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Deep neural network-based deep potentials (DP), developed by Tuo et al., have been used to compute the thermodynamic properties of free aluminum clusters with accuracy close to that of density functional theory. Although Jarrold and collaborators have reported extensive experimental measurements on the melting temperatures and heat capacities of free aluminum clusters, no reports exist for finite-temperature ab initio simulations on larger clusters (N > 55 atoms). We report the heat capacities and melting temperatures for 32 clusters in the size range of 48–342 atoms, computed using the multiple histogram technique. Extensive molecular dynamics (MD) simulations at twenty four temperatures have been performed for all the clusters. Our results are in very good agreement with the experimental melting temperatures for 19 clusters. Except for a few sizes, the interesting features in the heat capacities have been reproduced. To gain insight into the striking features reported in the experiments, we used structural and dynamical descriptors such as temperature-dependent mean squared displacements and the Lindemann index. Bimodal features observed in Al116 and the weak shoulder seen in Al52 are attributed to solid–solid structural transitions. In confirmation of the earlier reports, we observe that the behavior of the heat capacities is significantly influenced by the nature of the ground state geometries. Our findings show that the sharp drop in the melting temperature of the 56-atom cluster is a consequence of the change in the geometry of Al55. Mulliken population analysis of Al55 reveals that the charge-induced local electric field is responsible for the strong bonding between core and surface atoms, leading to the higher melting temperature. Our calculations do not support the lower melting temperature observed in experimental studies of Al69. Our results indicate that Al48 is in a liquid state above 600 K and does not support the high melting temperature reported in the experiment. It turns out that the accuracy of the DP model by Tuo et al. is not reliable for MD simulations beyond 750 K. We also report low-lying equilibrium geometries and thermodynamics of 11 larger clusters (N = 147–342) that have not been previously reported, and the melting temperatures of these clusters are in good agreement with the experimental ones. [ABSTRACT FROM AUTHOR]

We present the results for energy landscapes of hexapeptides obtained using interfaces to the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) program. We have used basin-hopping global optimization and discrete path sampling to explore the landscapes of hexapeptide monomers, dimers, and oligomers containing 10, 100, and 200 monomers modeled using a residue-level coarse-grained potential, Mpipi, implemented in LAMMPS. We find that the dimers of peptides containing amino acid residues that are better at promoting phase separation, such as tyrosine and arginine, have melting peaks at higher temperature in their heat capacity compared to phenylalanine and lysine, respectively. This observation correlates with previous work on the same uncapped hexapeptide monomers modeled using atomistic potential. For oligomers, we compare the variation in monomer conformations with radial distance and observe trends for selected angles calculated for each monomer. The LAMMPS interfaces to the GMIN and OPTIM programs for landscape exploration offer new opportunities to investigate larger systems and provide access to the coarse-grained potentials implemented within LAMMPS. [ABSTRACT FROM AUTHOR]

In this study, we performed a numerical investigation of the thermophysical properties of liquid (U, Zr) mixtures, which are particularly relevant in the context of hypothetical nuclear accidents and the formation of in-vessel coriums. To do so, atomistic simulations leveraging classical molecular dynamics and an interatomic potential developed for solid (U, Zr) structures are performed. Our methodology is first validated by comparing the predictions of our model for the melting temperature and the structure factors to experimental, phase diagram, and ab initio data. We then use the approach to evaluate the temperature and composition dependence of four fundamental properties in the context of coriums: density, heat capacity, compressibility, and viscosity. Systematic comparisons to the existing experimental data are performed and discussed. In particular, the viscosity of liquid (U, Zr) mixtures is investigated by comparing diffusion calculations and the Stokes–Einstein formula as well as the results obtained with the Green–Kubo methodology, empirical predictions, and experimental data. Notably, the viscosity of the mixtures is predicted to be significantly higher than that of the single-element liquids, which is unexpected and could have crucial consequences on the early stages of the formation and flow of in-vessel corium. [ABSTRACT FROM AUTHOR]

Thermal properties of materials are essential to many applications of thermal electronic devices. Density functional theory (DFT) has shown capability in obtaining an accurate calculation. However, the expensive computational cost limits the application of the DFT method for high-throughput screening of materials. Recently, machine learning models, especially graph neural networks (GNNs), have demonstrated high accuracy in many material properties' prediction, such as bandgap and formation energy, but fail to accurately predict heat capacity(C V) due to the limitation in capturing crystallographic features. In our study, we have implemented the material informatics transformer (MatInFormer) framework, which has been pretrained on lattice reconstruction tasks. This approach has shown proficiency in capturing essential crystallographic features. By concatenating these features with human-designed descriptors, we achieved a mean absolute error of 4.893 and 4.505 J/(mol K) in our predictions. Our findings underscore the efficacy of the MatInFormer framework in leveraging crystallography, augmented with additional information processing capabilities. [ABSTRACT FROM AUTHOR]

We present a detailed study on the temperature-dependent THz spectra of the polycrystalline amino acids, L-serine and L-cysteine, for wavenumbers from 20 to 120 cm−1 and temperatures from 4 to 300 K. Even though the structure of these two amino acids is very similar, with a sulfur atom in the side chain of cysteine instead of an oxygen atom in serine, the excitation spectra are drastically different. Obviously, the vibrational dynamics strongly depend on the ability of cysteine to form sulfur–hydrogen bonds. In addition, cysteine undergoes an order–disorder type phase transition close to 80 K, documented by additional specific heat experiments, with accompanying anomalies in the THz results. On increasing temperatures, well-defined vibrational excitations exhibit significant shifts in the eigenfrequencies with concomitant line-broadening yielding partly overlapping modes. Interestingly, several modes completely lose all their dipolar strength and are unobservable under ambient conditions. Comparing the recent results to the published work utilizing THz, Raman, and neutron-scattering techniques, as well as with ab initio simulations, we aim at a consistent analysis of the results ascribing certain eigenfrequencies to distinct collective lattice modes. We document that THz spectra can be used to fine-tune the parameters of model calculations and as fingerprint properties of certain amino acids. In addition, we analyzed the low-temperature heat capacity of both the compounds and detected strong excess contributions compared to the canonical Debye behavior of crystalline solids, indicating soft excitations and a strongly enhanced phonon-density of states at low frequencies. [ABSTRACT FROM AUTHOR]

Numerical methods for analyzing diffusion phenomena involving strong discontinuities and complicated interfaces are of great scientific and technical importance. In this paper, we extend the existing step-balanced random walk, which overcomes the problem of detailed balance of a random walker in three-dimensional (3D), diffusion-tensor discontinuous systems, to particle density (ρ) discontinuous systems, and introduce volumetric heat capacity C and temperature T by considering ρ as heat density, i.e., ρ = C T , to apply it to thermal problems. Two types of thermophysical simulations are demonstrated: one is steady-state heat flow due to a temperature difference at the end surfaces on a two-phase slab model unit cell with periodic boundary conditions; the other is the time variation of temperature distribution due to heat diffusion from a point heat source in a repeated two-phase slab model with no periodic boundary conditions. We see the correct behavior of heat and temperature expected in 3D discontinuous systems composed of two phases with anisotropic thermal conductivity. The applicability to problems other than pure diffusion and the limitations of the method are also discussed. [ABSTRACT FROM AUTHOR]

