Thermodynamic Calculation Method Research Articles

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.

FED evaluation in a small double-suction reversible pump turbine considering sediment erosion

Double-suction pump-turbines are a special type of reversible pump-turbine which serves the pumped storage hydro power plant. Enhancing the energy conversion efficiency of the power station can be effectively achieved by reducing the internal Flow Energy Dissipation (FED) within the pump-turbine. The key to addressing this challenge lies in the identification of high FED regions and conducting visualized analyses. In this study, computational fluid dynamics (CFD), thermodynamic calculation methods and the Finnie erosion model are combined to perform two-phase flow numerical simulations of a specific double-suction pump-turbine model under both pump and turbine operating modes. We analyzed the FED in different regions off wall. The energy loss distribution is provided within these five regions for the volute casing, suction chamber, and impeller separately, and conducted an analysis of component wear. The research findings revealed that, in the pump mode, FED primarily concentrates within the volute casing, while in the turbine mode, it is concentrated within the suction chamber, with both regions accounting for over 70 % of the total energy dissipation. The proportion of internal FED in five regions at varying distances from the wall for each component showed significant disparities under different operating conditions, closely related to the internal flow characteristics of the components. In pump mode, wear primarily occurs in the volute casing, while the wear in the suction chamber and impeller can be considered negligible. In turbine mode, each component experiences some level of wear. This provides a foundation for reducing flow energy losses and preventing sediment erosion.

Thermodynamic property calculation for pure component hydrogen isotopologues considering tritium processing technologies in fusion fuel cycle

In this study, the thermodynamic properties calculation methods for hydrogen isotopes are presented to be used in the process simulation of tritium handling processes in the fusion fuel cycle. To define appropriate temperature and pressure ranges for the calculations, applicable technologies of subsystems are investigated. Among various approaches, specific calculation methods and models for each property are suggested based on data gathered from a literature survey. Commonly used cubic equations of state, Peng-Robinson and Redlich-Kwong-Soave, are evaluated to ensure applicability in commercial simulation software. Hydrogen and deuterium data in the NIST REFPROP database are used as validation sets for proposed calculation approaches. The results show that Peng-Robinson and Redlich-Kwong-Soave equations of state have good agreement with NIST REFPROP in saturated liquid and gas states, as well as gas conditions up to 10 bar and 1000K. Finally, the proposed methods are applied to other isotopologues, and the trends of the properties are analyzed.

Influence of Alloying Elements Content on High Temperature Properties of Ti-V-Cr and Ti-Al-V Series Titanium Alloys: A JMatPro Program Calculation Study

For the issues of high temperature performance affected by the alloying elements content in Ti-V-Cr and Ti-V-Cr alloys, the thermodynamic calculation method based on JMatPro program was applied in this study. The research is mainly focused on the analysis of phase composition, thermodynamic parameters and mechanical properties of Ti-Al-V and Ti-V-Cr series alloys with different element proportions under high temperature environment. Those obtained results show that the proportion of Al in Ti-Al-V alloys has a great influence on the high temperature properties. Increasing the content of Al not only increases the transformation temperature of β single-phase structure and delays the transformation process of α/β microstructure to β single-phase structure, but also helps to improve the high temperature thermal conductivity and elastic deformation resistance of the alloy. In Ti-V-Cr alloys, the influence of V element on high temperature properties is mainly focused on the improvement of thermal conductivity and high temperature deformation properties, while the influence of Cr element is relatively weak. Besides, adding a small amount of Al element to Ti-V-Cr alloy can further improve the thermal conductivity of the alloy. The Young’s modulus of the Ti-V-Cr alloy increases when 0.3%-1% of C element is added. Finally, the effect of Si element on the high temperature elastic deformation of the alloy is relatively weak.

On chemical interactions between an inclusion engineered stainless steel (316L) and (Ti,Al)N coated tools during turning

Non-metallic inclusions offer one of the most effective routes for improving the machinability of steels. However, the wear-reducing mechanisms activated by such inclusions are not fully understood. The interactions are notoriously difficult to predict due to the wide variety of steel grades, cutting conditions, and tool materials employed in industry. The interaction between PVD (Ti,Al)N coated cemented carbide tools, non-metallic inclusions, atmospheric oxygen, and the stainless steel 316L in a turning operation is therefore investigated here as a case study. The study includes turning experiments, nanometer resolution microscopy, and thermodynamic calculations. The paper explains how not only too high a contact pressures hinder the formation of protective deposits at the tool edge, but also how too low a contact pressure leads to excessive wear. A range of conditions specified in this paper must therefore be met for the two observed protective non-metallic inclusions Mg1Al2O4 and Al2Ca2Si1O7 to be preferentially deposited on a tool. Hence the coating wear is experimentally investigated, explained, and a thermodynamic calculation method for predicting the protective or degenerative potential of a deposit on the coating is presented.

