Holographic Dark Energy Model with Modified Variable Chaplygin Gas
Paul, B. C.
2010-01-01
In this letter we consider a correspondence between holographic dark energy and variable modified Chaplygin gas to obtain a holographic dark energy model of the universe. The corresponding potential of the scalar field has been reconstructed which describes the modified variable Chaplygin gas. The stability of the holographic dark energy in this case is also discussed.
Dynamics of Warm Chaplygin Gas Inflationary Models With Quartic Potential
Jawad, Abdul; Rani, Shamaila
2016-01-01
Warm inflationary universe models in the context of generalized chaplygin gas, modified chaplygin gas, generalized cosmic chaplygin gas are being studied. The dissipative coefficient of the form $\\Gamma\\propto T$, weak and strong dissipative regimes are being considered. We use quartic potential $\\frac{\\lambda_{*}\\phi^{4}}{4}$, which is ruled out by current data in cold inflation but in our models it is analyzed that it is in agreement with the WMAP$9$ and latest Planck data. In these scenarios, the power spectrum, spectral index, and tensor to scalar ratio are being examined under the slow roll approximation. We show the dependence of tensor scalar ratio $r$ on spectral index $n_{s}$ and observe that the range of tensor scalar ratio is $r<0.05$ in generalized chaplygin gas, $r<0.15$ in modified chaplygin gas, and $r<0.12$ in generalized cosmic chaplygin gas models. Our results are in agreement with recent observational data like WMAP$9$ and latest Planck data.
Dynamics of warm Chaplygin gas inflationary models with quartic potential
Energy Technology Data Exchange (ETDEWEB)
Jawad, Abdul; Rani, Shamaila [COMSATS Institute of Information Technology, Department of Mathematics, Lahore (Pakistan); Butt, Sadaf [Lahore Leads University, Department of Mathematics, Lahore (Pakistan); Kinnaird College for Women, Department of Mathematics, Lahore (Pakistan)
2016-05-15
Warm inflationary universe models in the context of the generalized Chaplygin gas, the modified Chaplygin gas, and the generalized cosmic Chaplygin gas are being studied. The dissipative coefficient of the form Γ ∝ T, and the weak and the strong dissipative regimes are being considered. We use the quartic potential, (λ{sub *}φ{sup 4})/(4), which is ruled out by current data in cold inflation but in our models by analysis it is seen to be in agreement with the WMAP9 and the latest Planck data. In these scenarios, the power spectrum, the spectral index, and the tensor-to-scalar ratio are being examined in the slow-roll approximation. We show the dependence of the tensor-scalar ratio r on the spectral index n{sub s} and observe that the range of the tensor-scalar ratio is r < 0.05 in the generalized Chaplygin gas, r < 0.15 in the modified Chaplygin gas, and r < 0.12 in the generalized cosmic Chaplygin gas models. Our results are in agreement with recent observational data like WMAP9 and the latest Planck data. (orig.)
Limits from Weak Gravity Conjecture on Chaplygin-Gas-Type Models
Institute of Scientific and Technical Information of China (English)
WU Xing; ZHU Zong-Hong
2008-01-01
@@ The weak gravity conjecture is proposed as a criterion to distinguish the landscape from the swampland in string theory. As an application in cosmology of this conjecture, we use it to impose theoretical constraint on parameters of the Chaplygin-gas-type models. Our analysis indicates that the Chaplygin-gas-type models realized in quintessence field are in the swampland.
Interacting Entropy-Corrected Holographic Chaplygin Gas Model
Farooq, M. Umar; Jamil, Mubasher; Rashid, Muneer A.
2010-10-01
Holographic dark energy (HDE), presents a dynamical view of dark energy which is consistent with the observational data and has a solid theoretical background. Its definition follows from the entropy-area relation S( A), where S and A are entropy and area respectively. In the framework of loop quantum gravity, a modified definition of HDE called “entropy-corrected holographic dark energy” (ECHDE) has been proposed recently to explain dark energy with the help of quantum corrections to the entropy-area relation. Using this new definition, we establish a correspondence between modified variable Chaplygin gas, new modified Chaplygin gas and the viscous generalized Chaplygin gas with the entropy corrected holographic dark energy and reconstruct the corresponding scalar potentials which describe the dynamics of the scalar field.
Interacting entropy-corrected holographic Chaplygin gas model
Farooq, M Umar; Jamil, Mubasher
2010-01-01
Holographic dark energy (HDE), presents a dynamical view of dark energy which is consistent with the observational data and has a solid theoretical background. Its definition follows from the entropy-area relation $S(A)$, where $S$ and $A$ are entropy and area respectively. In the framework of loop quantum gravity, a modified definition of HDE called "entropy-corrected holographic dark energy" (ECHDE) has been proposed recently to explain dark energy with the help of quantum corrections to the entropy-area relation. Using this new definition, we establish a correspondence between modified variable Chaplygin gas, new modified Chaplygin gas and the viscous generalized Chaplygin gas with the entropy corrected holographic dark energy and reconstruct the corresponding scalar potentials which describe the dynamics of the scalar field.
First cosmological constraints on the Superfluid Chaplygin gas model
Lazkoz, Ruth; Salzano, Vincenzo
2012-01-01
In this work we set observational constraints of the Superfluid Chaplygin gas model, which gives a unified description of the dark sector of the Universe as a Bose-Einstein condensate (BEC) that behaves as dark energy (DE) while it is in the ground state and as dark matter (DM) when it is in the excited state. We first show and perform the various steps leading to a form of the equations suitable for the observational tests to be carried out. Then, by using a Markov Chain Monte Carlo (MCMC) code, we constrain the model with a sample of cosmology-independent long gamma-ray bursts (LGRBs) calibrated using their Type I Fundamental Plane, as well as the Union2.1 set and observational Hubble parameter data. In this analysis, using our cosmological constraints, we sketch the effective equation of state parameter and deceleration parameter, and we also obtain the redshift of the transition from deceleration to acceleration: $z_t$.
Viscous Chaplygin Gas Models as a Spherical Top-Hat Collapsing Fluids
Jawad, Abdul
2016-01-01
We study the spherical top-hat collapse in Einstein gravity and loop quantum cosmology by taking the non-linear evolution of viscous modified variable chaplygin gas and viscous generalized cosmic chaplygin gas. We calculate the equation of state parameter, square speed of sound, perturbed equation of state parameter, perturbed square speed of sound, density contrast and divergence of peculiar velocity in perturbed region and discussed their behavior. It is observed that both chaplygin gas models support the spherical collapse in Einstein as well as loop quantum cosmology because density contrast remains positive in both cases and the perturbed equation of state parameter remains positive at the present epoch as well as near future. It is remarked here that these parameters provide the consistence results for both chaplygin gas models in both gravities.
Modified Chaplygin gas as an interacting holographic dark energy model
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The modified Chaplygin gas (MCG) as an interacting model of holographic dark energy in which dark energy and dark matter are coupled together is investigated in this paper. Concretely, by studying the evolutions of related cosmological quantities such as density parameter Ω, equation of state w, deceleration parameter q and transition redshift zT, we find the evolution of the universe is from deceleration to acceleration, their present values are consistent with the latest observations, and the equation of state of holographic dark energy can cross the phantom divide w = -1. Furthermore, we put emphasis upon the geometrical diagnostics for our model, i.e., the statefinder and Om diagnostics. By illustrating the evolutionary trajectories in r - s, r - q, w -w and Om planes, we find that the holographic constant c and the coupling constant b play very important roles in the holographic dark energy (HDE) model. In addition, we also plot the LCDM horizontal lines in Om diagrams, and show the discrimination between the HDE and LCDM models.
Observational constraints on the new generalized Chaplygin gas model
Institute of Scientific and Technical Information of China (English)
Kai Liao; Yu Pan; Zong-Hong Zhu
2013-01-01
We use the latest data to investigate observational constraints on the new generalized Chaplygin gas (NGCG) model.Using the Markov Chain Monte Carlo method,we constrain the NGCG model with type Ⅰa supernovae from the Union2 set (557 data),the usual baryonic acoustic oscillation (BAO) observation from the spectroscopic Sloan Digital Sky Survey data release 7 galaxy sample,the cosmic microwave background observation from the 7-year Wilkinson Microwave Anisotropy Probe results,newly revised data on H(z),as well as a value of θBAO (z =0.55) =(3.90° ± 0.38°) for the angular BAO scale.The constraint results for the NGCG model are ωx=-1.0510(-0.1685)(+0.1563)(1σ)(-0.2398)(+0.2226)(2σ),η=1.0117(-0.0502)(+0.0469)(1σ)(-0.0716)(+0.0693)(2σ) and Ωx=0.7297(-0.0276)(+0.0229)(1σ)(-0.0402)(+0.0329)(2σ),which give a rather stringent constraint.From the results,we can see that a phantom model is slightly favored and the proba-bility that energy transfers from dark matter to dark energy is a little larger than the inverse.
Testing the (generalized) Chaplygin gas model with the lookback time-redshift data
International Nuclear Information System (INIS)
The Chaplygin gas (CG) and the generalized Chaplygin gas (GCG) models, proposed as candidates of the unified dark matter-dark energy (UDME), are tested with the look-back time (LT) redshift data. We find that the LT data only give a very weak constraint on the model parameter. However, by combing the LT with the baryonic acoustic oscillation peak, we obtain, at the 95.4% confidence level, 0.68 ≤ Ac ≤ 0.82 and 0.59 ≤ h ≤ 0.65 for the CG model , and 0.67 ≤ As ≤ 0.89 and −0.29 ≤ α ≤ 0.61 for the GCG model. This shows that both the CG and the GCG are viable as a candidate of UDME. Within the GCG model, we also find that the Chaplygin gas model (α = 1) is ruled out by these data at the 99.7% confidence level
Non-minimal kinetic coupling and Chaplygin gas cosmology
Granda, L N; Fernandez-Melgarejo, J J
2011-01-01
In the frame of the scalar field model with non minimal kinetic coupling to gravity, we study the cosmological solutions of the Chaplygin gas model of dark energy. By appropriately restricting the potential, we found the scalar field, the potential and coupling giving rise to the Chaplygin gas solution. Extensions to the generalized and modified Chaplygin gas have been made.
Reduced modified Chaplygin gas cosmology
Lu, Jianbo; Geng, Danhua; Xu, Lixin; Wu, Yabo; Liu, Molin
2015-02-01
In this paper, we study cosmologies containing the reduced modified Chaplygin gas (RMCG) fluid which is reduced from the modified Chaplygin gas p = Aρ - Bρ -α for the value of α = -1 /2. In this special case, dark cosmological models can be realized for different values of model parameter A. We investigate the viabilities of these dark cosmological models by discussing the evolutions of cosmological quantities and using the currently available cosmic observations. It is shown that the special RMCG model ( A = 0 or A = 1) which unifies the dark matter and dark energy should be abandoned. For A = 1 /3, RMCG which unifies the dark energy and dark radiation is the favorite model according to the objective Akaike information criteria. In the case of A , RMCG can achieve the features of the dynamical quintessence and phantom models, where the evolution of the universe is not sensitive to the variation of model parameters.
Constraints on the generalized Chaplygin gas model from Gamma-ray bursts
Energy Technology Data Exchange (ETDEWEB)
Freitas, R.C., E-mail: rc_freitas@terra.com.br [Grupo de Gravitacao e Cosmologia, Departamento de Fisica, Universidade Federal do Espirito Santo, 29075-910, Vitoria, Espirito Santo (Brazil); Goncalves, S.V.B., E-mail: sergio.vitorino@pq.cnpq.br [Grupo de Gravitacao e Cosmologia, Departamento de Fisica, Universidade Federal do Espirito Santo, 29075-910, Vitoria, Espirito Santo (Brazil); Velten, H.E.S., E-mail: velten@cce.ufes.br [Grupo de Gravitacao e Cosmologia, Departamento de Fisica, Universidade Federal do Espirito Santo, 29075-910, Vitoria, Espirito Santo (Brazil); Fakultaet fuer Physik, Universitaet Bielefeld, Bielefeld 33615 (Germany)
2011-09-14
We study the generalized Chaplygin gas model (GCGM) using Gamma-ray bursts as cosmological probes. In order to avoid the so-called circularity problem we use cosmology-independent data set and Bayesian statistics to impose constraints on the model parameters. We observe that a negative value for the parameter {alpha} is favoured in a flat Universe and the estimated value of the parameter H{sub 0} is lower than that found in literature.
Fitting the Supernova Type Ia Data with the Chaplygin Gas
Fabris, J C; De Souza, P E
2002-01-01
The supernova type Ia observational data are fitted using a model with cold dark matter and the Chaplygin gas. The Chaplygin gas, which is characterized by a negative pressure varying with the inverse of density, represents in this model the dark energy responsible for the accelaration of the universe. The fitting depends essentially on four parameters: the Hubble constant, the velocity of sound of the Chaplygin gas and the fraction density of the Chaplygin gas and the cold dark matter. The best fitting model is obtained with H_0 = 65 km/Mpc.s, $c_s^2 \\sim 0.92c$ and Omega_{c0} = 1, Omega_{m0} = 0, that is, a universe completely dominated by the Chaplygin gas. This reinforces the possibility that the Chaplygin gas may unify dark matter and dark energy, as it has already been claimed in the literature.
Testing the (generalized) Chaplygin gas model with the Lookback time-Redshift data
Li, Zhengxiang; Yu, Hongwei
2009-01-01
The Chaplygin gas (CG) and the generalized Chaplygin gas (GCG) models, proposed as candidates of the unified dark matter-dark energy (UDME), are tested with the look-back time (LT) redshift data. We find that the LT data only give a very weak constraint on the model parameter. However, by combing the LT with the baryonic acoustic oscillation peak, we obtain, at the 95.4% confidence level, $0.68\\leq A_c\\leq0.82$ and $0.59\\leq h\\leq0.65$ for the CG model, and $0.67\\leq A_s\\leq0.89$ and $-0.29\\leq \\alpha\\leq0.61$ for the GCG model. This shows that both the CG and the GCG are viable as a candidate of UDME. Within the GCG model, we also find that the Chaplygin gas model ($\\alpha=1$) is ruled out by these data at the 99.7% confidence level.
Viscous Chaplygin gas models as spherical top-hat collapsing fluids
Jawad, Abdul; Iqbal, Ayesha
2016-05-01
We study the spherical top-hat collapse in Einstein gravity and loop quantum cosmology (LQC) by taking the nonlinear evolution of viscous modified variable Chaplygin gas (CG) and viscous generalized cosmic chaplygin gas (GCCG). We calculate the equation of state (EoS) parameter, square speed of sound, perturbed (EoS) parameter, perturbed square speed of sound, density contrast and divergence of peculiar velocity in perturbed region and discussed their behavior. It is observed that both CG models support the spherical collapse (SC) in Einstein as well as LQC because density contrast remains positive in both cases and the perturbed EoS parameter remains positive at the present epoch as well as near future. It is remarked here that these parameters provide consistent results for both CG models in both gravities.
Warm intermediate inflationary Universe model in the presence of a generalized Chaplygin gas
Energy Technology Data Exchange (ETDEWEB)
Herrera, Ramon [Pontificia Universidad Catolica de Valparaiso, Instituto de Fisica, Valparaiso (Chile); Videla, Nelson [Universidad de Chile, Departamento de Fisica, FCFM, Santiago (Chile); Olivares, Marco [Universidad Diego Portales, Facultad de Ingenieria, Santiago (Chile)
2016-01-15
A warm intermediate inflationary model in the context of generalized Chaplygin gas is investigated. We study this model in the weak and strong dissipative regimes, considering a generalized form of the dissipative coefficient Γ = Γ(T,φ), and we describe the inflationary dynamics in the slow-roll approximation. We find constraints on the parameters in our model considering the Planck 2015 data, together with the condition for warm inflation T > H, and the conditions for the weak and strong dissipative regimes. (orig.)
