Combined FPPE–PTR Calorimetry Involving TWRC Technique II. Experimental: Application to Thermal Effusivity Measurements of Solids

Abstract

Photopyroelectric calorimetry in the front detection configuration (FPPE) and photothermal radiometry (PTR) were simultaneously used, together with the thermal-wave resonator cavity method (TWRC), in order to investigate the thermal effusivity of solids inserted as backing layers in a detection cell. A new combined FPPE-PTR-TWRC setup was designed. It was demonstrated experimentally that the PTR technique, combined with the TWRC method, is able to provide calorimetric information about the third layer of a detection cell. Applications on solids with different values of the thermal effusivity (starting from metals, down to thermal isolators) are presented. The values of the thermal effusivity obtained with the PTR technique are similar to those obtained with the PPE technique, and in agreement with literature values; the two methods reciprocally support each other. The accuracy of both methods is higher when the values of the thermal effusivity of the backing layer and coupling fluid are close.

Improved methods for measuring thermal parameters of liquid samples using photothermal infrared radiometry

“…Even though the term A f contains the effusivity of the sample and the substrate, it remains undetectable and just acts as an offset for the amplitude. We have done simulations for the full model, equation (5), and the reduced model, equation (7), and found that the reduced model is quite valid in our experimental range of frequencies. Equation ( 7) is particularly useful due to its rather direct and only exponential term to find the sample's thermal diffusivity evolution as a function of time, temperature or electric field.…”

“…In this paper, we propose the PTR technique as an alternative calorimetry. Concerning the accuracy of the investigations, in both techniques, when using sandwiched detection cells, it was demonstrated [23,5] that it is connected with the values of the thermal parameters of the layers of the detection cell; more exactly, the accuracy is increased when the values of the thermal effusivity of the liquid and backing layers are close. In the PTR configurations proposed in this paper, the backing layer is glass with a thermal effusivity rather close to the typical liquids, so the experiment is optimized in order to obtain high accuracy.…”

“…Nevertheless, knowledge of sample's density and specific heat capacity was needed to find the thermal conductivity. Dadarlat et al proposed a PPE-PTR combined detection of thermal parameters [4,5], but in this case, the performances were limited by the presence of a thin, opaque pyroelectric sensor as the first layer. The difficulty in the simultaneous detection of any two thermal quantities (e.g., α and κ) is mainly due to the increase in number of layers and also because of the comparable thermal thickness of the light-absorbing top layer compared to the sample layer thickness [6].…”

Proposal of novel measurement method for thermal diffusivity from infrared thermal movie

“…A few years ago, new methods were reported for the direct and simultaneous estimation of κ and C. One was a modified photopyroelectric (PPE) method 5,6) and the other was the combination of PPE and photothermal reflectance (PTR) methods. 7,8) The original PPE method [9][10][11][12][13] is a relatively simple and sensitive measurement technique for the thermal diffusivity α. In the PPE method, it is necessary to attach a temperature sensor to the sample.…”