Academic literature on the topic 'Equations of state and thermodynamic models Peng-Robinson'
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Journal articles on the topic "Equations of state and thermodynamic models Peng-Robinson"
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Durakovic and Skaugen. "Analysis of Thermodynamic Models for Simulation and Optimisation of Organic Rankine Cycles." Energies 12, no. 17 (August 27, 2019): 3307. http://dx.doi.org/10.3390/en12173307.
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Equations of state (EOSs) form the base of every thermodynamic model used in the design of industrial processes, but little work has been done to evaluate these in the context of such models. This work evaluates 13 EOSs for their accuracy, computational time and robustness when used in an in-house optimisation program that finds the maximum power output of an organic Rankine cycle. The EOSs represent popular choices in the industry, such as the simple cubic EOSs, and more complex EOSs such as the ones based on corresponding state principles (CSP). These results were compared with results from using the Groupe Européen de Recherches Gazières (GERG) EOS, whose error is within experimental uncertainty. It appears that the corresponding state EOSs find a solution to the optimisation problem notably faster than GERG without significant loss of accuracy. A corresponding state method which used the Peng–Robinson EOS to calculate the shape factors and a highly accurate EOS for propane as the reference EOS, was shown to have a total deviation of just 0.6% as compared to GERG while also being 10 times as fast. The CSP implementation was also more robust, being able to converge successfully more often.
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Trawiński, Paweł. "Development and implementation of mathematical models of working mediums for gas part of combined cycle gas turbine system in Python programming environment." E3S Web of Conferences 137 (2019): 01047. http://dx.doi.org/10.1051/e3sconf/201913701047.
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The working mediums in the gas turbine systems are: atmospheric air, natural gas and exhaust gases. For the detailed analysis of thermodynamic performance and values at characteristic points of the cycle it is necessary to know the relations defining: specific volume, specific isobaric and isochoric heat capacity, isentropic exponent, specific enthalpy and specific entropy. Mathematical models of thermodynamic parameters for the mentioned mediums were developed based on dependencies for mixtures of ideal and semi-ideal gases. The functions obtained for semi-ideal gas mixtures were extended by pressure correction factors derived from the Redlich-Kwong and Peng-Robinson equations of state. The thermodynamic parameters of the working mediums were dependent on the mass fractions of the components, temperature and pressure. Developed models approximated the behaviour and parameters of real gas mixtures. All calculation algorithms were implemented and optimized using appropriate numerical methods in the Python programming environment. As a result, mathematical models of working mediums for the gas part of the combined cycle gas turbine system were obtained.
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Mehl, Ana, Fabio P. Nascimento, Pedro W. Falcão, Fernando L. P. Pessoa, and Lucio Cardozo-Filho. "Vapor-Liquid Equilibrium of Carbon Dioxide + Ethanol: Experimental Measurements with Acoustic Method and Thermodynamic Modeling." Journal of Thermodynamics 2011 (May 24, 2011): 1–11. http://dx.doi.org/10.1155/2011/251075.
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Phase behavior of systems composed by supercritical carbon dioxide and ethanol is of great interest, especially in the processes involving supercritical extraction in which ethanol is used as a cosolvent. The development of an apparatus, which is able to perform the measurements of vapor-liquid equilibrium (VLE) at high pressure using a combination of the visual and the acoustic methods, was successful and was proven to be suited for determining the isothermal VLE data of this system. The acoustic method, based on the variation of the amplitude of an ultra-sound signal passing through a mixture during a phase transition, was applied to investigate the phase equilibria of the system carbon dioxide + ethanol at temperatures ranging from 298.2 K to 323.2 K and pressures from 3.0 MPa to 9.0 MPa. The VLE data were correlated with Peng-Robinson equation of state combined with two different mixing rules and the SAFT equations of state as well. The compositions calculated with the models are in good agreement with the experimental data for the isotherms evaluated.
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Ouaer, Hocine, Amir Hossein Hosseini, Menad Nait Amar, Mohamed El Amine Ben Seghier, Mohammed Abdelfetah Ghriga, Narjes Nabipour, Pål Østebø Andersen, Amir Mosavi, and Shahaboddin Shamshirband. "Rigorous Connectionist Models to Predict Carbon Dioxide Solubility in Various Ionic Liquids." Applied Sciences 10, no. 1 (December 31, 2019): 304. http://dx.doi.org/10.3390/app10010304.