Evolution of Holographic Dark Energy in Interacting Modified Chaplygin Gas Model
Institute of Scientific and Technical Information of China (English)
WANG Cong; WU Ya-Bo; LIU Fei
2009-01-01
We investigate the modified Chaplygin gas (MCG) with interaction between holographic dark energy proposed byb Li and dark matter. In this model, evolution of the universe is described in detail, which is from deceleration to acceleration. Specifically, the evolutions of related cosmological quantities such as density parameter, the equation of state of holographic dark energy, deceleration parameter and transition redshift are discussed. Moreover, we also give their present values which are consistent with the lately observations. Furthermore, the results given by us show such a model can accommodate a transition of the dark energy from a normal state wx > -1 to wx < -1 phantom regimes.
Effects of viscous pressure on warm inflationary generalized cosmic Chaplygin gas model
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Saleem, Rabia, E-mail: msharif.math@pu.edu.pk, E-mail: rabiasaleem1988@yahoo.com [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan)
2014-12-01
This paper is devoted to study the effects of bulk viscous pressure on an inflationary generalized cosmic Chaplygin gas model using FRW background. The matter contents of the universe are assumed to be inflaton and imperfect fluid. We evaluate inflaton fields, potentials and entropy density for variable as well as constant dissipation and bulk viscous coefficients in weak as well as high dissipative regimes during intermediate era. In order to discuss inflationary perturbations, we evaluate entropy density, scalar (tensor) power spectra, their corresponding spectral indices, tensor-scalar ratio and running of spectral index in terms of inflaton which are constrained using recent Planck, WMAP7 and Bicep2 probes.
Cosmic Microwave Background Radiation Constraints on a Modified Chaplygin Gas Model
Institute of Scientific and Technical Information of China (English)
LIU Dao-Jun; LI Xin-Zhou
2005-01-01
@@ A modified Chaplygin gas model of unifying dark energy and dark matter with the exotic equation of state p = Bρ- A/ρα , which can also explain the recent expansion of the universe, is investigated by means of constraining the location of the peak of the cosmic microwave background radiation spectrum. We find that the result of CMBR measurements does not exclude the nonzero value of parameter B, but allows it in the range -0.35 (＜～) B (＜～) 0.025.
Analysis to the entangled states from an extended Chaplygin gas model
Meng, X H; Ren, J; Meng, Xin He; Hu, Ming Guang; Ren, Jie
2006-01-01
With considerations of the recently released WMAP year three and supernova legacy survey (SNLS) data set analysis that favors models similar to the $% \\Lambda CDM$ model by possibly mild fluctuations around the vacuum energy or the cosmological constant, we extend the original Chaplygin Gas model (ECG) via modifying the Chaplygin Gas equation of state by two parameters to describe an entangled mixture state from an available matter and the rest component (which can take the cosmological constant or dark energy as in the current cosmic stage, or `curvature-like' term, or radiation component in the early epoch, as various phases) coexistence. At low redshifts, the connection of the ECG model and the Born-infeld field is set up. As paradigms, we use the data coming from the recently released SNLS for the first year and also the famous 157 type Ia supernova (Ia SNe) gold dataset to constrain the model parameters. The restricted results demonstrate clearly how large the entangled degree or the ratio between the en...
Colistete, R C; Goncalves, S V B
2004-01-01
The type Ia supernovae (SNe Ia) observational data are used to estimate the parameters of a cosmological model with cold dark matter and the generalized Chaplygin gas model (GCGM). The GCGM depends essentially on five parameters: the Hubble constant, the parameter $\\bar{A}$ related to the velocity of the sound, the equation of state parameter $\\alpha$, the curvature of the Universe and the fraction density of the generalized Chaplygin gas (or the cold dark matter). The parameter $\\alpha$ is allowed to take negative values and to be greater than 1. The Bayesian parameter estimation yields $\\alpha = - 0.86^{+6.01}_{-0.15}$, $H_0 = 62.0^{+1.32}_{-1.42} km/Mpc.s$, $\\Omega _{k0}=-1.26_{-1.42}^{+1.32}$, $\\Omega_{m0} = 0.00^{+0.86}_{-0.00}$, $\\Omega_{c0} = 1.39^{+1.21}_{-1.25}$, $\\bar A =1.00^{+0.00}_{-0.39}$, $t_0 = 15.3^{+4.2}_{-3.2}$ and $q_0 = -0.80^{+0.86}_{-0.62}$, where $t_0$ is the age of the Universe and $q_0$ is the value of the deceleration parameter today. Our results indicate that a Universe completely ...
Observational constraints on cosmological models with Chaplygin gas and quadratic equation of state
Sharov, G. S.
2016-06-01
Observational manifestations of accelerated expansion of the universe, in particular, recent data for Type Ia supernovae, baryon acoustic oscillations, for the Hubble parameter H(z) and cosmic microwave background constraints are described with different cosmological models. We compare the ΛCDM, the models with generalized and modified Chaplygin gas and the model with quadratic equation of state. For these models we estimate optimal model parameters and their permissible errors with different approaches to calculation of sound horizon scale rs(zd). Among the considered models the best value of χ2 is achieved for the model with quadratic equation of state, but it has 2 additional parameters in comparison with the ΛCDM and therefore is not favored by the Akaike information criterion.
Thermodynamics of the variable modified Chaplygin gas
Panigrahi, D.; Chatterjee, S.
2016-05-01
A cosmological model with a new variant of Chaplygin gas obeying an equation of state(EoS), P = Aρ ‑ B/ρα where B= B0an is investigated in the context of its thermodynamical behaviour. Here B0 and n are constants and a is the scale factor. We show that the equation of state of this `Variable Modified Chaplygin gas' (VMCG) can describe the current accelerated expansion of the universe. Following standard thermodynamical criteria we mainly discuss the classical thermodynamical stability of the model and find that the new parameter, n introduced in VMCG plays a crucial role in determining the stability considerations and should always be negative. We further observe that although the earlier model of Lu explains many of the current observational findings of different probes it fails the desirable tests of thermodynamical stability. We also note that for 0n big bang to the big rip in its whole evaluation process.
Cosmological Imprints of a Generalized Chaplygin Gas Model for the Early Universe
Energy Technology Data Exchange (ETDEWEB)
Bouhmadi-Lopez, Mariam; /Lisbon, CENTRA; Chen, Pisin; /Taiwan, Natl. Taiwan U. /KIPAC, Menlo Park /SLAC; Liu, Yen-Wei; /Taiwan, Natl. Taiwan U.
2012-06-06
We propose a phenomenological model for the early universe where there is a smooth transition between an early quintessence phase and a radiation-dominated era. The matter content is modeled by an appropriately modified Chaplygin gas for the early universe. We constrain the model observationally by mapping the primordial power spectrum of the scalar perturbations to the latest data of WMAP7. We compute as well the spectrum of the primordial gravitational waves as would be measured today. We show that the high frequencies region of the spectrum depends on the free parameter of the model and most importantly this region of the spectrum can be within the reach of future gravitational waves detectors.
Dark Matter, Dark Energy and the Chaplygin Gas
Bilic, Neven; Tupper, Gary B.; Viollier, Raoul D
2002-01-01
We formulate a Zel'dovich-like approximation for the Chaplygin gas equation of state P = -A/rho, and sketch how this model unifies dark matter with dark energy in a geometric setting reminiscent of M-theory.
Chaplygin gas and effective description of inhomogeneous universe models in general relativity
International Nuclear Information System (INIS)
In the framework of spatially averaged inhomogeneous cosmologies in classical general relativity, effective Einstein equations govern the dynamics of averaged scalar variables in a scale-dependent way. A particular cosmology may be characterized by a cosmic equation of state, closing the hierarchy of effective equations. In this context a natural candidate is provided by the Chaplygin gas, standing for a unified description of dark energy and dark matter. In this paper, we suppose that the inhomogeneous properties of matter and geometry obey the Chaplygin equation of state. The most extreme interpretation assumes that both dark energy and dark matter are not included as additional sources, but are both manifestations of spatial geometrical properties. This feature is an important conceptual difference in comparison with the standard approach of a Friedmann-LemaItre-Robertson-Walker universe filled with dust and another fundamental field characterized by the Chaplygin equation of state. We finally discuss the consequences of the resulting scenario for effective cosmological parameters in order to establish the framework of a future confrontation with observations, and we note that the standard Chaplygin gas may not be ruled out by them.
Chaplygin gas and effective description of inhomogeneous universe models in general relativity
Energy Technology Data Exchange (ETDEWEB)
Roy, Xavier; Buchert, Thomas, E-mail: roy@obs.univ-lyon1.f, E-mail: buchert@obs.univ-lyon1.f [Universite Lyon 1, Centre de Recherche Astrophysique de Lyon, CNRS UMR 5574, 9 avenue Charles Andre, F-69230 Saint-Genis-Laval (France)
2010-09-07
In the framework of spatially averaged inhomogeneous cosmologies in classical general relativity, effective Einstein equations govern the dynamics of averaged scalar variables in a scale-dependent way. A particular cosmology may be characterized by a cosmic equation of state, closing the hierarchy of effective equations. In this context a natural candidate is provided by the Chaplygin gas, standing for a unified description of dark energy and dark matter. In this paper, we suppose that the inhomogeneous properties of matter and geometry obey the Chaplygin equation of state. The most extreme interpretation assumes that both dark energy and dark matter are not included as additional sources, but are both manifestations of spatial geometrical properties. This feature is an important conceptual difference in comparison with the standard approach of a Friedmann-LemaItre-Robertson-Walker universe filled with dust and another fundamental field characterized by the Chaplygin equation of state. We finally discuss the consequences of the resulting scenario for effective cosmological parameters in order to establish the framework of a future confrontation with observations, and we note that the standard Chaplygin gas may not be ruled out by them.
Generalized Chaplygin gas as geometrical dark energy
Heydari-Fard, M
2007-01-01
The generalized Chaplygin gas provides an interesting candidate for the present accelerated expansion of the universe. We explore a geometrical explanation for the generalized Chaplygin gas within the context of brane world theories where matter fields are confined to the brane by means of the action of a confining potential. We obtain the modified Friedmann equations, deceleration parameter and age of the universe in this scenario and show that they are consistent with the present observational data.
Extended Analysis on New Generalized Chaplygin Gas
Institute of Scientific and Technical Information of China (English)
WANG Jun; WU Ya-Bo; WANG Di; YANG Wei-Qiang
2009-01-01
We extend the study of the new generalizeal Chaplygin gas (NGCG) based on [J.Cosmol.Astropart.Phys.0601 (2006) 003].Specifically,we not only discuss the change rates of the energy densities and the energy transfer of this model,but also perform the Om diagnostic to differentiate the ACDM model from the NGCG and the GCG models.Furthermore,in order to consider the influence of dark energy on structure formation,we also present the evolution of the growth index in this scenario with interaction.
Constraints on the generalized Chaplygin gas model from gamma-ray bursts
Energy Technology Data Exchange (ETDEWEB)
Freitas, Rodolfo Camargo; Goncalves, Sergio Vitorino de Borba; Velten, H.E.S. [Universidade Federal do Espirito Santo (UFES), ES (Brazil). Dept. de Fisica. Grupo de Gravitacao e Cosmologia
2011-07-01
Full text: One of the most important problems of Modern Cosmology is the determination of the matter content of the Universe. Combining data of the rotation curve of spiral galaxies, the dynamics of galaxy clusters and structure formation indicate that there is about ten times more pressureless matter in the Universe than can be afforded by the baryonic matter. Moreover, the Type Ia supernovae (SNe Ia) data indicates that the Universe is accelerating. Models considering matter content dominated by an exotic fluid whose pressure is negative is one of the proposals to explain this current accelerated phase of the Universe. At the same time, the position of the first acoustic peak in the spectrum of CMB anisotropies, as obtained by WMAP, favours a spatially flat Universe. If we consider the matter content of the Universe dominated by a fluid with negative pressure we have a scenario with a proportion of {Omega}{sub m} {approx} 0.27 and the {Omega}{sub de} {approx} 0.73, with respect to the critical density, for the fractions of the pressureless matter and dark energy, respectively. Much observational data that has been used for comparison with the theoretical cosmological models like the generalized Chaplygin gas model. The spectra of anisotropy of cosmic microwave background radiation, baryonic acoustic oscillations, the integrated Sachs-Wolfe effect, the matter power spectrum, gravitational lenses, X-ray data and ages estimates of high-z objects have been used in this sense. Gamma-ray bursts are jets that release {approx} 10{sup 51} - 10{sup 53} ergs or more for a few seconds and becomes, in this brief period of time, the most bright object in the Universe. The search for a self-consistent method to use the GRBs in cosmological problems is intense and promising. In a recent article Liang et al. employed a method to obtain the distance moduli {approx} of GRBs in the redshift range of SNe Ia and extend this result to very high redshift GRBs (z > 1.4) in a completely
Extended Chaplygin gas in Horava-Lifshitz gravity
Pourhassan, B.
2016-09-01
In this paper, we investigate cosmological models of the extended Chaplygin gas in a universe governed by Horava-Lifshitz gravity. The equation of state for an extended Chaplygin gas is a (n + 2) -variable equation determined by An, α, and B. In this work, we are interested to the case of second order (n = 2) equation of state which recovers quadratic barotropic equation of state. In that case there are four free parameters. We solve conservation equation approximately and obtain energy density in terms of scale factor with mentioned free parameters. Under some assumptions we relate free parameters to each other to have only one free independent parameter (A2) . It help us to obtain explicit expression for energy density in terms of scale factor. The allowed values of the second order extended Chaplygin gas parameter is fixed using the recent astrophysical and cosmological observational data. Thermodynamics of the model investigated based on the first and second law of thermodynamics.
Evolution of Variable Generalized Chaplygin Gas
Institute of Scientific and Technical Information of China (English)
YANG Xiu-Yi; WU Ya-Bo; L(U) Jian-Bo; LI Song
2007-01-01
@@ We consider the variable Generalized Chaplygin gas (VGCG) proposal for unification of dark matter and dark energy with p= pde and ρ = ρdm + ρde. The equation of state of the VGCG is given by p = -A0a-n/ρα, where a is the scale factor.
Chaplygin Gas Cosmology - Unification of Dark Matter and Dark Energy
Bilic, Neven; Tupper, Gary B.; Viollier, Raoul D
2006-01-01
The models that unify dark matter and dark energy based upon the Chaplygin gas fail owing to the suppression of structure formation by the adiabatic speed of sound. Including string theory effects, in particular the Kalb-Ramond field, we show how nonadiabatic perturbations allow a successful structure formation.
Accretion of Chaplygin gas upon black holes: formation of faster outflowing winds
International Nuclear Information System (INIS)
We study the accretion of modified Chaplygin gas upon different types of black holes. Modified Chaplygin gas is one of the best candidates for a combined model of dark matter and dark energy. In addition, from a field theoretical point of view the modified Chaplygin gas model is equivalent to that of a scalar field having a self-interacting potential. We formulate the equations related to both spherical accretion and disc accretion, and respective winds. The corresponding numerical solutions of the flow, particularly of velocity, are presented and analysed. We show that the accretion-wind system of modified Chaplygin gas dramatically alters the wind solutions, producing faster winds, upon changes in physical parameters, while accretion solutions qualitatively remain unaffected. This implies that modified Chaplygin gas is more prone to produce outflow which is the natural consequence of the dark energy into the system.
