Design of a multi-layer insulation(MLI) measurement system with a G-M cryocooler

Abstract

Multi-layer insulation (MLI) is widely used in cryogenic systems such as Aerospace propulsion systems and various cryostats. The effective thermal conductivity of MLI used in lab is measured by typical systems using bath cryostat, which is only able to maintain boundary temperatures at critical point of cryogen. A liquid cryogen-free apparatus based on a two stage G-M cryocooler has been developed to measure the effective thermal conductivity of multi-layer insulation(MLI) materials at temperatures ranging from 20-300 K. Unlike traditional measurement systems utilizing evaporation rate of liquid cryogen, a calorimeter supported by a calibrated rod is installed in this system to determine the heat flow through the testing blanket. This design eliminates the error caused by variation of environment pressure to the measured evaporation rate, and meanwhile, simplifies the system structure.