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Estimating the solubility of carbon dioxide in ionic liquids, using reliable models, is of paramount importance from both environmental and economic points of view. In this regard, the current research aims at evaluating the performance of two data-driven techniques, namely multilayer perceptron (MLP) and gene expression programming (GEP), for predicting the solubility of carbon dioxide (CO2) in ionic liquids (ILs) as the function of pressure, temperature, and four thermodynamical parameters of the ionic liquid. To develop the above techniques, 744 experimental data points derived from the literature including 13 ILs were used (80% of the points for training and 20% for validation). Two backpropagation-based methods, namely Levenberg–Marquardt (LM) and Bayesian Regularization (BR), were applied to optimize the MLP algorithm. Various statistical and graphical assessments were applied to check the credibility of the developed techniques. The results were then compared with those calculated using Peng–Robinson (PR) or Soave–Redlich–Kwong (SRK) equations of state (EoS). The highest coefficient of determination (R2 = 0.9965) and the lowest root mean square error (RMSE = 0.0116) were recorded for the MLP-LMA model on the full dataset (with a negligible difference to the MLP-BR model). The comparison of results from this model with the vastly applied thermodynamic equation of state models revealed slightly better performance, but the EoS approaches also performed well with R2 from 0.984 up to 0.996. Lastly, the newly established correlation based on the GEP model exhibited very satisfactory results with overall values of R2 = 0.9896 and RMSE = 0.0201.
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GUARDONE, ALBERTO, CALIN ZAMFIRESCU, and PIERO COLONNA. "Maximum intensity of rarefaction shock waves for dense gases." Journal of Fluid Mechanics 642 (December 23, 2009): 127–46. http://dx.doi.org/10.1017/s0022112009991716.
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Modern thermodynamic models indicate that fluids consisting of complex molecules may display non-classical gasdynamic phenomena such as rarefaction shock waves (RSWs) in the vapour phase. Since the thermodynamic region in which non-classical phenomena are physically admissible is finite in terms of pressure, density and temperature intervals, the intensity of RSWs is expected to exhibit a maximum for any given fluid. The identification of the operating conditions leading to the RSW with maximum intensity is of paramount importance for the experimental verification of the existence of non-classical phenomena in the vapour phase and for technical applications taking advantage of the peculiarities of the non-classical regime. This study investigates the conditions resulting in an RSW with maximum intensity in terms of pressure jump, wave Mach number and shock strength. The upstream state of the RSW with maximum pressure drop is found to be located along the double-sonic locus formed by the thermodynamic states associated with an RSW having both pre- and post-shock sonic conditions. Correspondingly, the maximum-Mach thermodynamic and maximum-strength loci locate the pre-shock states from which the RSW with the maximum wave Mach number and shock strength can originate. The qualitative results obtained with the simple van der Waals model are confirmed with the more complex Stryjek–Vera–Peng–Robinson, Martin–Hou and Span–Wagner equations of state for selected siloxane and perfluorocarbon fluids. Among siloxanes, which are arguably the best fluids for experiments aimed at the generation and measurement of an RSW, the state-of-the-art Span–Wagner multi-parameter equation of state predicts a maximum wave Mach number close to 1.026 for D6 (dodecamethylcyclohexasiloxane, [O-Si-(CH3)2]6). Such value is well within the capacity of the measurement system of a newly built experimental set-up aimed at the first-ever demonstration of the existence of RSWs in dense vapours.
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Sima, Sergiu, and Catinca Secuianu. "The Effect of Functional Groups on the Phase Behavior of Carbon Dioxide Binaries and Their Role in CCS." Molecules 26, no. 12 (June 18, 2021): 3733. http://dx.doi.org/10.3390/molecules26123733.
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In recent years we have focused our efforts on investigating various binary mixtures containing carbon dioxide to find the best candidate for CO2 capture and, therefore, for applications in the field of CCS and CCUS technologies. Continuing this project, the present study investigates the phase behavior of three binary systems containing carbon dioxide and different oxygenated compounds. Two thermodynamic models are examined for their ability to predict the phase behavior of these systems. The selected models are the well-known Peng–Robinson (PR) equation of state and the General Equation of State (GEOS), which is a generalization for all cubic equations of state with two, three, and four parameters, coupled with classical van der Waals mixing rules (two-parameter conventional mixing rule, 2PCMR). The carbon dioxide + ethyl acetate, carbon dioxide + 1,4-dioxane, and carbon dioxide + 1,2-dimethoxyethane binary systems were analyzed based on GEOS and PR equation of state models. The modeling approach is entirely predictive. Previously, it was proved that this approach was successful for members of the same homologous series. Unique sets of binary interaction parameters for each equation of state, determined for the carbon dioxide + 2-butanol binary model system, based on k12–l12 method, were used to examine the three systems. It was shown that the models predict that CO2 solubility in the three substances increases globally in the order 1,4-dioxane, 1,2-dimethoxyethane, and ethyl acetate. CO2 solubility in 1,2-dimethoxyethane, 1.4-dioxane, and ethyl acetate reduces with increasing temperature for the same pressure, and increases with lowering temperature for the same pressure, indicating a physical dissolving process of CO2 in all three substances. However, CO2 solubility for the carbon dioxide + ether systems (1,4-dioxane, 1,2-dimethoxyethane) is better at low temperatures and pressures, and decreases with increasing pressures, leading to higher critical points for the mixtures. By contrast, the solubility of ethyl acetate in carbon dioxide is less dependent on temperatures and pressures, and the mixture has lower pressures critical points. In other words, the ethers offer better solubilization at low pressures; however, the ester has better overall miscibility in terms of lower critical pressures. Among the binary systems investigated, the 1,2-dimethoxyethane is the best solvent for CO2 absorption.
