An apparatus to measure the apparent thermal conductivity of multilayer insulation (MLI)

Abstract

The design of a concentric cylinder calorimeter for measuring the apparent thermal conductivity of MLI blankets is presented. Unlike similar devices where a liquid cryogen is used to control the cold boundary temperature and the cryogen boil-off rate is used to obtain the heat transfer through blanket, the design presented in this paper utilizes mechanical refrigerators to control the boundary temperatures and a heat rate meter to determine the heat load. This approach ensures two unique features of the apparatus. First, the use of cryocoolers enables the user to set the boundary temperatures anywhere within the operating range of the refrigerators and therefore permits a wide range of temperature and temperature differences with the measurement. The other unique feature is that the total heat transfer through the blanket is obtained by measuring the heat conducted along a cold cylinder support rod of known thermal conductivity. To determine the absolute thermal conductivity, a calibration is needed to eliminate the temperature related effects on the support rod.

Design and Operation of a Calorimeter for Advanced Multilayer Insulation Testing

“…The coefficients − will be fitted for each of the six pairs of temperature sensor combinations: (1,2), (1,3), (1,4), (2,3), (2,4) and (3,4).…”

“…[1] [2] Similarly, a calorimeter has been developed at Florida State University that has capability at 20 K using cryocoolers as the heat sink. [3] Testing performed for the Cryogenic Propellant Storage and Transfer (CPST) and Self Supporting Multi-Layer Insulation (SS-MLI) projects measured higher heat loads than expected, the cause of which, could not be readily resolved. [4] Another calorimeter using a helium gas temperature difference is currently in the final stages of check out at the Technical University of Dresden, and while it also claims to be capable of cold boundary temperatures in the 20 K range, it has yet to be demonstrated.…”