초록 ▼

An apparatus for measuring insulation thermal performance is provided, particularly between ambient and cryogenic temperatures. A warm-temperature boundary has a continuous sample contact surface that is divided into a metered central zone and a boundary guard zone. Each zone is independently heated

An apparatus for measuring insulation thermal performance is provided, particularly between ambient and cryogenic temperatures. A warm-temperature boundary has a continuous sample contact surface that is divided into a metered central zone and a boundary guard zone. Each zone is independently heated, and the power necessary to maintain the central zone at constant temperature is directly equated to heat flux through the insulation at the temperature boundary conditions. Methods for measuring insulation thermal performance are also disclosed.

대표청구항 ▼

What is claimed is: 1. An apparatus to measure insulation thermal performance, comprising a warm-temperature boundary having a continuous thermally-conductive sample contact surface and a cold-temperature boundary, said continuous sample contact surface having a central metered zone and a boundary

What is claimed is: 1. An apparatus to measure insulation thermal performance, comprising a warm-temperature boundary having a continuous thermally-conductive sample contact surface and a cold-temperature boundary, said continuous sample contact surface having a central metered zone and a boundary guard zone surrounding said central metered zone, both said central metered zone and said boundary guard zone being heated zones and said central metered zone being heated independently of said boundary guard zone, wherein said apparatus is adapted to accommodate a sample of insulation between said sample contact surface and said cold-temperature boundary for measuring heat flux through the sample. 2. The apparatus of claim 1, further comprising a vacuum chamber, said warm-temperature boundary and said cold-temperature boundary being disposed within said vacuum chamber. 3. The apparatus of claim 1, further comprising a skirt of insulating material adapted to surround said sample of insulation, adjacent a perimeter thereof, when said sample is disposed between said sample contact surface and said cold-temperature boundary. 4. The apparatus of claim 1, comprising: a heater arrangement comprising a first heater plate and a second heater plate fixed in spaced parallel relationship, said sample contact surface being a surface of said first heater plate facing away from said second heater plate; a first heating element adapted to supply heat to the central metered zone and a second heating element adapted to supply heat to the boundary guard zone; and a third heating element adapted to supply heat to said second heater plate; said first, second and third heating elements being independently operable. 5. The apparatus of claim 4, said first heating element contacting said first heater plate and being coextensive and in register with the central metered zone of said sample contact surface, and said second heating element contacting said first heater plate and being coextensive and in register with the boundary guard zone of said sample contact surface. 6. The apparatus of claim 4, further comprising insulation material disposed in the space between said first and second heater plates. 7. The apparatus of claim 4, said second and third heating elements being operable to maintain said boundary guard zone and said third heater plate, respectively, at the same temperature as said central metered zone, whereby said central metered zone is operable adiabatically except in a direction toward said cold-temperature boundary, wherein power supplied to said first heating element to maintain said central metered zone at constant temperature is directly equatable to heat flux from said central metered zone. 8. The apparatus of claim 4, said first and second heater plates being coextensive and in register with one another. 9. The apparatus of claim 4, said second heater plate being a continuous plate and having a second central zone and a second boundary guard zone coextensive and provided in register with said central metered zone and said boundary guard zone, respectively, of the first heater plate, said third heating element being adapted to supply heat to said second central zone of said second heater plate, the apparatus further comprising a fourth heating element adapted to supply heat to said second boundary guard zone of said second heater plate, wherein said fourth heating element is independently operable from said first, second and third heating elements. 10. The apparatus of claim 4, said first heating element comprising a printed circuit having resistive copper traces in the form of a series of evenly-spaced concentric rings with electrical connections provided between adjacent rings. 11. The apparatus of claim 4, said second heating element comprising an array of printed circuit segments aligned around said first heating element, each said segment comprising resistive copper traces in the form of a series of evenly-space concentric arcs with electrical connections provided between adjacent arcs such that a single resistive circuit is formed in each segment. 12. The apparatus of claim 11, wherein all said printed circuit segments are electrically connected in series to provide said second heating element. 13. The apparatus of claim 4, said sample contact surface being a substantially horizontal surface, the apparatus further comprising a cryogenic storage vessel suspended above said sample contact surface, and having an outer bottom wall surface facing said sample contact surface, said outer bottom wall surface of said cryogenic storage vessel defining said cold-temperature boundary. 14. The apparatus of claim 13, said sample contact surface and said outer bottom wall surface both being circular, and disposed in register with and parallel to one another. 