Prediction of the thermal conductivity of fiberglass insulation using propagation constant: A technique overview

Abstract

This paper describes a novel technique for the prediction of the thermal performance of low density fiber glass insulation and other related fibrous insulation materials using a non-invasive acoustic apparatus. The project motivation is to create an enabling technology for in situ quality control testing of such fiber glass batts during production. Experimental results obtained in the laboratory show excellent correlation between the thermal conductivity and both the real and imaginary components of the propagation constant. Correlation of calculated propagation constant magnitude versus measured thermal conductivity gave an R2 of 0.94 for the range of typically manufactured fiber glass batt materials. Given the promise of such highly correlated measurements, the acoustic technique could be used to continuously predict the thermal conductivity of the material during its production, replacing current off-line methods. The mechanisms for energy transfer through the materials are distinctly different for the acoustical propagation versus the heat transfer. The nature and behavior of the mechanisms will be reviewed and compared.