International Journal of Thermophysics最新文献

Mass diffusion coefficient measurement techniques with high temporal and spatial resolution have become essential for the research and development of leading-edge technology in a wide range of cross-disciplinary fields, but cannot be achieved using conventional methods. We provide a comprehensive review of the state-of-the-art theoretical and experimental investigations on Soret forced Rayleigh scattering (SFRS), a grating excitation technique (GET) for measuring the mass diffusion coefficient of binary liquid mixtures. SFRS utilizes the Soret effect to create micrometer-order periodic spatial concentration modulation in a sample due to the absorption of an optical interference grating generated by two intersecting heating laser beams. The decay of the concentration modulation by the mass diffusion process within several milliseconds is detected by the diffraction of a probing beam. The theoretical considerations regarding deviations from the ideal mass diffusion conditions are the effects of: (1) the Gaussian beam intensity distribution, (2) the light absorbing material and (3) the cell wall. The proper settings for the optical system are also analyzed, e.g., the effect of coherency and polarization of the heating laser and the effect of the z-direction length of the interference region. We also consider the frame of reference, center of gravity invariance and effect of convection, which are particularly important for mass diffusion experiments. Using the correct implementation of the theory, the optimal SFRS apparatus design and its appropriate use are described in detail. Finally, two successful applications of SFRS are demonstrated using visible light laser heating and mid-wavelength infrared gas laser heating.

The eutectic mixtures consist of dl-menthol and acetic acid were prepared at five molar ratios (3:1, 2:1, 1:1, 1:2, 1:3). The vibrating-tube densimeter was used to measure the density of the DL-menthol/acetic acid mixtures, and the measurements were carried out from 293.15 K to 363.15 K and pressures from 0.1 MPa to 70 MPa. The measured densities of each dl-menthol/acetic acid mixture at different temperature and pressure were correlated by the Tait equation. In addition, the derived properties of dl-menthol/acetic acid mixtures including isothermal compressibility, isobaric thermal expansivity, and internal pressure were calculated. The effects of temperature, pressure, and molar ratios on the derived properties were compared and analyzed.

Measurements of the thermal conductivity were performed as a function of gas pressure from 10^–1 hPa up to 10⁵ hPa on several bimodal silica xerogels. The xerogels exhibit a mesopore and a macropore phase. The measurements were done using a hot-wire apparatus, which can do automated, gas pressure-dependent measurements of the thermal conductivity from 10^–3 up to 10⁵ hPa. Results were fitted with a bimodal gas pressure-dependent thermal conductivity model to gain information on the thermal conductivity of the materials, its various contributions and on structural parameters such as the two main pore sizes, the macro- and mesoporosities. The pore sizes and porosities were compared to values gained from mercury porosimetry and nitrogen adsorption measurements. The porosities from the thermal conductivity measurements are in very good agreement to the other measuring methods. The macropore sizes from the thermal conductivity measurements are mostly in agreement within the given uncertainty range and the mesopore sizes show a good estimate of the order of magnitude of the pores.

The explanation of the n-type silicon thermoelastic photoacoustic response is given by electro-acoustic analogies, which clarify the influence of excess free carriers as heat carriers. It was found that electro-acoustic analogies could interconnect different theoretical models of heat flow and carrier dynamics aiming to find the optimal experimental conditions for the efficient free carrier influence analysis of the sample thermoelastic photoacoustic response. Theoretical analysis was based on the comparison between the composite piston, surface recombination, and RC filter frequency response models, extrapolating the behavior of the photoacoustic response much beyond the experimental frequency domain. Experimental analysis was based on the open-cell photoacoustic setup operating under the transmission configuration within the modulation frequencies range from 20 Hz to 20 kHz. The accuracy of our predictions and the validity of electro-acoustic analogies are confirmed by measuring 875 μm plasma-thick and 35 μm plasma-thin silicon samples.

Alternative sources for an industrial production of essential substances represent an exciting field of study for many researchers. Based on the previous research, itaconic acid and its esters were intensively studied as one of the sources. This paper relates to a determination of the basic physical–chemical properties of bis(2-methylbutyl) itaconate and bis(3-methylbutyl) itaconate that are produced from itaconic acid and 2-methylbutan-1-ol and 3-methylbutan-1-ol, respectively, from biomass. According to our best knowledge, physical–chemical properties of these substances, such as density, viscosity, and saturated vapor pressure, are not presented in the literature, and these are important for the future research of their production.