Dynamical Evolution of Modified Chaplygin Gas
Institute of Scientific and Technical Information of China (English)
FU Ming-Hui; WU Ya-Bo; HE Jing
2008-01-01
Based our previous work [Mod.Phys.Lett.A 22 (2007) 783,Gen.Relat.Grav.39 (2007) 653],some properties of modified Chaplygin gas (MCG) as a dark energy model continue to be studied mainly in two aspects: one is the change rates of the energy density and energy transfer,and the other is the evolution of the growth index.It is pointed that the density of dark energy undergoes the change from decrease to increase no matter whether the interaction between dark energy and dark matter exists or not,but the corresponding transformation points are different from each other.Furthermore,it is stressed that the MCG model even supports the existence of interaction between dark energy and dark matter,and the energy of transfer flows from dark energy to dark matter.The evolution of the interaction term with an ansatz 3Hc2p is discussed with the MCG model.Moreover,the evolution of the growth index f in the MCG model without interaction is illustrated,from which we find that the evolutionary trajectory of f overlaps with that of the ACDM model when α> 0.7 and its theoretical value f≈0.566 given by us at z=0.15 is consistent with the observations.
The extreme limit of the generalized Chaplygin gas
Piattella, Oliver F
2009-01-01
It is widely renown that adiabatic unified models of dark matter and dark energy have problems from the viewpoint of their perturbative behaviour because of their speed of sound. Indeed, the latter has to be very small in order the model to be able to reproduce the observed features of our Universe. In this paper we address the generalized Chaplygin gas and the Integrated Sachs Wolfe effect. Through a very simple argument concerning the matter-radiation equivalence scale and the Meszaros effect we probe the \\alpha parameter space of the generalized Chaplygin gas model. We find that in the interval 10^{-3} < \\alpha < 350, the ISW effect cannot be neglected. We then discuss what are the implications on the background evolution of the Universe when very large values of \\alpha are considered.
Unified universe history through phantom extended Chaplygin gas
Pourhassan, B.
2015-01-01
We investigate the universe evolution from inflation to late-time acceleration in a unified way, using a two-component fluid constituted from extended Chaplygin gas alongside a phantom scalar field. We extract solutions for the various cosmological eras, focusing on the behavior of the scale factor, the various density parameters and the equation-of-state parameter. Furthermore, we extract and discuss bouncing solutions. Finally, we examine the perturbations of the model, ensuring about their...
Higher order corrections of the extended Chaplygin gas cosmology with varying G and Λ
Energy Technology Data Exchange (ETDEWEB)
Kahya, E.O. [Istanbul Technical University, Physics Department, Istanbul (Turkey); Khurshudyan, M. [Max Planck Institute of Colloids and Interfaces, Potsdam (Germany); Pourhassan, B. [Damghan University, School of Physics, Damghan (Iran, Islamic Republic of); Myrzakulov, R. [Eurasian National University, Eurasian International Center for Theoretical Physics, Astana (Kazakhstan); Pasqua, A. [University of Trieste, Department of Physics, Trieste (Italy)
2015-02-01
In this paper, we study two different models of dark energy based on the Chaplygin gas equation of state. The first model is the variable modified Chaplygin gas, while the second one is the extended Chaplygin gas. Both models are considered in the framework of higher order f(R) modified gravity. We also consider the case of time-varying gravitational constant G and Λ for bothmodels. We investigate some cosmological parameters such as the Hubble, the deceleration, and the equation of state parameters. Then we show that the model that we consider, the extended Chaplygin gas with time-dependent G and Λ, is consistent with the observational data. Finally we conclude with the discussion of cosmological perturbations of our model. (orig.)
Cosmic walls and filaments formation in modified Chaplygin gas cosmology
Karbasi, S
2016-01-01
We want to study the perturbation growth of an initial seed of an ellipsoidal shape in Top-Hat collapse model of structure formation in the Modified Chaplygin gas cosmology. Considering reasonable values of the constants and the parameters of the model under study, it is shown that a very small deviation from spherical symmetry (ellipsoidal geometry) in the initial seed leads to a final highly non-spherical structure which can be considered as a candidate for justifying already known cosmological structures as cosmic walls and filaments.
Generalized cosmic Chaplygin gas inspired intermediate standard scalar field inflation
Jawad, Abdul; Rani, Shamaila; Mohsaneen, Sidra
2016-08-01
We study the warm intermediate inflationary regime in the presence of generalized cosmic Chaplygin gas and an inflaton decay rate proportional to the temperature. For this purpose, we consider standard scalar field model during weak and strong dissipative regimes. We explore inflationary parameters like spectral index, scalar and tensor power spectra, tensor to scalar ratio and decay rate in order to compare the present model with recent observational data. The physical behavior of inflationary parameters is presented and found that all the results are agreed with recent observational data such as WMAP7, WMAP9 and Planck 2015.
Observational tests of non-adiabatic Chaplygin gas
Energy Technology Data Exchange (ETDEWEB)
Carneiro, S.; Pigozzo, C., E-mail: saulo.carneiro@pq.cnpq.br, E-mail: cpigozzo@ufba.br [Instituto de Física, Universidade Federal da Bahia, Campus de Ondina, Salvador, BA 40210-340 (Brazil)
2014-10-01
In a previous paper [1] it was shown that any dark sector model can be mapped into a non-adiabatic fluid formed by two interacting components, one with zero pressure and the other with equation-of-state parameter ω = -1. It was also shown that the latter does not cluster and, hence, the former is identified as the observed clustering matter. This guarantees that the dark matter power spectrum does not suffer from oscillations or instabilities. It applies in particular to the generalised Chaplygin gas, which was shown to be equivalent to interacting models at both background and perturbation levels. In the present paper we test the non-adiabatic Chaplygin gas against the Hubble diagram of type Ia supernovae, the position of the first acoustic peak in the anisotropy spectrum of the cosmic microwave background and the linear power spectrum of large scale structures. We consider two different compilations of SNe Ia, namely the Constitution and SDSS samples, both calibrated with the MLCS2k2 fitter, and for the power spectrum we use the 2dFGRS catalogue. The model parameters to be adjusted are the present Hubble parameter, the present matter density and the Chaplygin gas parameter α. The joint analysis best fit gives α ≈ - 0.5, which corresponds to a constant-rate energy flux from dark energy to dark matter, with the dark energy density decaying linearly with the Hubble parameter. The ΛCDM model, equivalent to α = 0, stands outside the 3σ confidence interval.
Inflationary cosmology with Chaplygin gas in Palatini formalism
Borowiec, Andrzej; Szydlowski, Marek; Wojnar, Aneta
2015-01-01
We present a simple generalisation of the $\\Lambda$CDM model which on the one hand reaches very good agreement with the present day experimental data and provides an internal inflationary mechanism on the other hand. It is based on Palatini modified gravity with quadratic Starobinsky term and generalized Chaplygin gas as a matter source providing, besides a current accelerated expansion, the epoch of endogenous inflation driven by type III freeze singularity. It follows from our statistical analysis that astronomical data favours negative value of the parameter coupling quadratic term into Einstein-Hilbert Lagrangian and as a consequence the bounce instead of initial Big-Bang singularity is preferred.
Constraints on modified Chaplygin gas from large scale structure
Paul, Bikash Chandra; Thakur, Prasenjit; Beesham, Aroon
2016-10-01
We study cosmological models with modified Chaplygin gas (MCG) to determine observational constraints on its EoS parameters using the background and the growth tests data. The background test data consists of H(z)-z data, Baryonic Acoustic Oscillations peak parameter, CMB shift parameter, SN Ia data and the growth test data consists of the linear growth function for the large scale structures of the universe are considered to study MCG in favor of dark energy. For a given range of redshift, the Wiggle-Z measurements and rms mass fluctuations from Ly-α data, employed for analyzing cosmological models numerically to constrain the MCG parameters. The Wang-Steinhardt ansatz for the growth index (γ ) and growth function (f) are also considered for numerical analysis. The best-fit values of EoS parameters determined here are used to study the variation of f, growth index (γ ), EoS parameter, squared sound speed and deceleration parameter with redshift. The constraints on the MCG parameters found here are compared with that of GCG (generalized Chaplygin gas) model for viable cosmology. Cosmologies with MCG satisfactorily describe late acceleration followed by a matter dominated phase. The range of values of EoS parameters, the associated parameters (f, γ , ω , Ω, c2s, q) are also determined from observational data in order to understand the suitability of the MCG model.
Spherical thin-shell wormholes and modified Chaplygin gas
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Azam, M., E-mail: msharif.math@pu.edu.pk, E-mail: azammath@gmail.com [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan)
2013-05-01
The purpose of this paper is to construct spherical thin-shell wormhole solutions through cut and paste technique and investigate the stability of these solutions in the vicinity of modified Chaplygin gas. The Darmois-Israel formalism is used to formulate the stresses of the surface concentrating the exotic matter. We explore the stability of the wormhole solutions by using the standard potential method. We conclude that there exist more stable as well as unstable solutions than the previous study with generalized Chaplygin gas [19].
Single-field inflation à la generalized Chaplygin gas
Energy Technology Data Exchange (ETDEWEB)
Campo, Sergio del, E-mail: sdelcamp@ucv.cl [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso (Chile)
2013-11-01
In the simplest scenario for inflation, i.e. in the single-field inflation, it is presented an inflaton field with properties equivalent to a generalized Chaplygin gas. Their study is performed using the Hamilton-Jacobi approach to cosmology. The main results are contrasted with the measurements recently released by the Planck data, combined with the WMAP large-angle polarization. If the measurements released by Planck for the scalar spectral index together with its running are taken into account it is found a value for the α-parameter associated to the generalized Chaplygin gas given by α = 0.2578±0.0009.
Single-field inflation à la generalized Chaplygin gas
International Nuclear Information System (INIS)
In the simplest scenario for inflation, i.e. in the single-field inflation, it is presented an inflaton field with properties equivalent to a generalized Chaplygin gas. Their study is performed using the Hamilton-Jacobi approach to cosmology. The main results are contrasted with the measurements recently released by the Planck data, combined with the WMAP large-angle polarization. If the measurements released by Planck for the scalar spectral index together with its running are taken into account it is found a value for the α-parameter associated to the generalized Chaplygin gas given by α = 0.2578±0.0009
Dissipative generalized Chaplygin gas as phantom dark energy
Energy Technology Data Exchange (ETDEWEB)
Cruz, Norman [Departamento de Fisica, Facultad de Ciencia, Universidad de Santiago, Casilla 307, Santiago (Chile)]. E-mail: ncruz@lauca.usach.cl; Lepe, Samuel [Instituto de Fisica, Facultad de Ciencias Basicas y Matematicas, Pontificia Universidad Catolica de Valparaiso, Avenida Brasil 2950, Valparaiso (Chile)]. E-mail: slepe@ucv.cl; Pena, Francisco [Departamento de Ciencias Fisicas, Facultad de Ingenieria, Ciencias y Administracion, Universidad de la Frontera, Avda. Francisco Salazar 01145, Casilla 54-D, Temuco (Chile)]. E-mail: fcampos@ufro.cl
2007-03-15
The generalized Chaplygin gas, characterized by the equation of state p=-A/{rho}{sup {alpha}}, has been considered as a model for dark energy due to its dark-energy-like evolution at late times. When dissipative processes are taken into account, within the framework of the standard Eckart theory of relativistic irreversible thermodynamics, cosmological analytical solutions are found. Using the truncated causal version of the Israel-Stewart formalism, a suitable model was constructed which crosses the w=-1 barrier. The future-singularities encountered in both approaches are of a new type, and not included in the classification presented by Nojiri and Odintsov [S. Nojiri, S.D. Odintsov, Phys. Rev. D 72 (2005) 023003].
Observational constraints on Modified Chaplygin Gas from Large Scale Structure
Paul, Bikash Chandra; Beesham, Aroonkumar
2014-01-01
We study cosmological models with modified Chaplygin gas (in short, MCG) to determine observational constraints on its EoS parameters. The observational data of the background and the growth tests are employed. The background test data namely, H(z)-z data, CMB shift parameter, Baryonic acoustic oscillations (BAO) peak parameter, SN Ia data are considered to study the dynamical aspects of the universe. The growth test data we employ here consists of the linear growth function for the large scale structures of the universe, models are explored assuming MCG as a candidate for dark energy. Considering the observational growth data for a given range of redshift from the Wiggle-Z measurements and rms mass fluctuations from Ly-$\\alpha$ measurements, cosmological models are analyzed numerically to determine constraints on the MCG parameters. In this case, the Wang-Steinhardt ansatz for the growth index $\\gamma$ and growth function $f$ (defined as $f=\\Omega_{m}^{\\gamma} (a)$) are also taken into account for the numeri...
Viability of Variable Generalised Chaplygin gas - a thermodynamical approach
Panigrahi, D
2016-01-01
The viability of the variable generalised Chaplygin gas (VGCG) model is analysed from the standpoint of its thermodynamical stability criteria with the help of an equation of state, $P = - \\frac{B}{\\rho^{\\alpha}}$, where $B = B_{0}V^{-\\frac{n}{3}}$. Here $B_{0}$ is assumed to be a positive universal constant, $n$ is a constant parameter and $V$ is the volume of the cosmic fluid. We get the interesting result that if the well-known stability conditions of a fluid is adhered to, the values of $n$ are constrained to be negative definite to make $ \\left(\\frac{\\partial P}{\\partial V}\\right)_{S} <0$ \\& $ \\left(\\frac{\\partial P}{\\partial V}\\right)_{T} <0$ throughout the evolution. Moreover the positivity of thermal capacity at constant volume $c_{V}$ as also the validity of the third law of thermodynamics are ensured in this case. For the particular case $n = 0$ the effective equation of state reduces to $\\Lambda$CDM model in the late stage of the universe while for $n <0$ it mimics a phantom-like cosmo...
Viscous Generalized Chaplygin Gas Interacting with f(R,T) gravity
Baffou, E H; Houndjo, M J S
2016-01-01
In this paper, we study in Friedmann-Robertson-Walker universe the interaction between the viscous generalized Chaplygin gas with $f(R,T)$ gravity, which is an arbitrary function of the Ricci scalar $R$ and the trace $T$ of the energy-momentum tensor. Assuming that the contents of universe is dominated by a generalized Chaplygin gas and dark energy, we obtained the modified Friedmann equations and also the time dependent energy density and pressure of dark energy due to the shear and bulk viscosities for three interacting models depending on an input parameter $Q$. Within the simple form of scale factor (power-law), we discuss the graphical representation of dark energy density parameter and investigate the shear and bulk viscosities effects on the accelerating expansion of the universe for each interacting model.