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OKONG'O, NORA A., and JOSETTE BELLAN. "Direct numerical simulation of a transitional supercritical binary mixing layer: heptane and nitrogen." Journal of Fluid Mechanics 464 (August 10, 2002): 1–34. http://dx.doi.org/10.1017/s0022112002008480.
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Direct numerical simulations (DNS) of a supercritical temporal mixing layer are conducted for the purpose of exploring the characteristics of high-pressure transitional mixing behaviour. The conservation equations are formulated according to fluctuation-dissipation (FD) theory, which is consistent with non-equilibrium thermodynamics and converges to kinetic theory in the low-pressure limit. According to FD theory, complementing the low-pressure typical transport properties (viscosity, diffusivity and thermal conductivity), the thermal diffusion factor is an additional transport property which may play an increasingly important role with increasing pressure. The Peng–Robinson equation of state with appropriate mixing rules is coupled to the dynamic conservation equations to obtain a closed system. The boundary conditions are periodic in the streamwise and spanwise directions, and of non-reflecting outflow type in the cross-stream direction. Due to the strong density stratification, the layer is considerably more difficult to entrain than equivalent gaseous or droplet-laden layers, and exhibits regions of high density gradient magnitude that become very convoluted at the transitional state. Conditional averages demonstrate that these regions contain predominantly the higher-density, entrained fluid, with small amounts of the lighter, entraining fluid, and that in these regions the mixing is hindered by the thermodynamic properties of the fluids. During the entire evolution of the layer, the dissipation is overwhelmingly due to species mass flux followed by heat flux effects with minimal viscous contribution, and there is a considerable amount of backscatter in the flow. Most of the species mass flux dissipation is due to the molecular diffusion term with significant contributions from the cross-term proportional to molecular and thermal diffusion. These results indicate that turbulence models for supercritical fluids should primarily focus on duplicating the species mass flux rather than the typical momentum flux, which constitutes the governing dissipation in atmospheric mixing layers. Examination of the passive-scalar probability density functions (PDFs) indicates that neither the Gaussian, nor the beta PDFs are able to approximate the evolution of the DNS-extracted PDF from its inception through transition. Furthermore, the temperature–species PDFs are well correlated, meaning that their joint PDF is not properly approximated by the product of their marginal PDFs; this indicates that the traditional reactive flow modelling based on replacing the joint PDF representing the reaction rate by the product of the marginal PDFs is not appropriate. Finally, the subgrid-scale temperature–species PDFs are also well correlated, and the species PDF exhibits important departures from the Gaussian. These results suggest that classic PDFs used in atmospheric pressure flows would not capture the physics of this supercritical mixing layer, either in an assumed PDF model at the larger scale, or at the subgrid scale.
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Prieto Jiménez, Natalia, and Germán González Silva. "Comparative Study of Equations of State for the Dew Curves Calculation in High Pressure Natural Gas Mixtures. [Estudio Comparativo de Ecuaciones de Estado para el Cálculo de Curvas de Rocío en Mezclas de Gas Natural a Alta Presión]." Revista Logos Ciencia & Tecnología 11, no. 1 (December 30, 2018): 152–64. http://dx.doi.org/10.22335/rlct.v11i1.743.
