International Journal of Thermophysics最新文献

In the present work, the thermal conductivity of composite materials based on glass, ceramic, and polystyrene microspheres, as well as fiberglass, bonded with a styrene-acrylic emulsion has been reported. The measurements were performed using a commercial SKZ1061C instrument manufactured by SKZ Industrial based on the transient plane source (TPS) method at room temperature and atmospheric pressure. The reliability of the measurements was confirmed through validation of two reference samples of extruded polystyrene foam with well-known thermal conductivity. The measured thermal conductivity values range between (0.0581 and 0.0905) W/(m⋅K) with an uncertainty of 2.5%.

Thermodynamic property data for solid argon have been analysed to construct a new fundamental equation of state (EOS) based on the Helmholtz energy. This approach is based on methodologies previously applied to solid CO₂ and benzene (Trusler in J Phys Chem Ref Data 40:043105, 2011; Xiao et al. in J Phys Chem Ref Data 50:043104, 2021). The EOS is capable of predicting thermodynamic properties of solid argon up to 760 K and 6300 MPa, using temperature and cell volume as independent variables. The model incorporates the quasi-harmonic approximation with a Debye oscillator framework for vibrons, along with an anharmonic term to address deviations near the triple point. In addition to literature data, the model was regressed to new measurements of argon’s solid cell volume conducted from (8 to 50) K using a high-intensity neutron diffractometer, the results of which are reported here. This new EOS achieves a high degree of accuracy in representing experimental data, with uncertainties (k = 1) estimated of 0.1 %, 0.5 %, and 0.5 % for the cell volume along the sublimation curve, along the melting curve, and in the compressed solid phase, respectively; 2 % to 10 % for the heat capacity along the sublimation curve in different temperature regions; 1 % to 10 % for the thermal expansivity on the sublimation curve; 2 % for the isothermal bulk modulus, 1 % for the isentropic bulk modulus, 0.2 % for the enthalpy of sublimation, 0.5 % to 2 % for the enthalpy of melting, 1 % for the sublimation pressure (T > 50 K), and 2 % to 5 % for melting pressure. The EOS maintains physically realistic behaviour across the range of conditions from absolute zero to high-pressure.

This manuscript investigates different properties of binary mixtures composed of methyl heptanoate and a series of 1-alkanols (from 1-propanol to 1-hexanol) at atmospheric pressure (0.1 MPa) and temperatures ranging from 293.15 K to 323.15 K. Our experimental data shows that weak intermolecular interactions between the methyl heptanoate and 1-alkanol. Additionally, we employed the PC-SAFT equation of state to accurately predict the density of the mixtures. On the other hand, two viscosity correlations (Redlich–Kister and Belda) were also tested, both of which provided a good fit to the experimental viscosity data.

Thermophysical properties encompassing specific heat, thermal conductivity, thermal diffusivity and thermal expansion and their temperature dependence is most sought after during selection of materials for various engineering applications. In this review a broad perspective on the thermal transport in metals and alloys, thermal energy carriers and factors affecting their mean free path is presented. Following the discussion on thermal transport, various techniques available for measuring thermal diffusivity, their principle of detection, merits and demerits are deliberated with an emphasis on laser flash analyzer. Theory of laser flash analysis, possible causes for deviation in the theoretical assumptions that affect the accuracy of measured diffusivity and ways and means of improving the same is dwelt upon. Finally, few typical case studies on thermal diffusivity measurements covering broad spectrum of materials differing in chemistry, degree of deformation, and heat treatment conditions are presented to demonstrate the sensitivity of thermal diffusivity to microstructural changes in materials.

In the present study, the effective thermal conductivity λ_eff of nanofluids containing metal oxide nanoparticles with a chemisorbed organic shell was investigated experimentally and theoretically. The model systems synthesized by a continuous-flow hydrothermal method consist of cyclohexane as organic base fluid and dispersed nearly spherical cerium dioxide (CeO₂) core nanoparticles with a decanoic acid shell chemically attached to their surface. From the differences between the hydrodynamic diameters of the two core–shell nanoparticle types with (8.6 or 9.1) nm determined by dynamic light scattering (DLS) and the nearly spherical CeO₂ core diameters obtained by analytical ultracentrifugation (AUC) and transmission electron microscopy (TEM), an estimation for the thickness of the entire hydrodynamic layer around the particle core in the range of about (1.1 to 1.3) nm could be deduced. Experimental data for λ_eff of the nanofluids and the thermal conductivity of the base fluid λ_bf were determined with a steady-state guarded parallel-plate instrument (GPPI) with an expanded (k = 2) relative uncertainty of 0.026 at atmospheric pressure over a temperature range from (283.15 to 313.15) K in steps of 10 K. The measurement results for the thermal-conductivity ratio λ_eff ·λ_bf^–1 are independent of temperature and increase with increasing volume fraction of the CeO₂ core nanoparticles up to about 0.023. It was found that the experimental results can be described by the Hamilton–Crosser model within their experimental uncertainties for all temperatures investigated.

In this study we report on the influence of poly(isobutylene) (PIB) and PIB-based dispersants on the high pressure thermodynamic properties and the viscosity of a mineral base oil used in passenger vehicle transmission fluids. Density was measured over a pressure range from 10 to 35 MPa at isotherms of 298, 323, 348, 373, and 398 K using a high pressure variable-volume view cell. The density data were then correlated with the Sanchez-Lacombe Equation of State from which the thermodynamic properties of isothermal compressibility, isobaric expansively and internal pressure were derived. Viscosity was measured over a pressure range from 10 to 45 MPa at 298, 323, 248, and 373 K using a uniquely designed high pressure rotational viscometer. Viscosity data were then correlated with density according to the free volume and density-scaling formalisms to provide further insights into molecular packing and interactions.