Reissner-Nordstroem thin-shell wormholes with generalized cosmic Chaplygin gas
Energy Technology Data Exchange (ETDEWEB)
Sharif, M. [University of the Punjab, Department of Mathematics, Lahore (Pakistan); Azam, M. [University of the Punjab, Department of Mathematics, Lahore (Pakistan); University of Education, Division of Science and Technology, Lahore (Pakistan)
2013-09-15
Following Visser's approach (Visser in Phys. Rev. D 39:3182, 1989; Nucl. Phys. B 328:203, 1989; Lorentzian wormholes. AIP Press, New York, 1996) of cut and paste, we construct Reissner-Nordstroem thin-shell wormholes by taking the generalized cosmic Chaplygin gas for the exotic matter located at the wormhole throat. The Darmois-Israel conditions are used to determine the dynamical quantities of the system. The viability of the thin-shell wormholes is explored with respect to radial perturbations preserving the spherical symmetry. We find stable as well as unstable Reissner-Nordstroem thin-shell wormhole solutions depending upon the model parameters. Finally, we compare our results with both generalized and modified Chaplygin gases. (orig.)
Reissner-Nordstroem thin-shell wormholes with generalized cosmic Chaplygin gas
International Nuclear Information System (INIS)
Following Visser's approach (Visser in Phys. Rev. D 39:3182, 1989; Nucl. Phys. B 328:203, 1989; Lorentzian wormholes. AIP Press, New York, 1996) of cut and paste, we construct Reissner-Nordstroem thin-shell wormholes by taking the generalized cosmic Chaplygin gas for the exotic matter located at the wormhole throat. The Darmois-Israel conditions are used to determine the dynamical quantities of the system. The viability of the thin-shell wormholes is explored with respect to radial perturbations preserving the spherical symmetry. We find stable as well as unstable Reissner-Nordstroem thin-shell wormhole solutions depending upon the model parameters. Finally, we compare our results with both generalized and modified Chaplygin gases. (orig.)
Study of Inflationary Generalized Cosmic Chaplygin Gas for Standard and Tachyon Scalar Fields
Sharif, M
2014-01-01
We consider an inflationary universe model in the context of generalized cosmic Chaplygin gas by taking matter field as standard and tachyon scalar fields. We evaluate the corresponding scalar fields and scalar potentials during intermediate and logamediate inflationary regimes by modifying the first Friedmann equation. In each case, we evaluate the number of e-folds, scalar as well as tensor power spectra, scalar spectral index and important observational parameter, i.e., tensor-scalar ratio in terms of inflatons. The graphical behavior of this parameter shows that the model remains incompatible with WMAP7 and Planck observational data in each case.
Study of inflationary generalized cosmic Chaplygin gas for standard and tachyon scalar fields
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Saleem, Rabia [University of the Punjab, Department of Mathematics, Lahore (Pakistan)
2014-07-15
We consider an inflationary universe model in the context of the generalized cosmic Chaplygin gas by taking the matter field as standard and tachyon scalar fields. We evaluate the corresponding scalar fields and scalar potentials during the intermediate and logamediate inflationary regimes by modifying the first Friedmann equation. In each case, we evaluate the number of e-folds, scalar as well as tensor power spectra, scalar spectral index, and the important observational parameter, the tensor-scalar ratio in terms of inflation. The graphical behavior of this parameter shows that the model remains incompatible with WMAP7 and Planck observational data in each case. (orig.)
Born-Infeld thin-shell wormholes supported by generalized Cosmic Chaplygin gas
Azam, M.
2016-03-01
This paper investigates thin-shell wormholes in Born-Infeld theory supported by generalized Cosmic Chaplygin gas (GCCG). We study their stability via radial perturbations for distinct values of charge and Born-Infeld parameter. The comparison of wormhole solutions corresponding to generalized Chaplygin gas, modified Chaplygin gas with GCCG quation of state is established. It is found that similar type of wormhole solutions exists for small value of charge and Born-Infeld parameter for all type of equation of state, while some extra stable as well as unstable solution are found corresponding to large value of charge and Born-Infeld parameter. Thus, it is concluded that GCCG and large value of charge may responsible for such extra solutions.
Born-Infeld Thin-shell Wormholes Supported by Generalized Cosmic Chaplygin Gas
Azam, M
2016-01-01
This paper investigates thin-shell wormholes in Born-Infeld theory supported by generalized Cosmic Chaplygin gas (GCCG). We study their stability via radial perturbations for distinct values of charge and Born-Infeld parameter. The comparison of wormhole solutions corresponding to generalized Chaplygin gas, modified Chaplygin gas with GCCG quation of state is established. It is found that similar type of wormhole solutions exists for small value of charge and Born-Infeld parameter for all type of equation of state, while some extra stable as well as unstable solution are found corresponding to large value of charge and Born-Infeld parameter. Thus, it is concluded that GCCG and large value of charge may responsible for such extra solutions.
Thin-shell wormholes in Born–Infeld electrodynamics with modified Chaplygin gas
International Nuclear Information System (INIS)
In this paper, we construct spherically symmetric thin-shell wormholes in the scenario of Born–Infeld electrodynamics theory. We take the modified Chaplygin gas for the description of exotic matter around the wormhole throat. The stability of static wormhole solutions with different values of charge and Born–Infeld parameter is investigated. We compare our results with those obtained for generalized Chaplygin gas [36] and conclude that stable static wormhole solutions also exist even for large value of Born–Infeld parameter. - Highlights: • Constructed thin-shell wormholes in Born–Infeld electrodynamics for modified Chaplygin. • Studied its stability with different values of charge and Born–Infeld parameter. • New stable solutions are found even for large value of Born–Infeld parameter. • Selection of EoS significantly changes the presence and stability of static solutions
Thin-shell wormholes in Born–Infeld electrodynamics with modified Chaplygin gas
Energy Technology Data Exchange (ETDEWEB)
Sharif, M., E-mail: msharif.math@pu.edu.pk [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan); Azam, M., E-mail: azam.math@ue.edu.pk [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan); Division of Science and Technology, University of Education, Township Campus, Lahore-54590 (Pakistan)
2014-07-25
In this paper, we construct spherically symmetric thin-shell wormholes in the scenario of Born–Infeld electrodynamics theory. We take the modified Chaplygin gas for the description of exotic matter around the wormhole throat. The stability of static wormhole solutions with different values of charge and Born–Infeld parameter is investigated. We compare our results with those obtained for generalized Chaplygin gas [36] and conclude that stable static wormhole solutions also exist even for large value of Born–Infeld parameter. - Highlights: • Constructed thin-shell wormholes in Born–Infeld electrodynamics for modified Chaplygin. • Studied its stability with different values of charge and Born–Infeld parameter. • New stable solutions are found even for large value of Born–Infeld parameter. • Selection of EoS significantly changes the presence and stability of static solutions.
Wormholes admitting conformal Killing vectors and supported by generalized Chaplygin gas
Energy Technology Data Exchange (ETDEWEB)
Kuhfittig, Peter K.F. [Milwaukee School of Engineering, Department of Mathematics, Milwaukee, WI (United States)
2015-08-15
When Morris and Thorne first proposed that traversable wormholes may be actual physical objects, they concentrated on the geometry by specifying the shape and redshift functions. This mathematical approach necessarily raises questions regarding the determination of the required stress-energy tensor. This paper discusses a natural way to obtain a complete wormhole solution by assuming that the wormhole (1) is supported by generalized Chaplygin gas and (2) admits conformal Killing vectors. (orig.)
Shabani, Hamid
2016-01-01
In this paper, we investigate the cosmological consequences of a scenario for the recently reported accelerated expansion of the Universe, in which the generalized Chaplygin gas (GCG) and the baryonic matter are responsible for this observed phenomenon. Here, we have worked in an isotropic and homogeneous FLRW space time in $f(R,T)$ theory of gravity. We consider three classes of models which include three different forms of $f(R,T)$ function; Class $I$, are those models which employ the standard Chaplygin gas (SCG), in class $II$, we use GCG in the high pressure regime and finally, models $III$ make use of GCG in the high density regimes. The effective equation of state (EoS), the deceleration parameter for these models are calculated and showed that the related present values are more observationally acceptable in $f(R,T)$ gravity, compared to the corresponding ones in the General Relativity (GR). And, among them class $III$ have a better situation; the predictions of these models are more consistent with t...
Observational constraints on modified Chaplygin gas in Horava–Lifshitz gravity with dark radiation
Indian Academy of Sciences (India)
B C Paul; P Thakur; M M Verma
2013-10-01
Cosmological models with modified Chaplygin gas (MCG) in the framework of Horava–Lifshitz (HL) theory of gravity, both with and without detailed balance, are obtained. The equation of state (EOS) for a MCG contains three unknown parameters namely, , , . The allowed values of some of these parameters of the EOS are determined using the recent astrophysical and cosmological observational data. Using observational data from $H(z)-z$, baryon acoustic oscillation (BAO) peak parameter and cosmic microwave background (CMB) shift parameter we study cosmologies in detailed-balance and beyond detailed-balance scenario. In this paper we take up the beyond detailed-balance scenario in totality and contribution of dark radiation in detailedbalance scenario on the parameters of the EOS. We explore the effect of dark radiation on the whole range of the effective neutrino parameter ($ N_{}$) to constrain matter contributing parameter in both the detailed-balance and the beyond detailed-balance scenarios. It has been observed that greater the dark radiation less the matter contribution in the MCG in both the scenario considered here. In order to check the validity of beyond detailed-balance scenario we plot supernovae magnitudes () with red-shift of Union2 data and then the variation of state parameter with redshift is studied. It is noted that beyond detailed-balance scenario is suitable for cosmological model in HL gravity with MCG.
Constraining Parameters of Generalized Cosmic Chaplygin Gas in Loop Quantum Cosmology
Ranjit, Chayan
2014-01-01
We have assumed the FRW universe in loop quantum cosmology (LQC) model filled with the dark matter and the Generalized Cosmic Chaplygin gas (GCCG) type dark energy where dark matter follows the linear equation of state. We present the Hubble parameter in terms of the observable parameters $\\Omega_{m0}$ and $H_{0}$ with the redshift $z$ and the other parameters like $A$, $B$, $w_{m}$, $ \\omega$ and $\\alpha$ which coming from our model. From Stern data set (12 points)\\& SNe Type Ia 292 data (from \\cite{Riess1,Riess2,Astier}) we have obtained the bounds of the arbitrary parameters by minimizing the $\\chi^{2}$ test. The best-fit values of the parameters are obtained by 66\\%, 90\\% and 99\\% confidence levels. Next due to joint analysis with Stern+BAO and Stern+BAO+CMB observations, we have also obtained the bounds of the parameters ($A,B$) by fixing some other parameters $\\alpha$, $w_{m}$ and $\\omega$. From the best fit values of the parameters, we have obtained the distance modulus $\\mu(z)$ for our theoretical...
Lu, Jianbo; Xu, Lixin; Tan, Hongyan; Gao, Shanshan
2014-03-01
Varying gravitational constant G(t) (VG) cosmology is studied in this paper, where the modified Friedmann equation and the modified energy conservation equation are given with respect to the constant-G theory. Considering the extended Chaplygin gas (ECG) as background fluid (or thinking that ECG fluid is induced by the variation of G), the unified model of dark matter and dark energy is obtained in VG theory. The parameter spaces are investigated in the VG-ECG model by using the recent cosmic data. Constraint results show β =-G/.HG =-0.003-0.020-0.055+0.021+0.034 for the VG-GCG unified model and β=-0.027-0.032-0.066+0.032+0.059 for the VG-MCG unified model. Equivalently, they correspond to the limits on the current variation of Newton's gravitational constant at 95.4% confidence level |G/.G|today≲4.1×10-12 yr-1 and |G/.G|today≲6.6×10-12 yr-1. And for z ≤3.5, bounds on the variation of G/.G in the VG-ECG unified model are in accordance with the experiment explorations of varying G. In addition, in VG theory the used observational data point still cannot distinguish the VG-GCG and VG-MCG unified model from the most popular ΛCDM cosmology. Furthermore, to see the effects of varying G and physical properties for VG-ECG fluid, we discuss the evolutionary behaviors of cosmological quantities in VG theory, such as G/.G, G./.G and equation of state w, etc. For β <0 a quintom scenario crossing over w=-1 can be realized in the VG-GCG model.
The exact Riemann solutions to the generalized Chaplygin gas equations with friction
Sun, Meina
2016-07-01
The exact solutions to the Riemann problem for the one-dimensional generalized Chaplygin gas equations with a Coulomb-like friction term are constructed explicitly. The delta shock wave arises in the Riemann solutions provided that the initial data satisfy some certain conditions, although the system is strictly hyperbolic and the two characteristic fields are genuinely nonlinear. The position, strength and propagation speed of delta shock wave are obtained from the generalized Rankine-Hugoniot conditions. It is shown that the Coulomb-like friction term make waves (including rarefaction, shock and delta shock) bend into parabolic shapes for the Riemann solutions.
Duality extended Chaplygin cosmologies with a big rip
Chimento, L P; Chimento, Luis P.; Lazkoz, Ruth
2006-01-01
We consider modifications to the Friedmann equation motivated by recent proposals along these lines pursuing an explanation to the observed late time acceleration. Here we show those modifications can be framed within a theory with self-interacting gravity, where the term self-interaction refers here to the presence of functions of $\\rho$ and $p$ in the right hand side of the Einstein equations. We then discuss the construction of the duals of the cosmologies generated within that framework. After that we investigate the modifications required to generate generalized and modified Chaplygin cosmologies and show that their duals belong to a larger family of cosmologies we call extended Chaplygin cosmologies. Finally, by letting the parameters of those models take values not earlier considered in the literature we show some representatives of that family of cosmologies display sudden future singularities, which indicates their behavior is rather different from generalized or modified Chaplygin gas cosmologies. T...
Duality gives rise to Chaplygin cosmologies with a big rip
Chimento, Luis P.; Lazkoz, Ruth
2006-05-01
We consider modifications to the Friedmann equation motivated by recent proposals along these lines pursuing an explanation to the observed late time acceleration. Here we show that these approaches can be framed within a theory with modified gravity, and we discuss the construction of the duals of the cosmologies generated within that framework. We then investigate the modifications required to generate extended, generalized and modified Chaplygin cosmologies, and then show that their duals belong to a larger family of cosmologies we call enlarged Chaplygin cosmologies. Finally, by letting the parameters of these models take values not earlier considered in the literature we show that some representatives of that family of cosmologies display sudden future singularities. This fact indicates that the behaviour of these spacetimes is rather different from that of generalized or modified Chaplygin gas cosmologies. This reinforces the idea that modifications of gravity can be responsible for unexpected evolutionary features in the universe.
