scholarly journals Thermodynamic Properties of Aqueous Species Calculated Using the HKF Model: How Do Different Thermodynamic and Electrostatic Models for Solvent Water Affect Calculated Aqueous Properties?

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-24 ◽  
Author(s):  
George D. Miron ◽  
Allan M. M. Leal ◽  
Alina Yapparova
Keyword(s):  
Experimental Data ◽  
Dielectric Properties ◽  
Thermodynamic Properties ◽  
Elevated Temperatures ◽  
Rock Interaction ◽  
Water Solvent ◽  
Wide Range ◽  
Temperature And Pressure ◽  
The Impact ◽  
Aqueous Species

Thermodynamic properties of aqueous species are essential for modeling of fluid-rock interaction processes. The Helgeson-Kirkham-Flowers (HKF) model is widely used for calculating standard state thermodynamic properties of ions and complexes over a wide range of temperatures and pressures. To do this, the HKF model requires thermodynamic and electrostatic models of water solvent. In this study, we investigate and quantify the impact of choosing different models for calculating water solvent volumetric and dielectric properties, on the properties of aqueous species calculated using the HKF model. We identify temperature and pressure conditions at which the choice of different models can have a considerable effect on the properties of aqueous species and on fluid mineral equilibrium calculations. The investigated temperature and pressure intervals are 25–1000°C and 1–5 kbar, representative of upper to middle crustal levels, and of interest for modeling ore-forming processes. The thermodynamic and electrostatic models for water solvent considered are: Haar, Gallagher and Kell (1984), Wagner and Pruß (2002), and Zhang and Duan (2005), to calculate water volumetric properties, and Johnson and Norton (1991), Fernandez and others (1997), and Sverjensky and others (2014), to calculate water dielectric properties. We observe only small discrepancies in the calculated standard partial molal properties of aqueous species resulting from using different water thermodynamic models. However, large differences in the properties of charged species can be observed at higher temperatures (above 500°C) as a result of using different electrostatic models. Depending on the aqueous speciation and the reactions that control the chemical composition, the observed differences can vary. The discrepancy between various electrostatic models is attributed to the scarcity of experimental data at high temperatures. These discrepancies restrict the reliability of the geochemical modeling of hydrothermal and ore formation processes, and the retrieval of thermodynamic parameters from experimental data at elevated temperatures and pressures.

Thermodynamic Properties of Pure and Mixed Thermal Plasmas Over a Wide Range of Temperature and Pressure

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Omid Askari
Keyword(s):  
Thermodynamic Properties ◽  
Specific Heat ◽  
Fluid Dynamic ◽  
Thermal Plasmas ◽  
Statistical Thermodynamic ◽  
Reference Source ◽  
Degree Of Ionization ◽  
Wide Range ◽  
Self Consistent ◽  
Temperature And Pressure

Chemical composition and thermodynamics properties of different thermal plasmas are calculated in a wide range of temperatures (300–100,000 K) and pressures (10−6–100 atm). The calculation is performed in dissociation and ionization temperature ranges using statistical thermodynamic modeling. The thermodynamic properties considered in this study are enthalpy, entropy, Gibbs free energy, specific heat at constant pressure, specific heat ratio, speed of sound, mean molar mass, and degree of ionization. The calculations have been done for seven pure plasmas such as hydrogen, helium, carbon, nitrogen, oxygen, neon, and argon. In this study, the Debye–Huckel cutoff criterion in conjunction with the Griem’s self-consistent model is applied for terminating the electronic partition function series and to calculate the reduction of the ionization potential. The Rydberg and Ritz extrapolation laws have been used for energy levels which are not observed in tabulated data. Two different methods called complete chemical equilibrium and progressive methods are presented to find the composition of available species. The calculated pure plasma properties are then presented as functions of temperature and pressure, in terms of a new set of thermodynamically self-consistent correlations for efficient use in computational fluid dynamic (CFD) simulations. The results have been shown excellent agreement with literature. The results from pure plasmas as a reliable reference source in conjunction with an alternative method are then used to calculate the thermodynamic properties of any arbitrary plasma mixtures (mixed plasmas) having elemental atoms of H, He, C, N, O, Ne, and Ar in their chemical structure.

