International Journal of Thermophysics最新文献

A wide-ranging model for the viscosity surface of methane (CH₄) was developed with a range of validity from the triple-point temperature to 625 K and pressures up to 1000 MPa. An extensive literature survey was undertaken and all available experimental data, to the extent of our knowledge, were considered in the development of the model. The correlation incorporates recent ab initio results for the dilute-gas contribution, Rainwater–Friend theory for the initial density dependence, and an empirical contribution for higher densities obtained using recently developed open-source symbolic regression software. The estimated uncertainty of the correlation (at k = 2) varies from a low of 0.13 % for the gas at pressures below 1 MPa over temperatures from 210 K to 392 K, to 0.8 % to 2 % depending on the temperature for the mid-pressure range of 1 MPa < p < 50 MPa, and is 4 % for pressures from 50 MPa to 1000 MPa for temperatures from 223 K to 625 K. In the liquid region at pressures up to 33 MPa, the estimated uncertainty is 3 %.

In the present study, hemoglobin calibration curves were developed by photoacoustic spectroscopy (PAS) using hemoglobin solutions with controlled concentrations. Two types of samples exhibiting different optical properties were obtained: optically opaque (20–180 mg/mL concentrations) and optically transparent (0.0312–2 mg/ml concentrations). Optical absorption spectra were recorded in the wavelength range of 250–750 nm. From these spectra, the Soret band absorption peak at 412 nm and a secondary absorption at 450 nm were identified, and their ratio was determined. The ratios, plotted as a function of hemoglobin concentration, were fitted to the most suitable mathematical model, enabling the estimation of unknown hemoglobin concentrations in various biological samples, both optically opaque (e.g., blood and organs) and optically transparent (e.g., urine and plasma). The results show a strong correlation between the photoacoustic signal and hemoglobin concentration, validating the applicability of this technique to complex biological systems. Accurate quantification of hemoglobin in biological media is essential for the diagnosis and monitoring of numerous diseases. PAS proves to be a reliable tool for clinical and biomedical research applications, offering advantages in sensitivity, specificity, and minimal sample volume requirements.

Synthetic hydroxyapatite is a biomaterial widely used for the production of medical ceramics and coatings, but its thermophysical properties have not been sufficiently studied. In this work, a comprehensive study of the thermal conductivity and the thermal diffusivity of ceramic samples sintered at different temperatures was carried out for the first time. The thermal diffusivity was measured over a wide temperature range (up to 1325 K) using the laser flash method. The isobaric heat capacity of hydroxyapatite was studied using the method of differential scanning calorimetry. Based on the obtained experimental results, the thermal conductivity was calculated. It was shown that with increase in the sintering temperature of green body up to 1473 K, its density increases (from 1955 kg·m^–3 to 2844 kg·m^–3), which leads to an increase in thermal diffusivity (from 0.196 m²·s^–1 to 0.460 m²·s^–1) and thermal conductivity (from 0.281 W·(m·K)^–1 to 0.963 W·(m·K)^–1) for a material having a temperature close to room temperature (293 K). Measurements at high temperatures indicate that the thermal diffusivity and the thermal conductivity of hydroxyapatite depend not only on the material density and temperature, but also on the concentration of hydroxyl groups in the hydroxyapatite crystal lattice. Increasing the material density shifts the thermal diffusivity and the thermal conductivity curves to higher values. The complete absence of hydroxyl groups, which is characteristic of the oxyapatite state, significantly changes the shape of the curve. The investigation indicates the importance of taking into account the degree of hydroxylation of apatite as it changes thermal properties of the material, which is very important and can be crucial in the manufacture of ceramic products.