A modified generalized Chaplygin gas as the unified dark matter-dark energy revisited
Energy Technology Data Exchange (ETDEWEB)
Deng, Xue-Mei, E-mail: xmd@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing (China)
2011-12-15
A modified generalized Chaplygin gas (MGCG) is considered as the unified dark matter-dark energy revisited. The character of MGCG is endued with the dual role, which behaves as matter at early times and as a quiescence dark energy at late times. The equation of state for MGCG is p = -{alpha}{rho}/(1 + {alpha}) - {upsilon}(z){rho}{sup -{alpha}/(1 + {alpha})}, where {upsilon}(z) = -[{rho}0{sub c}(1 + z){sup 3}] {sup (1+{alpha})} (1 - {Omega}{sub 0B}){sup {alpha} {l_brace}{alpha}{Omega}0{sub DM} + {Omega}{sub 0DE} [{omega}{sub DE} + {alpha}(1 +{omega}{sub DE})](1 + z){sup 3}{omega}DE(1+{alpha}){r_brace}}. Some cosmological quantities, such as the densities of different components of the universe {Omega}{sub i} (i, respectively, denotes baryons, dark matter, and dark energy) and the deceleration parameter q, are obtained. The present deceleration parameter q{sub 0}, the transition redshift z{sub T}, and the redshift z{sub eq}, which describes the epoch when the densities in dark matter and dark energy are equal, are also calculated. To distinguish MGCG from others, we then apply the Statefinder diagnostic. Later on, the parameters ({alpha} and {omega}{sub DE}) of MGCG are constrained by combination of the sound speed c{sup 2}{sub s} , the age of the universe t{sub 0}, the growth factor m, and the bias parameter b. It yields {alpha} = -3.07{sup +5.66} {sub -4.98} x 10{sup -2} and {omega}{sub DE} = -1.05 {sup +0.06} {sub -0.11}. Through the analysis of the growth of density perturbations for MGCG, it is found that the energy will transfer from dark matter to dark energy which reach equal at z{sub e}{approx} 0.48 and the density fluctuations start deviating from the linear behavior at z {approx} 0.25 caused by the dominance of dark energy. (author)
Friedman-Robertson-Walker Models with Late-Time Acceleration
Institute of Scientific and Technical Information of China (English)
Abdussattar; S. R. Prajapati2
2011-01-01
@@ In order to account for the observed cosmic acceleration, a modiGcation of the ansatz for the variation of density in Friedman-Robertson-Walker (FRW) FRW models given by Islam is proposed.The modified ansatz leads to an equation of state which corresponds to that of a variable Chaplygin gas, which in the course of evolution reduces to that of a modified generalized Chaplygin gas (MGCG) and a Chaplygin gas (CG), exhibiting late-time acceleration.%In order to account for the observed cosmic acceleration, a modification of the ansatz for the variation of density in Friedman-Robertson-Walker (FRW) FRW models given by Islam is proposed. The modified ansatz leads to an equation of state which corresponds to that of a variable Chaplygin gas, which in the course of evolution reduces to that ora modified generalized Chaplygin gas (MGCG) and a Chaplygin gas (CG), exhibiting late-time acceleration.
Interacting entropy-corrected holographic Chaplygin gas model
Farooq, M. Umar; Rashid, Muneer A.; Jamil, Mubasher
2010-01-01
Holographic dark energy (HDE), presents a dynamical view of dark energy which is consistent with the observational data and has a solid theoretical background. Its definition follows from the entropy-area relation $S(A)$, where $S$ and $A$ are entropy and area respectively. In the framework of loop quantum gravity, a modified definition of HDE called "entropy-corrected holographic dark energy" (ECHDE) has been proposed recently to explain dark energy with the help of quantum corrections to th...
Friedmann-Robertson-Walker Models with Late-Time Acceleration
Abdussattar,
2016-01-01
In order to account for the observed cosmic acceleration, a modification of the ansatz for the variation of density in Friedman-Robertson-Walker (FRW) models given by Islam is proposed. The modified ansatz leads to an equation of state which corresponds to that of a variable Chaplygin gas, which in the course of evolution reduces to that of a modified generalized Chaplygin gas (MGCG) and a Chaplygin gas (CG), exhibiting late-time acceleration.
Friedman—Robertson—Walker Models with Late-Time Acceleration
Abdussattar; Prajapati, S. R.
2011-02-01
In order to account for the observed cosmic acceleration, a modification of the ansatz for the variation of density in Friedman—Robertson—Walker (FRW) FRW models given by Islam is proposed. The modified ansatz leads to an equation of state which corresponds to that of a variable Chaplygin gas, which in the course of evolution reduces to that of a modified generalized Chaplygin gas (MGCG) and a Chaplygin gas (CG), exhibiting late-time acceleration.
Unification of Dark Matter and Dark Energy: the Inhomogeneous Chaplygin Gas
Bilic, Neven; Tupper, Gary B.; Viollier, Raoul D
2001-01-01
We extend the world model of Kamenshchik et al. to large perturbations by formulating a Zeldovich-like approximation. We sketch how this model unifies dark matter with dark energy in a geometric setting reminiscent of M-theory.
Generalized Chaplygin cosmology with changeable-signs interactions
Directory of Open Access Journals (Sweden)
XI Ping
2013-06-01
Full Text Available Using phase space analysis methods,we discuss two kinds of Generalized Chaplygin cosmology with changeable-signs interactions dynamically.Some new stable attractor solutions and heteroclinic trajectory solutions are found in these two types of models.
Instability of holographic dark energy models
Myung, Yun Soo
2007-01-01
We investigate the difference between holographic dark energy, Chaplygin gas, and tachyon model with constant potential. For this purpose, we examine their squared speeds of sound which are evaluated to zeroth order in perturbation theory and hence depends only on time. We find that the squared speed for holographic dark energy is always negative when choosing the future event horizon as the IR cutoff, while those for Chaplygin gas and tachyon are non-negative. This means that the perfect flu...
A Cosmological Model of the Early Universe Based on ECG with Variable Λ-Term in Lyra Geometry
Saadat, H.
2016-05-01
In this paper, we study interacting extended Chaplygin gas as dark matter and quintessence scalar field as dark energy with an effective Λ-term in Lyra manifold. As we know Chaplygin gas behaves as dark matter at the early universe while cosmological constant at the late time. Modified field equations are given and motivation of the phenomenological models discussed in details. Four different models based on the interaction term are investigated in this work. Then, we consider other models where Extended Chaplygin gas and quintessence field play role of dark matter and dark energy respectively with two different forms of interaction between the extended Chaplygin gas and quintessence scalar field for both constant and varying Λ. Concerning to the mathematical hardness of the problems we discuss results numerically and graphically. Obtained results give us hope that proposed models can work as good models for the early universe with later stage of evolution containing accelerated expansion.
Saadat, H
2015-01-01
In this paper, we study interacting extended Chaplygin gas as dark matter and quintessence scalar field as dark energy with an effective $\\Lambda$-term in Lyra manifold. As we know Chaplygin gas behaves as dark matter at the early universe while cosmological constant at the late time. Modified field equations are given and motivation of the phenomenological models discussed in details. Four different models based on the interaction term are investigated in this work. Then, we consider other models where Extended Chaplygin gas and quintessence field play role of dark matter and dark energy respectively with two different forms of interaction between the extended Chaplygin gas and quintessence scalar field for both constant and varying $\\Lambda$. Concerning to the mathematical hardness of the problems we discuss results numerically and graphically. Obtained results give us hope that proposed models can work as good models for the early universe with later stage of evolution containing accelerated expansion.
Constraining the Generalized and Superfluid Chaplygin Gas Models with the Sandage-Loeb Test
Zhu, Wen-Tao; Wu, Pu-Xun; Yu, Hong-Wei
2015-05-01
Not Available Supported by the National Natural Science Foundation of China under Grants Nos 11175093, 11222545, 11435006, and 11375092, the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No 20124306110001, and the K.C. Wong Magna Fund of Ningbo University.
Dieterici gas as a Unified Model for Dark Matter and Dark Energy
Sivaram, C; Arun, Kenath; Nagaraja, R.
2011-01-01
The dominance of dark energy in the universe has necessitated the introduction of a repulsive gravity source to make q0 negative. The models for dark energy range from a simple lambda-term to quintessence, Chaplygin gas, etc. We look at the possibility of how change of behaviour of missing energy density, from DM to DE, may be determined by the change in the equation of state of a background fluid instead of a form of potential. The question of cosmic acceleration can be discussed within the ...
Observational Constraints on the Unified Dark-Energy-Dark-Matter Model
Institute of Scientific and Technical Information of China (English)
WU Pu-Xun; YU Hong-Wei
2007-01-01
We investigate the constraints on a generalized Chaplygin gas (GCC) model using the gold sample type-Ia supernovae (She Ia) data, the new Supernova Legacy Survey (SNLS) She Ia data and the size of baryonic acoustic oscillation peak found in Sloan Digital Sky Survey (SDSS). In a spatially flat universe case we obtain, at a 95.4% confidence level, As = 0.76-0.07+0.07 and α = 0.028-0.238+0.322. Our results are consistent with the ACDM model (α = 0), but rule out the standard Chaplygin gas model (α = 1).
Nonholonomic LL systems on central extensions and the hydrodynamic Chaplygin sleigh with circulation
García-Naranjo, Luis C
2011-01-01
In this paper, we consider the motion of the hydrodynamic Chaplygin sleigh, a planar rigid body in a potential flow with circulation around the body, subject to a nonholonomic constraint modeling a fin or keel attached to the body. We show that the motion of this system can be described by Euler-Poincare-Suslov equations on a central extension of the special Euclidian group SE(2), where the cocycle used to construct the extension encodes the effects of circulation upon the body. In the second part of the paper, we then discuss nonholonomic systems on central extensions of Lie groups, where both the Lagrangian and the nonholonomic constraints are left invariant. We show that there is a one-to-one correspondence between invariant measures on the original group and on the extended group, and we use this result to characterize the existence of an invariant measure for the hydrodynamic Chaplygin sleigh. We finish with a qualitative discussion of the reduced dynamics.
Studies of systems with nonholonomic constraints: The Segway and the Chaplygin sleigh
Tuttle, Joseph T.
In this thesis, two systems with nonholonomic systems are investigated: the Segway and the Chaplygin sleigh. Using Lagrangian mechanics, the constrained nonlinear equations of motion for both systems are derived. By use of the nullspace of the constraint matrices, the unconstrained equations of motion can be obtained. For the Segway, these equations are linearized about a zero equilibrium state, placed into state space form and decoupled. A feedback controller is designed about the velocity and heading angle rate reference commands. To compare to the real data from the built Segway, measurement noise was also included in the model. Experimental data is taken for the case of both zero and constant reference commands. The data is then compared to the simulated results. The model is shown to be satisfactory, but better parameter measurements of the Segway is needed for a more conclusive comparison. The unconstrained equations of motion for the Chaplygin sleigh can not be linearized. Thus Lyapunov stability theory was used for analysis. The Chaplygin sleigh with constant input was shown to spiral outward and settle into a circle. If a PD feedback controller was designed about the heading angle, then the Chaplygin sleigh would be driven to the angle, but would eventually coast to a stop. From simulations, the addition of a sinusoidal component appears to move in the desired direction without slowing down. A sinusoidal component was also added to a constant input to result in roulette like paths in the simulation. Future investigation would require a more definite analysis of the sinusoidal term in the input.
Energy Technology Data Exchange (ETDEWEB)
1994-12-01
RAMSGAS, the Research and Development Analysis Modeling System World Natural Gas Model, was developed to support planning of unconventional gaseoues fuels research and development. The model is a scenario analysis tool that can simulate the penetration of unconventional gas into world markets for oil and gas. Given a set of parameter values, the model estimates the natural gas supply and demand for the world for the period from 1980 to 2030. RAMSGAS is based on a supply/demand framwork and also accounts for the non-renewable nature of gas resources. The model has three fundamental components: a demand module, a wellhead production cost module, and a supply/demand interface module. The demand for gas is a product of total demand for oil and gas in each of 9 demand regions and the gas share. Demand for oil and gas is forecast from the base year of 1980 through 2030 for each demand region, based on energy growth rates and price-induced conservation. For each of 11 conventional and 19 unconventional gas supply regions, wellhead production costs are calculated. To these are added transportation and distribution costs estimates associated with moving gas from the supply region to each of the demand regions and any economic rents. Based on a weighted average of these costs and the world price of oil, fuel shares for gas and oil are computed for each demand region. The gas demand is the gas fuel share multiplied by the total demand for oil plus gas. This demand is then met from the available supply regions in inverse proportion to the cost of gas from each region. The user has almost complete control over the cost estimates for each unconventional gas source in each year and thus can compare contributions from unconventional resources under different cost/price/demand scenarios.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
In this paper we investigate the two-dimensional compressible isentropic Euler equations for Chaplygin gases. Under the assumption that the initial data is close to a constant state and the vorticity of the initial velocity vanishes, we prove the global existence of the smooth solution to the Cauchy problem for twodimensional flow of Chaplygin gases.
Supernovae constraints on dark energy and modified gravity models
International Nuclear Information System (INIS)
We use the Type Ia Supernova gold sample to constrain the parameters of dark energy models namely the Cardassian, Dvali-Turner (DT) and generalized Chaplygin gas (GCG) models. In our best fit analysis for these dark energy proposals we consider flat and the non-flat priors. For all models, we find that relaxing the flatness condition implies that data favors a positive curvature; moreover, the GCG model is nearly flat, as required by Cosmic Microwave Background (CMB) observations
Vågsæther, Knut
2010-01-01
The content of this thesis is a study of gas explosions in complex geometries and presentation and validation of a method for simulating flame acceleration and deflagration to detonation transition. The thesis includes a description of the mechanisms of flame acceleration and DDT that need to be modeled when simulating all stages of gas explosions. These mechanisms are flame acceleration due to instabilities that occur in fluid flow and reactive systems, shock propagation, deflagration to det...
Statefinder Diagnostic for Dark Energy Models in Bianchi I Universe
Sharif, M
2013-01-01
In this paper, we investigate the statefinder, the deceleration and equation of state parameters when universe is composed of generalized holographic dark energy or generalized Ricci dark energy for Bianchi I universe model. These parameters are found for both interacting as well as non-interacting scenarios of generalized holographic or generalized Ricci dark energy with dark matter and generalized Chaplygin gas. We explore these parameters graphically for different situations. It is concluded that these models represent accelerated expansion of the universe.
Exactly solved models of interacting dark matter and dark energy
Chimento, Luis P
2012-01-01
We introduce an effective one-fluid description of the interacting dark sector in a spatially flat Friedmann-Robertson-Walker space-time and investigate the stability of the power-law solutions. We find the "source equation" for the total energy density and determine the energy density of each dark component. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities, their first derivatives, the total energy density with its derivatives up to second order and the scale factor. We solve the evolution equations of the dark components for both interactions, examine exhaustively several examples and show cases where the problem of the coincidence is alleviated. We show that a generic nonlinear interaction gives rise to the "relaxed Chaplygin gas model" whose effective equation of state includes the variable modified Chaplygin gas model while some others nonlinear interactions yield de Sitter and power-law scenarios.
Chakraborty, Shuvendu; Jamil, Mubasher; Myrzakulov, Ratbay
2011-01-01
In this work, we have calculated the deceleration parameter, statefinder parameters and EoS parameters for different dark energy models with variable G correction in homogeneous, isotropic and non-flat universe for Kaluza-Klein Cosmology. The statefinder parameters have been obtained in terms of some observable parameters like dimensionless density parameter, EoS parameter and Hubble parameter for holographic dark energy, new agegraphic dark energy and generalized Chaplygin gas models.
Chakraborty, Shuvendu; Debnath, Ujjal; Jamil, Mubasher; Myrzakulov, Ratbay
2012-07-01
In this work, we have calculated the deceleration parameter, statefinder parameters and EoS parameters for different dark energy models with variable G correction in homogeneous, isotropic and non-flat universe for Kaluza-Klein Cosmology. The statefinder parameters have been obtained in terms of some observable parameters like dimensionless density parameter, EoS parameter and Hubble parameter for holographic dark energy, new agegraphic dark energy and generalized Chaplygin gas models.
