Determinação simultânea da condutividade térmica e da difusividade térmica variando com a temperatura

Abstract

This work proposes an experimental technique for simultaneous estimation of temperaturedependent thermal diffusivity, α and thermal conductivity, λ of insulation materials. The thermal model used considers a transient one-dimensional heat transfer problem. In this model a heat flux is imposed on the frontal surface and the sample is isolated on the opposite surface. The simultaneous determination of these properties is done by using the principle of the Mixed technique. In this technique two objectives functions are defined, one in the frequency domain and another in the time domain. The objective function is the frequency domain is based on the square difference between experimental and calculated values of the phase angle. While the other objective function is the least square error function of experimental and calculated signals of temperature. The properties α and λ are obtained by using an experimental apparatus that basically consists of an oven with controlled temperature. The properties α and λ were estimated for 7 (seven) points of average temperature in a range from 20 ºC to 66 ºC. The properties are determined with an additional heating of approximately 4.5 K on the frontal surface. Analyses are also performed to determine the sensors location on the sample. Afterwards the temperature-dependent thermal properties α and λ are determined through the proposed technique.