In the pig houses with mist cooling systems, the layout design of airflow and spray is the important factor affecting the cooling effect of pigs. However, there is currently insufficient understanding of heat and mass transfer characteristics of pig-water-wet air (PWWA) under different design parameters. In order to guide the structural design of systems, the heat and mass transfer characteristics are analyzed for PWWA in a developed model based on heat–mass transfer theory and multi-model coupling method. The model is validated based on experimental data from literature. The results show that the maximum uncertainty between simulation and literature data is 9.1 %. Meanwhile, the influences of different design parameters are analyzed for the heat and mass transfer characteristics of PWWA. It can be found that when the spray height is 800–1200 mm and the spray angle is 40–80°, compared with other three nozzle shapes, the cooling performance between pigs and spray water can be improved when using solid-shaped nozzles. Further, this effect can be strengthened at lower spray heights. Through scheme comparison, the optimal structural design scheme is obtained for the mist cooling system. It is recommended to use a design scheme with s-shaped nozzles, a spray angle of 20° and a spray height of 700 mm. This is because compared with other schemes designed to obtain the optimal heat transfer rate and unit length pressure drop, the disturbance can be significantly increased for wet air around pigs and the mass transfer rate is not significantly changed for water-wet air under the recommended scheme. Although compared with the scheme designed to obtain optimal mass transfer rate, the mass transfer coefficient between spray water and wet air under the recommended scheme decreases by about 10 %, its heat transfer coefficient and unit length pressure drop increase by at most 42.7 % and 13.4 %, respectively. This study can provide a forward-looking theoretical guidance for the pre-design and application evaluation of mist cooling systems in pig houses.

Deep eutectic solvents (DESs) have been the subject of interest in literature with a focus on replacing traditional solvents due to their green solvent’s characteristics. This study presents the experimental data on preparation and physicochemical properties of choline chloride and propionic acid deep eutectic solvent (CC:PA DES) and their aqueous binary mixtures in (298.15 to 353.15) K temperature range. The experimental density ((rho)) data are fitted well by second degree polynomial equation in T. Molar entropy (({S}^{0})) and Lattice energy (({U}_{pot})) are also calculated to explain the behavior of thermodynamic properties. Excess molar volume (({V}^{E})) is showing positive deviation from ideal behavior and the minimum of ({V}^{E}) vs. ({x}_{1}) lies at ({x}_{1}=0.5) (({x}_{1}) = mole fraction of CC:PA DES in binary mixture). Plot of ({overline{V} }_{i}^{E}) vs. ({x}_{1}) also cross each other at ({x}_{1}=0.5). which supports the dominance of specific interactions. Viscosity deviation ((Delta eta)) is observed at ({x}_{1}=0.8), supporting the interstitial accommodation of components molecules into each other. Comparison of Vogel–Fulcher–Tammann (VFT) equation and Arrhenius equation to investigate the temperature dependence of viscosity ((eta)) for ({x}_{1}=0-1.0) shows that VFT is better fitted model in studied temperature range T = (298.15 to 353.15) K. We demonstrated that the PC-SAFT equation of state can reliably predict the density of the pseudobinary CC:PA DES + water system. In addition, PC-SAFT was capable of correctly capture the qualitative behavior of the excess molar volume.

As a direct way to obtain energy for hydrogen fuel cell vehicles, the hydrogen filling has been of great concern for its filling rate, quality and safety. However, there is a lack of indicators to scientifically evaluate the comprehensive performance of different filling strategies. To solve the above problem, a numerical model of hydrogen storage tank (HST) filling with fluid–solid coupling on the inner wall surface is established, and a comprehensive evaluation indicator is determined by using the analytic hierarchy process and entropy method in this study. The results show that the surface temperature of the outer wall of the HST and the maximum temperature difference between the hydrogen zone and the inner wall surface are the key indicators for evaluating the safety of the filling process. Moreover, the comprehensive evaluation indicator has five sub-indicators, with filling time having the greatest influence (59.06%) and state of charge having the least (0.66%). More importantly, the identified comprehensive evaluation indicator can be carefully and accurately evaluated according to user preferences while ensuring a certain degree of objective evaluation. These findings provide new ideas and important references for the evaluation study of the HST filling process.

The radioactive materials assistance has driven many contributions in diverse fields, including industrial, nuclear power plants, and medical treatments, while in fluid mechanics, these particles play a significant role in enhancing the velocity and temperature profiles. The objective of the study under consideration is to generate approximate solutions for the mathematical models representing radioactive materials contaminated in MHD blood flow involving slip and nonlinear convection using deep layered recurrent neural networks supported by Bayesian distributed optimization (LRNN-BDO). The development of the existing model is constructed by transforming PDEs into a system of nonlinear ODEs through suitable variations. Analysis is performed with multi-class parameters in the system model via magnetic interaction, Prandtl number, Eckert number, the linear/non-linear mixed convection, radiation, temperature, and non-dimensional nanofluid. The generated synthetic data is numerically formulated by exploiting an implicit backward differentiation scheme in the presence of uranium dioxide (UO₂) and thorium dioxide (ThO₂), with base fluid as blood. The proposed solutions of the LRNN-BDO consistently align with the reference solutions that the errors are approximately equals to zero, exhibiting robust, efficient, and reliable networks performance evaluated through various assessment metrics corresponds to iterative convergence on mean squared error, adaptive controlling measures of optimization, error frequency distribution on histograms and regression statistics for exhaustive validation for radioactive materials contaminated MHD blood flow model involving slip and nonlinear convection.