Thermodynamics of the Variable Modified Chaplyhin gas
Panigrahi, D
2015-01-01
A cosmological model with a new variant of Chaplygin gas obeying an equation of state(EoS), $P = A\\rho - \\frac{B}{\\rho^{\\alpha}}$ where $B= B_{0}a^{n}$ is investigated in the context of its thermodynamical behaviour. Here $B_{0}$ and $n$ are constants and $a$ is the scale factor. We show that the equation of state of this `Variable Modified Chaplygin gas' (VMCG) can describe the current accelerated expansion of the universe. Following Landau and Lifschitz's criteria we mainly discuss the classical thermodynamical stability of the model and find that the new parameter, $n$ introduced in VMCG plays a crucial role in determining the stability considerations and should be \\emph{negative.} We further observe that although the earlier model of J. Lu explains many of the current observational findings of different probes it fails the desirable tests of thermodynamical stability. We also note that for $n < 0$ our model points to a phantom type of expansion which is found to be compatible with current SNe Ia observ...
Modelling gas markets - a survey
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-12-31
This report reviews research of relevance to the analysis of present and future developments of the European natural gas market. The research activities considered are confined to (1) numerical models for gas markets, (2) analyses of energy demand, and (3) analyses of behaviour and cost structures in the transmission and distribution sector. Most of the market models are strictly micro economic and assume perfect competition or a game-theoretical equilibrium. They use sophisticated solution concepts, but very simplified specifications of supply and demand functions. Most of the research on demand is econometric analyses. These have more detailed model specification than have the aggregated market models. It is found, however, that the econometric literature based on neo-classical economics has not yielded unambiguous results and the specifications disregard important real world aspects of gas demand. The section on demand concludes that the extent of the gas grid is an important determinant for gas demand, but there has been virtually no research on what determines this variable. Data about transmission and distribution of gas in Europe is scarce and only a few non-econometric and virtually no econometric analyses are available. However, some conclusions can be made from relevant North American literature: (1) there has been significant autonomous technical progress in the transmission industry, (2) distribution costs strongly depend on geographical and other conditions, and (3) ownership, whether private or public, may be important for distribution costs and pricing policies. 56 refs., 3 figs., 1 tab.
Modelling gas markets - a survey
International Nuclear Information System (INIS)
This report reviews research of relevance to the analysis of present and future developments of the European natural gas market. The research activities considered are confined to (1) numerical models for gas markets, (2) analyses of energy demand, and (3) analyses of behaviour and cost structures in the transmission and distribution sector. Most of the market models are strictly micro economic and assume perfect competition or a game-theoretical equilibrium. They use sophisticated solution concepts, but very simplified specifications of supply and demand functions. Most of the research on demand is econometric analyses. These have more detailed model specification than have the aggregated market models. It is found, however, that the econometric literature based on neo-classical economics has not yielded unambiguous results and the specifications disregard important real world aspects of gas demand. The section on demand concludes that the extent of the gas grid is an important determinant for gas demand, but there has been virtually no research on what determines this variable. Data about transmission and distribution of gas in Europe is scarce and only a few non-econometric and virtually no econometric analyses are available. However, some conclusions can be made from relevant North American literature: (1) there has been significant autonomous technical progress in the transmission industry, (2) distribution costs strongly depend on geographical and other conditions, and (3) ownership, whether private or public, may be important for distribution costs and pricing policies. 56 refs., 3 figs., 1 tab
Steinhauer, L. C.; Kimura, W. D.
2006-11-01
We have developed a 1-D, quasi-steady-state numerical model for a gas-filled capillary discharge that is designed to aid in selecting the optimum capillary radius in order to guide a laser beam with the required intensity through the capillary. The model also includes the option for an external solenoid B-field around the capillary, which increases the depth of the parabolic density channel in the capillary, thereby allowing for propagation of smaller laser beam waists. The model has been used to select the parameters for gas-filled capillaries to be utilized during the Staged Electron Laser Acceleration — Laser Wakefield (STELLA-LW) experiment.
Energy Technology Data Exchange (ETDEWEB)
Pasqua, Antonio [University of Trieste, Department of Physics, Trieste (Italy); Rocha, Roldao da [Universidade Federal do ABC, Centro de Matematica, Computacao e Cognicao, Santo Andre, SP (Brazil); International School for Advanced Studies (SISSA), Trieste (Italy); Chattopadhyay, Surajit [Bengal Pailan Park, Pailan College of Management and Technology, Kolkata (India)
2015-02-01
Dark energy models are here investigated and studied in the framework of the Chern-Simons modified gravity model. We bring into focus the holographic dark energy model with Granda-Oliveros cut-off, the modified holographic Ricci dark energy model and a model with higher derivatives of the Hubble parameter. The relevant expressions of the scale factor a(t) for a Friedmann-Robertson-Walker Universe are derived and studied, and, in this context, the evolution of the scale factor is shown to be similar to the one displayed by the modified Chaplygin gas in two of the above models. (orig.)
Riemann problem with delta initial data for the isentropic relativistic Chaplygin Euler equations
Shao, Zhiqiang
2016-06-01
In this paper, we study the Riemann problem with the initial data containing the Dirac delta function for the isentropic relativistic Chaplygin Euler equations. Under suitably generalized Rankine-Hugoniot relation and entropy condition, we constructively obtain the global existence of generalized solutions including delta shock waves that explicitly exhibit four kinds of different structures. Moreover, it can be found that the solutions constructed here are stable for the perturbation of the initial data.
Off gas condenser performance modelling
International Nuclear Information System (INIS)
A suite of three programmes has been developed to model the ruthenium decontamination performance of a vitrification plant off-gas condenser. The stages of the model are: condensation of water vapour, NOx absorption in the condensate, RuO4 absorption in the condensate. Juxtaposition of these stages gives a package that may be run on an IBM-compatible desktop PC. Experimental work indicates that the criterion [HNO2] > 10 [RuO4] used to determine RuO4 destruction in solution is probably realistic under condenser conditions. Vapour pressures of RuO4 over aqueous solutions at 70o-90oC are slightly lower than the values given by extrapolating the ln Kp vs. T-1 relation derived from lower temperature data. (author)
Reduction of Almost Poisson brackets and Hamiltonization of the Chaplygin Sphere
Garcia-Naranjo, Luis C
2008-01-01
We construct different almost Poisson brackets for nonholonomic systems than those existing in the literature and study their reduction. Such brackets are built by considering non-canonical two-forms on the cotangent bundle of configuration space and then carrying out a projection onto the constraint space that encodes the Lagrange-D'Alembert principle. We justify the need for this type of brackets by working out the reduction of the celebrated Chaplygin sphere rolling problem. Our construction provides a geometric explanation of the Hamiltonization of the problem given by A. V. Borisov and I. S. Mamaev.
A Lattice-Gas Model of Microemulsions
Boghosian, B M; Emerton, A N; Boghosian, Bruce M.; Coveney, Peter V.; Emerton, Andrew N.
1995-01-01
We develop a lattice gas model for the nonequilibrium dynamics of microemulsions. Our model is based on the immiscible lattice gas of Rothman and Keller, which we reformulate using a microscopic, particulate description so as to permit generalisation to more complicated interactions, and on the prescription of Chan and Liang for introducing such interparticle interactions into lattice gas dynamics. We present the results of simulations to demonstrate that our model exhibits the correct phenomenology, and we contrast it with both equilibrium lattice models of microemulsions, and to other lattice gas models.
MODELLING INDONESIAN OIL AND GAS EXPORT
Directory of Open Access Journals (Sweden)
Sofyan Syahnur
2014-03-01
Full Text Available This study investigates factors affecting Indonesian oil and gas export to six main importing countries. A simultaenuous equation model containing demand and supply equation is used to analyze the problem. A two-stage least squares method is employed to estimate the model. The results show that exchange rate does not statistically influence Indonesian oil and gas export demanded. It also finds that the Gross Domestic Product (GDP of importing countries and Indonesian oil and gas price statistically affect the demand. From the supply model analysis, price statistically affects Indonesian oil and gas export supplied. In addition, Indonesian oil and gas production influences the supply.Keywords: Oil and gas export, simultaneous equation model, exchange rate, GDP.JEL classification number: F40, Q41AbstrakStudi ini menyelidiki faktor-faktor yang mempengaruhi ekspor minyak dan gas Indonesia ke enam negara importir utama. Model permintaan dan penawaran digunakan untuk menganalisis ekspor migas Indonesia dalam bentuk persamaan simultan. Metode Two-Stage Least Squares (2SLS dipakai untuk mengestimasi persamaan simultan tersebut. Hasil studi menunjukkan bahwa kurs tidak berpengaruh terhadap permintaan ekspor migas Indonesia. Studi ini juga menemukan bahwa Produk Domestik Bruto (PDB negara pengimpor dan harga migas Indonesia berpengaruh terhadap permintaan ekspor migas Indonesia. Dari hasil analisis model penawaran didapatkan bahwa harga dan produksi migas Indonesia mempengaruhi penawaran ekspor migas Indonesia.Kata Kunci: Ekspor minyak dan gas, model persamaan simultan, kurs, PDBJEL classification numbers: F40, Q41
The global nonlinear stability of self-gravitating irrotational Chaplygin fluids in a FRW geometry
LeFloch, Philippe G
2015-01-01
We analyze the global nonlinear stability of FRW (Friedmann-Robertson-Walker) spacetimes in presence of an irrotational perfect fluid. We assume that the fluid is governed by the so-called (generalized) Chaplygin equation of state relating the pressure to the mass-energy density. We express the Einstein equations in wave gauge as a systems of coupled nonlinear wave equations and by performing a suitable conformal transformation, we are able to analyze the global behavior of solutions in future timelike directions. We establish that the (3+1)-spacetime metric and the mass density and velocity vector describing the evolution of the fluid remain globally close to a reference FRW solution, under small initial data perturbations. Our analysis provides also the precise asymptotic behavior of the perturbed solutions in the future directions.
Modeling of gas sample behavior in gas chromatography column
Gniazdowski, Zenon; Kowalski, Pawel
2016-01-01
The equilibrium-dispersive model of the linear GC (gas chromatography) was derived using both assumptions and the method of its derivation different from the known in literature. It was concluded that this model is a specific case of the Fokker-Planck equation for diffusion with drift. The resolution of this derived equation for assumed initial conditions is the normal distribution with movable mean value. At the end of the GC column the standard deviation of this distribution was investigate...
Comparison of dark energy models after Planck 2015
Xu, Yue-Yao
2016-01-01
We make a comparison for ten typical, popular dark energy models according to theirs capabilities of fitting the current observational data. The observational data we use in this work include the JLA sample of type Ia supernovae observation, the Planck 2015 distance priors of cosmic microwave background observation, the baryon acoustic oscillations measurements, and the direct measurement of the Hubble constant. Since the models have different numbers of parameters, in order to make a fair comparison, we employ the Akaike and Bayesian information criteria to assess the worth of the models. The analysis results show that, according to the capability of explaining observations, the cosmological constant model is still the best one among all the dark energy models. The generalized Chaplygin gas model, the constant $w$ model, and the $\\alpha$ dark energy model are worse than the cosmological constant model, but still are good models compared to others. The holographic dark energy model, the new generalized Chaply...
Modelling gas generation in radioactive waste repositories
International Nuclear Information System (INIS)
In a repository containing low- and intermediate-level waste, gas generation will occur principally by the coupled processes of metal corrosion and microbial degradation of cellulosic waste. This Paper describes a mathematical model design to address gas generation by these mechanisms. The metal corrosion model incorporates a three-stage process encompassing both aerobic and anaerobic corrosion regimes; the microbial degradation model simulates the activities of eight different microbial populations, which are maintained as functions both of pH and of the concentrations of particular chemical species. Gas concentrations have been measured over a period of three years in large-scale drum experiments designed to simulate repository conditions. Model predictions are confirmed against the experimental measurements, and a prediction is then made of gas concentrations and generation rates over an assessment period of one million years in a radioactive waste repository. (author)
Modelling gas generation in radioactive waste repositories
International Nuclear Information System (INIS)
In a repository containing low- and intermediate-level waste, gas generation will occur principally by the coupled processes of metal corrosion and microbial degradation of cellulosic waste. This paper describes a mathematical model designed to address gas generation by these mechanisms. The metal corrosion model incorporates a three-stage process encompassing both aerobic and anaerobic corrosion regimes; the microbial degradation model simulates the activities of eight different microbial populations, which are maintained as functions both of pH and of the concentrations of particular chemical species. Gas concentrations have been measured over a period of three years in large-scale drum experiments designed to simulate repository conditions. Model predictions are confirmed against the experimental measurements, and a prediction is then made of gas concentrations and generation rates over an assessment period of one million years in a radioactive waste repository. (Author)
Computational modeling of intraocular gas dynamics
Noohi, P.; Abdekhodaie, M. J.; Cheng, Y. L.
2015-12-01
The purpose of this study was to develop a computational model to simulate the dynamics of intraocular gas behavior in pneumatic retinopexy (PR) procedure. The presented model predicted intraocular gas volume at any time and determined the tolerance angle within which a patient can maneuver and still gas completely covers the tear(s). Computational fluid dynamics calculations were conducted to describe PR procedure. The geometrical model was constructed based on the rabbit and human eye dimensions. SF6 in the form of pure and diluted with air was considered as the injected gas. The presented results indicated that the composition of the injected gas affected the gas absorption rate and gas volume. After injection of pure SF6, the bubble expanded to 2.3 times of its initial volume during the first 23 h, but when diluted SF6 was used, no significant expansion was observed. Also, head positioning for the treatment of retinal tear influenced the rate of gas absorption. Moreover, the determined tolerance angle depended on the bubble and tear size. More bubble expansion and smaller retinal tear caused greater tolerance angle. For example, after 23 h, for the tear size of 2 mm the tolerance angle of using pure SF6 is 1.4 times more than that of using diluted SF6 with 80% air. Composition of the injected gas and conditions of the tear in PR may dramatically affect the gas absorption rate and gas volume. Quantifying these effects helps to predict the tolerance angle and improve treatment efficiency.
Adsorption Model for Off-Gas Separation
Energy Technology Data Exchange (ETDEWEB)
Veronica J. Rutledge
2011-03-01
The absence of industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other countries. Thus, it is essential to model complex series of unit operations to simulate, understand, and predict inherent transient behavior and feedback loops. A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes will provide substantial cost savings and many technical benefits. The specific fuel cycle separation process discussed in this report is the off-gas treatment system. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed in gPROMS software. Inputs include gas stream constituents, sorbent, and column properties, equilibrium and kinetic data, and inlet conditions. It models dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions for a multiple component gas stream. The simulation outputs component concentrations along the column length as a function of time from which the breakthrough data is obtained. It also outputs temperature along the column length as a function of time and pressure drop along the column length. Experimental data will be input into the adsorption model to develop a model specific for iodine adsorption on silver mordenite as well as model(s) specific for krypton and xenon adsorption. The model will be validated with experimental breakthrough curves. Another future off-gas modeling goal is to develop a model for the unit operation absorption. The off-gas models will be made available via the server or web for evaluation by customers.
Adsorption Model for Off-Gas Separation
International Nuclear Information System (INIS)
The absence of industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other countries. Thus, it is essential to model complex series of unit operations to simulate, understand, and predict inherent transient behavior and feedback loops. A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes will provide substantial cost savings and many technical benefits. The specific fuel cycle separation process discussed in this report is the off-gas treatment system. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed in gPROMS software. Inputs include gas stream constituents, sorbent, and column properties, equilibrium and kinetic data, and inlet conditions. It models dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions for a multiple component gas stream. The simulation outputs component concentrations along the column length as a function of time from which the breakthrough data is obtained. It also outputs temperature along the column length as a function of time and pressure drop along the column length. Experimental data will be input into the adsorption model to develop a model specific for iodine adsorption on silver mordenite as well as model(s) specific for krypton and xenon adsorption. The model will be validated with experimental breakthrough curves. Another future off-gas modeling goal is to develop a model for the unit operation absorption. The off-gas models will be made available via the server or web for evaluation by customers.
