Thermodynamic Method Research Articles

A new thermodynamic modeling method for Brayton cycle schemes based on heat flux of the heat source

The supercritical carbon dioxide Brayton cycle is a promising option for power generation. However, the existing models for assessing its performance lack universality for various layouts and rely on challenging-to-acquire thermodynamic parameters at state points (such as the inlet temperature of the turbine). The present study proposes a modular thermodynamic modeling method, making it suitable for various layouts. A parameter-matching method is proposed using the heat flux of the heat source as an input, making it more practical than methods relying on parameters at state points. The method's accuracy is verified with a deviation not exceeding ±1.5%. Subsequently, four typical schemes including simple recuperation, recompression, intercooling, and reheating cycles are analyzed. The effect of heat flux on power generation and thermal efficiency of each scheme is also evaluated. It is found that the simple recuperation cycle is capable of operating effectively within lower thresholds for both maximum pressure and temperature. For maximizing power generation, the intercooling cycle offers an advantage. As for thermal efficiency, the simple recuperation cycle is best suited for heat fluxes under 1.6 MW/m2, while the recompression cycle is recommended for fluxes exceeding this limit. The outcomes can guide the designing and optimization of Brayton cycle schemes.

Heuristic algorithm for calculating the component composition of recombination gas without an adapted equation of state

Background. To conduct laboratory research of projects of gas enhanced oil recovery methods, a large volume of reservoir system is required. Often its replenishment by depth and/or separator samples is not economically feasible. Therefore, the task of fluid recombination from wellhead liquid sample and natural gas simulator arises. Objective. To calculate the component composition of recombination gas under the conditions of the task. Materials and methods. The heuristic calculation algorithm uses the tools of: modeling, inverse problems of physics, set theory, mathematical programming. Special focus is given to its empirical and theoretical justification. Results. The paper considers the limitations of the thermodynamic method. The conditions of the problem to be solved are outlined and justified. The applied algorithm of the solution is formulated and derived. The efficiency of the algorithm for oil systems is experimentally confirmed. Conclusions. The work will be of interest for specialists in the field of laboratory research projects of gas enhanced oil recovery methods. The issues of improving the accuracy of the applied algorithm and its further development are still under discussion.

Study on the effect of rare earth Ce on the modification of sulfide inclusions in U71Mn heavy rail steel

In this paper, the directional modification behavior of rare earth Ce on sulfide inclusions in steel is studied by thermodynamic calculation and experiment methods, and the mechanism of directional modification of rare earth Ce on sulfide inclusions in U71Mn heavy rail steel is proved. The results show that U71Mn heavy rail steel contained more large-sized inclusions and their distribution is more concentrated without the addition of rare earth Ce element. After the addition of rare earth Ce element, the average size of sulfur-containing inclusions in the steel decrease from 5.22 μm to 1.85 μm, and the number density of sulfur-containing inclusions in the steel increase from 83.65 mm-2 to 217.68 mm-2, indicating that the number of sulfur-containing inclusions in the steel increases after the addition of Ce element, and more small-sized sulfur-containing inclusions will form in the steel. The addition of rare earth Ce element can effectively reduce the existence of large-sized inclusions in the steel and modify large-sized inclusions into small-sized inclusions.

Multi-objective optimization and off-design performance analysis on the ammonia-water cooling-power/heating-power integrated system

The utilization of ammonia-water as a working fluid in energy conversion systems presents a promising approach for efficient geothermal energy development. In this paper, a novel ammonia-water cooling-power/heating-power integrated system is presented, a structure design method suitable for the integrated thermal system is developed, and a comprehensive analysis of system performance using thermodynamic, economic, and off-design analytical methods is conducted. This study explores the impact of various variables on system design and off-design performance. The results demonstrate that optimal design performance is achieved at evaporation temperatures of 3.5 °C (cooling-power) and 20 °C (heating-power), and the hot-part temperature difference is 21 °C. Lower mass flow rate and ambient temperature lead to improved off-design performance. Due to the influence of pressure on the phase transition temperature of geothermal water, the position of the phase transition zone has shifted, resulting in a change in the mass flow rate of ammonia-water. When the pressure ratio drops below 0.9, the heat release during the phase transition of geothermal water is incomplete, leading to a significant decrease in pump speeds by 44.76 % and 41.14 % in the two modes respectively. This work provides valuable insights and references for the design and optimization of integrated thermal systems.

