Study of thermal parameters’ temperature dependence in solids using photothermal radiometry (original) (raw)

Identification of temperature-dependent thermal properties of solid materials

Journal of The Brazilian Society of Mechanical Sciences and Engineering, 2008

This work proposes an experimental technique for the simultaneous estimation of temperature-dependent thermal diffusivity, α, and thermal conductivity, λ, of insulation materials. The thermal model used considers a transient one-dimensional heat transfer problem. The determination of these properties is done by using the principle of the Mixed technique. In this technique two objective functions are defined, one in the frequency domain and the other in the time domain. The objective function in 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 a Polyvinyl Chloride (PVC) sample exposed to different temperatures inside an oven. The temperature inside the oven is controlled by a PID temperature controller. 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 were determined with an additional heating of approximately 4.5 K on the frontal surface. Analyses of sensitivity, sensors location and sample dimensions were also made.

Self-normalized photothermal techniques for thermal diffusivity measurements

Journal of Applied Physics, 2000

Two self-normalized photothermal techniques, to carry out thermal diffusivity measurements of condensed phase materials, are presented. These simple methodologies involve linear fitting procedures of the signal amplitude and phase. These procedures lead to the elimination of the usual requirement for instrumental transfer-function normalization. The thermal diffusivities for two dental resins and two pure liquids are measured with these simple methodologies and very good agreement is found with values reported in the literature, where more involved analysis is usually required.

Measurement of the Thermal Diffusivity of Solids with an Improved Accuracy

2003

A photothermal radiometry technique is being developed at the NPL with the goal of improving the accuracy of thermal diffusivity measurements. The principle is to perform a laser-induced thermal experiment while simultaneously making accurate measurements of the experimental boundary conditions. A numerical three-dimensional heat diffusion model based on thermal transfer functions has been developed to account for the measured boundary conditions. The thermal diffusivity is determined from the experimental data by a nonlinear, least-squares fit to the model. Experiments carried out on pure metals at 900 K demonstrate good agreement between the theoretical predictions and experimental data, and uncertainties of about 1.5% for the thermal diffusivities of platinum, titanium, and germanium were obtained.

Cross-comparison of thermal diffusivity measurements by thermal methods

Infrared Physics & Technology, 2002

Thermal diffusivity is measured applying three techniques: (a) thermal wave generation by thermoelectric device; (b) non-adiabatic flash method with correction for non-ideal Dirac pulse by deconvolution; (c) photothermal deflection. They are applied on a sample of AISI 304. Results are compared with those obtained by the standard laser flash method. Ó 2002 Published by Elsevier Science B.V.

Thermal diffusivity measurements by “instantaneous phase portrai” method

Diamond and Related Materials, 1995

A new method of "instantaneous phase portrait" was developed for measurements of thermal diffusivity x of thin films with high values of x, such as diamond films. This method is based on the registration of the air layer refractive index spatial distribution by means of double exposure holographic interferometry and the derivation of the thermal diffusivity value x from the spatial distribution. The values of thermal diffusivity for copper and steel foils measured by this technique coincide with the tabular ones. The method was also applied to measure thermal diffusivity of thin diamond films. The measured values were in 2-3 cm* s-l range.