Steam Gasification in a Fluidized Bed with Various Methods of In-Core Coal Treatment

The aim of this work is to study coal steam gasification with various methods of coal in-core treatment in FB using a newly developed thermodynamic calculation method. A calculational study of subbituminous coal steam non-catalytic gasification was carried out using four different methods of coal in-core treatment in single-vessel multisectional fluidized-bed gasifiers. A semi-empirical model based on the entropy maximization thermodynamic method and “restricted equilibria” based on previously obtained experimental data has been developed. Based on thermodynamic calculations, the effect of the leading thermochemical processes and operating parameters of the fluidized bed (temperature, fluidization number, steam/coal ratio feed rate) was revealed. New information was obtained regarding the composition of char and syngas at the gasifier outlet, the syngas heating value, and the cold gas efficiency of the steam gasification of Borodinskiy subbituminous coal char. The results indicate the possibility of significantly accelerating and improving non-catalytic steam gasification in fluidized bed gasifiers through the appropriate organization of in-core coal treatment. Based on the results obtained, the following recommendation is made—when designing multi-section and multi-vessel steam-blown gasifiers, the ratio of residence times should be set in favor of increasing the coal residence time in the steam-blown carbonization zone. Structurally, this can be achieved by increasing the volume and/or area of the steam-blown carbonization section (vessel).

Ab initio molecular dynamics calculation and vacuum distillation experimental study on the interaction mechanism of PbS–FeS

An important way to obtain PbS and FeS is the thermal decomposition of Jamesonite. However, the mechanism of PbS–FeS interaction is unknown. In order to explore the separation effect of PbS and FeS, thermodynamic calculation, dynamic simulation and vacuum distillation experiments were used to explore the interaction mechanism of PbS and FeS. The decomposition and volatilization temperatures of PbS and FeS were obtained by thermodynamic calculation. The difference of saturated vapor pressure indicates that there is a tendency of separation between them. The ab initio molecular dynamics method was used to calculate the density of states of PbS and FeS at different temperatures, indicating that the FeS(114) structure is more stable than the PbS(200) structure, and the Pb–S bond is easier to break than the Fe–S bond at the same temperature. The experimental results of vacuum distillation show that the volatilization temperature of PbS is much lower than that of FeS, and FeS can only volatilize into the gas phase at a higher temperature. The theoretical calculation method is consistent with the experimental results, which shows that the thermodynamic calculation and dynamic simulation methods are reliable in predicting the volatilization and separation of crystal structures. The interaction mechanism between PbS and FeS was explored from the theoretical point of view to provide theoretical guidance for vacuum distillation experiment.

Theoretical calculation and experimental study on the separation mechanism of PbS-Sb2S3

Jamesonite (Pb4FeSb6S14) is a complex antimony sulfide mineral and an important raw material for the extraction of lead and antimony. Under vacuum conditions, the internal interaction mechanism of PbS and Sb2S3 during thermal decomposition is unclear and difficult to separate. In order to explore the interaction mechanism between PbS and Sb2S3, the thermodynamic data of Pb-S and Sb-S systems were firstly calculated by thermodynamic calculation method, PbS and Sb2S3 cluster substances that may exist in the gas phase were obtained under the given temperature conditions. On this basis, ab initio molecular dynamics was used to calculate the mean square displacement and diffusion coefficient of PbS and Sb2S3 gas phase clusters. The vacuum distillation experiments of lead sulfide and antimony trisulfide confirmed the volatilization and diffusion of PbS and Sb2S3, and verified the theoretical calculation results. According to the experiment, the volatilization temperature of Sb2S3 is much lower than that of PbS. The theoretical calculation results are consistent with the experimental results, which indicates that the calculation of the diffusion properties of PbS and Sb2S3 gas phase clusters by molecular dynamics simulation is reliable. This is also an effective and simple method to predict whether the mixed melt of PbS and Sb2S3 can be separated, which provides theoretical guidance for the vacuum separation of PbS and Sb2S3.