ТЕРМОДИНАМИКАЛЫҚ ЖҮЙЕДЕГІ ФИЗИКАЛЫҚ ҮДЕРІСТЕРДІ ЗЕРТТЕУ ӘДІСІ

The article uses the thermodynamic method to study the effect of temperature on the Gibbs free energy, the determination of its coefficient and the dependence of the melting temperature of phases on pressure. Nerns's thermal theorem was revised by the method of quantum statistics, and it was discussed in detail and proved that isothermal processes occur without a change in entropy as the temperature approaches T→0, and that changes in free energy (∆G), enthalpy (∆H) are characterized by a tangent parallel to abscissa axis.

Comparison of methods for calculating the enthalpy of vaporization of binary azeotropic mixtures

Objectives. To calculate the molar enthalpy of vaporization of binary homogeneous mixtures based on isothermal and isobaric vapor–liquid equilibrium data, and to compare the results of calculation of molar enthalpy of vaporization by different methods with experimental data.Methods. Simulation of the vapor–liquid equilibrium of binary systems according to the Non-Random Two Liquid “local compositions” equation and thermodynamic calculations of molar vaporization enthalpies of binary mixtures at different conditions of vapor–liquid equilibrium were used.Results. Arrays of calculated data were obtained with regard to molar enthalpies of vaporization for 25 compositions of binary azeotropes (isothermal, isobaric conditions of phase equilibrium), and the full range of compositions of the benzene–ethanol system at atmospheric pressure.Conclusions. The accuracy of thermodynamic methods for calculating the vaporization enthalpy of binary azeotropic mixtures according to vapor–liquid equilibrium data is higher in 85% of cases for isothermal, and in 75% of cases for isobaric conditions. By taking into account the influence of temperature on the activity coefficients of components in the liquid phase, the values of excess molar enthalpy both for azeotrope compositions and for the full concentration range of the benzene–ethanol system under isobaric conditions of liquid–vapor phase equilibrium can be accurately reproduced.

Study on Evolution Behavior of Carbides in Industrial‐Grade American Iron and Steel Institute M35 High‐Speed Steel Produced by Electroslag Remelting

In order to optimize the heating schedule before forging and improve the breaking and deformation effects of carbides in high‐speed steel, it is of great significance to study the transformation of M2C carbides at high temperatures. The evolution of carbides in the industrial‐grade American Iron and Steel Institute M35 steel produced by electroslag remelting (ESR) is analyzed and observed using thermodynamic calculations and experimental methods. The results indicate that the carbides in the ESR ingot are mainly MC and M2C, and the microstructures of M2C carbides with the highest volume fraction are lamellar and brain like. As the heating temperature increases and holding time prolongs, the lamellar M2C carbides gradually transform into MC and M6C carbides, accompanied by protrusion, dissolution, separation, and spheroidization of the microstructure, until significant coarsening occurs at 1180 °C for 90 min. The newly transformed carbides are embedded and stacked with each other, occupying the original position of M2C carbides. Based on the theories of Gibbs free energy and atomic diffusion, the evolution mechanism of M2C carbides is discussed. Ultimately, the appropriate heating schedule is proposed, and it is validated by combining the characteristics of carbides after forging.

An Orthogonal Workflow of Electrochemical, Computational, and Thermodynamic Methods Reveals Limitations of Using a Literature-Reported Insulin Binding Peptide in Biosensors.