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he success during the operation of natural gas processing plants depends on the correct estimation of thermodynamic properties of the system. This paper calculates the equilibrium curves of real and synthetic natural gas mixtures means of three Equations of State (EOS). These equilibrium curves were constructed and compared with experimental data found in the literature covered. The results showed that, above 4 MPa the Peng-Robinson equation presented a considerable deviation with respect to the experimental data, reaching an absolute error of 4.36%; therefore, the GERG2008 equation is recommended for systems that operate at high pressures when the components present in the mixture apply.Keywords:Gas Mixtures, Dew curves, Equations of State; Peng-Robinson, Soave-Redlich-Kwong, GERG2008.ResumenEl éxito durante la operación de plantas de tratamiento de gas natural depende de la correcta estimación de las propiedades termodinámicas del sistema. Este artículo calcula las curvas de equilibrio de mezclas de gas natural reales y sintéticas por medio de tres ecuaciones de estado (EOS). Estas curvas de equilibrio fueron construidas y comparadas con datos experimentales presentes en la literatura. Los resultados mostraron que, por encima de 4 MPa la ecuación de Peng-Robinson presentó una desviación considerable con respecto a los datos experimentales, alcanzando un error absoluto de 4,36%; por lo cual se recomienda la ecuación de GERG2008 para sistemas que operen a altas presiones cuando los componentes presentes en la mezcla apliquen.Palabras clave: Mezclas de gas, Curvas de rocío, Ecuaciones de estado, Peng-Robinson, Soave-Redlich-Kwong, GERG2008.ResumoO sucesso na operação de usinas de tratamento de gás natural depende da correta estimação das propriedades termodinâmicas do sistema. Este artigo calcula as curvas de equilíbrio de misturas de gás natural reais e sintéticas por meio de três equações de estado (EOS). As curvas de equilíbrio foram construídas e comparadas com dados experimentais presentes na literatura. Os resultados mostraram que, acima de 4 Mpa a equação de Peng-Robinson apresentou um desvio considerável em relação aos dados experimentais, atingindo um erro absoluto de 4,36%; por tanto, é recomendável a equação de GERG2008 para sistemas que operam em alta pressão quando os componentes presentes no sistema apliquem.Palavras-chave:Misturas de gás, Curvas de orvalho, Equações de estado, Peng-Robinson, Soave-Redlich-Kwong, GERG2008.
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Hussain, B., and M. Ahsan. "A Numerical Comparison of Soave Redlich Kwong and Peng-Robinson Equations of State for Predicting Hydrocarbons’ Thermodynamic Properties." Engineering, Technology & Applied Science Research 8, no. 1 (February 20, 2018): 2422–26. http://dx.doi.org/10.48084/etasr.1644.
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Mixture phase equilibrium and thermodynamic properties have a significant role in industry. Numerical analysis of flash calculation generates an appropriate solution for the problem. In this research, a comparison of Soave Redlich Kwong (SRK) and Peng-Robinson (PR) equations of state predicting the thermodynamic properties of a mixture of hydrocarbon and related compounds in a critical region at phase equilibrium is performed. By applying mathematical modeling of both equations of states, the behavior of binary gases mixtures is monitored. The numerical analysis of isothermal flash calculations is applied to study the pressure behavior with volume and mole fraction. The approach used in this research shows considerable convergence with experimental results available in the literature.
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Palmer, S. C., and S. V. Shelton. "Sensitivity Analysis of Absorption Cycle Fluid Thermodynamic Properties." Journal of Energy Resources Technology 121, no. 2 (June 1, 1999): 137–41. http://dx.doi.org/10.1115/1.2795069.
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Absorption heat pump technology may be improved by new cycle configurations by new working fluids. In this study, the effect of hypothetical working fluids on performance improvement is explored. The performance of two cycles is studied using three fluid property sources for ammonia/water, i.e., curve-fit experimental data, an ideal solution model, and the Peng-Robinson equation of state model. The models require only minimal fundamental thermodynamic property data for the two pure components. This allows investigation into the influence of each fundamental property on cycle performance, providing insight into desirable properties for new absorption fluid pairs. Variations of fundamental fluid properties are used as input to the models, showing that the volatilities of the refrigerant and absorbent have the greatest effect on cycle performance.
Dissertations / Theses on the topic "Equations of state and thermodynamic models Peng-Robinson"
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Attia, Ben Amor Afef. "Contribution à la modélisation thermodynamique d'un atelier de purification d'acide acrylique." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0254/document.
