New High-Temperature Guarded Hot-Box Facility for Reflective Insulation

Abstract

All-metal reflective insulation, used to insulate commercial nuclear power plants, requires special test considerations because of its nonhomogeneous nature. Internal convection and conduction paths that exist in the field must be preserved in the laboratory if the results are to be representative of field performance. The existing guarded hot-box method, ASTM Test for Thermal Conductance and Transmittance of Built-Up Sections by Means of the Guarded Hot Box (C 236-66), although intended for testing nonhomogeneous structures, does not properly consider these effects which could result in large measurement errors. A modified high-temperature guarded hot box, constructed for testing reflective insulation panels, can test one full-size, 914-mm (36 in.) square, flat panel up to 203 mm (8 in.) thick. This facility can operate at hot surface temperatures up to 811 K (1000°F) and can be rotated to test a panel in either the horizontal or vertical orientation. The facility was verified for testing both homogeneous and nonhomogeneous insulations, and data are presented to illustrate the effect that internal convection and orientation can have on heat loss. Large-scale experiments are planned to verify the performance of individual units of insulation in a system environment.