International Journal of Thermophysics最新文献

The present work reviews thermophysical property data such as density, surface tension, normal spectral emissivity, and molar heat capacity for liquid binary Al–Ti alloys measured by electromagnetic levitation (EML). The data are studied as functions of temperature and composition. In EML, forces generated by an inhomogeneous magnetic AC field stably position the specimen against gravity. Melting is achieved by inductive heating. Density (volume) is determined from the droplet’s edge curve in the shadow graph profile. Surface tension is determined from the frequency spectrum of the time-dependent radius. Normal spectral emissivity is determined by a direct radiance method, and the laser modulation calorimetry methods is used for the determination of the molar heat capacity. The results are discussed on the basis of thermodynamic solution models, and the obtained excess properties are compared with each other. A great similarity is hereby found demonstrating the pronounce non-ideality of the Al–Ti system.

The solubility of 2,4,6-trinitrotoluene in ethanol + water mixed solvents was systematically determined using the gravimetric method within the temperature range from 298.15 K to 338.15 K and under a pressure of 0.1 MPa. The experimental results indicate that in this binary solvent system, the solubility of 2,4,6-trinitrotoluene increases monotonically with the rise in the molar fraction of ethanol. Furthermore, over the investigated temperature range, the solubility also increases with temperature. To enhance the applicability of the solubility data, the experimental results were correlated using four thermodynamic models: the modified Apelblat model, the van’t Hoff model, the Yaws model, and the CNIBS/R–K model. The correlation performance of each model was evaluated based on relative deviation, average relative deviation, and root mean square deviation. The results demonstrate that all models exhibit satisfactory correlation accuracy in the selected solvent system, with the CNIBS/R–K model showing the best performance. This study provides important fundamental data for the optimization of the synthesis process of 2,2′4,4′6,6′-hexanitrostilbene.

This study experimentally investigates the intermolecular forces governing n-undecane +2-alkanol (C₃–C₇) at varying temperatures using density and viscosity measurements. Excess molar volumes (V^E) and viscosity deviations (Δη) were calculated to characterize the mixing behavior. Positive V^E values suggest that n-undecane disrupts the hydrogen bonding network within the 2-alkanols, leading to volumetric expansion. The trend of decreasing V^E with increasing alkanol chain length indicates improved molecular packing. Negative Δη values suggest a reduction in viscosity compared to ideal mixing, with longer alkanols exhibiting more negative deviations, implying a greater disruption of cohesive forces. The PC-SAFT equation of state was used to correlate the mixture densities, yielding results in excellent accord with the experimental data by optimizing the adjustable parameters (k_ij), as confirmed by small absolute average deviations. The highest observed deviation between experimental and predicted densities was 0.64%, which was found in the undecane +2-heptanol mixture. The results offer valuable insights into the thermodynamic properties of alkane–alcohol mixtures, with implications for fuel formulation and chemical process engineering.

Liposomal products enable new therapies through the protection and controlled release of encapsulated medicines. The diffusion coefficient of a liposome is associated with its size and surface properties, and its measurement is important in the evaluation of the product and design of new drug delivery systems. We propose a rapid and label-free diffusion sensing method using light-induced dielectrophoresis for high-throughput analysis of liposomal products. In this study, the diffusion coefficient of liposomes with a diameter of approximately 100 nm was measured by observing the mutual diffusion within a few seconds. Prior to the measurement, a parametric study of the excitation conditions was performed to achieve highly efficient manipulation of liposomes by light-induced dielectrophoresis. The validation of the proposed measurement method for liposomes was demonstrated by comparing the result of observation by the transmission electron microscope. The effect of the surface functional groups of the liposomes was quantitatively evaluated using diffusion coefficient measurements. Furthermore, the thermo-sensitive liposomes were measured to demonstrate their sensitivity to phase transition during temperature change.

Passive cooling and air-conditioning methods are being developed for both night-time and daytime cooling of buildings. A passive cooling skylight under development at Åbo Akademi demonstrated a night-time passive cooling effect of ~ 100 W/m². This depends strongly on the gas used inside the skylight, picking up (long wavelength, LW) thermal radiation via a lower window and after a natural convection transfer inside the skylight, releasing the heat to the sky via an upper window. Proof-of-concept work utilised air, carbon dioxide, ammonia and, for best results, pentafluoro ethane, HFC-125. The 2016 Kigali Amendment to the 1986 Montreal Protocol on HFCs necessitates using a low-global warming potential (GWP) alternative for HFC-125: future refrigeration installations cannot contain a GWP > 150 gas under European regulation. The key gas property is high emissivity/absorption in the LW range 8–14 µm, the “atmospheric window”, thus HFC-152a or HFC-41 could replace HFC-125. CFD simulations (Ansys Fluent 2024 R1) were used to calculate the passive cooling heat fluxes, temperatures, convection flow fields, and transported heat inside the skylight, comparing gases. Results show that HFC-152a (117.8 W/m²) and slightly less so HFC-41 (115.4 W/m²), both with a GWP < 150, can match the performance achieved earlier with HFC-125 (117.3 W/m²).