Magnetocaloric properties of hexagonally structured Mn 5 − x Fe x Ge 3 (x = 0.15 , 0.3, and 0.5) alloys have been investigated using DC magnetization and heat capacity measurements. The maxima of entropy change, − Δ S m max ∼ 5.04 (5.57) J/kg K, along with an adiabatic temperature change of Δ T a d max ∼ 5.05 (7.25) K was observed for x = 0.15 (0.5) at an applied magnetic field H = 5 T. With the scaling analysis of − Δ S m , the rescaled curves collapse onto a single universal curve anticipated by the mean-field theory, revealing a second-order type of magnetic transition. Furthermore, − Δ S m max follows a power law of H n with n = 0.597 (3) , 0.591(3), and 0.586(3) for Mn 5 − x Fe x Ge 3 (x = 0.15 , 0.3, and 0.5) alloys, respectively. The refrigerant capacity (RC) is increased from 400 J/kg (for x = 0.15) to 420 J/kg (for x = 0.5) with Fe doping in Mn 5 Ge 3. Moreover, the coefficient of refrigerant performance (CRP) enhances with Fe doping from 0.06 (for x = 0.15) to 0.1 (for x = 0.5). Thus, high RC and reasonable CRP values for earth-abundant Mn-based Mn–Fe–Ge alloys promise the potential to replace the high-cost rare-earth (Gd) and heavy metal-based metallic magnetocaloric systems for use in environment-friendly magnetic refrigeration technology. [ABSTRACT FROM AUTHOR]

The exponential-6 (exp-6) potential is commonly used to model fluids at high densities. In this paper, I propose a new equation of state (EOS) in the form of an analytical expression for the excess Helmholtz free energy of an exp-6 fluid. The EOS is based on extensive Monte Carlo simulations and therefore combines the excellent accuracy of the simulations with the numerical efficiency of a polynomial expression. The mean relative error in compressibility factor and internal energy is 0.14% and 0.25% respectively, which is a significant improvement over statistical mechanical theories. The EOS was implemented into a thermochemical code in order to optimize gas parameters and evaluate its performance on pure gas data, shock compression and detonation properties. Predicted gas densities, heat capacities and speed of sound for pure gases were generally within experimental uncertainties at pressures up to 1 GPa and temperatures above 300 K. For polar molecules, a simple free energy correction was introduced which greatly improved accuracy at low temperature. Calculated shock Hugoniots showed excellent agreement with experimental values up to 150 GPa and 10 000 K, and the detonation performance was accurately predicted for a number of different types of explosives. [ABSTRACT FROM AUTHOR]

Contrary to the case of solids and gases, where Debye theory and kinetic theory offer a good description for most of the physical properties, a complete theoretical understanding of the vibrational and thermodynamic properties of liquids is still missing. Liquids exhibit a vibrational density of states (VDOS) which does not obey Debye law, and a heat capacity which decreases monotonically with temperature, rather than growing as in solids. Despite many attempts, a simple, complete and widely accepted theoretical framework able to formally derive the aforementioned properties has not been found yet. Here, we revisit one of the theoretical proposals, and in particular we re-analyze the properties of liquids within the soft-potential model, originally formulated for glasses. We confirm that, at least at a qualitative level, many characteristic properties of liquids can be rationalized within this model. We discuss the validity of several phenomenological expressions proposed in the literature for the density of unstable modes, and in particular for its temperature and frequency dependence. We discuss the role of negative curvature regions and unstable modes as fundamental ingredients to have a linear in frequency VDOS. Finally, we compute the heat capacity within the soft potential model for liquids and we show that it decreases with temperature, in agreement with experimental and simulation data. [ABSTRACT FROM AUTHOR]

In this paper, we apply a theoretical model for fluid state thermodynamics to investigate simulated water in supercooled conditions. This model, which we recently proposed and applied to sub- and super-critical fluid water [Zanetti-Polzi et al., J. Chem. Phys. 156(4), 44506 (2022)], is based on a combination of the moment-generating functions of the enthalpy and volume fluctuations as provided by two gamma distributions and provides the free energy of the system as well as other relevant thermodynamic quantities. The application we make here provides a thermodynamic description of supercooled water fully consistent with that expected by crossing the liquid–liquid Widom line, indicating the presence of two distinct liquid states. In particular, the present model accurately reproduces the Widom line temperatures estimated with other two-state models and well describes the heat capacity anomalies. Differently from previous models, according to our description, a cluster of molecules that extends beyond the first hydration shell is necessary to discriminate between the statistical fluctuation regimes typical of the two liquid states. [ABSTRACT FROM AUTHOR]

We report on efforts to improve the speed of low-G far-infrared transition-edged-sensed bolometers. We use a fabrication process that does not require any dry etch steps to reduce heat capacity on the suspended device and measure a reduction in the detector time constant. However, we also measure an increase in the temperature-normalized thermal conductance (G) and a corresponding increase in the noise-equivalent power (NEP). We employ a new near-IR photon-noise technique using a near-IR laser to calibrate the frequency-domain multiplexed AC system and compare the results to a well-understood DC circuit. We measure an NEP white noise level of 0.8 aW/rtHz with a 1/f knee below 0.1 Hz and a time constant of 3.2 ms. [ABSTRACT FROM AUTHOR]

Monocarboaluminate is the major phase in calcium aluminate cements and is the main AFm phase in modern cement that incorporates limestone additions, including limestone calcined clay cement. This study reports thermal, elastic, and transport properties of monocarboaluminate obtained from molecular simulations. Properties and structural features are computed as a function of the relative humidity (RH) and water content. Full elastic, thermal expansion and thermal conductivity tensors are provided. Quantum‐corrected estimates are provided for the heat capacity and thermal conductivity. Self‐diffusion of interlayer species is also quantified, accounting for the subdiffusive regime. This work contributes to completing property data for critical phases in cement systems. [ABSTRACT FROM AUTHOR]

In this study, corundum-magnesium aluminate spinel (C-MAS) composite heat storage ceramics were synthesized by co-adding MgO and TiO 2 to Al 2 O 3. The effects of TiO 2 and the Al 2 O 3 /MgO ratio on the heat storage performance were evaluated. The findings reveal that Ti4+ integrates into the corundum and MAS lattice, leading to lattice distortion and facilitating solid-phase reaction and MAS generation. Optimal performance is observed at an Al 2 O 3 /MgO ratio of 95:5, with dense structure, minimal pores, and uniform grain size, exhibiting exceptional thermal shock resistance. They withstand 30 thermal shocks (RT-1100 °C) with a 7.12 % increase in bending strength. Moreover, the addition of MgO and TiO 2 significantly enhances the specific heat capacity, characterized by an average specific heat capacity of 1.06 J·g−1·°C−1 and a heat storage density of 1443.83 kJ·kg−1 (RT-1100 °C). TiO₂ introduces additional point defects or alters existing ones in the Al₂O₃ matrix, increasing heat capacity through defect thermal motion. The formation of MAS leads to higher specific heat capacity, due to the greater degrees of freedom and complex lattice vibrations of the spinel structure. These properties position C-MAS composite ceramics as promising candidates for the heat storage materials of the new generation of solar thermal power generation. [ABSTRACT FROM AUTHOR]