Developing a continuous insulin-monitoring biosensor is of great importance for both the cellular biomanufacturing industry and for treating diabetes mellitus. Such a sensor needs to be able to effectively monitor insulin across a range of temperatures and pHs and with varying concentrations of competing analytes. One of the two main components of any biosensor is the recognition element, which is responsible for interacting with the molecule of interest. Prior literature describes an insulin-binding peptide (IBP) that was reported to bind to insulin with a 3 nM affinity. Here, we used orthogonal and complementary electrochemical, computational, and thermodynamic characterization methods to evaluate IBP's appropriateness for use in a biosensor. Unfortunately, all three methods failed to produce evidence of IBP-insulin binding either on surfaces or in solution. This indicates that the binding exhibited in previous reports is likely restricted to a limited set of conditions and that IBP is not a suitable recognition element for a continuous insulin biosensor.

Study of slag formation behavior in iron ore pellets based on thermodynamic calculations and experiments

To investigate the mechanism of slag formation during pellet consolidation, we combined thermodynamic calculations and experimental methods to study the effects of roasting temperature, basicity, and SiO2 content on slag formation. The results indicate that as the temperature increases, the solid phases clinopyroxene, orthopyroxene, and melilite transform into slag within the pellet. The roasting temperature and basicity of slags formed by different particles varied considerably. At 1250 °C, the slag content is less than 5 % in low-silica fluxed pellets, less than 15 % in medium-silica fluxed pellets, and up to approximately 20 % in high-silica fluxed pellets. Phase diagram analysis showed that CaFe2O4 and Ca2Fe2O5 formed in the pellet due to basicity differences SEM-EDS analysis showed that the slag in fluxed pellets primarily comprises the silicates Ca3Fe2(SiO4)3 and (Mg, Fe)2SiO4, as well as ferrate. The slag is distributed in a reticulated pattern within the pellets, with some quartz remaining undissolved in the slag phase and existing independently in pores.

Bose-Einstein Condensation of Photons in a Four-Site Quantum Ring.

Thermalization of radiation by contact to matter is a well-known concept, but the application of thermodynamic methods to complex quantum states of light remains a challenge. Here, we observe Bose-Einstein condensation of photons into the hybridized ground state of a coupled four-site ring potential. In our experiment, the periodically closed ring lattice superimposed by a weak harmonic trap for photons is realized inside a spatially structured dye-filled microcavity. Photons thermalize to room temperature, and above a critical photon number macroscopically occupy the symmetric linear combination of the site eigenstates with zero phase winding, which constitutes the ground state of the system. The mutual phase coherence of photons at different lattice sites is verified by optical interferometry.

A method to obtain the trapping energy and trapping range between hydrogen and defects at finite temperature

The binding energy between hydrogen (H) and defects in solid phase materials has been widely studied, which is of vital importance to understand the H retention effects and defect growth mechanisms. However, present studies of binding energy through density functional theory (DFT) or the molecular statics (MS) method were usually performed at 0 K, which could not take the influence of entropy into consideration. In this work, a thermodynamic method has been proposed to obtain the trapping energy between H and defects at finite temperatures. The method is based on the rate theory, which uses trapping energy (V) and trapping range (δ) to describe the trapping properties of defects. Ultimately, a parameterized H spatial cumulative distribution function at thermodynamic equilibrium state could be given. The trapping energy and trapping range parameters in the function can be determined by contrast with the results obtained from molecular dynamics or other methods. This method has been applied to calculate the trapping energies and trapping ranges of H to helium bubble and grain boundary, respectively. Further discussion has been made on the discrepancy between trapping energies obtained by this method and the conventional DFT/MS method.

