International Journal of Thermophysics最新文献

The density and viscosity of binary mixtures of triethanolamine (TEA) and glycerol were investigated over the full composition range at temperatures from 293.15 K to 323.15 K, under atmospheric pressure. The experimentally measured density and viscosity data were correlated with temperature-dependent equations. The excess molar volume (V^E) and viscosity deviation (Δη) were determined and fitted using the Redlich–Kister polynomial equation. In addition, thermodynamic parameters, including partial molar volumes, apparent molar volumes, and thermal expansion coefficients, were evaluated to provide further insight into the mixing behavior of the system. Negative values of V^E and Δη were observed over the entire range of temperatures and compositions investigated, indicating the presence of strong specific interactions between TEA and glycerol molecules. These interactions were further elucidated through Density Functional Theory (DFT) calculations. The computational results are consistent with the experimental observations, providing molecular-level support for the non-ideal volumetric and viscosity behavior of the mixtures.

This study investigates the thermophysical characteristics of binary mixtures involving the low-global warming potential refrigerant 3,3,3-trifluoropropene (R-1243zf) and two polyol ester (POE) lubricants (RL 32 and RL 68). Experimental measurements of solubility, liquid density, and dynamic viscosity were conducted over a temperature range of 298–353 K. These outcomes imply that R-1243zf exhibits complete miscibility with both POE oils across the studied conditions, with higher solubility observed in POE RL 32 compared to POE RL 68. The dissolution of R-1243zf significantly reduces the flow characteristics of the lubricants, particularly in the oil-rich phase, while its effect on liquid density is relatively minor. A satisfactory correlation of the phase equilibrium data was achieved with the non-random two-liquid model, and mixture densities and viscosities were accurately represented using an excess-property approach combined with Redlich–Kister expansions. Additionally, Daniel charts were constructed to illustrate the viscosity–pressure–temperature–concentration relationships for both mixtures, providing practical guidance for the selection of lubricating oils in R-1243zf-based refrigeration systems. The findings suggest that POE RL 68 offers better viscosity retention under high-temperature conditions, making it more suitable for severe operating environments.

Microstructures and thermal properties of solid alloys of the Bi–Ge system with a Ge content of 15.1 at.%, 40.8 at.%, 51.8 at.%, 70.3 at.%, and 85.4 at.% were investigated in the present study. Microstructural analysis was performed using scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS). It was noticed that phase morphology of the primary germanium varies based on alloy composition from polygonal faceted to plate- and rod-like structures. Thermal diffusivity was measured by the xenon flash method in the temperature interval from 25 °C to 150 °C. The nearly constant thermal conductivity in the range of about 7 W·m⁻¹·K⁻¹ to 9 W·m⁻¹·K⁻¹ was observed over a wide compositional interval of Bi–Ge alloys, followed by its rapid increase with higher Ge content. Thermal conductivity of the studied alloys slightly decrease with the temperature increasing. Density dependence on composition at room temperature was determined using indirect Archimedean method. The obtained results from the alloy’s density measurements indicate the existence of a positive excess volume. Phase transition temperatures and latent heat of eutectic melting were measured using differential scanning calorimetry (DSC) and compared with the results of thermodynamic calculation based on the CALPHAD (calculation of phase diagram) method. Empirical equation for the estimation of the latent heat for Bi–Ge alloys was obtained.

Multiparameter equations of state (MP EOSs) are available for many fluids. Despite their accuracy, they are not suitable for all applications. In contrast to MP EOSs, cubic equations offer a Van der Waals loop with a single inflection, which is suitable for modeling phase interfaces. They are also amiable for modeling mixtures. We present a method of tailoring a cubic equation of state to a MP EOS. Four temperature-dependent parameters of the previously developed Generalized 4-Parameter Cubic Equation of State (G4C EOS) are matched to the second virial coefficient, liquid density, compressibility, and Gibbs energy. Consequently, the G4C EOS is more accurate than conventional cubic equations of state. The liquid properties are matched along a “sew-on line”, which coincides with the saturated liquid density at lower reduced temperatures and bypasses the critical region. The method is tested for argon, propane, and water. The range of temperatures in which the parameters of G4C EOS can be determined (feasibility interval) covers the validity range of the reference MP EOS with exception for water, where the high-temperature limit is 754 K or 909 K depending on the variant of data used for the second virial coefficient. Parameters of the G4C EOS and ideal gas properties are tabulated in the Supplementary Information and an interpolation scheme is provided. All thermodynamic properties can be computed for the tested fluids with provided relations and tables. Since the method has been successfully applied to three fluids with very different molecular interactions, we assume that it is applicable to a wide range of fluids. It can also be used to other equations of state with four temperature-dependent parameters.