This paper aims to compare the thermal performances of the conical solar collector (CSC) system and the spot Fresnel lens system (SFL) using water and CuO nanofluid as the working fluids. The studied CFD models for both systems were validated using experimental data. At an optimal flow rate of 6 L/min, the SFL system showed higher optical and thermal performance in comparison with that of the CSC system. In the case of the SFL system, the availability of a greater amount of solar energy per unit collector area caused an increase in thermal energy. Moreover, in the case of the CSC system, the non-uniform distribution of solar flux on the absorber's outer surface leads to an increase in temperature gradient and heat losses. As a heating medium, the CuO nanofluid outperformed the water in terms of higher thermal conductivity and heat capacity. The average thermal efficiencies of 64.7% and 61.2% were achieved using SFL with and without CuO nanofluid, respectively, which were 2.4% and 0.5% higher than those of the CSC with and without nanofluid. CFD simulations show a 2.80% deviation for SFL and 2.92% for CSC, indicating acceptable accuracy compared to experimental data. [ABSTRACT FROM AUTHOR]

Ba0.75Ca0.25TiO3 ceramics were successfully synthesized by a simple solid-state reaction method. This study examined the influence of sintering temperature on the structure, microstructure, dielectric properties and electrical behavior of the material. The XRD analysis reveals that the tetragonal phase (P4mm) is dominant in all the synthesized materials, with those sintered at T = 1400 °C and T = 1450 °C being single-phase, while others exhibit a minor orthorhombic phase (Pbnm). Higher sintering temperatures promoted better grain boundary formation and larger grain sizes. The electric permittivity increased with temperature up to T = 1400 °C, followed by a sharp decline at T = 1450 °C. Additionally, the Curie temperature decreased with increasing sintering temperature, indicating changes in phase transition characteristics. Thermal analysis showed that higher sintering temperatures led to sharper heat capacity peaks, while pyroelectric and thermally stimulated depolarization currents were maximized at T = 1400 °C due to oxygen vacancies. These findings highlight the significant impact of sintering temperature on the material's structural and functional properties. [ABSTRACT FROM AUTHOR]

Thermal runaway is a frequent source of process safety issues, and the uncontrolled release of chemical energy puts reactors at risk. The design of the exothermic reactor faces challenges due to the selective sensitivity of the product to high temperatures and the need to increase the lifetime of the catalyst, optimize the product distribution, and improve the thermodynamic properties. Phase change material (PCM) encapsulation is recommended to reduce leakage, phase separation, and volume change problems. This work introduces encapsulated PCMs to improve reactor temperature control and minimize thermal runaway in exothermic processes. The warning temperature value setting effectively inhibits fugitive exothermic reactions and enhances heat transfer. When a sufficient quantity of encapsulated PCMs is input, the response speed will automatically accelerate. Spontaneous acceleration of the reaction rate due to thermal runaway of the reaction may be completely avoided by adding a sufficient amount of encapsulated PCM. Microencapsulation is used to control volume changes and inhibit thermal reactions. Preventive strategies include cooling, depressurization, safety release, emergency resources, and reaction containment. Encapsulated PCMs improve mechanical and thermal properties, surface-to-volume ratio, heat transfer surface, thermal capacity, and efficiency. [ABSTRACT FROM AUTHOR]

Numerical investigations were conducted to analyze the heat transfer characteristics in a single square minichannel with supercritical C10H22 (sC10H22) and supercritical CO2 (sCO2). A single symmetric minichannel with a square cross-section of 1 mm × 1 mm and a length of 400 mm was selected, the top surface of which is applied with a uniform heat flux from 100 to 300 kW/m2. The inlet temperatures are varied from 20 to 150 °C and the inlet mass fluxes are ranged from 300 to 500 kg/(m2·s) in the physical model. The flow and heat transfer processes of the fluids were simulated in COMOSOL Multiphysics® software with RANS k-ω low-Reynolds number turbulence model. Results show that the heat removal capacity of sCO2 at 8 MPa is superior, which is 8 times that of sC10H22 at 3 MPa at the inlet temperature of 20 °C. When the inlet temperature and heat flux increase, the heat transfer performance of sCO2 drops sharply, while the overall performance of sC10H22 rises steadily. It suggests that sCO2 is more suitable for the heat transfer process with high-efficient cooling system at a lower inlet temperature, while sC10H22 is capable of a stable and long-time heat transfer process at a higher inlet temperature. [ABSTRACT FROM AUTHOR]

We explored the use of the front photopyroelectric (FPPE) configuration and the reference sample method to determine the thermal properties of liquid samples such as extra virgin olive oil and aqueous glycerol (GL), ethylene glycol (EG), and sodium chloride (NaCl) solutions. The thermal diffusivity (α) and thermal conductivity (k) were determined from photopyroelectric phase and amplitude signals, respectively, using water as a reference. The thermal effusivity (e) and volumetric heat capacity (ρc) were also determined based upon both obtained thermal properties. All thermal properties of GL and EG in aqueous solutions decrease as their volume fraction increases at an average rate of 5% for concentrations higher than 20% and between 23% and 10% for concentrations less than 20%. The Matvienko and Mandelis' model for α and our proposed expression for ρc described this trend with a reliable approximation to the experimental data with R2 about 0.97 and 0.99, respectively. Moreover, the frequency of a specific angle is proportional to α as established by the theory for the phase signal for thermally thick samples. In the case of aqueous NaCl solutions, the α and k values were slightly below 4.6% and 3% from water values reported at room temperature. The proposed method allows the simultaneous determination of α and k by using only the FPPE configuration with test and reference liquid samples, reducing time and uncertainties from the use of more than one experimental setup, and providing the complete thermal characterization. [ABSTRACT FROM AUTHOR]

Recent studies suggest the observed seasonal delay of rainfall over the Sahel is mainly driven by anthropogenic aerosol forcing, which features a robust east–west contrasting changes in recent decades, with negative and positive top-of-the-atmosphere shortwave radiative forcing in South and East Asia (SA&EA) and in North America and Europe (NA&EU), respectively. Their individual effects on the Sahel rainfall annual cycle remain unclear. Here, by designing idealized sensitivity experiments based on Community Earth System Model (CESM1.2), we show that both negative radiative forcing over SA&EA and positive radiative forcing over NA&EU contribute to the delayed phase and enhanced amplitude of Sahel rainfall annual cycle. To understand the underlying physical processes, both the convective quasi-equilibrium (CQE) and atmospheric energetic frameworks are utilized. Both frameworks can well explain the seasonal delay in the rainfall annual cycle over the Sahel under the regional radiative forcings, with the CQE framework showing stronger explanatory power. Based on the insights from both frameworks, we conducted a moisture budget analysis and found that the negative radiative forcing over SA&EA causes an anomalous low-level anticyclonic circulation, which transports more moisture to the Sahel. As the anomalous anticyclone is stronger in summer and fall compared to spring, rainfall is delayed in the Sahel. Under the influence of the positive radiative forcing over NA&EU, more warming in the northern hemisphere causes northward transport of moisture to the northern tropics associated with the cross-equatorial transport of energy. The moisture transport increases relative humidity over the Sahel and enhances the effective atmospheric heat capacity that delays the seasonal rainfall. [ABSTRACT FROM AUTHOR]