Influence of electron and hole doping on structural, Magnetic, and magnetocaloric properties of Ba2FeMoO6 double perovskite

The impact of Sm3+ and Ag+ doping at the Ba2+ site on the structural, magnetic, and magnetocaloric properties of Ba2FeMoO6 (BFMO) double perovskite was compared. Samples were synthesized using the sol–gel method. Rietveld refinement patterns of samples Ba2-xAxFeMoO6 (A=Sm, Ag, x = 0.0, 0.025) showed all samples had cubic structures with Fm-3 m space group and no impurity. The lattice parameters and unit cell of the Ba1.975Sm0.025FeMoO6 (BSFMO), and Ba1.975Ag0.025FeMoO6 (BAFMO) samples decreased compared to the parent sample. X-ray photoelectron spectroscopy confirmed that Fe and Mo ions were mixed valence for all samples. The results of magnetization versus temperature (M−T) showed an increase for BSFMO and a decrease for BAFMO samples under an external magnetic field of 0.05 T. The magnetic study indicated a decrease in the transition temperature for BSFMO (∼303 K) and an increase for BAFMO (∼321 K) to compare with the parent sample (∼310 K). The maximum value of magnetic entropy changes (ΔSMmax)of the BFMO, BSFMO, and BAFMO samples at H=3 T obtained 0.92 Jkg-1K−1, 0.75 Jkg-1K−1, and 0.39 Jkg-1K−1, respectively, and the second-order magnetic phase occurred around the transition temperature. For BFMO, BSFMO, and BAFMO, the relative cooling power (RCP) is 34.48 J/kg, 32.25 J/kg, and 21.97 J/kg, respectively. The second-order magnetic phase transition occurred around the transition temperature for all samples using the energy criterion as well as the universal curve method. In addition, we used Widom’s law to determine the critical exponent of the samples, which provides a new thermodynamic method to determine the magnetic phase transition. The results of the magnetocaloric effect indicate that although the maximum entropy changes and relative cooling decrease with doping Ag and Sm ions, they have a wide temperature range of magnetic entropy changes compared to the pristine sample, which can be candidates for magnetic cooling.

From onset of Cadomian subduction to forearc-arc-continent collision: Insights from the Neoproterozoic Calzadilla Metaophiolite (SW Iberia)

ABSTRACT The Cadomian basement of SW Iberian Massif appears in the so-called Ossa-Morena Complex, which contains several allochthonous terranes that are key for deciphering the evolution of the Gondwana margin during the Neoproterozoic. In this context, the Calzadilla Ophiolite represents the remnants of an oceanic Ediacaran lithosphere formed by a boninitic mafic crust that overlies a serpentinized ultramafic section, the latter being the biggest outcrop of Cadomian serpentinites in Europe. In this work, the petrological and geochemical nature of the mantle section is analysed, as well as the tectonothermal evolution of both, the mafic crust and the ultramafic section. The algebraic analysis of whole rock geochemistry of the serpentinites indicates that the protolith corresponds to harzburgite. The geochemical fingerprint of the serpentinites, as well as the primary spinel crystals composition, shows that peridotites underwent high degrees of partial melting (up to 16%) in a forearc setting. Thermodynamic modelling and average PT methods were applied to serpentinites and mafic dykes from the ultramafic section as well as to amphibolites from the mafic section, both of which experienced progradation up to 4–5 kbar and 525–575°C. According to the data, the protoliths of the Calzadilla Ophiolite were formed in a peri-Gondwanan arc system developed during the subduction of oceanic crust below Gondwana. The roll-back of the subducting slab would induce the opening of the forearc basin at c. 602 Ma, protolith age of amphibolites from crustal section, with an extensive partial melting of the mantle wedge and the formation of boninitic-affinity magmas that constitute the mafic section of the Calzadilla Ophiolite. Metasomatism and serpentinization of the mantle wedge would occur via melt- and fluid–rock interactions. A compression-dominated stage at c. 540 led to the emplacement of the Calzadilla Ophiolite onto the Cadomian magmatic arc, with the development of the amphibolite-facies metamorphic imprint.

