Insulation test cryostat with lift mechanism

摘要

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.

主权项

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.