15. The apparatus of claim 13, further comprising a vacuum chamber, said heater arrangement and said cryogenic storage vessel being disposed within said vacuum chamber. 16. The apparatus of claim 15, said cryogenic storage vessel being suspended from a removable lid of said vacuum chamber. 17. The apparatus of claim 13, further comprising a skirt of insulating material adapted to surround said sample of insulation, adjacent a perimeter thereof, when said sample is disposed between said sample contact surface and said outer bottom wall surface. 18. The apparatus of claim 17, said skirt of insulating material further comprising a series of heating elements operable and adapted to develop a predetermined temperature profile in said skirt that approximates an anticipated or known temperature profile in said sample of insulation during operation of said apparatus. 19. The apparatus of claim 13, the height of said heater arrangement being supported by an adjustable support system capable to raise and lower said heater arrangement to thereby adjust the distance between said sample contact surface and said outer bottom wall surface of said cryogenic storage vessel. 20. The apparatus of claim 4, said adjustable support system comprising a vertical actuator device coupled to and supporting said heater arrangement via a gimbal joint. 21. The apparatus of claim 20, said adjustable support system comprising a plurality of said vertical actuator devices, each coupled to and supporting said heater arrangement via a respective gimbal joint, wherein the vertical actuator devices are thus independently operable to adjust the height and planar orientation of the heater arrangement. 22. The apparatus of claim 20, further comprising a vacuum chamber having a base, said heater arrangement being disposed within said vacuum chamber, said vertical actuator device being aligned with and extending through an opening through said base, wherein said opening is sealed so as to provide a vacuum-tight seal during operation of said apparatus. 23. The apparatus of claim 22, said opening being sealed via an extensible bellows disposed around said vertical actuator device. 24. An apparatus to measure insulation thermal performance, comprising a warm-temperature boundary having a continuous sample contact surface and a cryogenic storage vessel having an outer surface adapted to provide a cold-temperature boundary, said continuous sample contact surface having a central metered zone and a boundary guard zone surrounding said central metered zone, both said central metered zone and said boundary guard zone being heated zones and said central metered zone being heated independently of said boundary guard zone, wherein said apparatus is adapted to accommodate a sample of insulation between said sample contact surface and said cold-temperature boundary for measuring heat flux through the sample. 25. The apparatus of claim 24, wherein the distance between said sample contact surface and said outer surface of said storage vessel is adjustable. 26. A method for measuring thermal performance of a sample of insulation, comprising: a) providing an apparatus to measure insulation thermal performance, comprising a warm-temperature boundary having a continuous sample contact surface and a cold-temperature boundary, said continuous sample contact surface having a central metered zone and a boundary guard zone surrounding said central metered zone, both said central metered zone and said boundary guard zone being heated zones and said central metered zone being heated independently of said boundary guard zone, wherein said apparatus is adapted to accommodate a sample of insulation between said sample contact surface and said cold-temperature boundary for measuring heat flux through the sample; b) providing a cryogenic storage vessel having an outer surface; c) disposing a sample of insulation between said sample contact surface and said storage vessel outer surface; d) separately maintaining said central metered zone and said boundary guard zone at a constant warm-boundary temperature; e) measuring the power required to separately maintain said central metered zone at said constant warm-boundary temperature; and f) equating said power to heat flux through said sample of insulation. 27. The method of claim 26, further comprising providing a skirt of insulating material having a series of heating elements surrounding the perimeter of said sample of insulation, and operating said series of heating elements to develop a temperature profile in said skirt that approximates an anticipated or known temperature profile in said sample of insulation. 28. The method of claim 26, said apparatus comprising a heater arrangement comprising a first heater plate and a second heater plate fixed in spaced parallel relationship with said first heater plate, said sample contact surface being a surface of said first heater plate facing away from said second heater plate; the method further comprising maintaining said boundary guard zone and said third heater plate at the same temperature as said central metered zone, wherein said central metered zone is operated adiabatically except in a direction toward said cold-temperature boundary. 29. The method of claim 28, said heater arrangement further comprising first and second heating elements in contact with the first heater plate, said first heating element being adapted to supply heat to the central metered zone and said second heating element being adapted to supply heat to the boundary guard zone; and a third heating element in contact with the second heater plate adapted to supply heat thereto; said first, second and third heating elements being independently operable to independently heat said central metered zone, said boundary guard zone and said second heater plate, respectively.