The wide use of clay minerals in various applications, particularly the production of fired bricks for buildings, has led to the continuous depletion of clay deposits. Moreover, a considerable amount of waste is generated globally which negatively impacts the environment and is constantly increasing. To conserve the environment and reduce clay depletion, it has become popular to incorporate these wastes into clays for fired brick production. Biomass-based wastes are advantageous when used as additives because they enhance the technological properties of the bricks, reduce energy and cost requirements, and alleviate the effect of climate change on buildings. This work reviews the influence of biomass-based additives on the physical, mechanical, and thermal properties of fired clay bricks. We considered recent articles (2014–2024) on various biomass-based additives, describing how the dosage of the additives influences the shrinkage, porosity, water absorption, bulk density, compressive strength, and thermal conductivity of fired bricks. The optimum values of the technological properties from the studies reviewed were highlighted. Moreover, the knowledge gaps were identified, and future perspectives were presented. In general, the incorporation of biomass-based materials in fired bricks decreased the thermal conductivity and density, which is suitable for sustainable lightweight thermally insulating bricks.

Gabapentin, as an anticonvulsant drug with its low-permeability feature in the gastrointestinal region, is one of the commonly prescribed medications for the treatment of epilepsy. Recently surface-active ionic liquids (SAILs) have been utilized to resolve this issue in aqueous solutions. Understanding the thermophysical and micellization behavior of SAILs is of paramount importance as it enables the design of efficient SAILs, and allows for drug property enhancement in pharmaceutical formulations. This study explores the thermophysical and micellization behavior of SAILs (2-hydroxyethyl)ammonium octanoate [2-HEA][Oc], bis(2-hydroxyethyl)ammonium octanoate [bis-HEA][Oc], tris(2-hydroxyethyl)ammonium octanoate [tris-2-HEA][Oc] in varied aqueous gabapentin solutions through the utilization of electrical conductivity, surface tension measurement, and conductor like screening model (COSMO) analysis. The electrical conductivity measurement for aqueous SAILs were conducted at temperature range of 298.15 K to 318.15 K and for the SAILs in aqueous gabapentin solution at varying concentration of 0.0100 to 0.0500 mol kg⁻¹ were conducted at 298.15 K. The surface tension measurements were conducted for the aqueous SAILs and SAILs in aqueous gabapentin solution with varying concentration at 298.15 K. The both of the techniques were employed to evaluate the critical micelle concentration (CMC) and its related thermophysical properties. For better understanding the interactions between these components, COSMO was utilized. The study revealed that CMC values increased with temperature but decreased with increasing gabapentin concentration. Thermodynamic parameters of micellization were calculated through electrical conductivity and surface tension measurement. Finally, interactions between SAILs and gabapentin were investigated through limiting molar conductivity (Lambda_{0}), and association constant (K_{A}), determination.

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Understanding the influence of magnetism on thermal transport is crucial for ensuring the stability and reliability of heat dissipation in magnetic devices. In this study, we examine the magnetism's impact on thermal transport using the widely utilized Nd-Ce-Fe-B sintered magnet as our focal point. By integrating transient hot wire measurements and multiscale simulations, we assess how magnetism affects thermal conductivity (κ) between its ferromagnetic (FM) and paramagnetic (PM) states. Our analysis reveals that the thermal conductivity in the FM state is lower than in the PM state, indicating magnetism's inhibitory effect on thermal transport in Nd-Ce-Fe-B magnet. This phenomenon can be attributed to the suppressed electron transport in the FM state, which effectively reduces the electronic contribution to κ. To validate our findings, we conduct practical heating experiments at the device level alongside multiscale simulations. This research would significantly contribute to the understanding of thermal transport in magnetic materials, laying the groundwork for the thermal design of innovative devices that incorporate magnetism.

Pulsating heat pipes are effective heat transfer devices that can provide passive thermal management solutions for electronics and electric vehicle batteries. In this work, the thermal performance and startup characteristics of a specially designed multiplanar PHP are investigated. Hybrid CuO + Fe₃O₄-water (2 wt. %) nanofluid is used as the working fluid in pulsating heat pipes. The improvement in cooling performance is assessed and compared to that of water. In mobile applications of PHPs like electric vehicle battery thermal management, components are regularly exposed to the vibrations induced by vehicle systems, and hence working characteristics of PHP under vibrations need a detailed investigation. Hence, this work also explores the effect of vibrations (~ 30 Hz) on the thermal performance of pulsating heat pipe to study its feasibility for electric vehicle battery thermal management application. The findings of this work show that with nanofluids, the startup temperature of pulsating heat pipe reduces marginally, and thermal resistance decreases by a maximum of 13.49%. Results also show that under vibrations, pulsating heat pipe shows significantly low startup temperature and reduced thermal resistance. A maximum decrease in thermal resistance under vibrations is observed at 45° pulsating heat pipe inclination; it is 11.40% for water and 8.05% for nanofluid. Also, a regression analysis is conducted to formulate a correlation to predict the thermal resistance of pulsating heat pipes based on different input parameters. The mean absolute percentage deviation (MAPD) between the predicted and experimental data is observed as 4.67% for the correlation based on current study data.