The design integration of absorption and adsorption cooling systems is a recently emerging research field in which the inherent advantages of both these systems are intended to be combined so as to maximize system performance. However, a vast majority of the conventional integration approaches reported in the literature still suffer from the following drawbacks: (a) the inability to provide a continuous cooling effect of the integrated design during the switching period of the adsorption component, (b) the lack of incorporation of the mass/heat recovery cycles and its subsequent effects upon the integrated performance, and (c) the lack of functional dependence of all thermodynamic variables including heat capacities and adsorption enthalpy upon operational parameters such as temperature and pressure. This study presents the first attempt of a numerically validated performance prediction of such an integrated system with parallel functionality to facilitate a continuous cooling operation. An empirical model of mass recovery cycle has been formulated for the very first time which adequately describes the sorption dynamics during mass transfer. All thermodynamic variables have been expressed as functions of operational parameters during the cooling cycle. For a mean driving temperature predicted to be as low as 38 °C and a mean cycle time of 11.82 min, the proposed integrated design has been predicted to yield a cycle-averaged specific cooling power of 48.93 W kg−1 and a minimum achievable coefficient of performance of 0.74 compared to the corresponding values of 27.64 W kg−1 and 0.57 for the benchmark stand-alone silica gel/water adsorption chiller. [ABSTRACT FROM AUTHOR]

In the present investigation, we report the theoretical analysis of mithramycin A (MTA) and mithramycin SK (MSK) binding to salmon testes DNA utilizing a modified Zimm and Bragg theory to explain the melting behavior and heat capacity of the DNA before and after drug binding. The sensitivity parameter and half width were employed in tandem to analyze the melting transition's sharpness. According to the results, a number of metrics, including transition profile, sharpness of transition, heat capacity curve, and half widths, were in good agreement with the experimental observations. The development of novel medications would be made easier by having a better understanding of the molecular interactions between pharmaceuticals and DNA. This theoretical investigation brings us a step closer to the objective of comprehending the stability of nucleic acid interactions with medications and has potential applications in the biomedical industry. [ABSTRACT FROM AUTHOR]

• A comprehensive evaluation index for the internal heat exchanger is provided. • The failure boundary of the heat recovery effectiveness coupling optimization is specified. • Predictive correlations for optimal heat recovery effectiveness and optimal discharge pressure are given. • An optimal internal heat exchanger selection method is proposed. In the background of energy shortage and climate change, transcritical CO 2 heat pump(HTP) technology has attracted lots of attention because of its energy-saving and environmentally friendly advantages. In this research, an experimentally verified simulation model of transcritical CO 2 HTP is established to investigate multi-factor coupling optimization of heat recovery effectiveness(η IHX). First, the coupling optimization mechanism of η IHX and discharge pressure(p dis) is analyzed. Moreover, this research explores the influence of η IHX on heating capacity, power consumption, discharge temperature(t dis), and internal heat exchanger(IHX) cost, and further proposes a comprehensive heat recovery index to optimize the above factors. Based on this index the optimal heat recovery effectiveness(η IHX,opt) for each operating condition is obtained. Also, a failure boundary for the coupling optimization of the η IHX is also indicated. In addition, the optimal discharge pressure(p dis,opt) prediction correlation for different η IHX s is proposed, which can be used for heat recovery effectiveness collaborative optimization control. Finally, a general method for evaluating IHX is provided. Taking Xi'an as an example, the optimal heat recovery area(A IHX,opt) of this HTP system is 0.42m2, with which the optimized HTP system operates safely at extreme operating conditions, resulting in an annual lucre of 1,211 CNY. [ABSTRACT FROM AUTHOR]

As is well known, Paul Drude put forward the very first quantitative theory of electrical conduction in metals in 1900. He could successfully account for the Wiedemann–Franz law which states that the ratio of thermal to electrical conductivity divided by temperature is a constant called the Lorenz number. As it turns out, in Drude's derivation there is a lucky cancellation of two errors. Drude's underestimatation (by an order of 100) of the value of square of the average electron velocity compensated for his overestimatation of the electronic heat capacity (by the same order of 100). This compensation or cancellation of two errors lead to a value of the Lorenz number very close to its experimental value; which is well known. There is another error of a factor of two which Drude made when he calculated two different relaxation times for heat conductivity and electrical conductivity; in this article we highlight how and why this error occurred in Drude's derivation and how it was removed 5 years later (in 1905) by Hendrik Lorentz when he used the Boltzmann equation and a single relaxation time. This article is of pedagogical value and may be useful to undergraduate/graduate students learning solid state physics. [ABSTRACT FROM AUTHOR]

We characterized the mechanical and thermophysical properties of the compressed earth bricks (CEB) incorporating cotton waste ash. The obtained values of compressive strength are acceptable, as they are well above the limits set by the standards for CEB in Cameroon. Regarding the thermophysical properties, the measured heat capacity decreases by 17% compared to cement stabilization, which is an improvement in the material's ability to store heat. Thermal conductivity is reduced by 28% compared to the cement formulation. Therefore, the incorporated material improves the natural thermal comfort of buildings. Water absorption tests have shown that these materials absorb less water. [ABSTRACT FROM AUTHOR]

Nanofibers act as carriers in systems containing functional materials produced via electrospinning method. By this way, it is possible to transport functional materials with polymer nanofibers, besides having a large surface area compared to their volume, the encapsulation process, which includes complex preparation processes, is eliminated here, and functional materials such as phase‐change materials (PCMs) can be conveniently integrated directly into the carrier material by electrospinning method. The resulting nanofiber membrane can also be used in combination with textile fabrics. This study aims to develop PCM containing nanofibrous membrane coated knitted fabric structures with heat regulation capabilities. Two types of PCMs, hexadecane and octadecane loaded into thermoplastic polyurethane (TPU) and cellulose acetate (CA) nanofibers, directly electrospun on cotton (CO), cotton/polyester (CO/PES), cotton/acrylic (CO/PAC) knitted fabrics for thermoregulation. These nanofiber‐coated fabrics were characterized by scanning electron microscopy (SEM) and differential scanning colorimetry (DSC), and their comfort properties were evaluated by water vapor and air permeability tests and compared with a commercial microcapsule impregnated fabric. According to DSC results, PCM incorporated CA nanofibers had better heat storage capacity than TPU nanofibers and microcapsule applied fabrics. Although PCM‐loaded CA nanofibers may not block airflow as effectively as TPU nanofibers, when a proper coating is achieved air permeability can be decreased to 21.70 L/m2/s, along with a heat storage capacity of 26.38 J/g and still having permeability to water vapor (%40). Highlights: Phase change materials were integrated directly to the carrier material by electrospinningPCM integrated nanofiber coating reduced air permeabilityPCM integrated nanofiber coating did not block water vapor permeabilityElectrspun cellulose acetate +PCM coating had better heat storage capacity [ABSTRACT FROM AUTHOR]

