feedthrough conduit to singularly fill and to vent one of the upper vessel, test vessel, and lower vessel;
a vertical machine jack screw for positioning a carriage engagable to the lid of the vacuum canister for positioning the cold mass suspended from the lid into the lower cylindrical portion;
a vacuum system for producing and measuring a cold vacuum pressure within the vacuum canister; and
a boil-off calorimeter measuring system for determining boil-off flow rate coincident with a stable thermal environment of a test specimen positioned around the cold mass.

21. The method of claim 1 , wherein filling via the respective top fed feedthroughs comprises gravity filling by manually pouring the liquid into a funnel that communicates with the respective top fed feedthroughs while allowing simultaneous venting of gas from the respective vessels through the top fed feedthroughs.

22. The apparatus of claim 20 , further comprising a funnel that communicates with one of the feedthrough conduits to manually pour liquid into each of the three feedthrough conduits and allowing simultaneous venting of gas from the respective vessels.

23. The apparatus of claim 20 , further comprising a common reservoir surge vessel that is maintained at a slightly higher pressure above prevailing room pressure to offset daily cyclic variations in barometric pressure and that receives venting from the three top feedthrough conduits.

24. The apparatus of claim 20 , further comprising a common reservoir surge vessel that is maintained at a slightly higher pressure above prevailing room pressure to offset daily cyclic variations in barometric pressure and that receives venting from the three top feedthrough conduits.

25. An apparatus for measuring thermal conductivity or heat flux, comprising:
a vacuum canister having a lid attachable and sealable to a lower cylindrical portion;
a cold mass comprising:
a vertical cylindrical stack of an upper vessel, a test vessel

Assignees

• Nasa

Inventors

• Fesmire James E
• Dokos Adam G

Classifications

• G01N25/18 Primary

  by investigating thermal conductivity (by calorimetry G01N25/20; by measuring change of resistance of an electrically-heated body G01N27/18) · CPC title

• G01K17/00

  Measuring quantity of heat (measuring temperature by calorimetry G01K3/00 - G01K11/00; specially adapted for measuring thermal properties of materials, e.g. specific heat, heat of combustion G01N) · CPC title