Ceramic matrix composite phase change materials suffer from inherently low thermal conductivity due to solid particle contact limitations in ceramic skeleton, restricting concentrated solar energy storage applications. This study presents a bioinspired heterostructured composite that emulates the hierarchical sieve tube structures in Bombax ceiba vascular bundles to create anisotropic phonon transport channels. Integrating directionally aligned silicon carbide fibers within a porous SiC matrix via centrifugal flow-assisted alignment achieves three-dimensional anisotropic thermal conductivity. This design bypasses the high thermal resistance of sintered particle junctions using biomimetic "sieve plate-like" fiber networks. Elongated SiC fibers act as unidirectional heat conduits, minimizing phonon scattering at grain boundaries. At the expense of 9.4% total energy storage capacity, this anisotropic CPCM significantly optimized equipment performance in the required heat transfer direction. Compared to pure sodium acetate trihydrate and ordinary CPCM, the thermal conductivity in the expected direction improved by 281.19 % and 29.63 %, respectively. The energy storage rate increased by 60.54 % and 36.6 %. The maximum temperature difference in the heat transfer direction decreased by 50.39 % and 31.75 %, and the junction temperature difference reaching the working limit was reduced by 66.83 % and 52.18 %. Therefore, this CPCM efficiently and stably realized thermal energy storage, providing a research basis for building and distributed energy storage.

Fuel blends incorporating oxygenated additives are increasingly explored to enhance combustion efficiency and reduce greenhouse gas emissions. Understanding the thermodynamic behavior of such mixtures is essential for optimizing their formulation. In this study, the excess molar enthalpy (({H}_{m}^{E})) a key property reflecting molecular interactions and non-ideality was measured for four ternary blends containing 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-methoxyethanol, and 2-phenoxyethanol, each mixed with ethanol, at 298.15 and 313.15 K under 0.1 MPa using a quasi-isothermal flow calorimeter. The experimental results were correlated using the Redlich–Kister, NRTL, and UNIQUAC models, while the predictive performance of the Modified UNIFAC (Dortmund) model was also assessed. Positive ({H}_{m}^{E}) values were obtained for all mixtures, indicating endothermic mixing and dominant dispersive–dipolar interactions. Among the applied models, the Redlich–Kister equation provided the best correlation with experimental data. The results contribute valuable thermodynamic benchmarks for modeling the energetics of oxygenated fuel blends and improving predictive approaches for complex liquid mixtures.

The experimental data of densities, ρ, speeds of sound, u, and refractive indices, n_D, are reported for pure compounds and their two binary mixtures of acetonitrile + aromatic hydrocarbons, namely: acetonitrile + n-propylbenzene and acetonitrile + iso-propyllbenzene, at five temperatures, in the range of T = (298.15 to 318.15) K with ΔT = 5 K, on the entire composition range and under atmospheric pressure, p = 0.1 MPa. The values obtained from experimental measurements have been correlated by the Jouyban-Acree model with good accuracy. Based on the experimental data, the excess and deviation quantities, as: excess molar volumes, (V_{m}^{E}), partial/ apparent molar volumes, deviation in speeds of sound, Δu, excess isentropic compressibilities, ({kappa_{S}^{E} }), excess molar isentropic compressibilities, (K_{S,m}^{E}), refractive index deviations, Δn_D, and excess molar refractions, ({R_{m}^{E} }), respectively, have been calculated. For each of the studied mixtures, all these excess properties have been correlated with the Redlich–Kister polynomial equation and the coefficients of correlations were reported. In addition, in this paper, the Perturbed Chain Statistical Associating Fluid Theory Equation of State (PC-SAFT EoS) was used for modeling the density as predictive approach. On the other hand, PC-SAFT + two models were used for calculate the speed of sound of binary mixtures, and PC-SAFT + four mixing rules were used for compute the refractive index of binary mixtures.