This work describes a meta-analysis performed in an effort to better understand the parameters controlling flame stability in shock-tube flame experiments. The data set used in the analysis was aggregated from multiple prior studies employing the shock-tube flame speed method, as well as previously unreported results. Flames are first qualitatively classified as being smooth, distorted, or wrinkled based on end-wall images. A subset of trials capturing the stability transition from stable to unstable flames are then selected from each set of experiments. Across all data sets, the transition between stable and unstable flames is analyzed as a binary classification problem using logistic regression. The resulting classification model, cast in terms of a multivariate power-law expression for the critical temperature ($${T_{{\rm{crit}}}}$$ T crit ) at which flames become unstable, is found to be highly predictive of the stability transition. Consideration of the trained model coefficients allows the effects of different experimental parameters on $${T_{{\rm{crit}}}}$$ T crit to be identified. Model parameters provide significant new insight into the selection of diluents in experiments; the use of a test gas with a high heat capacity ratio is found to have the most beneficial effect toward increasing $${T_{{\rm{crit}}}}$$ T crit , while the effects of Lewis number and molecular weight are determined to be negligible. Ignition-location and pressure effects are less well quantified due to limited available data and are identified as key areas of further study. [ABSTRACT FROM AUTHOR]

In the present study, the isobaric heat capacity of ultralight magnesium-lithium alloys with composition of 21, 25 and 30 at. pct Li were measured in the temperature range 185–775 K, most measurements were made for the first time. Measurements were performed by the method of differential scanning calorimetry using a DSC 404 F1 setup. The estimated uncertainty of the obtained results was 2–3 pct. The temperature dependences and the tables of recommended data on their basis were developed for scientific and practical application. For all studied Mg-Li alloys an abrupt change in the heat capacity was observed at the temperatures of about 220–260 K, which is apparently caused by the martensitic phase transformation. It was found that the specific molar heat capacity values of Mg-Li alloys containing 21–30 at. pct Li in the temperature interval of 250–685 K practically coincide with each other and can be estimated within the limits of DSC measurement uncertainties using the heat capacity temperature dependence of solid magnesium. It is possible to estimate the heat capacity of the studied alloys (with an accuracy not exceeding the measurement uncertainty) using the Neumann-Kopp rule, but in a much narrower temperature range of 250–456 K. [ABSTRACT FROM AUTHOR]

Introduction: ER aminopeptidase 1 (ERAP1) is a polymorphic intracellular aminopeptidase with key roles in antigen presentation and adaptive immune responses. ERAP1 allotype 10 is highly protective toward developing some forms of autoimmunity and displays unusual functional properties, including very low activity versus some substrates. Methods: To understand the molecular mechanisms that underlie the biology of allotype 10, we studied its enzymatic and biophysical properties focusing on its unique polymorphisms V349M and Q725R. Results: Compared to ancestral allotype 1, allotype 10 is much less effective in trimming small substrates but presents allosteric kinetics that ameliorate activity differences at high substrate concentrations. Furthermore, it is inhibited by a transition-state analogue via a non-competitive mechanism and is much less responsive to an allosteric small-molecule modulator. It also presents opposite enthalpy, entropy, and heat capacity of activation compared to allotype 1, and its catalytic rate is highly dependent on viscosity. Polymorphisms V349M and Q725R significantly contribute to the lower enzymatic activity of allotype 10 for small substrates, especially at high substrate concentrations, influence the cooperation between the regulatory and active sites, and regulate viscosity dependence, likely by limiting product release. Conclusions: Overall, our results suggest that allotype 10 is not just an inactive variant of ERAP1 but rather carries distinct enzymatic properties that largely stem from changes at positions 349 and 725. These changes affect kinetic and thermodynamic parameters that likely control rate-limiting steps in the catalytic cycle, resulting in an enzyme optimized for sparing small substrates and contributing to the homeostasis of antigenic epitopes in the ER. [ABSTRACT FROM AUTHOR]

The isobaric heat capacity of pyrochlore gadolinium titanate Gd2Ti2O7 is measured in the 2–1825 K range of temperatures. Thermodynamic functions (entropy, enthalpy change, reduced Gibbs energy) are calculated using consistent smoothed values of heat capacity. The Gibbs energy of the formation of Gd2Ti2O7 from oxides in the high temperature range is estimated. [ABSTRACT FROM AUTHOR]

With the upgrade of aircraft and the increasingly harsh service environment, it is urgent to develop high-performance thermal structural materials. In this study, inspired by foliar and root water uptake of trees, we propose a one-step facile method to achieve an autonomous gradient in C/C–ZrC–SiC sharp leading edge composites. The gradual increase of SiC content from top to bottom is beneficial to improve the heat transfer capacity of the composites. After oxyacetylene ablation for 60 s, the mass and linear ablation rates of the samples with gradient structure are 0.83 mg/s and 0.5 μm/s, 35 % and 83 % lower than conventional samples. The composites with gradient structure of ZrC and SiC are favorable to the formation of a compact and smooth ZrO 2 oxide protective layer, which not only protects the composites from further penetration of O 2 , but also resists the mechanical denudation. The novel gradient structure composites with enhanced ablation resistance show a bright application prospect in next-generation thermal protection systems. [ABSTRACT FROM AUTHOR]

Understanding enzyme catalysis as connected to protein motions is a major challenge. Here, based on temperature kinetic studies combined with isotope effect measurements, we obtain energetic description of C-H activation in NAD-dependent UDP-glucuronic acid C4 epimerase. Approach from the ensemble-averaged ground state (GS) to the transition state-like reactive conformation (TSRC) involves, alongside uptake of heat ( Δ H ‡ = 54 kJ mol−1), significant loss in entropy (− T Δ S ‡ = 20 kJ mol−1; 298 K) and negative activation heat capacity ( Δ C p ‡ = −0.64 kJ mol−1 K−1). Thermodynamic changes suggest the requirement for restricting configurational freedom at the GS to populate the TSRC. Enzyme variants affecting the electrostatic GS preorganization reveal active-site interactions important for precise TSRC sampling and H-transfer. Collectively, our study captures thermodynamic effects associated with TSRC sampling and establishes rigid positioning for C-H activation in an enzyme active site that requires conformational flexibility in fulfillment of its natural epimerase function. Enzymes involve structural flexibility in their function, but understanding enzyme catalysis as connected to protein motions is a major challenge. Here, the authors obtain energetic description of C-H activation in nicotinamide coenzyme-dependent UDP-glucuronic acid C4 epimerase based on temperature kinetic studies and isotope effect measurements. [ABSTRACT FROM AUTHOR]