On modelling the market for natural gas
Energy Technology Data Exchange (ETDEWEB)
Mathiesen, Lars
2001-12-01
Several features may separately or in combination influence conduct and performance of an industry, e.g. the numbers of sellers or buyers, the degree of economies of scale in production and distribution, the temporal and spatial dimensions, etc. Our main focus is on how to model market power. In particular, we demonstrate the rather different solutions obtained from the price-taking behavior versus the oligopolistic Coumot behavior. We also consider two approaches to model the transportation of natural gas. Finally, there is a brief review of previous modeling efforts of the European natural gas industry. (author)
Combustion modeling in advanced gas turbine systems
Energy Technology Data Exchange (ETDEWEB)
Smoot, L.D.; Hedman, P.O.; Fletcher, T.H. [Brigham Young Univ., Provo, UT (United States)] [and others
1995-10-01
The goal of the U.S. Department of Energy`s Advanced Turbine Systems (ATS) program is to help develop and commercialize ultra-high efficiency, environmentally superior, and cost competitive gas turbine systems for base-load applications in the utility, independent power producer, and industrial markets. Combustion modeling, including emission characteristics, has been identified as a needed, high-priority technology by key professionals in the gas turbine industry.
Model developed for economic gas dispatch
International Nuclear Information System (INIS)
Essex County Gas Co. is using at new, highly efficient approach to simulate the daily economic dispatch of gas supplies to meet market requirements under FERC Order 636. Although sophisticated in its design, the modeling environment permits straightforward model construction with richly detailed components that can be readily changed as needed by gas utility personnel after only a short training period. It provides a mechanism for very detailed simulation of the market and supply balances governing LDC operations. The model serves as Essex County Gas' primary what if? tool for testing the operational and economic consequences of a wide variety of supply and demand-side-management alternatives. The model, developed by consultant E.J. Curtis, is driven by Effective Heating Degree-Day daily weather patterns, such as design, normal, warm and extreme. The model is driven by weather patterns input as time series, so other independent variables such as general inflation factors, energy cost projections and economic model results can also be input as time-series data. Alternatively, detailed submodels for such components can be imbedded within the model to automatically generate this information. It incorporates supply and market simulation elements, permitting ready adaptation for use not only in conventional supply planning but also integrated resource management. Comparative 'what if?' cases can be run with specific demand-side management initiatives toggled on and off
International Nuclear Information System (INIS)
The Gas Analysis Modeling System is a large computer-based model for analyzing the complex US natural gas industry, including production, transportation, and consumption activities. The model was developed and first used in 1982 after the passage of the NGPA, which initiated a phased decontrol of most natural gas prices at the wellhead. The categorization of gas under the NGPA and the contractual nature of the natural gas market, which existed at the time, were primary factors in the development of the basic structure of the model. As laws and regulations concerning the natural gas market have changed, the model has evolved accordingly. Recent increases in competition in the wellhead market have also led to changes in the model. GAMS produces forecasts of natural gas production, consumption, and prices annually through 2010. It is an engineering-economic model that incorporates several different mathematical structures in order to represent the interaction of the key groups involved in the natural gas market. GAMS has separate supply and demand components that are equilibrated for each year of the forecast by means of a detailed transaction network
Scale Factor Self-Dual Cosmological Models
dS, U Camara; Sotkov, G M
2015-01-01
We implement a conformal time scale factor duality for Friedmann-Robertson-Walker cosmological models, which is consistent with the weak energy condition. The requirement for self-duality determines the equations of state for a broad class of barotropic fluids. We study the example of a universe filled with two interacting fluids, presenting an accelerated and a decelerated period, with manifest UV/IR duality. The associated self-dual scalar field interaction turns out to coincide with the "radiation-like" modified Chaplygin gas models. We present an equivalent realization of them as gauged K\\"ahler sigma models (minimally coupled to gravity) with very specific and interrelated K\\"ahler- and super-potentials. Their applications in the description of hilltop inflation and also as quintessence models for the late universe are discussed.
Modeling internal ballistics of gas combustion guns.
Schorge, Volker; Grossjohann, Rico; Schönekess, Holger C; Herbst, Jörg; Bockholdt, Britta; Ekkernkamp, Axel; Frank, Matthias
2016-05-01
Potato guns are popular homemade guns which work on the principle of gas combustion. They are usually constructed for recreational rather than criminal purposes. Yet some serious injuries and fatalities due to these guns are reported. As information on the internal ballistics of homemade gas combustion-powered guns is scarce, it is the aim of this work to provide an experimental model of the internal ballistics of these devices and to investigate their basic physical parameters. A gas combustion gun was constructed with a steel tube as the main component. Gas/air mixtures of acetylene, hydrogen, and ethylene were used as propellants for discharging a 46-mm caliber test projectile. Gas pressure in the combustion chamber was captured with a piezoelectric pressure sensor. Projectile velocity was measured with a ballistic speed measurement system. The maximum gas pressure, the maximum rate of pressure rise, the time parameters of the pressure curve, and the velocity and path of the projectile through the barrel as a function of time were determined according to the pressure-time curve. The maximum gas pressure was measured to be between 1.4 bar (ethylene) and 4.5 bar (acetylene). The highest maximum rate of pressure rise was determined for hydrogen at (dp/dt)max = 607 bar/s. The muzzle energy was calculated to be between 67 J (ethylene) and 204 J (acetylene). To conclude, this work provides basic information on the internal ballistics of homemade gas combustion guns. The risk of injury to the operator or bystanders is high, because accidental explosions of the gun due to the high-pressure rise during combustion of the gas/air mixture may occur. PMID:26239103
Statistical Modeling Efforts for Headspace Gas
Energy Technology Data Exchange (ETDEWEB)
Weaver, Brian Phillip [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-03-17
The purpose of this document is to describe the statistical modeling effort for gas concentrations in WIPP storage containers. The concentration (in ppm) of CO_{2} in the headspace volume of standard waste box (SWB) 68685 is shown. A Bayesian approach and an adaptive Metropolis-Hastings algorithm were used.
Does Bulk Viscosity Create a Viable Unified Dark Matter Model?
Li, Baojiu
2009-01-01
We investigate in detail the possibility that a single imperfect fluid with bulk viscosity can replace the need for separate dark matter and dark energy in cosmological models. With suitable choices of model parameters, we show that the background cosmology in this model can mimic that of a LCDM Universe to high precision. However, as the cosmic expansion goes through the decelerating-accelerating transition, the density perturbations in this fluid are rapidly damped out. We show that,although this does not significantly affect structure formation in baryonic matter, it makes the gravitational potential decay rapidly at late times, leading to modifications in predictions of cosmological observables such as the CMB power spectrum and weak lensing. This model of unified dark matter is thus difficult to reconcile with astronomical observations. We also clarify the differences with respect to other unified dark matter models where the fluid is barotropic, i.e., p=p(rho), such as the (generalized) Chaplygin gas mo...
Mechanical Model of Domestic Gas Explosion Load
Institute of Scientific and Technical Information of China (English)
HAN Yongli; CHEN Longzhu
2008-01-01
With the increase of domestic gas consumption in cities and towns in China, gas explosion accidents happened rather frequently, and many structures were damaged greatly.Rational physical design could protect structures from being destroyed, but the character of explosion load must be learned firstly by establishing a correct mechanical model to simulate vented gas explosions.The explosion process has been studied for many years towards the safety of chemical industry equipments.The key problem of these studies was the equations usually involved some adjustable parameters that must be evaluated by experimental data, and the procedure of calculation was extremely complicated, so the reliability of these studies was seriously limited.Based on these studies, a simple mathematical model was established in this paper by using energy conservation,mass conservation, gas state equation, adiabatic compression equation and gas venting equation.Explosion load must be estimated by considering the room layout; the rate of pressure rise was then corrected by using a turbulence factor, so the pressure-time curve could be obtained.By using this method, complicated calculation was avoided, while experimental and calculated results fitted fairly well.Some pressure-time curves in a typical rectangular room were calculated to investigate the influences of different ignition locations, gas thickness, concentration, room size and venting area on the explosion pressure.The results indicated that: it was the most dangerous condition when being ignited in the geometry centre of the room; the greater the burning velocity, the worse the venting effect; the larger the venting pressure, the higher the peak pressure; the larger the venting area, the lower the peak pressure.
Comparison of dark energy models: A perspective from the latest observational data
Li, Miao; Zhang, Xin
2009-01-01
In this paper, we compare some popular dark energy models with the assumption of a flat universe by using the latest observational data including the type Ia supernovae Constitution compilation, the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey and the Two Degree Field Galaxy Redshift Survey, and the cosmic microwave background measurement given by the five-year Wilkinson Microwave Anisotropy Probe observations. Model comparison statistics such as the Bayesian and Akaike information criteria are applied to assess the worth of the models. These statistics favor models that give a good fit with fewer parameters. Based on this analysis, we find that the simplest cosmological constant model that has only one free parameter is still preferred by the current data. For other dynamical dark energy models, we find that some of them, such as the $\\alpha$ dark energy, constant $w$, generalized Chaplygin gas, and holographic dark energy models, can provide good fits to the current data, and th...
Observation Constraints on the Simplified GCG Model
Institute of Scientific and Technical Information of China (English)
DONG Su-Mei; WU Pu-Xun
2007-01-01
A simplified version of generalized Chaplygin gas (GCG) as a dark energy model is studied. By using the latest 162 ESSENCE type la supernovae (Sne la) data, 30 high redshift Sne la data, the baryonk acoustic oscillation peak from SDSS and the CMB data from WMAP3, a strong constraint on this simplified GCG model is obtained. At the 95.4% confidence level we obtain 0.21 ≤ Ωm ≤ 0.31 and 0.994 ≤ a ≤ 1.0 with the best fit fim = 0.25 and a = 1. This best fit scenario corresponds to an accelerating universe with qo ～_0.65 and z ～- 0.81 (a redshift of cosmic phase transition from deceleration to acceleration).
Multisite Interactions in Lattice-Gas Models
Einstein, T. L.; Sathiyanarayanan, R.
For detailed applications of lattice-gas models to surface systems, multisite interactions often play at least as significant a role as interactions between pairs of adatoms that are separated by a few lattice spacings. We recall that trio (3-adatom, non-pairwise) interactions do not inevitably create phase boundary asymmetries about half coverage. We discuss a sophisticated application to an experimental system and describe refinements in extracting lattice-gas energies from calculations of total energies of several different ordered overlayers. We describe how lateral relaxations complicate matters when there is direct interaction between the adatoms, an issue that is important when examining the angular dependence of step line tensions. We discuss the connector model as an alternative viewpoint and close with a brief account of recent work on organic molecule overlayers.
Diffusive description of lattice gas models
DEFF Research Database (Denmark)
Fiig, T.; Jensen, H.J.
1993-01-01
lattice gases are described by a diffusion equation without any bulk noise. The open lattice gas exhibits a crossover behavior as the probability for introducing particles at the edge of the system becomes small. The power spectrum changes from a 1/f to a 1/f2 spectrum. The diffusive description, proven......We have investigated a lattice gas model consisting of repulsive particles following deterministic dynamics. Two versions of the model are studied. In one case we consider a Finite open system in which particles can leave and enter the lattice over the edge. In the other case we use periodic...... boundary conditions. In both cases the density fluctuations exhibit a 1/f power spectrum. The individual particles behave asymptotically like ordinary random walkers. The collective behavior of these particles shows that due to the deterministic dynamics the particles behave as if they are correlated...
Numerical modeling of fires on gas pipelines
International Nuclear Information System (INIS)
When natural gas is released through a hole on a high-pressure pipeline, it disperses in the atmosphere as a jet. A jet fire will occur when the leaked gas meets an ignition source. To estimate the dangerous area, the shape and size of the fire must be known. The evolution of the jet fire in air is predicted by using a finite-volume procedure to solve the flow equations. The model is three-dimensional, elliptic and calculated by using a compressibility corrected version of the k - ξ turbulence model, and also includes a probability density function/laminar flamelet model of turbulent non-premixed combustion process. Radiation heat transfer is described using an adaptive version of the discrete transfer method. The model is compared with the experiments about a horizontal jet fire in a wind tunnel in the literature with success. The influence of wind and jet velocity on the fire shape has been investigated. And a correlation based on numerical results for predicting the stoichiometric flame length is proposed. - Research highlights: → We developed a model to predict the evolution of turbulent jet diffusion flames. → Measurements of temperature distributions match well with the numerical predictions. → A correlation has been proposed to predict the stoichiometric flame length. → Buoyancy effects are higher in the numerical results. → The radiative heat loss is bigger in the experimental results.
Mathematical analysis of intermittent gas injection model in oil production
Tasmi, Silvya, D. R.; Pudjo, S.; Leksono, M.; Edy, S.
2016-02-01
Intermittent gas injection is a method to help oil production process. Gas is injected through choke in surface and then gas into tubing. Gas forms three areas in tubing: gas column area, film area and slug area. Gas column is used to propel slug area until surface. A mathematical model of intermittent gas injection is developed in gas column area, film area and slug area. Model is expanding based on mass and momentum conservation. Using assume film thickness constant in tubing, model has been developed by Tasmi et. al. [14]. Model consists of 10 ordinary differential equations. In this paper, assumption of pressure in gas column is uniform. Model consist of 9 ordinary differential equations. Connection of several variables can be obtained from this model. Therefore, dynamics of all variables that affect to intermittent gas lift process can be seen from four equations. To study the behavior of variables can be analyzed numerically and mathematically. In this paper, simple mathematically analysis approach is used to study behavior of the variables. Variables that affect to intermittent gas injection are pressure in upstream valve and in gas column. Pressure in upstream valve will decrease when gas mass in valve greater than gas mass in choke. Dynamic of the pressure in the gas column will decrease and increase depending on pressure in upstream valve.
Modelling and Simulation of Gas Engines Using Aspen HYSYS
Directory of Open Access Journals (Sweden)
M. C. Ekwonu
2013-12-01
Full Text Available In this paper gas engine model was developed in Aspen HYSYS V7.3 and validated with Waukesha 16V275GL+ gas engine. Fuel flexibility, fuel types and part load performance of the gas engine were investigated. The design variability revealed that the gas engine can operate on poor fuel with low lower heating value (LHV such as landfill gas, sewage gas and biogas with biogas offering potential integration with bottoming cycles when compared to natural gas. The result of the gas engine simulation gave an efficiency 40.7% and power output of 3592kW.
Modelling the Molecular Gas in NGC 6240
Tunnard, R; Garcia-Burillo, S; Carpio, J Graciá; Fuente, A; Tacconi, L; Neri, R; Usero, A
2015-01-01
We present the first observations of H$^{13}$CN$(1-0)$, H$^{13}$CO$^+(1-0)$ and SiO$(2-1)$ in NGC 6240, obtained with the IRAM PdBI. Combining a Markov Chain Monte Carlo (MCMC) code with Large Velocity Gradient (LVG) modelling we derive posterior probability density functions (pdfs) for the dense gas parameters, including mass$-$luminosity conversion factors, finding a large amount of dense molecular gas $(\\sim10^{10}M_\\odot)$ in cold, dense clouds ($T_k\\sim10$ K, $n_{{\\rm H}_2}\\sim10^6$ cm$^{-3}$) with a small volume filling factor $(<0.002)$. Including literature CO data we present simultaneously fitted multi-species, two phase models which spontaneously separate into a hot, diffuse phase ($\\log_{10}\\left(T_k / [{\\rm K}]\\right) = 3.2^{3.3}_{3.1}$, $\\log_{10}\\left(n_{{\\rm H}_2} / [{\\rm cm}^{-3}]\\right)=3.6^{3.8}_{3.5}$) and a cold, dense phase ($\\log_{10}\\left(T_k / [{\\rm K}]\\right) = 0.9^{0.9}_{0.8}$, $\\log_{10}\\left(n_{{\\rm H}_2} / [{\\rm cm}^{-3}]\\right)=6.6^{6.8}_{6.3}$). A restricted three phase model...