Influence of Organic-Inorganic Composition on the Adsorption of Niutitang Formation Shale in Huijunba Syncline

To study the influence of different organic-inorganic composition on the adsorption in shale, taking the Niutitang Formation shale in the Huijunba syncline in southern Hanzhong as the research object, based on acid treatment to extract kerogen and wet chemicals. Extracting mineral components by oxidation method, a series of isothermal adsorption experiments were carried out on the original rock, kerogen, and mineral components of the samples. Through the three-dimensional Langmuir model fitting and adsorption thermodynamic calculation method, the adsorption thermodynamic parameters such as the isometric heat of adsorption and the standard adsorption entropy are obtained. The research results show that organic matter is the primary factor affecting the methane adsorption of shale and clay minerals also affect the adsorption to a certain extent. When the burial depth is relatively shallow, diagenesis has a promoting effect on the total amount of adsorption. As the depth increases, the diagenesis will turn into an inhibitory effect on the total amount of adsorption. Through the component weighting method, the lower limit ratio of the adsorbed amount of organic matter to the total amount in the shale is 29.3%~46.7% when the depth reaches to 3000 m, while the upper limit ratio of the adsorption of mineral components is 66.4%~73.6%.

Effect of TiC on Microstructure and Properties of Wear-Resistant Mo2FeB2 Claddings.

Alloy blocks with different TiC content were designed, and Mo2FeB2 cermets were prepared by carbon arc surfacing process. The interaction law of TiC content and the microstructure, phase, composition, hardness and wear resistance of the cladding were studied in detail by the combination of experiment and theoretical analysis. On the other hand, the phase transition process of the weldpool is theoretically analyzed by thermodynamic calculation method. XRD test results show that in addition to Mo2FeB2 synthesized in situ, the cladding also forms phases such as TiC, CrB, MoB and Fe-Cr. The number of Mo2FeB2 hard phases gradually increases when TiC content varies from 0% to 15%. The average microhardness of the cladding with 0%, 5%, 10%, and 15% TiC was 992 HV0.5, 1035 HV0.5, 1018 HV0.5 and 689 HV0.5, respectively, with 5% TiC being the largest. Moreover, the cladding with 5% TiC content has excellent wear resistance, which is 14.6 times that of the substrate.

Progress and performance of energetic materials: open dataset, tool, and implications for synthesis

The abundant dataset of detonation parameters for energetic materials is reported, empirical and thermodynamic calculation methods are benchmarked, and implications for design of novel promising compounds provided.

Investigation on abrasive wear mechanism of single diamond grain in flexible scribing titanium alloy

Abrasive belt grinding technique has been gradually used in precision machining those attractive materials of aerospace field. The excellent performance of rigid-flexible composited diamond belt shows great application prospect while its abrasive wear mechanism is deeply revealed. Therefore, a series of theoretical and experimental studies are performed to explore the wear mechanism of single diamond grain in flexible scribing titanium alloy in this work. Three-dimensional finite element simulation model was built to investigate the elastic frictional wear process between a diamond grain and the titanium alloy sample under different combinations of processing parameters. The simulation results showed that the normal force and grain size contributed much to frictional stress and the friction speed had the greatest effect on the frictional temperature. On this basis, the flexible scribing experiments of titanium alloy sample by using single diamond grain were conducted to verify the effect of scribing parameters on diamond grain wear. Raman scattering analysis, chemical thermodynamic calculation and X-ray photoelectron spectroscopy analysis methods were proposed to further research the essential wear of diamond grain at elevated temperature. The results indicated that the physical wear caused by higher scribing force was the main pattern at lower temperature. When the temperature reached up to 1100 K, Raman shifts peak of graphite corresponding to 1544 cm−1 was detected to illustrate the graphite transformation of diamond crystal structure, and the existence of TiO2 and CO bond were confirmed to explain the oxidation wear of diamond grain at the atmosphere of air medium. This research work provides an important theoretical basis for restraining the diamond belt wear in precision grinding operation of titanium alloys.

Novel design and analysis of a solar PVT system using LFR concentrator and nano-fluids optical filter

The current study proposes a novel solar PV and thermal (PVT) system based on the combination of linear Fresnel reflector (LFR) concentrator and ITO-EG nano-fluids optical filter. Preparation and relevant measurements of the ITO nano-particles as well as the ITO-EG nano-fluids are conducted. The test results reveal that the optical filter has an average absorptivity of 30.9% in the spectrum range of 250.0–2500.0 nm. The solar concentration behaviour of the PVT system is revealed and the sensitivity analysis results of sun tracking error indicate that when the north-south tracking error is 0.2°, the overall optical efficiency is 90.12%, which means the PVT system has a relatively good adaptive faculty on sun tracking error. Theoretical thermodynamic calculation and CFD simulation methods are utilized to estimate the operation behaviour of the PVT system. The results demonstrate that the PVT system has a photoelectric conversion efficiency of 29.6% as well as a thermal efficiency of 18.52%. Parametric analysis results show that the thermal efficiency of the PVT system can be improved by increasing the inlet nano-fluids flow velocity as well as the ambient temperature, or by reducing the inlet nano-fluids temperature or convection heat transfer coefficient.

