International Journal of Thermophysics最新文献

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.

Due to their high thermal conductivity compared to traditional coolants, nanofluids are preferred; however, their high thermal conductivity alone is meaningless without ensuring their stability. Therefore, when determining the appropriate mixing ratio (hybrid ratio) for hybrid nanofluids, which are starting to replace mono nanofluids today, the primary factor to consider should be stability. In this study, sedimentation and zeta potential measurements, which are methods for evaluating stability, were used to assess the stabilities of mono Al₂O₃/water and SiO₂/water nanofluids with mass fractions of 1 %, 2 %, and 3 %, as well as hybrid Al₂O₃/SiO₂/water (2 % to 1 %, 1 % to 2 %) nanofluids together for the first time in the literature, and the optimum Al2O₃/SiO₂ hybrid ratio was determined in terms of stability. The results showed that the optimal hybrid ratios for the stability of Al₂O₃–SiO₂/water nanofluids are 1 and 0.714. Furthermore, the thermal conductivities of stable mono and hybrid nanofluids were measured between 25 and 60 °C, and a new correlation valid for both mono and hybrid nanofluids was proposed by modeling with artificial neural networks (MSE = 8.2175E−5 and R² = 0.99958), with a maximum deviation ratio of 3.839 % (for mono SiO₂/water) from the experimental measurements.

The study presents experimental data of the viscosity and specific heat capacity of the near eutectic gallium–indium–tin alloy. Viscosity data cover the temperature range from the alloy’s melting point of 283.85 K (10.70 °C) to about 370.47 K (97.32 °C). Two independent teams using a capillarity viscosimeter and an oscillating cup viscosimeter obtained almost identical values. Below 373 K (100 °C) the data follow the Arrhenius correlation. Specific heat capacity data result from differential scanning calorimetry measurements and reach from 236 K (− 37 °C) to 340 K (67 °C). The Neumann–Kopp rule gives neither the solid nor the liquid state a satisfactory representation of the data. Approximation functions represent these two regions separately in an excellent manner. The study discusses several issues related to the thermophysical properties, namely melting and crystallisation, and a possible liquid-to-liquid crossover.

This paper presents new wide-ranging correlations for the viscosity and thermal conductivity of acetone (2˗propanone or dimethyl ketone) based on critically evaluated experimental data. Both correlations are designed to be used with a Helmholtz-energy equation of state (EOS) that extends from the triple point to 550 K, at pressures up to 700 MPa. The viscosity correlation is valid from the triple point to 550 K and up to 162 MPa pressure, while the thermal conductivity is valid from the triple point to 550 K and 700 MPa. The estimated uncertainty (at a 95 % confidence level) for the viscosity varies from a low of 2 % for the low-pressure gas (p < 0.5 MPa) to 5.5 % for the liquid phase at pressures up to 162 MPa, and for thermal conductivity varies from a low of 3.5% for the low-pressure gas up to 6.2% for the thermal conductivity at pressures up to 700 MPa.

A versatile penta-hybrid nanofluid has been successfully developed by combining silver (Ag), single-walled carbon nanotubes (SWCNTs), titanium dioxide (TiO₂), copper (Cu), and iron oxide (Fe₃O₄) nanoparticles with a base fluid. This nanofluid is utilized in a range of advanced applications, including coatings, sensors, energy storage, water purification, enhanced heat transfer, biomedical uses, and lubricants. The synergistic properties of these nanoparticles significantly enhance the performance of the base fluid, offering substantial benefits across various industries. Therefore, this study delves into the influence of localized magnetic fields, augmented by machine learning, on vortex dynamics under the light of penta-hybrid nanofluid flow, confined in a horizontal cavity with a 2:1 aspect ratio. The Stream-Vorticity formulation tackles the dimensionless governing partial differential equation. Single-phase model has been employed to model the nanofluid. An Alternating Direction Implicit (ADI) technique has been employed to address the governing equations. The research highlights a significant increase in the Nusselt number (Nu) with intensified magnetic fields. Additionally, introducing more nanoparticles enhances Nu with varied effects for different particles. Silver (Ag) and Copper (Cu) exhibit the highest increase in Nu (53%), indicating robust thermal-fluid coupling, while Titanium Dioxide (TiO₂) shows lower increases (37%), implying weaker coupling in the flow. These findings hold relevance for diverse applications, including transportation, energy, medical technology, materials science, and fundamental physics.

Heat exchangers are widely used in most heat transfer applications, and further improvements are necessary to limit the growing energy demand. In this context, performance improvement studies of shell-and-tube heat exchangers have gained importance. Although many studies have been conducted on this heat exchanger in the literature, research on the Utube channels remain limited. To address this gap in the literature, a detailed investigation of energy, entropy, and exergy analysis was conducted on this geometry using numerical methods. Both passive and active heat transfer enhancement methods were utilized to improve the thermo-hydraulic performance of the U-tube. As a passive method, dimpled fins and MWCNT-Fe₃O₄/water hybrid nanofluid at volume fractions of 0.001 and 0.003 were employed. As an active method, DC and AC (f = 2 Hz and square wave) magnetic fields with strengths of B = 0.16 T and 0.30 T were applied. The flow conditions in the analysis corresponded to the laminar flow regime at Dean numbers of 117.1, 175.7, and 234.2. Effects of hybrid nanofluid fractions, U-tube positions, flow regime, magnetic field strength, and current type on each other were discussed and compared in detail with previous results. Findings were carefully evaluated, and conclusions were drawn in the context of similar research. Results indicated that the U-tube position did not affect thermo-hydraulic performance. However, it was calculated that dimpled finned U-tube increased convective heat transfer by up to 30% compared to plain U-tube. Moreover, MWCNT-Fe₃O₄/water hybrid nanofluid at 0.003 volume fraction increased this rate by an additional 5.0%.

Fiber-reinforced polymers are crucial for insulating electrical equipment, necessitating accurate thermal property data for an effective thermal analysis. This case study uses a cost-effective method to thermally characterize a glass fiber-reinforced epoxy resin used in air-core reactor insulation. The approach simultaneously estimates temperature-dependent thermal conductivity (k) and specific heat (c_p) for class H/180 insulation. By analyzing transient heat conduction in a 3D composite sample under vacuum and at various temperatures, the method optimizes sensor placement, enabling accurate property estimation with a single thermocouple. The estimated through-thickness thermal conductivity at room temperature deviates by less than 6% from standard guarded hot plate measurements. The method’s reliability is confirmed by accurately retrieving the applied heat flux using the estimated properties and measured temperature data. The results are valuable for designing accurate simulation models to predict and manage the thermal behavior of air-core reactors, as implemented by GE Grid Solutions in Itajubá, Brazil.

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