International Journal of Thermophysics最新文献

Short-chain alcohols and glycol ethers are increasingly being considered as promising additives or components in biofuels due to their favorable physicochemical properties and alignment with the growing demand for sustainable and low-emission energy sources in the transportation sector. This study presents experimental data for five binary mixtures of 2-propanol with glycol ethers: 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-methoxyethanol, 2-phenoxyethanol, and 2-butoxyethanol. Measurements of excess molar enthalpy (({H}_{m}^{E})), density (ρ), speed of sound (u), and refractive index (n_D) were performed over the temperature range 293.15 K–323.15 K at 0.1 MPa. Derivative thermodynamic properties, excess molar volume (({V}^{E})), isentropic compressibility (k_s), and refractive index deviation (Δn_D), were calculated from the experimental data. Density data were correlated using PC-SAFT and Peng–Robinson equations of state, while polynomial equations were employed to fit ρ, u, n_D, and k_s as functions of composition. The Redlich–Kister equation was used to fit ({V}^{E}) and Δn_D. Excess molar enthalpy (({H}_{m}^{E})) was modeled using both the Redlich–Kister correlation and thermodynamic activity coefficient models, UNIQUAC, NRTL, and Modified UNIFAC, to interpret molecular interactions. All the studied mixtures exhibit endothermic behavior. The results contribute to a deeper understanding of the behavior of alcohol/glycol ether mixtures and their potential application in fuel formulations.

This investigation explores the volumetric and viscometric behavior of binary systems containing acetylacetone (ACAC) and a series of 1-alkanols, specifically from 1-hexanol to 1-decanol and at 293.15–323.15 K. The main purpose was to characterize the molecular interactions and non-ideal behavior within these systems. Our findings indicate that the excess molar volumes for all analyzed systems are positive across the entire composition range. Furthermore, these positive deviations in volume were observed to amplify with both increasing temperature and the extension of the carbon backbone. In contrast, the viscosity deviations were consistently negative for all mixtures, with the magnitude of these negative deviations becoming more pronounced as the carbon number of the alcohol component increased. To further interpret the volumetric behavior of the binary mixtures, the PC-SAFT equation was implemented to model the liquid densities. The calculated densities from PC-SAFT showed strong agreement with the measured values across all systems and temperatures. The highest observed deviation between experimental and predicted densities was 0.87%, which was found in the acetylacetone + 1-decanol mixture. This level of accuracy demonstrates the reliability of the PC-SAFT approach in capturing the complex interactions within these non-ideal binary systems.

The regolith on the shallow lunar surface was formed through micrometeorite impacts over time. Investigating the thermophysical properties of the regolith provides valuable insights into the thermal history of the Moon as recorded by these surface materials and offers critical data for future lunar exploration. In several studies, the thermophysical properties of the regolith layer and rocks have been examined, but few studies have focused on individual regolith particles because of their limited size and irregular shapes, which are generally believed to have formed following intense activities, such as micrometeorite impacts. In this study, the local thermal diffusivity of individual particles from Apollo 17 sample 70161 was measured via the lock-in thermography (LIT) technique, and subsequently, the distribution of in-plane thermal diffusivity was provided. The particle was confirmed to be a typical breccia using X-ray tomography (XCT) assisted by X-ray diffraction (XRD). The local average thermal diffusivity values ranged from 2.9 m²·s⁻¹ to 3.6 × 10⁻⁷ m²·s⁻¹ and showed an anisotropic distribution. In addition, we calculated the representative thermal conductivity and thermal inertia of the particles via the specific heat and density, which are 0.738 ± 0.088 W.m⁻¹·K⁻¹ (300 K) and (1.231 ± 0.086) × 10³ J·m⁻²·s^−1/2·K⁻¹ (300 K), respectively. The specific heat was also obtained by differential scanning calorimetry (DSC) of fine samples from 70161. The density was calculated from the measured weight, and the volume was determined via XCT. On the one hand, our experimental results are in good agreement with previously reported measurements of Apollo lunar rocks (in terms of average values). On the other hand, our measurements also reveal an anisotropic distribution of thermal diffusivity within localized regions of the particle. This anisotropy is attributed to factors such as cracks and defects, which locally weaken heat conduction.

In this research, nanocapsules of polyethylene glycol (PEG) as the phase change material (PCM) were synthesized and used to prepare a heat transfer fluid. The phase change nanocapsules were prepared using a novel sequential sedimentation approach by controlling the core and shell solubility parameters through temperature changes in the solvent. These nanocapsules consist of a PEG core with a molecular weight of 2000, as the PCM, and a thermally conductive polystyrene/activated carbon (PS-AC) shell (PEG@PS/AC). Adding up to one weight percent of these nanocapsules in distilled water significantly improved the thermophysical properties of the heat transfer fluid. The specific heat capacity increased from 4300 J·kg⁻¹·K⁻¹ for pure water to 5800 J·kg⁻¹·K⁻¹ for the prepared heat transfer fluid. This represents a significant improvement of approximately 35 % compared to pure water. The thermal energy absorption also showed improvements of about 17 %. Furthermore, the thermal diffusivity of the heat transfer fluid was significantly reduced by 82 %, from 12 × 10^–7 for water to 2.17 × 10^–7 m²·s⁻¹ due to the latent heat absorption of the PCM used in the nanocapsule. Based on the results, it is suggested that the developed PEG@PS/AC nanocapsules be used in heat transfer fluids to effectively manage thermal energy.