Experimental Phase Equilibria and Isopleth Section of 8Nb-TiAl Alloys

The 8Nb isopleth section of a Ti-Al-Nb system is experimentally determined based on thermal analysis and thermodynamic calculation methods to obtain the phase transformation and equilibrium relations required for material design and fabrication. The phase transus and relations for the 8Nb-TiAl system show some deviations from the calculated thermodynamic results. The ordered βo phase transforms from the disordered β/α phases at 1200–1400 °C over a large Al concentration range, and this transformation is considered to be an intermediate type between the first- and second-order phase transitions. Moreover, the βo phases are retained at the ambient temperature in the 8Nb-TiAl microstructures. The ωo phase transforms from the highly ordered βo phase, rather than from α2 or βo with a low degree of atom ordering B2 (LOB2) structure, with Al concentration of 32–43 at% at approximately 850 °C. From the experimental detection, the transition of the ωo phase from the βo phase is considered to be a further ordering process.

1, 10-phenanthroimidazole derivatives as efficient corrosion inhibitors for mild steel in 1 M HCl: synthesis, gravimetric, electrochemical and theoretical investigation

The anticorrosive performances of 1,10-phenanthroimidazole derivatives 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline (IPB) and 1,4-di (1H-imidazo [4,5-f] [1,10] phenanthrolin-2-yl)benzene (DIPB) for mild steel (MS) in 1 M HCl media were surveyed via gravimetric, electrochemical and thermodynamic calculation methods. IPB and DIPB could adsorb spontaneously on the MS by two adsorption modes with predominant chemisorption, and the process obeyed Langmuir adsorption isotherm. Furthermore, IPB and DIPB were mixed-type inhibitors. Meanwhile, the UV-vis absorption spectroscopy was used to investigate the forming of complex between inhibitor and Fe. The structure-activity relationship was also discussed by means of theoretical calculation. Those results demonstrate that this type of compounds with multiple active sites exhibit great potential in corrosion inhibition of MS in acidic media.

Effect of adding yttrium on precipitation behaviors of inclusions in E690 ultra high strength offshore platform steel

AbstractThe mechanism of inclusions precipitation of the E690 offshore platform steel, with and without addition of yttrium, was studied using the thermodynamic calculation method. The results show that in the E690 steel in the absence of yttrium, the MnS inclusions were precipitated in the liquid phase at the solidification front. By adding the yttrium, MnS inclusions were replaced by spindle and spherical yttrium-containing oxide and sulfide complex inclusions, and the precipitation sequence of yttrium-containing inclusions in the liquid steel was Y2O3, Y2O2S, and YS. However, Y2S3 inclusions cannot be precipitated in the liquid steel under the experimental conditions. It was also found that Al2O3 inclusions can be formed in the liquid steel with and without addition of yttrium. The thermodynamic calculation results are in accordance with the experimental results.

Numerical analysis and modified thermodynamic calculation methods for the furnace in the 1000 MW supercritical CO2 coal-fired boiler

Supercritical carbon dioxide (S–CO2) coal-fired power generation technology is considered as the transformative technology in the energy sector due to its high efficiency, simple turbomachinery and high power density though the concept design of S–CO2 boiler is still in the infancy stage. This study constructs a modified combustion and heat transfer thermodynamic calculation method of the S–CO2 boiler adapted for multi-zone furnace. The effects of parameters and configurations on the characteristics of the S–CO2 boiler are compared and analyzed. The results show that the increase in the separated over-fired air ratio can effectively equalize the heat duty distribution. And the increasing of the furnace wall temperature will affect the furnace radiation heat transfer performance, which increases the flue gas average temperature. The boiler configurations including the flue gas recirculation, double furnace strategy, thermal insulation strategy and boiler local expansion strategy have the positive effects on decreasing the furnace heat duty to ensure the boiler safety. Finally, the novel S–CO2 boiler configurations are proposed and the comprehensive evaluations are conducted on the boiler combustion, heat transfer and burnout characteristics, which show that the novel S–CO2 boiler performance is promising and can provide a basis for the design of S–CO2 boiler.

