Thermal conductivity of aerogel blanket insulation under cryogenic-vacuum conditions in different gas environments

Cryogenic Engineering Conference 2017

材料科学;物理学

Fesmire, J.E.^1 ; Ancipink, J.B.^1 ; Swanger, A.M.^1 ; White, S.^2 ; Yarbrough, D.^3

NASA Kennedy Space Center, Cryogenics Test Laboratory, UB-R1, KSC, FL

32899, United States^1

Aspen Aerogels, Inc., 30 Forbes Rd, Northborough

MA

01532, United States^2

RandD Services Inc., PO Box 2400, Cookeville

TN

38501, United States^3

关键词: Boundary temperature;    Component materials;    Heat transfer analysis;    Low-density materials;    Reinforcement fibers;    Residual gas composition;    Space launch vehicles;    Thermal insulation systems;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/278/1/012198/pdf
DOI  :  10.1088/1757-899X/278/1/012198

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

Thermal conductivity of low-density materials in thermal insulation systems varies dramatically with the environment: cold vacuum pressure, residual gas composition, and boundary temperatures. Using a reference material of aerogel composite blanket (reinforcement fibers surrounded by silica aerogel), an experimental basis for the physical heat transmission model of aerogel composites and other low-density, porous materials is suggested. Cryogenic-vacuum testing between the boundary temperatures of 78 K and 293 K is performed using a one meter cylindrical, absolute heat flow calorimeter with an aerogel blanket specimen exposed to different gas environments of nitrogen, helium, argon, or CO2. Cold vacuum pressures include the full range from 1×10-5torr to 760 torr. The soft vacuum region, from about 0.1 torr to 10 torr, is complex and difficult to model because all modes of heat transfer - solid conduction, radiation, gas conduction, and convection - are significant contributors to the total heat flow. Therefore, the soft vacuum tests are emphasized for both heat transfer analysis and practical thermal data. Results for the aerogel composite blanket are analyzed and compared to data for its component materials. With the new thermal conductivity data, future applications of aerogel-based insulation systems are also surveyed. These include Mars exploration and surface systems in the 5 torr CO2environment, field joints for vacuum-jacketed cryogenic piping systems, common bulkhead panels for cryogenic tanks on space launch vehicles, and liquid hydrogen cryofuel systems with helium purged conduits or enclosures.