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Ce travail porte sur la contribution à la modélisation thermodynamique d'un atelier de purification d'acide acrylique. Après l'identification des principaux produits intervenant dans l'étape de purification et la collecte de leurs propriétés thermodynamiques disponibles dans la littérature, nous avons effectué une série de mesures expérimentales pour un ensemble de mélanges contenant des acides carboxyliques (en particulier : diagrammes d'équilibres liquide-liquide et équilibres liquide-vapeur, enthalpies d'excès et volumes d'excès). L'ensemble des données (nos mesures et les valeurs de la littérature) a été exploité selon deux approches de modélisation des équilibres liquide-vapeur : une approche symétrique (φ-φ) appliquée aux équations d'état de Peng-Robinson (P-R) et de PC-SAFT et une approche dissymétrique (γ-φ) appliquée aux modèles de coefficients d'activité en phase liquide NRTL, UNIQUAC et Van Laar associés à diverses équations d'état en phase vapeur (gaz parfait, Viriel, Hayden et O'Connell et Nothnagel). Nous avons finalement retenu le modèle UNIQUAC associé à la corrélation de Hayden et O'Connell en phase vapeur. Des nouveaux paramètres d'interaction ont été déterminés et conduisent à des résultats homogènes et satisfaisants en comparaison avec nos mesures expérimentales et aux données de la littérature. Ils permettent également de décrire convenablement les diagrammes d'équilibres liquide-vapeur et les volatilités relatives des mélanges étudiésThis work focuses on the contribution in the thermodynamic modeling of an acrylic acid purification unit. After identifying the main products involved in the purification step and collecting their thermodynamic properties available in the literature, we conducted a series of experimental measurements for a range of mixtures containing carboxylic acids(mainly liquid-liquid equilibrium and vapor-liquid equilibrium diagrams, excess enthalpies and excess volumes).The data set-our measurements and literature values-was used according to two approaches for modeling vapor-liquid equilibrium: a symmetric approach(φ-φ) applied to the equations of state Peng-Robinson (P-R) and PC-SAFT and an asymmetrical approach (γ-φ) applied to the models of activity coefficients in the liquid phase NRTL, UNIQUAC and Van Laar associated with various equations of state in the vapor phase(ideal gas, Viriel, Hayden O'Connell and Nothnagel). We have finally chosen the UNIQUAC thermodynamic model associated with the correlation of Hayden O'Connell in vapor phase. New binary parameters were determined and led to consistent and satisfactory results in comparison with our experimental measurements and literature data. These parameters can also be used to adequately describe the diagrams of vapor-liquid equilibrium and the relative volatilities of the mixtures studied
Book chapters on the topic "Equations of state and thermodynamic models Peng-Robinson"
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Mohamed Mansour, Eman. "Equation of State." In Inverse Heat Conduction and Heat Exchangers. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.89919.
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An equation of state (EOS) is a thermodynamic expression that relates pressure (P), temperature (T), and volume (V). This equation is used to describe the state of reservoir fluids at given conditions. The cubic equations of state (CEOS) such as Van der Waals, Redlich-Kwong, Soave, and Peng-Robinson are simple models that have been widely used in the oil industry. This chapter expressed literature for EOS that varies from simple expressions to multiple constant and convoluted types of equations. Many attempts have been made to describe the thermodynamic behavior of fluids to predict their physical properties at given conditions. So, several forms of the equation of state have been presented to the oil industry in order to calculate reservoir fluid properties. The heat exchanger is important in wildly fields as in aerospace, petrochemical industry, refrigeration, and other fields. The optimization design of the heat exchanger is a great significance to industry process to reduce production cost, realize energy conservation, and reduce energy consumption.
Conference papers on the topic "Equations of state and thermodynamic models Peng-Robinson"
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Ayala, Luis F., Eltohami S. Eltohami, and Michael A. Adewumi. "A Unified Two-Fluid Model for Multiphase Flow in Natural Gas Pipelines." In ASME 2002 Engineering Technology Conference on Energy. ASMEDC, 2002. http://dx.doi.org/10.1115/etce2002/prod-29119.
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A unified two-fluid model for multiphase natural gas and condensate flow in pipelines is presented. The hydrodynamic model consists of steady-state one-dimensional mass and continuity balances for each phase and a combined energy equation to give a system of five first-order ordinary differential equations. The hydrodynamic model is coupled with a phase behavior model based on the Peng-Robinson equation of state to handle the vapor-/liquid equilibrium calculations and thermodynamic property predictions. The model handles single and two-phase flow conditions and is able to predict the transition between them. It also generates profiles for pressure, temperature, and the fluid velocities in both phases as well as their holdups. The expected flow patterns as well as their transitions are modeled with emphasis on the low liquid loading character of such systems. The expected flow regimes for this system are dispersed liquid, annular-mist, stratified smooth as well as stratified wavy.
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Li, Longjian, Jianbang Zeng, Quan Liao, and Wenzhi Cui. "A New Lattice Boltzmann Model for Phase Transition Process." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-10961.