Design, Synthesis, and Characterization of Al‐Containing Multicomponent Alloys for Hydrogen Storage and Compression

AbstractIn this paper, compositions within the TiZrAlCrMn, TiZrAlCrFe, and TiZrAlMnFe alloy systems that form the C14 Laves phase are investigated. The design, synthesis, structural, and hydrogen storage characterizations for an equiatomic and a non‐equiatomic composition for each alloy system are presented. Additionally, the further development of a thermodynamic method for the calculation of pressure‐composition‐isotherms (PCIs) is presented of C14 Laves phase alloys that absorb hydrogen by solid solution. Overall, the results shown in this paper indicate that Al‐containing multicomponent alloys can present promising hydrogen storage performance under high pressures. Nonetheless, high concentrations of aluminum in highly concentrated (equiatomic) alloys can have a negative impact on the hydrogenation properties. The Ti0.29Zr0.05Al0.05Cr0.26Mn0.35 composition showed promising hydrogenation/dehydrogenation properties. The gravimetric capacity of this alloy is ≈1.76 wt.% H2 and the PCIs measured indicate that this material has potential for high‐pressure hydrogen storage and compression applications. The use of the presented thermodynamic model for the design of multicomponent alloys is suggested.

Constructing carbon nanotube (CNTs)/silica superhydrophobic coating with multi-stage rough structure for long-term anti-corrosion and low-temperature anti-icing in the marine environment

The rough superhydrophobic surface is beneficial for capturing more gases underwater, which enhances corrosion and ice resistance for marine equipment. In this work, a PVAc-PVDF-FMCS (PPFMCS) multi-stage rough superhydrophobic coating was manufactured by a cold spraying method, significantly improving the anti-corrosion and anti-icing of aluminium alloy. The point-line structure was designed by cross-linking between multi-walled carbon nanotubes (MWCNTs) and silicon dioxide (SiO2), which facilitated the formation of multi-stage rough surface. The porous skeleton and interfacial adhesion of the PPFMCS coating were attributed to the introduction of polyvinylidenefluoride (PVDF) and polyvinylacetate (PVAc), respectively. The PPFMCS coating had good superhydrophobicity with a water contact angle of 163.5°, while exhibiting the outstanding performance of long-term anti-corrosion and anti-icing. The |Z|0.01 Hz value of the PPFMCS coating was still 9.62 × 109 Ω cm2 in 3.5 wt% NaCl solution for 35 days, only two orders of magnitude lower than that of the original coating, the equivalent circuits were further investigated and the metal protection is evaluated on the shore or in the deep ocean of the South China Sea. The PPFMCS coating was able to obviously delay icing for 5 min at −20 °C, the ice adhesion of its surface was as low as 85.5 kPa. The icing phase transition was analysed by a thermodynamic method. The coating also had good stability and drag reduction performance. This high-performance coating based on point-line structural design is expected to have practical applications in marine transportation, oil exploration and polar exploration.

An initial value insensitive constrained linear predictive evolution algorithm for gas–liquid phase equilibrium calculation problems

Heuristic algorithms are gradually becoming a type of new promising methods for solving phase equilibrium calculation problems since they do not have to calculate an initial value in advance like traditional methods such as direct Newton's method and indirect thermodynamic method. A new heuristic optimizer, constrained linear prediction evolution algorithm (CLPE) for phase equilibrium calculation under given volume, temperature, and moles (NVT-flash) is proposed in this paper. CLPE employs the total Helmholtz free energy of the NVT-flash problem as its objective function and employs the volume and moles vector of a certain phase as decision variables. Numerical experiments are conducted on four NVT-flash problems. The consistency between the experimental results and those obtained by some traditional methods verifies that the proposed CLPE is effective. The comparative advantage in computational overhead over the similar algorithms indicates the significance of this study. The success of CLPE can drive more heuristic algorithms to solve NVT-flash problems more efficiently, so as to advance the field of phase equilibrium calculation.