This study examines a linear relationship between the frequency shifts, $\lpar {1/w} \rpar \lpar {\partial w/\partial T} \rpar _p$(1/w)(∂w/∂T)p, and the variation of the dielectric constant, $\lpar {1/\epsilon } \rpar \lpar {\partial \epsilon /\partial T} \rpar _p$(1/ϵ)(∂ϵ/∂T)p, close to phase transitions in ferroelectric crystalline systems, in particular, ferroelectric NaNO2 as studied here. Both quantities (frequency and dielectric constant) are described by the power-law formulae below the Curie temperature Tc (ferroelectric phase), Tc < T < Ti (incommensurate phase) and T > Ti (paraelectric phase). The divergence behaviour of the mode Grüneisen parameter (ɣp) is obtained, whose temperature dependence can also be described by a power-law formula in NaNO2. It is also shown that the heat capacity Cp can be evaluated from the thermal expansion (αp) by means of the same critical exponent since they exhibit similar critical behaviour near Tc and Ti in this crystal. [ABSTRACT FROM AUTHOR]

The article discusses the technology of combined production of electrical and thermal energy using preliminary air conversion of the pyrolysis liquid of automobile tires into synthesis gas, with its subsequent supply to the battery of an electrochemical generator. The electrical power of the installation is 100 kW, the network heater is 126 kW. The main energy characteristics of the installation were determined using the methods of physicochemical modeling and compilation of energy balances. It has been shown that the specific consumption of pyrolysis liquid for the production of electrical energy is 108 g/kW∙h (169 g r.f./(kW∙h)), and the heat consumption is 30 kg/GJ (196 kg r.f./Gcal). The specific consumption of natural and conventional fuels is compared with the specific fuel consumption at power plants operating on hydrocarbon natural fuels. They are slightly inferior to them, with the exception of the specific electricity generation from external heat consumption. Fuel utilization rate 46.4%. Recommendations are given for the use of pyrolysis liquid to generate electrical and thermal energy using a high-temperature fuel cell based on SOFC. [ABSTRACT FROM AUTHOR]

This study investigates the implementation of a cryogenic chiller utilizing a mixed-refrigerant cascade refrigeration cycle (MRCRC). In this setup, R-404A is employed in the high-temperature circuit (HTC), while a mixture of refrigerants is utilized in the low-temperature circuit (LTC). Unlike a conventional MRCRC that operates without a receiver to maintain the composition ratio, this research explores the impact of receiver installation on system performance. Experiments were conducted with and without a receiver to assess performance improvements and device behavior. With a fixed refrigerant charge of 4 kg, the suction and discharge pressures of the LTC compressor remained low and stable after the receiver's installation. The addition of a receiver significantly reduced the cooling time, with further reductions observed as the refrigerant charge increased. The system achieved evaporative heat capacities of 0.59, 1.76, and 2 kW for refrigerant charges of 4, 7, and 9 kg, respectively. Notably, at the maximum refrigerant charge of 11 kg, the evaporative heat capacity peaked at 3.3 kW. These findings indicate that incorporating a receiver is crucial for enhancing the cooling performance of cryogenic coolers using mixed refrigerants and stabilizing device operation. This contrasts with previous studies that omitted receivers due to concerns over potential alterations in the composition ratio of the mixed refrigerant. [ABSTRACT FROM AUTHOR]

In large-format pouch cells for electric vehicles, the issues of elevated and non-uniform temperatures resulting from heat generation are intensified, necessitating the use of liquid cooling systems. The design factors of the liquid cooling system influence the maximum temperature and temperature differences in the module as well as the pumping power of the cooling system. Although it is known that these design factors interact, research on these interactions and their effects is currently lacking. In this study, the individual as well as interaction effects of design factors on the performance of the liquid cooling system for a large-format pouch cell module were investigated using design of experiment and analyzed through statistical methods. Electrochemical–thermal fluid coupled analysis was used to calculate the performance according to the design factors of the liquid cooling system. The wall and channel widths are factors that directly determine the coolant flow velocity and cooling plate heat capacity, and they exhibited major effects on all three responses. Moreover, the influence of each design factor tended to change in response to variations in the other design factors. Thus, the effects of each factor individually and of interactions between factors were quantitatively compared and evaluated for significance. The width of the walls was found to contribute the most to the maximum temperature (36.00%) and pumping power (57.56%), while the width of the channels contributed the most to the temperature difference (38.24%), indicating that they are the main influencing factors. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) have emerged as an intriguing option for the storage of thermal energy because of their remarkable capacity to store latent heat. However, the practical application of these materials is hindered by their low thermal conductivity and limited photo-absorbance. For this investigation, graphene nanoplatelets (GNP) and multiwall carbon nanotubes (MWCNT) hybrid nanoparticles were disseminated in RT-54HC organic PCMs at different weight fractions. The nanoparticles were incorporated into the base PCMs using a melt blending technique. Based on the findings, one combination of GNP to MWCNT in a 0.25:0.75 ratio has shown the highest thermal conductivity, with an increase of 40% (0.28 Wm−1 K−1) compared to other hybrid combinations. This breakthrough could potentially open new avenues in the field of thermal energy storage. The chemical stability of the hybrid nanoparticle dispersed composites was assessed through FTIR analysis. In addition, the composites exhibited excellent thermal stability, maintaining their structural integrity even at temperatures as high as 300 ℃. The melting temperature of the composites also showed minimal variation. Based on the evaluation of latent heat enthalpy, the organic PCM known as base RT-54HC demonstrated a heat storage capacity of 230 J/g. However, the composites exhibited a slight decrease in latent heat with increasing nanoparticle weight fraction. In addition, the composite with added hybrid nanoparticles demonstrated an increase in optical absorbance, accompanied by a decrease in transmissibility. Therefore, the hybrid nano-enhanced composites have demonstrated enhanced thermo-physical properties, making them not only suitable but also highly promising for use in applications with mid-range melting temperatures. [ABSTRACT FROM AUTHOR]

In this study, ultrafine linear nanostructured SiC with high wettability and large specific surface area were synthesized via the carbothermal reduction method. These nanowires were impregnated with Na2SO4 ⋅ 10H2O, CaCl2 ⋅ 6H2O, MgCl2 ⋅ 6H2O, and CaMg2Cl6 ⋅ 12H2O to obtain composite phase change materials (CPCMs), which demonstrated improved phase separation and significantly reduced supercooling. In particular, the supercooling degree of CaCl2 ⋅ 6H2O was minimized to 0.1 °C. The SiC nanowires effectively prevented issues of dehydration and deliquescence in hydrated salts. The thermal storage capacities of the CPCMs exceeded 90 %, with Na2SO4 ⋅ 10H2O and MgCl2 ⋅ 6H2O reaching 107.10 % and 103.35 %, respectively. Furthermore, the CPCMs exhibited greater sensitivity to changes in temperature compared with the pure hydrated salt phase change materials (PCMs). These results indicate that ultra‐fine SiC nanowires can act as a versatile carrier for hydrated salt PCMs at low and intermediate temperatures. [ABSTRACT FROM AUTHOR]