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A new lattice Boltzmann model, which is based on Shan-Chen (SC) model, is proposed to describe liquid-vapor phase transitions. The new model is validated through simulation of the one-component phase transition process. Compared with the simulation results of van der Waals fluid and the Maxwell equal-area construction, the results of new model are closer to the analytical solutions than those of SC model and Zhang model. Since the range of temperature and the maximum density ratio are increased, and the value of maximum spurious current is between those of SC and Zhang models, it is believed that this new model has better stability than SC and Zhang models. Therefore, the application scope of this new model is expanded. According to the principle of corresponding states in Engineering Thermodynamics, the simulations of water and ammonia phase transition process are implemented by using this new model with different equations of state. Compared to the experimental data of water and ammonia, the results show that the Peng-Robinson equation of state is more suitable to describe the water, ammonia and other substances phase transition process. Therefore, these simulation results have great significance for the real engineering applications.
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Hasselmann, Karsten, Stefan aus der Wiesche, and Eugeny Y. Kenig. "Assessment of Compressible RANS and LES Methods for Organic Vapor Flows Past a NACA4412 Airfoil." In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-4843.
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Abstract In this contribution, an assessment of compressible Reynolds Averaged Navier Stokes equations (RANS) and Large Eddy Simulation (LES) is presented using transonic organic vapor flow past a NACA4412 airfoil as a case study. The NACA4412 represents a canonical geometry, which, in case of air, has been well investigated numerically and experimentally. The results of the real gas simulations are compared with those of air simulations. For the real gas, the organic vapor Novec 649® is chosen as a representative fluid. The thermodynamic behavior of Novec 649® is modeled with the Peng-Robinson equation of state. Different inlet Mach numbers are applied, namely, a sub-critical, the critical, and a super-critical Mach number. It turns out, that the critical Mach number of the NACA4412 airfoil increases when Novec 649® is used as working fluid. Furthermore, it is shown that real gas flow simulations cause additional difficulties for the computational fluid dynamics (CFD) analysis. Although the speed of sound of Novec 649® is lower than the speed of sound of air, a finer grid resolution is required for the real gas simulations due to its high density. Based on an extensive simulation study, an assessment of different numerical modelling strategies and methods is given.
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Kumar, Sumit K., Rainer Kurz, and John P. O’Connell. "Equations of State for Gas Compressor Design and Testing." In ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-012.
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In the design and testing of gas compressors, the correct determination of the thermodynamic properties of the gas. such as enthalpy, entropy and density from pressure, temperature and composition, plays an important role. Due to the wide range of conditions encountered, pressure, specific volume and temperature (p-v-T) equations of state (EOS) and ideal gas heat capacities, along with measured data, are used to determine the isentropic efficiency of a compressor configuration and to model the actual behavior of real gases and compressors. There are many possible model choices. The final selection should depend on the applicability of the EOS to the gas and the temperature dependence of the heat capacities, as well as the particular process of interest along with the range of pressures and temperatures encountered. This paper compares the thermodynamic properties from five commonly used equations in the gas compressor industry: the Redlich-Kwong (RK), Redlich-Kwong-Soave (RKS), Peog-Robinson (PR), Benedict-Webb-Rubin-Starling (BWRS), and Lee-Kesler-Plocker (LKP) models. It also compares them with a high accuracy EOS for methane from Wagner and Setzmann in the common range for gas compressors. The validity of a linear temperature dependence for ideal gas heat capacities is also evaluated. The objective was to determine if the models give significant differences in their predicted efficiencies. It was found that different EOS gave somewhat different enthalpy changes for methane, ethane and nitrogen for real compressions. This appeared to be connected to the different densities given by the models. Interestingly, the isentropic enthalpy changes are quite similar, suggesting that the effect is canceled out when two properties are involved. However, since the efficiency is the ratio of isentropic enthalpy change to actual enthalpy change, the EOS yield different efficiencies. These differences are on the same order as the typical tolerances allowed for prediction and testing of industrial gas compressors (3 to 5%) and comparisons with the highly accurate equation of state for pure methane from Wagner and Setzmann (1991) showed similar differences. Commonly, the ideal gas heat capacity is assumed linear in temperature from 10 to 150°C (50 to 300°F). Comparison of this form with a quadratic expression from the literature and the highly accurate equation of Wagner and Setzmann for methane, showed insignificant differences among the methods for temperatures up to 600°K (1080°R).
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Robertson, Miles C., Peter J. Newton, Tao Chen, and Ricardo F. Martinez-Botas. "Development and Commissioning of a Blowdown Facility for Dense Gas Vapours." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91609.
