ISSN Online: 2377-424X
ISBN Print: 978-1-56700-421-2
International Heat Transfer Conference 15
Analysis of Improved Lumped Models for Estimating the Thermal Conductivity Augmentation in Composite Materials
Abstrakt
This paper presents an analysis of distinct approximate one-dimensional fin models for estimating the thermal
conductivity augmentation in composite materials with respect to the conductivity of the matrix material alone.
The augmentation is calculated using estimates for the Biot number on the surface that exchanges heat with
the environment for different test samples, which can be obtained from infrared temperature measurements on
the same surface. Both classical lumped-capacitance models and improved lumped-approximation schemes
are presented. Preliminary experimental results from infrared measurements are presented and compared with
experimental data obtained using the Guarded Heat Flow Meter method, showing that the improved-lumped
approach yields better results than the classical lumped system analysis. After these results, the distinct onedimensional models are compared using simulated experimental data generated with a two-dimensional solution
of the problem. The results again show that the improved lumped models give better results. They also
show that the estimated Biot numbers are worse for conditions in which the actual Biot number is larger, and
for cases with a relatively larger fin thickness. Moreover, it is seen that a model for the surface temperature must be used rather than the average one, as the latter yields worse results, especially for large Biot numbers – while this is indifferent for the classical lumped system analysis, it makes a notable difference for improved lumped models. Finally, the results give an indication that an experiment with uniform flux at the fin base will give better results than one that is done with a constant base temperature.
SCHLÜSSELWÖRTER:
Thermophysical Properties, Measurement and Instrumentation, Conduction, Analytical Methods