Life cycle assessment and feasibility analysis of a combined chemical looping combustion and power-to-methane system for CO2 capture and utilization

The ability to store effectively excess of electrical energy from peaks of production is key to the development of renewable energies. Power-To-Gas, and specifically Power-To-Methane represents one of the most promising option. This works presents an innovative process layout that integrates Chemical Looping Combustion of solid fuels and a Power-to-Methane system. The core of the proposed layout is a multiple interconnected fluidized bed system (MFB) equipped with a two-stage fuel reactor (t-FR). Performances of the system were evaluated by considering a coal as fuel and CuO supported on zirconia as oxygen carrier. A kinetic scheme comprising both heterogeneous and homogeneous reactions occurring in the MFB was considered. The methanation unit was modelled developing a thermodynamic calculation method based on minimization of the free Gibbs energy. The performance of the system was evaluated by considering that the CO/CO2 stream coming from the t-FR reacts over Ni supported on alumina catalyst with a pure H2 stream generated by an array of electrolysis cells. The number of cells to be stacked in the array was evaluated by considering that a constant H2 production able to convert the whole CO/CO2 stream produced by the CLC process should be attained. The environmental performance of the proposed process was quantified using the Life Cycle Assessment (LCA) methodology. The analysis shows i) that the majority originate from the production and disposal of the oxygen carrier used in the t-FR, and ii) that reusing part of the oxygen produced by the electrolysis cells improves significantly the environmental performance of the proposed process.

Structure and physical properties of Ba(PO3)2–AlF3–BaSO4 fluoro‐sulfo‐phosphate glasses

AbstractAlkali‐earth‐metaphosphate‐based fluoro‐sulfo‐phosphate M(PO3)2–AlF3–MSO4 (MPFS, M = Ca, Sr, Ba) glasses have been developed via simultaneously incorporating fluoride and sulfate into metaphosphate glass. Their glass‐forming regions were efficiently determined under the guidance of thermodynamic calculation method. The physical and structural properties of BaPFS glass were investigated in detail. Furthermore, near‐infrared spectroscopic properties of Er3+‐doped BaPFS (Er–BaPFS) glass were studied. Physical parameters, such as Abbe's number νd (55‐75) and nonlinear refractive index n2 (1.17‐1.86 × 10−13 esu), of BaPFS glass are strongly depended on P/F/S ratio. The structure of BaPFS glass gradually depolymerizes and tends to become multianionic when Ba(PO3)2 is substituted by AlF3 and BaSO4. Anion‐substitution strategy effectively modulates the property and structure of glass, providing a scheme to derive glass materials. In addition, enhanced emission at ~1.5 μm has been observed from Er–BaPFS glass along with large emission cross section (5.0‐5.5 × 10−21 cm2) and long lifetime (6.7‐7.3 ms), resulting in large figure of merit (3.46‐3.84 × 10−23 cm2·s), which is a promising candidate for solid‐state laser.

Glass‐forming regions and enhanced 2.7 μm emission by Er3+ heavily doping in TeO2–Ga2O3–R2O (or MO) glasses

AbstractEr3+‐doped fiber lasers operating at 2.7 μm have attracted increasing interest because of their various important applications; however, the intrinsic self‐terminating effect of Er3+ and the reliability of glass hosts hindered the development of Er3+‐doped fiber lasers. Herein, the glass‐forming regions of a series TeO2–Ga2O3–R2O (or MO) (R = Li, Na, and Rb; M = Mg, Sr, Ba, Pb, and Zn) glasses are predicted by the thermodynamic calculation method. On this basis, the physical and optical properties of TeO2–Ga2O3–ZnO (TGZ) glass are investigated in detail as an example. Under the excitation of 980 nm laser diode, the fluorescence intensity at 2.7 μm reaches a maximum in the heavily Er3+‐doped TGZ glass. By contrast, the accompanying near‐infrared fluorescence at 1.5 μm and upconversion green emissions at 528 nm and 546 nm are all effectively weaken. Furthermore, the lifetime gap between the 4I11/2 upper laser level and 4I13/2 lower laser level is sharply narrowed from 2.81 ms to 0.59 ms, which is beneficial to overcome the population conversion bottleneck. All results demonstrate that these newly developed ternary tellurite glass systems are promising candidates for near‐/mid‐infrared laser glass fiber, fiber amplifiers, and fiber lasers.