This investigation examined the density and viscosity of five binary mixtures of propyl butyrate with 1-alkanols (C₅–C₁₀). The properties were measured across the complete composition range at temperatures from 293.15 to 323.15 K. Experimental analysis showed positive excess molar volumes, and the magnitude of these values increased with both temperature and the chain length of the 1-alkanol. These results are consistent with volume expansion upon mixing for the systems studied. A Physics-Informed Neural Network (PINN) was also developed to predict the excess molar volumes. This model, which incorporates thermodynamic constraints, was applied to the mixtures. For the datasets in this study, the model yielded an Average Absolute Deviation (AAD) of 0.0053 cm³/mol and a mean relative error of 3.23 %. Furthermore, R² values for the model’s predictions exceeded 0.99 for all tested systems. This indicates a strong correlation between the predicted and experimental data under these specific conditions, particularly for the longer-chain alkanols and at higher temperatures.

The high-temperature sensitivity of the mechanical properties of composite ice and pure ice materials makes thermal risk prediction and careful thermal management essential for ensuring the stability and durability of composite ice shell buildings. Based on previous studies on the radiation spectra of composite ice and pure ice, this study established two dynamic solar radiation and heat transfer models for composite ice and pure ice structures. Compared with temperature data from previous field tests, the average root mean square errors for the composite ice structure model and pure ice structure model were 0.86 °C and 0.91 °C, with mean absolute errors of 0.74 °C and 0.79 °C, respectively. In addition, the degree of influence of four meteorological parameters on the surface temperature of both ice structures was investigated, covering indoor and outdoor air temperatures, outdoor wind speed, and solar irradiance. The application of the two models was further extended through response surface methodology experiments to investigate the variations in the surface temperature and thermal risk of ice structures under the simultaneous effects of meteorological parameters with significant impacts, the addition ratio of reinforcing materials, and the structural thickness. Multivariate regression prediction models for the surface temperatures of ice structures were subsequently established. The results provide a method for simulating the dynamic solar radiation and heat transfer in spectrally selective ice structures in real time, as well as directly predicting the thermal risk, thus providing important references for the future operation and maintenance of composite ice shell buildings.

γ-Butyrolactone (GBL) and 1,4-butanediol (BDO) represent a promising liquid organic hydrogen carrier (LOHC) system, for which a lack of thermophysical property data at process-relevant conditions exists. For this LOHC system, the Fick diffusivity D₁₁, thermal diffusivity a, thermal conductivity λ, and density ρ were investigated at about 0.1 MPa as a function of temperature T and mixture composition at GBL amount fractions x_GBL = (0.00, 0.25, 0.50, 0.75, and 1.00) using light scattering and conventional techniques. Vibrating U-tube densimetry and a guarded parallel-plate instrument were employed to determine ρ between T = (283 and 473) K and λ between T = (283 and 363) K. Dynamic light scattering allowed simultaneous access to a and D₁₁ between T = (298 and 473) K in macroscopic thermodynamic equilibrium, while polarization-difference Raman spectroscopy was applied after calibration to monitor the composition. The onset of a certain decomposition or structural rearrangement was observed above about T = 398 K, depending on the sample composition and experimental boundary conditions. When such effects are small, the data for ρ, a, and D₁₁ increase with increasing x_GBL at a given T, whereas λ has the opposite trend. With the help of the results for ρ, a, and λ, values for the specific isobaric heat capacity c_p could be derived. The present measurement results agree with the few experimental data for ρ and λ available in the literature for the pure mixture components and contribute to a significant extension of the thermophysical property database for this highly promising LOHC system.