The thermodynamic properties of mixed phospholipid bilayers: a theoretical analysis

1984 ◽  
Vol 62 (8) ◽  
pp. 796-802 ◽  
Author(s):  
Maryse Mondat ◽  
A. Georgallas ◽  
D. A. Pink ◽  
M. J. Zuckermann
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
Reasonable Agreement ◽  
Phospholipid Bilayers ◽  
Scanning Calorimetry ◽  
Phase Separations ◽  
Lipid Mixtures ◽  
Wide Range ◽  
Acyl Chains ◽  
Gel Phase

A theoretical model is presented with the intention of describing lateral phase separations in binary lipid mixtures in which the acyl chains of the components differ in their length. The model includes explicitly interactions between the acyl chains and between polar heads of the lipid molecules. Phase diagrams and thermodynamic properties of binary lipid mixtures were calculated using a wide range of interaction parameters. It is shown that the occurrence of immiscibility in the gel phase is related to the interactions between the polar heads of the lipid molecules. The calculated results for binary lipid mixtures are compared with the available experimental data. In particular, the calculated specific heat for dilauroyl phosphatidylcholine – distearoyl phosphatidylcholine is in reasonable agreement with experimental results obtained from differential scanning calorimetry measurements.

Process Design for Superalloys Sheet Rotary Forming

2020 ◽  
Vol 985 ◽  
pp. 91-96
Author(s):  
Krzysztof Zaba ◽  
Sandra Puchlerska ◽  
Tomasz Pieja ◽  
Jaroslaw Pyzik
Keyword(s):  
Process Design ◽  
Elevated Temperatures ◽  
Nickel Superalloy ◽  
Inconel 625 ◽  
Quality Factors ◽  
Forming Process ◽  
Plastic Properties ◽  
Temperature Oxidation ◽  
Wide Range ◽  
The Impact

Inconel 625 is a nickel superalloy, characterized by high fatigue strength. The alloy is resistant to a wide range of corrosive environments, including high-temperature oxidation. For this reason, it is an attractive material for the chemical, shipbuilding and aviation industries. Inconel 625 alloy is designed for plastic working. However, the significant difficulty is the appropriate process design, due to the high deformation resistance. In order to improve the plastic properties of the alloy, processing at elevated temperatures is practiced. In this work, attempts were made to implement rotary forming process of Inconel 625 superalloy. For this purpose, an experiment was designed, investigating the impact of three variables on the process – feed rate, spinning rate and heating. For the tests were used Inconel 625 metal plates in the shape of discs. Axial-symmetrical products were formed, using a spinning machine. The geometry of the products according to selected quality factors was investigated. Optimal process parameters were chosen using multivariate statistical optimization. These parameters will be used to set up processes to obtain product that meets quality requirements.

Drought and water management in the German agricultural sector - a participatory system dynamics approach

2020 ◽  
Author(s):  
Rodrigo Valencia ◽  
Sabine Egerer ◽  
María Máñez
Keyword(s):  
Climate Change ◽  
Water Management ◽  
Water Balance ◽  
System Dynamics ◽  
Model Building ◽  
Elevated Temperatures ◽  
Agricultural System ◽  
Group Model ◽  
Wide Range ◽  
The Impact

<p>Higher temperatures and changes in precipitation patterns caused by climate change may potentially affect water availability for agriculture and increase the risk of crop loss in Northeast Lower Saxony (NELS), Germany. The drought of 2018 showed that an intensification of irrigation might be a temporary solution. However, a long-term increase in water extraction, especially during drought periods, is not a sustainable solution. To assess possible water management solutions, we implement a participatory system dynamics approach, namely Group Model Building, to develop a qualitative system dynamics model (QSDM) describing the agricultural system and its relation to water resources in NELS.</p><p>The development of the QSDM seeks to understand the complexity of the interactions between agriculture and hydrological systems, recognize the stakeholders’ needs and identify risks and weaknesses of both systems. By understanding this, we expect to reinforce the adaptation process, reduce conflict and be able to suggest tailored solutions and adaptation measures. The QSDM incorporates a wide range of perceptions, as twenty stakeholders ranging from farmers, government agencies, environmental protection organizations and local water authorities were involved in the QSDM development. Their perceptions were recorded in the QSDM through individual interviews and a group workshop.</p><p>Through the QSDM, we identified and mapped the structure and connections between agriculture and the water balance. It was also possible to identify the strongest feedback loops governing both sectors as well as their influence on the current situation. The loops represent behaviors and structures, which might become unmanageable under climate change conditions. The causal loops include the different uses for the available water of the region, the impact of irrigation, the significance of crop selection and the importance of sustainable soil management.</p><p>By analyzing the system this way, we confirmed that climate change poses a risk to the region as elevated temperatures could increase the crop water demand and increase the need for irrigation. In the same way, changes in the rain patterns could affect the water balance of the region. The agricultural system has, however, potential to adapt by implementing new water management strategies such as restructuring water rights, water storage and reuse and conjunctive water use. Other measures include increasing the irrigation efficiency, changing crops and enhancing the soil quality, among others.</p>

