AN APPARATUS TO MEASURE THERMAL CONDUCTIVITY OF SPRAY-ON FOAM INSULATION.

A guarded-hot-plate apparatus has been developed to measure the thermal conductivity of various spray-on foam insulations (SOFI) at temperatures ranging from 20–300 K. The apparatus is designed to accept 222 mm (8.75″) diameter, 25.4 mm (1″) thick insulation samples, although different thicknesses can be accommodated. The apparatus is cooled with a two stage, pulse tube cryocooler, and the temperature is controlled with thin film etched foil heaters. This system allows thermal conductivity measurements to be made at low delta-T (ΔT<20 K) throughout the temperature range. Platinum and Cernox™ sensors are used to measure the temperature difference across the sample and to monitor other temperatures throughout the apparatus. Multiple thermal guards are employed to confine heat flow axially through the sample. A gas handling system allows testing with different residual gases and pressures. To check for potential systematic errors, a finite element analysis was performed to examine temperature distribution and heat flow in the experimental chamber. [ABSTRACT FROM AUTHOR]