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

Abstract

High accuracy, non-contact measuring methods for finding thermal properties of liquid samples using photothermal infrared radiometry (PTR) are presented. The use of transparent windows to confine micro volume liquid samples and the implementation of front and/or back signal detection procedures helped the successful implementation of the PTR technique for measuring liquids with high proficiency. We present two configurations, the so-called back–front photothermal infrared radiometry and back photothermal infrared radiometry to find thermal diffusivity and thermal effusivity of liquid samples. Sensitivity studies and error analyses included prove the robustness of each method. As an illustration of the temperature and electric field varying studies, we have included the experimental results on a 5CB (4-cyano-4′-pentylbiphenyl) liquid crystal.

Maxwell-Wagner-Sillars effects on the thermal-transport properties of polymer-dispersed liquid crystals

“…We have used an improved photothermal radiometry (PTR) technique [8,29] for measuring thermal parameters of PDLC samples. The experiments were done using the back-PTR (B-PTR) configuration because of its high sensitivity and simultaneous detectability to both the thermal diffusivity and effusivity of the sample under investigation.…”

“…Thus, a sample's thermal diffusivity, as a function of EF or f e , can be calculated from the phase data and the effusivity from the combined amplitude and phase signals, provided that the sample is at a quasithermally thick (μ s ≈ d) regime. The analytical expressions for a sample's thermal diffusivity (α s ) and thermal effusivity (e s ) are given by [8] …”

“…We selected PS/5CB composites for our studies because of their well-known thermo-physical properties. Recently the photothermal radiometry technique (PTR) has been demonstrated as a simple and capable technique for measuring dynamic thermal parameters of liquid samples with high precision and resolution [8]. In particular, the noncontact capability of the PTR technique helps to extract the thermal parameters from EF-varying experiments with fewer precautions, whereas many efforts are required with contact techniques, such as photopyroelectric (PPE), to facilitate experiments free from EF-induced errors.…”

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

“…It is not a noncontact measurement method for α. The PTR method [14][15][16][17][18][19][20] measures the thermal effusivity b optically, using a phenomenon in which the surface reflectivity depends on the temperature. It is a noncontact measurement method.…”

“…However, the development of infrared thermometer technology in the past two decades enables the advanced noncontact measurement of thermal property, by replacing the thermocouple with an infrared thermometer. 20,21) There are many studies on advanced noncontact measurement methods, such as those based on the flash method for measuring temperature difference at two different times, [22][23][24][25] based on the DC heating method for measuring the time dependence of temperature, 26,27) based on the AC heating method for measuring the phase of the temperature signal, [28][29][30] and based on the optothermal method for the measuring the spatial distribution of temperature. 31,32) In the above noncontact methods, the infrared thermometer is used as a temperature sensor.…”