This study presents new experimental measurements of density and viscosity for binary mixtures of propanal with 1-alkanols (from 1-propanol to 1-heptanol) at 0.1 MPa over the temperature range of 293.15 K–323.15 K. Theoretical excess molar volume values, calculated using the Peng–Robinson cubic equation of state with van der Waals mixing rules and the Redlich–Kister correlation, show qualitative agreement with the experimental data reported. The results indicate strong attractive interactions between propanal and the alcohols, leading to negative excess molar volumes and positive viscosity deviations.

The in-plane thermal conductivity (k) of ultrathin films is of great scientific and engineering importance as the ultrafine thickness will cause remarkable energy carrier scattering. However, the in-plane k is extremely difficult to measure as the in-plane heat conduction is highly overshadowed by the substrate. To date, very rare experimental data and understanding have been reported. Here we report an advanced differential transient electro-thermal (TET) technique to characterize the in-plane k of supported nm-thin Iridium films down to < 2 nm thickness. The ultrathin (500 nm) organic substrate and its low k makes it possible to distinguish the in-plane k of the film with high confidence. The radiation effect is rigorously treated and subtracted from the measured k. Also measurements under different temperature rise levels allow us to determine the k at the zero temperature rise limit. All these physics treatments lead to high accuracy determination of the in-plane k, and understanding of the strong structural effects. The k of ultrathin Ir films supported on polyethylene terephthalate is determined to be 11.7 W·m⁻¹·K⁻¹, 20.1 W·m⁻¹·K⁻¹, 23.5 W·m⁻¹·K⁻¹, and 34.3 W·m⁻¹·K⁻¹ for thicknesses of 1.83 nm, 3.11 nm, 5.86 nm, and 9.16 nm, respectively. This is more than one order of magnitude reduction from the bulk’s k of 147 W·m⁻¹·K⁻¹. The film’s electrical conductivity is found to have more than two orders of magnitude reduction from that of bulk Ir (1.96 × 10⁷ Ω⁻¹·m⁻¹). The Lorenz number of the studied Ir films increases significantly with decreased film thickness, and is upto 14-fold higher (3.97 × 10^–7 W·Ω·K⁻²) than that of bulk Ir (2.54 × 10^–8 W·Ω·K⁻²). It underscores the significant and deviated influence of structure and film dimension on heat and electrical conductions and provides invaluable knowledge for future applications in nanoelectronics.

The present work reviews different approaches from the literature and suggests an empirical correlation scheme for calculating Fick diffusion coefficients in binary electrolyte mixtures. The mixtures consist of either an electrolyte component dissolved in a molecular solvent or of two electrolyte components sharing a common ion. For both types of mixtures, the diffusive mass transport is characterized by a single Fick diffusion coefficient D₁₁. Prediction models for electrolytes and non-electrolytes mixtures are evaluated, considering experimental D₁₁ data in the literature from dynamic light scattering experiments for binary mixtures, which have a solute amount fraction of 0.05 and include a systematic variation of the solute and solvent components. It could be shown that including information about the fluid structure obtained from molecular dynamics (MD) simulations, such as the formation of solvation shells, the predictive performance of the models can be greatly improved. In general, most models are able to predict D₁₁ in mixtures where the ions are well dissociated by the solvent molecules, but can fail for mixtures where the ionic species tend to aggregate. For binary electrolyte mixtures based on a molecular solvent, an empirical correlation is developed, which can predict D₁₁ for all mixtures with an average absolute relative deviation (AARD) of 21% from the experimental values. For binary mixtures consisting of two electrolyte components sharing a common ion, it could be shown that D₁₁ can be predicted by using only the self-diffusivities of the three ions with an AARD of 15% from experimental data.

The gradient theory of the interface is combined with the cubic plus association and perturbed chain statistical association fluid theory equations of state to estimate the surface tension of (monoethanolamine + water) system for the first time. For each equation of state, three cases of association scheme and two forms of influence parameters have been used. Two forms of influence parameters are also applied to the gradient theory. The second form contains two exponents that lead to the accuracy of surface tension estimations, especially at low mole fractions of monoethanolamine. The highest and lowest AADs% of surface tension are 5.24 and 1.11, respectively. The interfacial density profiles show the enrichment of the surface layer with monoethanolamine. However, the enrichment of the surface layer does not exist at high concentrations of monoethanolamine in the mixture. The overall AADs% of the present model confirm its reliability for description of (monoethanolamine + water) interface.