First-Principles Calculations of Elastic and Thermodynamic Properties of Cubic CdTe

2011 ◽  
Vol 268-270 ◽  
pp. 886-891
Author(s):  
Ben Hai Yu ◽  
Dong Chen
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Thermodynamic Properties ◽  
Bulk Modulus ◽  
First Principles ◽  
Debye Model ◽  
First Principles Calculations ◽  
Lattice Constants ◽  
Temperature And Pressure ◽  
The Relationship

the equilibrium lattice constants, elastic and thermodynamic properties of cubic CdTe are systemically investigated at high temperature using the plane-wave pseudopotential method as well as the quasi-harmonic Debye model. The bulk modulus of CdTe are calculated as a function of temperature up to 1000K, the relationship between bulk modulusBand pressure is also obtained. The results gained from this model will provide overall predictions accurately for the temperature and pressure dependence of various quantities such as the bulk modulus, the heat capacity and the thermal expansion coefficient. More over, the dependences between Debye temperature and temperature are also successfully obtained. Our results are compared with the experimental data and discussed in light of previous works.

The Significance of Vibration in Concrete Mixing

2012 ◽  
Vol 220-223 ◽  
pp. 509-512 ◽  
Author(s):  
Hong Shen ◽  
Zhi Shan Duan ◽  
Fei Li
Keyword(s):  
Experimental Data ◽  
Mechanical Engineering ◽  
Uniform Density ◽  
Linear Fitting ◽  
Wide Range ◽  
Vibration Technology ◽  
The Impact

With a wide range of applications of vibration technology in mechanical engineering, the vibratory mixing has been a hot topic and one of concrete mixing mechanical’s development directions. As the previous study of the significance about vibration used into concrete mixing is only limited on the experience and the experimental data, the linear fitting of experimental data is made by using MATLAB language. Then, the impact and significance that of vibration and fresh concrete’s microscopic uniform density is analyzed.

Compact Analytical Models of Effective Thermal Conductivity of Rough Spheroid Packed Beds

2004 ◽  
Author(s):  
M. Bahrami ◽  
M. M. Yovanovich ◽  
J. R. Culham
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Present Model ◽  
Thermal Analyses ◽  
Contact Load ◽  
Analytical Models ◽  
Packed Beds ◽  
Wide Range ◽  
Temperature And Pressure

New compact analytical models for predicting the effective thermal conductivity of regularly packed beds of rough spheres immersed in a stagnant gas are developed. Existing models do not consider either the influence of the spheres roughness or the rarefaction of the interstitial gas on the conductivity of the beds. Contact mechanics and thermal analyses are performed for uniform size spheres packed in SC and FCC arrangements and the results are presented in the form of compact relationships. The present model accounts for the thermophysical properties of spheres and the gas, contact load, spheres diameter, spheres roughness and asperities slope, and temperature and pressure of the gas. The present model is compared with experimental data for SC and FCC packed beds and good agreement is observed. The experimental data cover a wide range of the contact load, surface roughness, interstitial gas type, and gas temperature and pressure.

scholarly journals Thermodynamic description of alkali metal hydroxides over a wide range of temperatures, pressures and densities of aqueous fluids

2019 ◽  
Vol 98 ◽  
pp. 05001 ◽  
Author(s):  
Nikolay Akinfiev
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
Alkali Metal ◽  
Quantum Chemical ◽  
Dissociation Constants ◽  
Thermodynamic Description ◽  
Metal Hydroxides ◽  
Alkali Metal Hydroxides ◽  
Wide Range

