Paper Submission
09. Heat and Mass Transfer
Investigation of Technique for Simultaneous Measurement of Thermophysical Properties of Liquids by Photoacoustic Method
In this study, we investigated a method to simultaneously measure the thermal diffusivity and thermal effusivity of liquids using the photoacoustic method. This method is a non-contact and non-invasive measurement method that does not require any pre-treatment. To evaluate the thermophysical properties from the measurement data, we adopted a model consisting of four layers: air, thin metal plate, liquid sample, and metal container. Numerical calculations were performed for this model. In the experiment, a modulated laser was irradiated onto a thin metal plate, and the thermal response caused by the absorption of heat diffusing into the liquid and the metal container was measured as an acoustic signal. Since the phase delay of the sound relative to the incident light is related to the thermal properties of the liquid sample, the phase delay as a function of the laser modulation frequency was obtained as the output. It was found that the thermal diffusivity and thermal effusivity of liquids can be obtained simultaneously by searching for the optimal thermophysical properties of liquids for the obtained measurement data.
To verify the measurement accuracy, the thermophysical properties of pure liquid substances such as pure water and toluene were measured. Based on the analysis of the results, the factors affecting the measurement were extracted and quantitatively evaluated. Numerical calculations were used to quantitatively investigate the conditions for sample thickness to simultaneously measure the thermal diffusivity and thermal effusivity of the liquid sample, as well as the effects of the interface between the liquid sample and a thin metal plate or metal container. In addition to pure liquid substances, ionic liquids were also measured. Ionic liquids are attracting attention as solvents and electrolytes that are safe for users because they are non-volatile and flame-retardant. The temperature dependence of the thermophysical properties of the liquids was also evaluated by changing the temperature of the liquids.
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Author Information
Atsumasa Yoshida
Prof.
Corresponding author, Presenting author
Shinichi Kinoshita
Prof.
Kakeru Kagata
Prof.