Speaker
Description
This report presents and discusses the results of repeatability experiments gathered from the multi-layer insulation thermal conductivity experiment (MIKE) for the measurement of the apparent thermal conductivity of multi-layer insulation (MLI) at variable boundary temperatures. Our apparatus uses a calibrated thermal link between the lower temperature shield of a concentric cylinder insulation assembly and the cold head of a cryocooler to measure the heat leak. In addition, thermocouple readings are taken in-between the MLI layers. These measurements are part of a two-phase NASA-Yetispace-FSU collaboration to better understand the repeatability of thermal conductivity measurements of MLI. During both phases of testing, the cold boundary was maintained at 77±3 K, and warm boundary at 293±2 K for a duration of four hours at a steady state variance of less than 0.1 K/hr on both cylinders. Temperatures from three Cernox® temperature sensors on each of the two cylinders are averaged to determine the boundary temperatures. A high vacuum, less than 10-5 torr, is maintained for the duration of testing. Yetispace fabricated five identical MLI blankets with twelve layers for each phase with dimensions matching our testing rig. A temperature profile across the MLI is generated. Layer density varied from 19.9 – 26.0 layers/cm. The average measured heat load was 2.40±0.31 W for phase-one and 2.92±0.47 W for phase-two. This suggests there is a high variance of MLI performance. It has been concluded, variations in the insulation installation heavy effect the apparent thermal conductivity and are not solely dependent on layer density.
Acknowledgements: We would like to thank our collaborators Wesley Johnson at NASA and Jessica Wood and Susan Bowden at Yetispace. This research is funded by Yetispace, grant# 227000-524-037894. This work was preformed at the National High Magnetic Field Laboratory, which is supported by NSF DMR-1157490 and the State of Florida.