Cup cryostat thermal conductivity analyzer

Patent metadata

Field	Value
Publication number	US-10656109-B1
Application number	US-201715603393-A
Country	US
Kind code	B1
Filing date	May 23, 2017
Priority date	Jun 12, 2009
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

A test apparatus for evaluating thermal properties of a test specimen across a wide range of thermal conductivities and temperature ranges using a flat plate cup cryostat. The test apparatus includes: a heater assembly having an upper surface to receive a test specimen; a cold plate positioned on top of the test specimen; a vessel comprising an outer cylindrical tube closed on a bottom end by the cold plate; an inner cylindrical tube concentrically received in an upper portion of the outer cylindrical tube above the vessel to vent the vessel; insulation material surrounding at least the heater assembly, test specimen, cold plate, and vessel; a sensor that detects boiloff or evaporation rate of liquid from the vessel vented from the inner cylindrical tube; temperature sensors positioned to detect temperatures of the heater assembly and the cold plate; and a data recording device to record the boiloff or evaporation rates and temperature values.

First claim

We claim:

1. A test apparatus for evaluating thermal properties of a test specimen, the test apparatus comprising:
a base comprised of a base cup closed along a bottom edge by a base lower plate, including a bottom top plate extending radially and outwardly from the base cup to present a bottom plurality of holes;
a top plate having a central passage and a top plurality of holes that correspond respectively to the bottom plurality of holes of the bottom top plate;
a heater assembly supported on a lower heater plate, the heater assembly positioned atop the base lower plate;
a cold plate positioned above the heater assembly defining a test specimen cavity between the heater assembly and the cold plate;
a first tube having an open top extending from the central passage to the cold plate, forming a cold cup atop the cold plate to receive a quantity of liquid;
a compression assembly comprising a plurality of longitudinally-adjustable, threaded rods, each threaded rod attachable respectively between the top plurality of holes and the bottom plurality of holes, wherein a height of the test specimen cavity is defined by inserting the plurality of threaded rods through the plurality of holes and attaching a plurality of top nuts and a plurality of bottom nuts to the plurality of threaded rods;
a specimen holder placed adjacent to the heater assembly that annularly corresponds to the first tube;
a cup wrap that laterally surrounds and insulates the first tube; and
one or more annular centering rings placed in the base to correspond to and compressibly receive an underside of the cup wrap.

2. The test apparatus of claim 1 , further comprising one or more spacers selectably insertable into the test specimen cavity to center the test specimen or to facilitate a selected one of a granular and powder type test specimen placed in the test specimen cavity.

3. The test apparatus of claim 2 , wherein the one or more spacers have a vertical height that is not more than 20% of the diameter of the test specimen cavity.

4. The test apparatus of claim 1 , further comprising a layer of thermally conductive grease coating an undersurface of the cold plate to contact a test specimen.

5. The test apparatus of claim 1 , wherein the cup wrap comprises an aerogel blanket wrap that is compressed by engaging the compression assembly, the aerogel blanket wrap adsorbing air from the environment during cool down to create stable thermalization for testing.

6. The test apparatus of claim 5 , wherein the aerogel blanket wrap comprises: (i) insulation blanket layers that engage a top surface of a top-most centering ring to form a tortuous air path to mitigate thermal heat transfer from lateral air movement and comprises (ii) vapor barrier layers to create thermal stability of the cup wrap in the lateral direction through the insulation blanket layers and minimize the time to reach thermalization with the ambient environment, wherein the vapor barrier layers terminate above a bottom portion of the insulation blanket layers to enable air adsorption from the test specimen cavity and to enable compression of the aerogel blanket wrap.

7. The test apparatus of claim 1 , further comprising:
a series of vertically-spaced temperature sensors positioned inside the cold cup that determine an approximate level of liquid in the cold cup based on the temperature readings among the vertically-spaced temperature sensors.

8. The test apparatus of claim 7 , further comprising a personal computer that receives a prompt and presents a human-perceptible alert to refill the cold cup at a specified level of liquid.

9. The test apparatus of claim 7 , further comprising an automated liquid dispenser that receives the prompt and dispenses a quantity of liquid into the cold cup in response to the prompt.

10. The test apparatus of claim 1 , wherein the specimen holder separates the heater assembly from the one or more annular centering rings, the specimen holder having an upwardly presented chamfered edge on an outer diameter to mitigate thermal conduction from the heater assembly to the cold cup.

11. The test apparatus of claim 1 , further comprising:
a second tube concentrically received in an upper portion of the first tube and having a bottom centering ring affixed to the inner diameter of the first tube and the outer diameter of the second tube to define a top of the cold cup, the second tube sized to receive the quantity of liquid and provide a path for boiloff gas from the quantity of liquid;
insulation material placed in an annular space between the first and second tubes; and
a top centering ring affixed to the inner diameter of the first tube and the outer diameter of the second tube to hold the insulation material between the first and second tubes;
wherein the boiloff gas creates a convective refrigeration effect for heat flow rates (Q) corresponding to effective thermal conductivity (k e ) above approximately 60 mW/m-K that is controlled by respective dimensions of the first and second tubes and selected insulation material and enables testing over a wide range of thermal performances of a heat flux range of 80-1000 W/m 2 .

12. The test apparatus of claim 11 , wherein the first tube, second tube, top centering ring, and bottom centering ring are comprised of a glass fiber reinforced composite material for high mechanical strength and low thermal conductivity in all directions.

13. The test apparatus of claim 11 , wherein the top centering ring and the bottom centering ring are permanently joined to the inner diameter of the first tube and the outer diameter of the second tube using an epoxy adhesive, wherein the test apparatus is hermetically sealed and resistant to thermal shocks between temperatures of −321 degrees F. and 300 degrees F.

14. The test apparatus of claim 11 , wherein the insulation material is a breathable, super-hydrophobic, bulk-fill material comprising at least one of silica aerogel beads and silica aerogel granules.

Assignees

• Us Administrator Of The National Aeronautics And Space Administration
• Nasa

Inventors

• Fesmire James E
• Johnson Wesley L
• Sass Jared P

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