Understanding the evolution of frozen soil thermal conductivity under thermo-mechanical coupling is critical for predicting heat transfer in porous media. In this paper, the thermal conductivity evolution of sandy silt under thermal–mechanical coupling was systematically investigated using a thermal constant analyzer, focusing on the phase transition zone (PTZ, − 0.5 °C, − 1 °C, and − 5 °C). We quantified the effects of temperature (20 °C, − 0.5 °C, − 1 °C, and − 5 °C) and stress ranges (0 kPa, 25 kPa, 50 kPa, and 100 kPa) on thermal conductivity of sandy silt using thermal constant analysis and in-situ magnetic resonance imaging (MRI), while revealing microstructural drivers via pore-scale moisture distribution. The findings demonstrated an asymmetric thermal conductivity evolution between the unfrozen zone and the phase transition zone, with pronounced nonlinear behavior at subzero temperatures. One of the most significant enhancements (up to 55.7 %) occurred in the phase transition zone, where ice formation and stress-optimized particle contact cooperatively promoted heat transfer. The discrete ice crystal (− 0.5 °C) triggered a gradual increase in the thermal conductivity. At − 1 °C, the ice lens body gradually formed a continuous network, causing a sudden jump. Eventually, it was gradually frozen at − 5 °C, and the ice skeletal restructuring enabled steady enhancement through heat path optimization. The phase transition zone led to a significant increase in the microporosity of the sandy silt, forming an interconnected pore network that enhanced the heat transfer pathway. The results provide essential information for evaluating the thermal conductivity of fine-grained soils under freeze–thaw conditions and offer fundamental insights into heat transfer within porous media undergoing phase transition change.

Densities and sound speeds of the ternary system {propan-1-ol + pyridine + nitrobenzene} were measured at T = (293.15, 298.15, 303.15, 313.15, and 323.15) K and atmospheric pressure over the entire composition range, together with those of the corresponding binaries. Excess molar volumes and excess isentropic compressibilities, derived from the experimental data, were correlated using the Redlich–Kister and Cibulka equations for binary and ternary systems, respectively. The composition and temperature dependence of these properties provided information on intermolecular interactions and structural effects. Densities were modeled with the predictive PC-SAFT equation of state, while Schaaff’s Collision Factor Theory and Nomoto’s relation predicted sound speeds. The Jouyban-Acree model correlated density, sound speed, and their derived properties (isentropic compressibility and isobaric thermal expansivity) with a small number of adjustable parameters. Ternary excess properties were further compared with predictions from symmetric (Kohler, Muggianu) and asymmetric (Hillert, Toop) geometric models. Model performance was assessed using statistical indicators, demonstrating the applicability of both theoretical and empirical approaches to describe the thermophysical behavior of these mixtures.

The speeds of sound of ternary refrigerant mixtures, namely, R-444A (difluoromethane (R-32)/1,1-difluoroethane (R-152a)/trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)) with respective mass fractions of 0.1194/0.0519/0.8287), R-457B (R-32/2,3,3,3-tetrafluoropropene (R-1234yf)/R-152a with respective mass fractions of 0.3489/0.5495/0.1016), and R-407C (R-32/pentafluoroethane (R-125)/R-152a with respective mass fractions of 0.5178/0.2480/0.2342), were measured using a dual-path pulse-echo technique at temperatures ranging between 230 K and 345 K and pressures between 0.14 MPa and 30 MPa. The standard uncertainties in temperature and pressure were 5 mK and 0.014 MPa, respectively. The average combined expanded uncertainty for all speed of sound data was 0.07%. Greater uncertainties were encountered as the system approached the critical regions where the speed of sound is more sensitive to changes in pressure. The experimental speed of sound data was used to assess the predictive capabilities of default REFPROP v10.0 mixture models with binary interaction parameters fit using mainly vapor–liquid equilibria and/or density data. We quantify the improvements for ternary mixture predictions when using updated binary interaction parameters that included speed of sound data in the fitting procedure. Reductions of 1.64%, 1.50%, and 0.11% in the average absolute deviations for R-444A, R-457B, and a R-125/1234yf/152a (0.3521/0.5465/0.1014 mass composition) mixture, respectively, are obtained with the updated binary interaction parameters. Further improvements to the mixture models could be made by refitting both the pure component equations of state and interaction parameters of certain hydrofluorocarbon binary pairs.

This study evaluates the potential of free cooling to improve marine HVAC efficiency under the coastal climate of Porbandar, India and examines the benefits of integrating thermal energy storage (TES) using phase change materials (PCMs). Analysis of hourly weather data for 2023 shows that free cooling is feasible for 45 % of the year, comprising 6 % (525 h) full free cooling and 39 % (3416 h) partial free cooling, which can reduce compressor load by 50 %. For a ship operating in harbor, this corresponds to annual fuel savings of 71,500 l, a reduction of 191.8 t of CO₂ emissions, and cost savings of ₹6.8 million. The highest potential occurs from November to February, particularly between the period 20:30 and 11:30, with over half of the air-conditioned hours during peak months allowing free cooling at a 27 °C supply air temperature set point. TES–PCM integration further reduces compressor load by 30 % and enhances onboard temperature stability. The methodology provides a framework to assess free cooling potential in other coastal regions and for ships at sea, demonstrating its viability as an energy-efficient, cost-saving, and sustainable solution for the maritime sector. The validation with real climatic data demonstrates measurable benefits in fuel consumption, emissions, and operational costs, underscoring both the scientific and practical significance of the findings in supporting sustainable and decarbonized maritime sector. This work is novel in extending free cooling and TES–PCM concepts, widely studied in buildings, to marine HVAC systems where research remains scarce.