Dissipative fracton superfluids

We present a comprehensive study of hydrodynamic theories for superfluids with dipole symmetry. Taking diffusion as an example, we systematically construct a hydrodynamic framework that incorporates an intrinsic dipole degree of freedom in analogy to spin density in micropolar (spinful) fluids. Subsequently, we study a dipole condensed phase and propose a model that captures the spontaneous breaking of the U(1) charge. The theory explains the role of the inverse Higgs constraint for this class of theories, and naturally generates the gapless field. Next, we introduce finite temperature theory using the Hamiltonian formalism and study the hydrodynamics of ideal fracton superfluids. Finally, we postulate a derivative counting scheme and incorporate dissipative effects using the method of irreversible thermodynamics. We verify the consistency of the dispersion relations and argue that our counting is systematic.

Thermodynamic geometry of charged rotating black holes in Einsteinian cubic gravity

We study the thermodynamic geometry of two types of asymptotically anti-de Sitter black holes in four-dimensional Einsteinian cubic gravity, including the uncharged rotating and charged non-rotating black holes, applying the Ruppeiner thermodynamic geometry method. The divergence of the scalar curvature of the Ruppeiner metric ([Formula: see text]) is found to be related to the vanishing of the heat capacity. The stability of the solutions is shown to be affected by the Einsteinian cubic gravity coupling constant [Formula: see text]. In the unstable phase of the rotating black hole, the [Formula: see text] appeared to possess additional diverging points, where the number of these points and the behavior of [Formula: see text] are controlled by the angular momentum parameter. Also, for the charged non-rotating black hole case, we show that depending on the values of [Formula: see text], the solution may enjoy two types of phase transition and [Formula: see text] behaviors. The characteristic behavior of [Formula: see text] of these two types of black holes enabled us to recognize the types of interactions between microscopic degrees of freedom.

Grain boundary segregation for the Fe-P system: Insights from atomistic modeling and Bayesian inference

In this work we re-assess experimental data for grain boundary (GB) segregation of P in bcc Fe with thermodynamic and statistical methods. The data are based on Auger-Electron-Spectroscopy (AES) measurements which have provided P GB concentrations for various bulk contents and temperatures for ferrite. While in the previous investigations of this system a single-site McLean equation was used to extract segregation enthalpy and entropy, we employ multi-site segregation models as suggested by atomistic simulations. We use a recently introduced methodology based on inter-atomic potentials to calculate the segregation energy spectrum, as well as vibrational entropy and solute-solute interactions of P in polycrystalline Fe, thereby obtaining a three-dimensional distribution of energy, entropy and interactions. Using this trivariate distribution we predict P GB concentrations and compare them to the experimental measurements. Furthermore, we calibrate the parameters of physical models of increasing complexity to the experimental data with an inverse modeling approach based on Bayesian inference. While it is not possible to seamlessly link the results from AES to atomistic modeling, our investigation provides significant new insights for thermodynamic modeling of GB segregation. The vibrational entropy deduced from experiment differs from physics based atomistic simulations even when taking the spectral nature of energy, entropy and interactions into account. However, the correlations of the quantities are in good agreement when considering the trivariate model. Our investigation highlights the need for new and more accurate experimental datasets of GB segregation.

The active regulatory effects of magnesium on the preparation, microstructure and mechanical properties of a novel Al-Bi based γ-ray shielding material by casting method

The effects of Mg on the solidification behavior, microstructure and mechanical properties of Al-20Bi immiscible alloy were systematically investigated based on thermodynamic and experimental methods. The results showed that Mg was an interfacial active element to Al-Bi alloy. Mg tended to adsorb on the Al-Bi liquid-liquid interface, resulting in a reduction of the miscibility gap and thus a decrease of the interfacial tension. Al-20Bi and Al-20Bi-3Mg alloys were prepared by casting method. The newly-formed Mg3Bi2 particles with high thermal stability were more evenly dispersed in Al-20Bi-3Mg alloy compared to Al-20Bi alloy. Furthermore, Mg3Bi2 was a ductile phase with higher strength than that of Bi. It was well elucidated that Mg had an active regulatory effect on the preparation, microstructure and properties of Al-Bi alloy. This research provides a new way for low-cost large-scale preparation of Al-Bi based γ-ray shielding material with high-performance.