The noise caused by various temperature effects in the sensitive frequency band will cause errors in the detection results of space gravitational wave. Therefore, it is important to suppress the temperature noise of space-borne gravitational wave detectors. In this paper, a method is proposed to suppress temperature noise using a multi-layer composite structure consisting of low thermal conductivity material (R) and high specific heat capacity material (C). The arrangement in which heat flow passes through high specific heat capacity material first is “CR.” The thermal simulation model is established to study the temperature noise transfer characteristics, and accuracy of the model is verified by experiments. The results show that the temperature noise of CRC is 90 % lower than that of RCR. The arrangement which heat flow passes through high specific heat capacity material first has an optimal high specific heat capacity material’s proportion of 60 % to 70 %. When the number of composite layers is not less than 3 layers, the more the composite layers’ number is, the better the suppression effect of multi-layer composite structure on temperature noise is. However, there is a limit to the way of obtaining noise reduction effect by increasing the number of layers. This paper provides a guidance for the suppression of temperature noise in gravitational wave detection.

In this study, an artificial neural network (ANN) model was developed based on molecular descriptors to predict the surface tension of liquids. A dataset containing various features was constructed by collecting experimental data from 25 different fluids and extracting molecular structural descriptors. Feature selection was performed using the forward search wrapper method based on Random Forest, identifying 7 significant features (Temperature, MinAbsEStateIndex, LabuteASA, MolMR, Chi1v, qed and FpDensityMorgan3) for surface tension prediction. Subsequently, an ANN model was constructed with the selected features as inputs to predict the surface tension of liquids. The derived model demonstrates high accuracy with a correlation coefficient (R) exceeding 0.999 and a notably low mean square error (MSE = 1.843e−5). Moreover, the ANN model exhibited a total average absolute deviation (AAD) of 0.98 %, comparable to that of the REFPROP, which had a total AAD of 1.26 %. This quantitative model serves an easy tool for gaining insights into the molecular underpinnings of surface tension and predicting its value across various fluids.

An acoustic gas thermometry system, which introduces a one-liter quasi-spherical resonator (QSR) made of oxygen-free copper, built at the National Metrology Institute of Japan (NMIJ/AIST), has been employed to measure thermodynamic temperatures from the triple point of water down to the triple point of mercury. The measurement adopted a thermostatic bath operated down to 263.15 K and a new one that can operate down to lower temperatures. The present acoustic gas thermometry system measured the speed of sound in argon on the isothermal curves of the triple point of water, 268.15 K, 263.15 K, 253.15 K, 243.15 K and at the triple point of mercury under the pressure range from 500 kPa down to around 60 kPa. Based on the measured speed of sound, the thermodynamic temperatures at the mentioned isotherms were determined relatively from the speed of sound at the triple point of water. Using the measured thermodynamic temperature T, the difference between T and the temperature T₉₀, based on the International Temperature Scale of 1990 (ITS-90), (T − T₉₀), along with the associated uncertainties, u(T − T₉₀), were determined to be − 0.4 ± 1.1 mK for 268.15 K, − 1.0 ± 0.9 mK for 263.15 K, − 1.9 ± 0.9 mK for 253.15 K, − 2.5 ± 0.9 mK for 243.15 K and − 2.7 ± 0.9 mK for 234.3156 K. The present (T − T₉₀) values were found to be consistent in all cases within the estimated uncertainty with the currently reported values existing in overlapping temperature range.

Thermal diffusivity is an essential thermophysical factor for designing thermal protection materials. At present, the laser flash method is widely employed for measuring thermal diffusivity, and reasonable determination of experimental parameters is a prerequisite for accurate measurement. In this paper, high-purity graphite is used as the reference specimen, and measurement temperature ranges from 25 °C to 1500 °C. Besides, experimental investigations on the influence of the laser flash method such as specimen thickness, laser pulse energy, and temperature increase rate on the measurement of thermal diffusivity for high-purity graphite are carried out. The results indicate that for high-purity graphite samples, a sample thickness of 3 mm is more appropriate. Additionally, the setting of laser pulse voltage and width is related to the measurement temperature, and the measurement results are more easily affected by the laser pulse width. When measuring temperatures below 600 °C, it is necessary to set both the laser pulse width and voltage to the smallest possible values, provided that a stable signal can be collected. When the temperature is above 600 °C, the laser pulse voltage does not affect the measurement results, but the influence of laser pulse width still needs to be considered to a certain extent. It is only when the measured temperature exceeds 900 °C that neither the laser pulse voltage nor the laser pulse width influences the measurement results. Furthermore, the temperature increase rate has a relatively small impact on the measurement results and can be adjusted according to the measured temperature. The research results can provide a basis for the calibration of experimental parameters in the high-temperature flash method measuring instrument.