Pyroxenes (AMX2O6) consisting of infinite one-dimensional edge-sharing MO6 chains and bridging XO4 tetrahedra are fertile ground for finding quantum materials. Thus, here, we have studied calcium cobalt germanate (CaCo-Ge2O6) and calcium cobalt silicate (CaCoSi2O6) crystals in depth. Heat capacity data show that the spins in both compounds are dominantly Ising-like, even after being manipulated by high magnetic fields. On cooling below the Néel temperatures, a sharp field-induced transition in magnetization is observed for CaCoGe2O6, while multiple magnetization plateaus beneath the full saturation moment are spotted for CaCoSi2O6. Our analysis shows that these contrasting behaviors potentially arise from the different electron configurations of germanium and silicon, in which the 3d orbitals are filled in the former but empty in the latter, enabling electron hopping. Thus, silicate tetrahedra can aid the interchain superexchange pathway between cobalt(II) ion centers, while germanate ones tend to block it during magnetization. [ABSTRACT FROM AUTHOR]

The Suspended Thermoreflectance (STR) technique is described in this paper. This optoelectronic measurement tool performs thermal characterization of freestanding micro-/nanoscale materials. STR performs thermal mapping at the submicron level and produces unconstrained thermal conductivity unlike other optical measurement techniques where independent conductivity measurement is not possible due to their reliance on heat capacity. STR works by changing the temperature of a material and collecting the associated change in light reflection from multiple points on the sample surface. Reflection is a function of the material being tested, the wavelength of the probe light, geometry, and the composition of the specimen for transparent and quasi-transparent materials. In this article, Si μ-cantilevers are studied. In addition, a thermal analytical model is developed and incorporated with optical equations to characterize the conductivity of the Si μ-cantilevers. The analytical model is compared with a finite element model to check its applicability in the STR experiment and data analysis. To validate the technique, the thermal conductivity of 2 and 3 µm thick Si μ-cantilevers was determined using STR at a temperature range of 20–350 K and compared to simulations using the equation of phonon radiative transfer and literature values. [ABSTRACT FROM AUTHOR]

Melting and solidification of a phase change material (PCM) is investigated experimentally by applying a partial filling strategy to the hybrid enhancement of heat pipe–metal foam (HP‐MF) in a vertical cylinder. HP‐MF enhancement can improve the heat transfer capacity of the PCM system as it combines HP's efficient heat transfer capacity with MF's highly effective thermal conductivity capability. The experimental results demonstrate that the partial filling strategy in the melting and solidification of HP‐MF PCM can be optimized for effective MF utilization in the HP‐MF PCM system. A filling ratio of 83% of MF in HP‐MF PCM shows almost identical total melting and solidification along with a temperature distribution to that of an HP‐MF PCM (95% porosity, 20 pore density [PPI]). It is plausible to conclude that the removal of 33% or less mass had no significant effect on the overall melting process of HP‐MF PCM. It should be noted that the HP‐MF PCM system's HP heat transfer efficiency significantly decreased during the melting process when the MF filling ratio was 37.5% and 12.5%. [ABSTRACT FROM AUTHOR]

Perovskite materials are promising for thermochemical energy storage due to their ability to undergo redox cycling over a wide temperature range. Although BaCoO3 exhibits excellent air cycling properties, its heat storage capacity in air remains suboptimal. This study introduces Na into the lattice structure to enhance oxygen vacancy formation and mobility. DFT+U simulations of the surface structure of Na-doped BaCoO3−δ indicate that incorporating Na improves surface stability and facilitates the formation of surface oxygen vacancies. NaxBa1−xCoO3−δ compounds were synthesized using a modified sol–gel method, and their properties were investigated. The experimental results demonstrate that Na doping significantly enhances the redox activity of the material. The heat storage capacity increased by above 50%, with the Na0.0625Ba0.9375CoO3−δ solid solution achieving a heat storage density of up to 341.7 kJ/kg. XPS analysis reveals that Na doping increases the concentration of surface defect oxygen, leading to more active oxygen release sites at high temperatures. This enhancement in redox activity aligns with DFT predictions. During high-temperature cycling, the distribution of Na within the material becomes more uniform, and no performance degradation is observed after 300 cycles. Even after 450 cycles, Na0.0625Ba0.9375CoO3−δ retains over 96% of its initial redox activity, significantly outperforming fresh BaCoO3−δ. These findings elucidate the mechanism by which Na doping enhances the thermochemical heat storage performance of BaCoO3−δ and provide new insights for the design of perovskite-based materials. [ABSTRACT FROM AUTHOR]

In this article in memory of academician A.F. Andreev, we consider the results of experiments in superfluid 3 He-B at ultralow temperatures. These experiments directly demonstrate the existence of gapless Majorana quasiparticles, which appear as Andreev bound states at the boundary of superfluid 3 He-B (Silaev and Volovik in JETP 119:1042, 2014). Precision measurements of the heat capacity of superfluid 3 He-B showed that at a temperature of 0.12 mK, Majorana fermions can account for up to 50 % of the heat capacity of 3 He-B in our experimental conditions. [ABSTRACT FROM AUTHOR]

We study the structural, magnetic, and magneto-thermal properties of the GdRhIn compound. The room-temperature X-ray diffraction measurements show a hexagonal crystal structure. Temperature and field dependence of magnetization suggest two magnetic transitions—antiferromagnetic to ferromagnetic at 16 K and ferromagnetic to paramagnetic at 34 K. The heat capacity measurements confirm both the magnetic transitions in GdRhIn. The magnetization data were used to calculate isothermal magnetic entropy change and refrigerant capacity in GdRhIn, which was found to be 10.3 J/Kg-K for the field change of 70 kOe and 282 J/Kg for the field change of 50 kOe, respectively. The large magnetocaloric effect in GdRhIn suggests that the material could be used for magnetic refrigeration at low temperatures. [ABSTRACT FROM AUTHOR]

This research experimentally demonstrates the practicability of using large-sized direct solar frying as an alternative technology for the predominantly biomass-based injera baking method. The system was designed and developed with fryers 40, 50, and 55 cm in diameter and two operational options: continuous mode and alternating mode. Extensive experimental testing was conducted on each prototype to demonstrate solar frying and determine the relative performance. The findings indicate that the 2 kW heating capacity of the 40 cm-sized solar fryer model conducted baking processes at a relatively lower system temperature in both application modes compared to the larger-sized fryers. As a result, this system maintained a consistent average fryer temperature distribution and shorter initial heating time, without the requirement of a reheating process during the subsequent baking cycles. The experimental testing also demonstrated that alternating-mode applications were more practical for the 40 cm-sized fryers than for the larger ones. Overall, direct solar frying is more efficient and convenient for the 40 cm-sized solar fryers. In contrast, the larger-sized systems required a larger fryer thermal storage capacity coupled with larger-size solar concentrators to maintain equivalent stable operational conditions, conversely leading to a lack of application simplicity and higher system costs. [ABSTRACT FROM AUTHOR]