A solar still is a simple and sustainable device that converts saline or brackish water into potable water using solar energy. However, its practical use is limited due to low distillate yield. This study aims to enhance the performance of pyramid-type solar stills (PSS) by integrating magnetic fields to improve evaporation dynamics and thermal efficiency. The central hypothesis is that applying magnetic fields can alter the physical properties of saline water—reducing surface tension and specific heat capacity—to accelerate the evaporation process. Two configurations were investigated: the Conventional Pyramid Solar Still (CPSS) and the Magnetically Modified Pyramid Solar Still (MPSS). Outdoor experiments were performed under Baghdad’s climatic conditions (33.3°N, 44.6°E) from April to June 2025, supported by theoretical modeling using the enthalpy–porosity method to simulate coupled heat and mass transfer. The results revealed that magnetic field application markedly improved system performance, with freshwater productivity increasing by up to 68.2 % and thermal efficiency reaching 49.24 % at a magnetic intensity of 2430 mT. Positioning the magnetic plates inside the basin enhanced yield by 13.76 %, while a parallel plate arrangement generated the most uniform magnetic flux and highest evaporation rate. Economic evaluation indicated that the MPSS achieved a faster cost recovery (272 vs. 492 days) and a higher lifetime profit ($6057.76 vs. $1783.81) compared to the CPSS. The findings confirm that magnetic field integration offers a viable route to improve the thermal and economic performance of solar distillers, providing a promising low-cost and eco-friendly solution for freshwater production in arid regions.

This work reports the fabrication and characterization of high-quality tungsten-doped vanadium dioxide (W_xV_1-xO₂, x = 0 ~ 3 at. %) by thermal oxidation of sputtered tungsten-vanadium alloyed thin films with different atomic percentages and high-temperature annealing in an extremely low oxygen atmosphere (5 ppm to 20 ppm) along with reduction of surface over-oxides in high vacuum (1 mPa). Oxidation parameters such as temperature, time and nitrogen purging rate are first optimized for obtaining high-quality undoped VO₂ thin film. Insulator-to-metal (IMT) phase transition behavior of VO₂ thin films fabricated in a low-O₂ environment is characterized with temperature-dependent spectral infrared transmittance and electrical resistivity measurements, where there is 15 % higher infrared transmittance change and additional 1 order change in resistivity in comparison with VO₂ thin films fabricated in a O₂-rich environment. Grazing angle X-ray diffraction scan confirms no presence of higher oxides in the VO₂ oxidized in low-O₂ environment, which improves its quality significantly. Comprehensive studies on thermal annealing and vacuum reduction for tungsten-doped VO₂ thin films are also carried out to find the optimal fabrication conditions. With the tungsten at. % measured by X-ray photoelectron spectroscopy, the optimal WVO₂ thin films fabricated through this streamlined oxidation, annealing and reduction processes in extremely low-O₂ furnace environment exhibit lowered IMT temperature at − 23 °C per at.% of tungsten dopants from 68 °C without doping. This low-cost and scalable fabrication method could facilitate the wide development of tunable WVO₂ coatings in thermal and energy applications.

Specific heat of liquid iron, nickel, and zirconium has been measured by a new kind of aerodynamic levitation facility. The heating is ensured by a laser and a three-color pyrometer has been developed to measure dynamically both temperature and absorptivity of the sample at laser wavelength. A heat balance on a temperature plateau allows to determine the heat losses, and the cooling is then used to determine the specific heat. This new method provides results for a large temperature range above the melting point and without the assumption of constant emissivity. Results are compared with data obtained by others contactless methods available in literature, and present good agreement. This original method offers the specific heat of iron between 2000 K and 2337 K. The specific heat of nickel is determined between 1838 K and 2162 K. The specific heat of liquid zirconium is measured between 2283 K and 2754 K. Proposed values complete or extend a very limited literature for these materials at the liquid state.