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Abstract The Organic Rankine Cycle is a candidate technology for low grade heat recovery, from sources as diverse as geothermal, solar and industrial/vehicle waste heat. The organic working fluids used within these systems often display significant real-gas effects, especially in proximity of the thermodynamic critical point. Significant research has therefore been performed on the design of real-gas expansion devices, including both positive displacement and rotordynamic machinery. 3D Computational Fluid Dynamics (CFD) is commonly used for performance prediction and flow field analysis within expanders, and experimental validation of these simulations within a real-gas environment are scarce within the literature. This paper therefore presents a dense-gas blowdown facility constructed at Imperial College London, for the purpose of experimentally validating numerical simulations of these fluids. The system-level design process for the blowdown rig is detailed within this paper, including the sizing and specification of major components. A hemispherically-ended 3.785 L cylinder was selected as the main blowdown vessel, allowing a designpoint pressure and temperature of 3751 kPa and 477 K, respectively. Regulating valves were placed either side of the test section, allowing a Pressure Ratio to be fixed across the measurement section. The primary design focus of this paper is that of the test section — a converging-diverging nozzle producing an expansion of Mach 2 at the nozzle exit plane. The nozzle profile is generated by Method of Characteristics (MoC) modified to account for real-gas effects. Both mechanical and fluid dynamic design are discussed, along with location and thermal management of the nine pressure transducers, located along the nozzle centreline. A series of blowdown tests are conducted, firstly for a fluid conforming closely to the ideal gas Equation of State - Nitrogen (N2) at room temperature. A comparison between the experimental measurements and a CFD analysis of these results is taken as a benchmarking example. A second set of tests with refrigerant R1233zd(E) are run, across multiple inlet pressures - CFD simulations are subsequently performed, with the refrigerant modeled by Ideal Gas, Peng-Robinson, and Helmholtz energy (via REF-PROP) Equations of State. An error analysis is conducted for each, identifying that an increase in fluid model fidelity leads to reduced deviation between simulation and experiment. An average discrepancy of 11.1% in nozzle Pressure Ratio with the Helmholtz energy EoS indicates an over-prediction of expander power output within the CFD simulation.
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Delplanque, J. P., J. Labs, C. S. Lengsfeld, and T. E. Parker. "Effect of Thermodynamic Conditions on Droplet Size in Diesel Engines: Importance of an Advanced Surface Tension Model." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39057.
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The effort described in this extended abstract aims at elucidating how droplet secondary breakup is affected by surface tension behavior at thermodynamic conditions relevant to diesel engine operation. The droplet surface tension coefficient is calculated using the method of MacLeod and Sugden, which takes into account mixture and high-pressure phase equilibrium effects. To this end, high-pressure binary phase equilibrium is computed for prescribed droplet interface conditions using a Peng-Robinson equation of state. Finally, droplet propensity to secondary breakup is estimated based on recently developed criteria. The model thus obtained is compared to spray sizing data acquired in a Diesel Engine Simulator for dodecane.
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Müller, H., and M. Pfitzner. "Large-eddy simulation of transcritical liquid oxygen/methane jet flames." In Progress in Propulsion Physics – Volume 11. Les Ulis, France: EDP Sciences, 2019. http://dx.doi.org/10.1051/eucass/201911177.
Full textAbstract:
A numerical method to perform large-eddy simulations (LES) of nonpremixed liquid oxygen/methane (LOx/CH4) combustion at supercritical pressures is presented and the computational results are compared with available experimental data. The injection conditions of the considered test case resemble those in typical liquid-propellant rocket engines (LRE). Thermodynamic nonidealities are modeled using the Peng–Robinson (PR) equation of state (EoS) in conjunction with a novel volume-translation method to correct deficiencies in the transcritical regime. The resulting formulation is more accurate than the standard cubic EoS's without deteriorating their good computational efficiency. The real-gas thermodynamics model is coupled with the steady laminar flamelet model (SLFM) for turbulent nonpremixed combustion to incorporate chemical reactions at reasonable computational cost in the LES. A reduced reaction mechanism, which is validated with respect to the full mechanism, is used to generate a flamelet library. A comparison of the LES result with available OH* measurements shows that important flow features are well predicted.
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Jie, H. E., B. P. Xu, J. X. Wen, R. Cooper, and J. Barnett. "Predicting the Decompression Characteristics of Carbon Dioxide Using Computational Fluid Dynamics." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90649.