All available experimental data on dissociation constants of aqueous hydroxides of Na, K, and Li were critically assembled and together with quantum chemical estimations used to evaluate parameters of the AD EoS [1] for corresponding aqueous molecules NaOH(aq), KOH(aq), and LiOH(aq). Use of the proposed approach allows proper prediction of the whole set of thermodynamic properties of these hydroxides over a wide range of temperatures (0 – 800 °C), pressures (0.1 – 800 MPa) and solvent densities (0.03 – 1.1 g·cm-3).

scholarly journals REE Characteristics of Lower Cretaceous Limestone Succession in Gümüşhane, NE Turkey: Implications for Ocean Paleoredox Conditions and Diagenetic Alteration

Minerals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 683 ◽  
Author(s):  
Merve Özyurt ◽  
M. Ziya Kırmacı ◽  
Ihsan Al-Aasm ◽  
Cathy Hollis ◽  
Kemal Taslı ◽  
...  
Keyword(s):  
Lower Cretaceous ◽  
Elevated Temperatures ◽  
Basaltic Magma ◽  
Sudden Change ◽  
Hydrothermal Activity ◽  
Rock Interaction ◽  
Diagenetic Alteration ◽  
General Chemical ◽  
Wide Range ◽  
Micritic Limestones

Trace and rare earth elements (REEs) are considered to be reliable indicators of chemical processes for the evolution of carbonate systems. One of the best examples of ancient carbonate successions (Berdiga Formation) is widely exposed in NE Turkey. The Lower Cretaceous limestone succession of Berdiga Formation may provide a case study that reveals the effect of ocean paleoredox conditions on diagenetic alteration. Measurement of major, trace and REEs was carried out on the Lower Cretaceous limestones of the Berdiga Formation, to reveal proxies for paleoredox conditions and early diagenetic controls on their geochemistry. Studied micritic limestone microfacies (MF-1 to MF-3) indicate deposition in the inner platform to a deep shelf or continental slope paleoenvironment during the Hauterivian-Albian. The studied limestone samples mainly exhibit low Mg-calcite characteristics with the general chemical formula of Ca98.35–99.34Mg0.66–1.65(CO3). They are mostly represented by a diagnostic REE seawater signature including (1) slight LREE depletion relative to the HREEs (ave. 0.72 of Nd/YbN and ave. 0.73 of Pr/YbN), (2) negative Ce anomalies (Ce/Ce* = 0.38–0.81; ave. 0.57), (3) positive La anomaly (La/La* = 0.21–3.02; ave. 1.75) and (4) superchondritic Y/Ho (ave. 46.26). Studied micritic limestones have predominantly low Hf (bdl to 0.5 µg/g), Sc (bdl to 2 µg/g) Th (bdl to 0.9 µg/g) contents suggesting negligible to minor shale contamination. These findings imply that micritic limestones faithfully record chemical signals of their parental and diagenetic fluids. The succession also exhibits high ratios of Eu/Eu* (1.01–1.65; ave. 1.29 corresponding to the positive Eu anomalies), Sm/Yb (1.26–2.74; ave. 1.68) and La/Yb ratios (0.68–1.35; ave. 0.9) compared to modern seawater and wide range of Y/Ho ratios (29.33–70.00; ave. 46.26) which are between seawater and hydrogenetic Fe-Mn crusts. Several lines of geochemical evidence suggest water-rock interaction between parental seawater and basaltic rocks at elevated temperatures triggered by hydrothermal activity associated with Early Cretaceous basaltic magma generation. The range of Ce/Ce* values is suggestive of mostly oxic to dysoxic paleoceanographic conditions, with a sudden change to dysoxic conditions (Ce/Ce* = 0.71–0.81), in the uppermost part of the MF-1. This is followed by an abrupt deepening paleoenvironment with a relative increase in the oxic state of the seawater and deposition of deeper water sediments (MF-2 and MF-3) above a sharp transition. The differences in microfacies characteristics and foraminifera assemblage between MF-1 and overlying facies (MF-2 and MF-3) may also confirm the change in paleoceanographic conditions. Therefore, REEs data obtained from studied limestones have the potential to contribute important information as to regional paleoceanographic conditions of Tethys during an important period in Earth history.

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