Orientation and Position Dependant Thermal Conductivity

Abstract

Thermal conductivity is a critical thermophysical property to be monitored while manufacturing foam insulation for industries from construction to appliances. Formulators rely on lab based testing to measure thermal conductivity of new materials that are under development to assure that the product meets the needs of the customer. Quality control engineers rely on lab based testing to periodically measure thermal conductivity of the product to assure that the goals of the formulators are being realized on a consistent basis.

Lab based testing has been dominated by traditional guarded hot plate techniques which require access to both sides of a flat, prepared sample of fixed dimension. The entire volume of the sample is measured during testing, providing the average thermal conductivity of the sample as the result.

This study has measured the variation in thermal conductivity across the profile of polyurethane. Further investigation focused on detecting thermal conductivity anisotropy in foam as related to foam rise direction. This research was facilitated by the use of a new technique that has been developed for thermal conductivity testing which requires access to only one side of the sample. With this interfacial transient technique, testing time dictates the penetration depth of the heat wave, and therefore the amount of material tested. This technique does not require set sample configurations, which eliminates the need to mock up samples for evaluation.