Full textAbstract:
In a previous paper, we reported the development of CFD-DECOM, a Computational Fluid Dynamics (CFD) model based on the Arbitrary Lagrangian Eulerian (ALE) approach and the Homogeneous Equilibrium Method (HEM) for simulating multi-phase flows, to predict the transient flow following the rupture of pipelines conveying rich gas or pure carbon dioxide (CO2). The use of CFD allows the effect of pipe wall heat transfer and friction to be quantified. Here, the former is considered through the implementation of a conjugate heat transfer model while the two-phase pipe wall friction is computed using established correlations. The model was previously validated for rich gas and to a limited extent dense phase CO2 decompression against the available shock tube test data. This paper describes the extension of the model to the decompression of both gaseous and dense phase CO2 with impurities. The Peng-Robinson-Stryjek-Vera Equation Of State (EOS), which is capable of predicting the real gas thermodynamic behaviour of CO2 with impurities, has been implemented in addition to the Peng-Robinson and Span and Wagner EOSs. The liquid-vapour phase equilibrium of a multi-component fluid is determined by flash calculations. The predictions are compared with the measurements of some of the recent gaseous and dense phase CO2 shock tube tests commissioned by National Grid. The detailed comparison is presented showing reasonably good agreement with the experimental data. Further numerical study has also been carried out to investigate the effects of wall friction and heat transfer, different EOSs and impurities on the decompression behaviour.
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Huh, Cheol, Seong Gil Kang, Sup Hong, Jong Su Choi, Il Sung Moon, Chonn Ju Lee, Mang Ik Cho, and Jong Hwa Baek. "Onshore and Offshore Transport Process Design for Carbon Dioxide Sequestration in a Marine Geological Structure." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-80077.
Full textAbstract:
In response to climate change, the Kyoto Protocol, and the need to reduce greenhouse gas emissions, researchers are looking to marine geological storage of CO2 as one of the most promising options. Marine geological storage of CO2 involves the capture of CO2 from major point sources (such as a power plant) and the transport of CO2 to storage sites in marine geological structures such as a deep sea saline aquifer. Since 2005, we have developed relevant technologies for marine geological storage of CO2. Those technologies include possible storage site surveys and basic designs for CO2 transport and storage processes. To design a reliable CO2 marine geological storage system, we devised a hypothetical scenario and used a numerical simulation tool to study its detailed processes. The process of transport CO2 from the capture sites to the storage sites can be simulated with a thermodynamic equation of state. We compared and analyzed the relevant equation of state, including the Benedict-Webb-Rubin-Starling (BWRS), Peng-Robinson (PR), Peng-Robinson-Boston-Mathias (PRBM) and Soave-Redlich-Kwong (SRK) equations of state. To evaluate the predictive accuracy of the equation of state, we compare the results of numerical calculations with experimental reference data. In a supercritical state (above 31.1°C and 73.9bar), which corresponds to the thermodynamic conditions of CO2 reservoir sites, the BWRS, PR, and PRBM equations of state showed a good predictive capability. On the other hand, the SRK equation of state showed a high error rate of 300% in the supercritical state. This paper analyzes the major design parameters that are useful for constructing onshore and offshore CO2 transport systems. On the basis of a parametric study of the hypothetical scenario, we suggest relevant variation ranges for the design parameters, particularly the flow rate, diameter, temperature, and pressure. Using the hypothetical scenario, we also studied how the thermodynamic conditions of CO2 affect on the fluid flow behavior and thermal characteristics of a pipeline transport system. In summary, this paper presents our analysis and deductions of the major design parameters that are useful for constructing onshore and offshore CO2 transport systems.
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Mobinipouya, Neda. "Deviation of the Calculated of Density of Refrigerant Fluids in Both Super and Sub Critical Regions." In ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2011. http://dx.doi.org/10.1115/icnmm2011-58132.
Full textAbstract:
A numerical procedure has successfully predicted accurate values of thermodynamic properties in seven cubic equations of state (EOS) in predicting thermodynamic properties of nine ozone-safe refrigerants both in super and sub-critical regions. Refrigerants include R22, R32, R123, R124, R125, R134a, R141b, R143, and R152a and equations of state, considered here, are Ihm-Song-Mason (ISM), Peng-Robinson (PR) [2], Redlich-Kwong (RK), Soave-Redlikh-Kwong (SRK), Modified Redlickh-Kwong (MRK), Nasrifar-Moshfeghian (NM), and TCC were shown in this paper. In general, the results are in favor of the preference of TCC and PR EOS over other remaining EOS’s in predicting gas densities of all aforementioned refrigerants in both super and sub critical regions. Typically, PR and SRK are in good agreement with those obtained from recent correlations and speed of sound measurements. Therefore, these two EOS stand over other EOS both in sub and super critical regions. All EOS follow two-parameter principle of corresponding states at T/Tc higher than 8 and lower than 1 except NM EOS. In the temperature range 1<T/Tc<8, PR and SRK still follow above mentioned principle. The same trend has been observed for other refrigerants.