Determinação simultânea de propriedades térmicas usando apenas uma superfície de acesso: estimação nos domínios do tempo e da freqüência

Abstract

A new method for simultaneous determination of thermal conductivity, k, and diffusivity, a of the non-metalic materiais is presented. The use of experimental data from only one surface access is the main novelty of the technique. For the thermal diffusivity estimation an one-dimensional thermal model is used. A heat flux history is imposed at the frontal surface of a sample while the other surface is isolated. The same experimental data are used to thermal conductivity determination. However, at this case, the heat flux and temperature evolution at the frontal surface are used in a semi-infinite thermal model. In this sense, the thermal effusivity is also estimated. It can be observed that the thecnique proposed uses the parameter estimation thecnique in the time and the frequency domain. In the time domain, the minimum square is used at the experimental and theoretical temperatures to the thermal diffusivity estimation. In the frequency, the input impedance, Z/,e, a ratio of heat flux and temperature evolution is, then, defined. The difference between experimental and theoretical values of is minimized for the thermal effusivity estimation. It should be observed that the experimental data have been numerically simulated. The temperature evolution are calculated from the analytical thermal model solution and from the random error summation. These random errors are located at a range of uncertainty of temperature measurements error using thermocouples. At the end, is also presented an error and uncertainty analyses of the technique.