In order to explore the influence of laser power on the evolution of molten pool and convective heat transfer of laser cladding Incoloy 926 on stainless steel surface, a three-dimensional thermal fluid multi-field coupled laser cladding numerical model was established in this paper. The variation of latent heat during solid-liquid phase transformation was treated by apparent heat capacity method. The change in the gas–liquid interface was tracked using the mesh growth method in real time. The instantaneous evolution of temperature field and velocity flow field of laser cladding Incoloy 926 on a stainless steel surface under different laser power was discussed. The solidification characteristic parameters of the cladding layer were calculated based on the temperature-time variation curves at different nodes. The mechanism of the impact of laser power on the microstructure of the cladding layer was revealed. The experiment of laser cladding Incoloy 926 on 316L surface was carried out under different laser power. Combined with the numerical simulation results, the effects of laser power on the geometrical morphology, microstructure and element distribution of the cladding layer were compared and analyzed. The results show that with the increase in laser power, the peak temperature and flow velocity of the molten pool surface both increase significantly. The thermal influence of the molten pool center on the edge is enhanced. The temperature gradient, solidification rate, and cooling rate increased gradually. The microstructure parameters (G/R) are relatively small when the laser power is 1000 W. In the experimental range, the dilution rate and wetting angle of the cladding layer both increase with the increase in laser power. When the laser power is 1000 W, the alloying elements of the cladding layer are more evenly distributed and the microstructure is finer. The experimental results are in good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

This study, based on the analysis of existing experimental data, presents a third generation Calphad description of lithium, covering all temperature ranges, using nonlinear least squares in Matlab. We have expanded the SGTE database's description of lithium phases (face-centered cube, body-centered cube, liquid) down to 0 K with reasonable accuracy, taking into account the significant effort required to reconstruct the database for each element. During the evaluation process, it was determined that the low-temperature phase of lithium is fcc. The heat capacity of crystalline Li was accurately described using the extended Debye model. The third generation Calphad description of lithium utilized the two-state model and the extended Einstein model, leading to improved agreement with experimental data compared to previous assessments. [ABSTRACT FROM AUTHOR]

Typical textbook analyses of heat engines assume that the temperatures of thermal reservoirs do not change; that is, the reservoirs have infinite heat capacity. Several authors have investigated the performance of reversible heat engines for which reservoirs have finite heat capacities and thus the reservoir temperatures do change with time. We find that previous studies have been too restrictive in that they assumed that the reservoir temperature change per cycle is infinitesimal and that the engine ceases operation when the hot reservoir cools to match the temperature of the cold reservoir. We model a Carnot-like engine and show that (1) the problem can be solved exactly with no requirement for infinitesimal temperature changes and (2) there is nothing special about the instant when the temperatures converge, with the device transitioning smoothly from a heat engine to a refrigerator. We find explicit expressions for the limiting reservoir temperature and the total efficiency. Editor's Note: Most textbook thermodynamics problems assume thermal reservoirs of infinite heat capacity and consequently unchanging temperatures. Analyses involving engines operating between finite reservoirs are not unknown, but they typically assume that the temperature change per cycle is infinitesimal and that the engine stops operating when the hot reservoir has come to the temperature of the cold reservoir. This paper considers a Carnot-like engine operating between a finite hot reservoir and an infinite cold one, showing that the problem can be solved exactly with no requirement for infinitesimal changes and also that when the reservoir temperatures converge, the device simply transitions from being a heat engine to a refrigerator. Explicit expressions are developed for the limiting initially-hot reservoir temperature and the total efficiency. Appropriate for upper-level thermodynamics courses. [ABSTRACT FROM AUTHOR]

A large amount of grinding heat is generated during the high-efficiency grinding process, which causes workpiece burnout. Although the utilization of a significant quantity of coolant can lower grinding temperature, it inevitably leads to environmental pollution and damages the health of operators. To reduce coolant usage, it is worth considering reducing the grinding temperature by enhancing the thermal performance of grinding wheels. In this study, a new type of phase change heat storage grinding wheel (PCHS grinding wheel) with a high heat transfer coefficient and large heat capacity is developed utilizing the boiling heat transfer principle and heat storage technology, whose structure and working principle are explained. In addition, a visual device was made to simulate the internal heat transfer and heat storage process of PCHS grinding wheels, and the effects of heat flux, injection amount of working fluid, heat dissipation conditions, and heat capacity on the boiling heat transfer coefficient, start-up time of working fluid entering the boiling heat transfer state, and grinding temperature control are analyzed. Eventually, a comparative experiment of dry grinding 45 steel was carried out. Results show that the boiling heat transfer coefficient of PCHS grinding wheels is in the range of 1000–7000 W/m2·°C, the start-up time is 5–8 s, and increasing the heat capacity of grinding wheels can effectively slow down the heating rate. Besides, the grinding temperature is reduced by 22% compared with the maximum temperature of 375 °C when using traditional grinding wheels, and the heat transfer coefficient is increased by 2–3 times, which shows that improving the thermal performance of grinding wheels has significant advantages in reducing grinding temperature. [ABSTRACT FROM AUTHOR]

As modern electronic devices are increasingly miniaturized and integrated, their performance relies more heavily on effective thermal management. In this regard, two-phase cooling methods which capitalize on thin-film evaporation atop structured porous surfaces are emerging as potential solutions. In such porous structures, the optimum heat dissipation capacity relies on two competing objectives that depend on mass and heat transfer. Optimizing these objectives for effective thermal management is challenging due to the simulation costs and the high dimensionality of the design space which is often a voxelated microstructure representation that must also be manufacturable. We address these challenges by developing a data-driven framework for designing optimal porous microstructures for cooling applications. In our framework, we leverage spectral density functions to encode the design space via a handful of interpretable variables and, in turn, efficiently search it. We develop physics-based formulas to simulate the thermofluidic properties and assess the feasibility of candidate designs based on offline image-based analyses. To decrease the reliance on expensive simulations, we generate multi-fidelity data and build emulators to find Pareto-optimal designs. We apply our approach to a canonical problem on evaporator wick design and obtain fin-like topologies in the optimal microstructures which are also characteristics often observed in industrial applications. [ABSTRACT FROM AUTHOR]

For offshore HPHT wells, the string has been serving in a harsh environment for a long time, which leads to string mechanical properties degradation and a worse wellhead growth phenomenon. In this article, the mechanical properties of P110 and N80 strings varied with temperature through the MTS experiment. And based on wellbore temperature and pressure conduction method, a new high-accuracy wellhead growth calculation model is established combined with thermal-induced string mechanical properties degradation. The difference between the calculated results and the measured data is less than 8%. And the influence of string mechanical properties degradation on wellbore safety is studied. The results show that high temperature leads to a sudden drop in wellbore safety factors and a sharp increase in wellhead growth. And the maximum critical safety production is recommended to be 85 × 10 4 m 3 / d when the case well is worked for 500 days. Attenuation of the string elastic modulus leads to a slight decrease in axial force and a slight increase in wellhead growth. The increase in the thermal expansion coefficient of string has a noticeable influence on wellhead growth. Reducing string thermal expansion capacity and increasing material stiffness can alleviate the wellhead growth phenomenon. [ABSTRACT FROM AUTHOR]