Modeling of Thermal Resistance Test Configurations that Use Thin Heaters

Abstract

The usefulness of a large unguarded thin screen heater as an integral part of a ther mal resistance measurement apparatus for insulations has been demonstrated. Ther mal modeling of existing and proposed test configurations can be used to establish applicability. HEATINGS, a general purpose conduction program, has been used to obtain the temperature distributions encountered in linear and radial heat flow testers with thin heaters.

Thermal simulations of the existing screen tester have been used to determine the effects of specimen thickness and thermal resistance on measurement errors. Simula tion results were obtained for test configurations in order to provide a basis for design improvement, i.e., the effect of increasing levels of edge insulations on the ap parent thermal conductivities obtained with the tester.

The extent to which limited edge guarding extends the operating range of a flat tester has been examined using HEATING5. A gradient guard along the edge of the specimen in the tester reduces the measurement errors due to edge heat loss. The pre dicted improvement in measurement accuracy of a thin heater apparatus due to edge guarding that approximately matches the mean temperature on the edges with the mean temperature in the metering section has been examined experimentally.