Mathematical modeling of gas turbine cooled elements
Energy Technology Data Exchange (ETDEWEB)
Pashayev, A.; Askerov, D.; Sadiqov, R.; Samedov, A. [Academy of Aviation, Baku (Azerbaijan). Dept. of Mathematical Modeling and Design of Gas Turbine Engines
2007-07-01
The profile section of a gas turbine blade with convective cooling was modelled. Converging quadrature processes were used to determine the stationary and quasi-stationary temperature field of the profile part of the blade. Profiles were visualized using the least squares method along with automatic conjecture, device spline, smooth replenishment, and neural nets. Heat exchange boundary conditions were characterized using the finite difference method; finite element analysis (FEA); the Monte Carlo method; and the boundary integral equations method (BIEM). Boundary conditions included the heat quantity assigned by convection of the cooler transmitted by heat conduction of the blade material to the surface of cooling channels. Errors were investigated using a quadratures method and Tikhonov regularization. A Kirchhoff permutation was used to linearize tasks. The developed equation was then transformed into a Laplace equation. The model was then compared with experimental investigations to validate heat and hydraulic characteristics, as well as the temperature field of the blade cross section. It was concluded that the model can be used to assess the reliability of gas turbine engine designs. 3 refs., 1 fig.
Modeling of greenhouse gas emission from livestock
Directory of Open Access Journals (Sweden)
Sanjo eJose
2016-04-01
Full Text Available The effects of climate change on humans and other living ecosystems is an area of on-going research. The ruminant livestock sector is considered to be one of the most significant contributors to the existing greenhouse gas (GHG pool. However the there are opportunities to combat climate change by reducing the emission of GHGs from ruminants. Methane (CH4 and nitrous oxide (N2O are emitted by ruminants via anaerobic digestion of organic matter in the rumen and manure, and by denitrification and nitrification processes which occur in manure. The quantification of these emissions by experimental methods is difficult and takes considerable time for analysis of the implications of the outputs from empirical studies, and for adaptation and mitigation strategies to be developed. To overcome these problems computer simulation models offer substantial scope for predicting GHG emissions. These models often include all farm activities while accurately predicting the GHG emissions including both direct as well as indirect sources. The models are fast and efficient in predicting emissions and provide valuable information on implementing the appropriate GHG mitigation strategies on farms. Further, these models help in testing the efficacy of various mitigation strategies that are employed to reduce GHG emissions. These models can be used to determine future adaptation and mitigation strategies, to reduce GHG emissions thereby combating livestock induced climate change.
Viscous dark fluid Universe: a unified model of the dark sector?
Zimdahl, W; Hipólito-Ricaldi, W S; 10.1142/S2010194511001413
2011-01-01
The Universe is modeled as consisting of pressureless baryonic matter and a bulk viscous fluid which is supposed to represent a unified description of the dark sector. In the homogeneous and isotropic background the \\textit{total} energy density of this mixture behaves as a generalized Chaplygin gas. The perturbations of this energy density are intrinsically nonadiabatic and source relative entropy perturbations. The resulting baryonic matter power spectrum is shown to be compatible with the 2dFGRS and SDSS (DR7) data. A joint statistical analysis, using also Hubble-function and supernovae Ia data, shows that, different from other studies, there exists a maximum in the probability distribution for a negative present value of the deceleration parameter. Moreover, the unified model presented here favors a matter content that is of the order of the baryonic matter abundance suggested by big-bang nucleosynthesis. A problem of simple bulk viscous models, however, is the behavior of the gravitational potential and ...
Evaluation of the gas production economics of the gas hydrate cyclic thermal injection model
Energy Technology Data Exchange (ETDEWEB)
Kuuskraa, V.A.; Hammersheimb, E.; Sawyer, W.
1985-05-01
The objective of the work performed under this directive is to assess whether gas hydrates could potentially be technically and economically recoverable. The technical potential and economics of recovering gas from a representative hydrate reservoir will be established using the cyclic thermal injection model, HYDMOD, appropriately modified for this effort, integrated with economics model for gas production on the North Slope of Alaska, and in the deep offshore Atlantic. The results from this effort are presented in this document. In Section 1, the engineering cost and financial analysis model used in performing the economic analysis of gas production from hydrates -- the Hydrates Gas Economics Model (HGEM) -- is described. Section 2 contains a users guide for HGEM. In Section 3, a preliminary economic assessment of the gas production economics of the gas hydrate cyclic thermal injection model is presented. Section 4 contains a summary critique of existing hydrate gas recovery models. Finally, Section 5 summarizes the model modification made to HYDMOD, the cyclic thermal injection model for hydrate gas recovery, in order to perform this analysis.
Models of the Intergalactic Gas in Stephan's Quintet
Hwang, Jeong-Sun; Renaud, Florent; Appleton, Philip N
2009-01-01
We use smoothed particle hydrodynamics (SPH) models to study the large-scale morphology and dynamical evolution of the intergalactic gas in Stephan's Quintet, and compare to multiwavelength observations. Specifically, we model the formation of the hot X-ray gas, the large-scale shock, and emission line gas as the result of NGC 7318b colliding with the group. We also reproduce the N-body model of Renaud and Appleton for the tidal structures in the group.
Tachyon cosmology with non-vanishing minimum potential: a unified model
Energy Technology Data Exchange (ETDEWEB)
Li, Huiquan, E-mail: hqli@ustc.edu.cn [Interdisciplinary Center for Theoretical Study, University of Science and Technology of China, Hefei, Anhui 230026 (China)
2012-07-01
We investigate the tachyon condensation process in the effective theory with non-vanishing minimum potential and its implications to cosmology. It is shown that the tachyon condensation on an unstable three-brane described by this modified tachyon field theory leads to lower-dimensional branes (defects) forming within a stable three-brane. Thus, in the cosmological background, we can get well-behaved tachyon matter after tachyon inflation, (partially) avoiding difficulties encountered in the original tachyon cosmological models. This feature also implies that the tachyon inflated and reheated universe is followed by a Chaplygin gas dark matter and dark energy universe. Hence, such an unstable three-brane behaves quite like our universe, reproducing the key features of the whole evolutionary history of the universe and providing a unified description of inflaton, dark matter and dark energy in a very simple single-scalar field model.
A FORTRAN program for modeling methane gas desorption from coal
Nguyen, V. U.
Coal has a strong affinity for methane gas, and the process of gas adsorption (or desorption) is modeled customarily by empirical relations between the amount of gas adsorbed (or desorbed) and time. In this paper, a new and unified theory formulated to depict the process and mechanism of methane gas transport in coal is presented. The theory is validated by conventional sorption tests on cylindrical cores, and its description coded in FORTRAN is presented.
Adsorption modeling for off-gas treatment
Energy Technology Data Exchange (ETDEWEB)
Ladshaw, A.; Sharma, K.; Yiacoumi, S.; Tsouris, C. [Georgia Institute of Technology, Atlanta, GA 30332-0459 (United States); De Paoli, D.W. [Oak Ridge National Laboratory: Oak Ridge, TN 37831-6181 (United States)
2013-07-01
Off-gas generated from the reprocessing of used nuclear fuel contains a mixture of several radioactive gases including {sup 129}I{sub 2}, {sup 85}Kr, HTO, and {sup 14}CO{sub 2}. Over the past few decades, various separation and recovery processes have been studied for capturing these gases. Adsorption data for gaseous mixtures of species can be difficult to determine experimentally. Therefore, procedures capable of predicting the adsorption behavior of mixtures need to be developed from the individual isotherms of each of the pure species. A particular isotherm model of interest for the pure species is the Generalized Statistical Thermodynamic Adsorption isotherm. This model contains an adjustable number of parameters and will therefore describe a wide range of adsorption isotherms for a variety of components. A code has been developed in C++ to perform the non-linear regression analysis necessary for the determination of the isotherm parameters, as well as the least number of parameters needed to describe an entire set of data. (authors)
Dynamic Modeling and Analysis of an Industrial Gas Suspension Absorber for Flue Gas Desulfurization
DEFF Research Database (Denmark)
Cignitti, Stefano; Mansouri, Seyed Soheil; Sales-Cruz, Mauricio;
2016-01-01
In this work, semidry desulfurization of flue gas using a gas suspension absorber (GSA) is studied. A simple dynamic model which can properly represent the GSA was developed. In order to model the reaction kinetics, an empirical reaction rate expression was introduced. The reaction rate expression...
GASCAP: Wellhead Gas Productive Capacity Model documentation, June 1993
International Nuclear Information System (INIS)
The Wellhead Gas Productive Capacity Model (GASCAP) has been developed by EIA to provide a historical analysis of the monthly productive capacity of natural gas at the wellhead and a projection of monthly capacity for 2 years into the future. The impact of drilling, oil and gas price assumptions, and demand on gas productive capacity are examined. Both gas-well gas and oil-well gas are included. Oil-well gas productive capacity is estimated separately and then combined with the gas-well gas productive capacity. This documentation report provides a general overview of the GASCAP Model, describes the underlying data base, provides technical descriptions of the component models, diagrams the system and subsystem flow, describes the equations, and provides definitions and sources of all variables used in the system. This documentation report is provided to enable users of EIA projections generated by GASCAP to understand the underlying procedures used and to replicate the models and solutions. This report should be of particular interest to those in the Congress, Federal and State agencies, industry, and the academic community, who are concerned with the future availability of natural gas
Numerical model of compressible gas flow in soil pollution control
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Based on the theory of fluid dynamics in porous media, a numerical model of gas flow in unsaturated zone is developed with the consideration of gas density change due to variation of air pressure. This model is characterized of its wider range of availability. The accuracy of this numerical model is analyzed through comparison with modeling results by previous model with presumption of little pressure variation and the validity of this numerical model is shown. Thus it provides basis for the designing and management of landfill gas control system or soil vapor ex.action system in soil pollution control.
Modeling of Fission Gas Release in UO2
Energy Technology Data Exchange (ETDEWEB)
MH Krohn
2006-01-23
A two-stage gas release model was examined to determine if it could provide a physically realistic and accurate model for fission gas release under Prometheus conditions. The single-stage Booth model [1], which is often used to calculate fission gas release, is considered to be oversimplified and not representative of the mechanisms that occur during fission gas release. Two-stage gas release models require saturation at the grain boundaries before gas is release, leading to a time delay in release of gases generated in the fuel. Two versions of a two-stage model developed by Forsberg and Massih [2] were implemented using Mathcad [3]. The original Forsbers and Massih model [2] and a modified version of the Forsberg and Massih model that is used in a commercially available fuel performance code (FRAPCON-3) [4] were examined. After an examination of these models, it is apparent that without further development and validation neither of these models should be used to calculate fission gas release under Prometheus-type conditions. There is too much uncertainty in the input parameters used in the models. In addition. the data used to tune the modified Forsberg and Massih model (FRAPCON-3) was collected under commercial reactor conditions, which will have higher fission rates relative to Prometheus conditions [4].
International Nuclear Information System (INIS)
The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of integrated Analysis and Forecasting of the Energy information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. The NGTDM is the model within the NEMS that represents the transmission, distribution, and pricing of natural gas. The model also includes representations of the end-use demand for natural gas, the production of domestic natural gas, and the availability of natural gas traded on the international market based on information received from other NEMS models. The NGTDM determines the flow of natural gas in an aggregate, domestic pipeline network, connecting domestic and foreign supply regions with 12 demand regions. The methodology employed allows the analysis of impacts of regional capacity constraints in the interstate natural gas pipeline network and the identification of pipeline capacity expansion requirements. There is an explicit representation of core and noncore markets for natural gas transmission and distribution services, and the key components of pipeline tariffs are represented in a pricing algorithm. Natural gas pricing and flow patterns are derived by obtaining a market equilibrium across the three main elements of the natural gas market: the supply element, the demand element, and the transmission and distribution network that links them. The NGTDM consists of four modules: the Annual Flow Module, the Capacity F-expansion Module, the Pipeline Tariff Module, and the Distributor Tariff Module. A model abstract is provided in Appendix A
Energy Technology Data Exchange (ETDEWEB)
NONE
1995-02-17
The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of integrated Analysis and Forecasting of the Energy information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. The NGTDM is the model within the NEMS that represents the transmission, distribution, and pricing of natural gas. The model also includes representations of the end-use demand for natural gas, the production of domestic natural gas, and the availability of natural gas traded on the international market based on information received from other NEMS models. The NGTDM determines the flow of natural gas in an aggregate, domestic pipeline network, connecting domestic and foreign supply regions with 12 demand regions. The methodology employed allows the analysis of impacts of regional capacity constraints in the interstate natural gas pipeline network and the identification of pipeline capacity expansion requirements. There is an explicit representation of core and noncore markets for natural gas transmission and distribution services, and the key components of pipeline tariffs are represented in a pricing algorithm. Natural gas pricing and flow patterns are derived by obtaining a market equilibrium across the three main elements of the natural gas market: the supply element, the demand element, and the transmission and distribution network that links them. The NGTDM consists of four modules: the Annual Flow Module, the Capacity F-expansion Module, the Pipeline Tariff Module, and the Distributor Tariff Module. A model abstract is provided in Appendix A.
Ou, Chenghua; Li, ChaoChun; Ma, Zhonggao
2016-10-01
A water-bearing carbonate gas reservoir is an important natural gas resource being developed worldwide. Due to the long-term water/rock/gas interaction during geological evolution, complex gas/water distribution has formed under the superposed effect of sedimentary facies, reservoir space facies and gravity difference of fluid facies. In view of these challenges, on the basis of the conventional three-stage modeling method, this paper presents a modelling method controlled by four-stage facies to develop 3D model of a water-bearing carbonate gas reservoir. Key to this method is the reservoir property modelling controlled by two-stage facies, and the fluid property modelling controlled by another two-stage facies. The prerequisite of this method is a reliable database obtained from solid geological investigation. On the basis of illustrating the principles of the modelling method controlled by four-stage facies, this paper further implements systematically modeling of the heterogeneous gas/water distribution of the Longwangmiao carbonate formation in the Moxi-Gaoshiti area, Sichuan basin, China.
Modeling biogenic gas bubbles formation and migration in coarse sand
Ye, S.
2011-12-01
Shujun Ye Department of Hydrosciences, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China; sjye@nju.edu.cn Brent E. Sleep Department of Civil Engineering, University of Toronto, Toronto, ON, M5S 1A4 CANADA; sleep@ecf.utoronto.ca Methane gas generation in porous media was investigated in an anaerobic two-dimensional sand-filled cell. Inoculation of the lower portion of the cell with a methanogenic culture and addition of methanol to the bottom of the cell led to biomass growth and formation of a gas phase. The formation, migration, distribution and saturation of gases in the cell were visualized by the charge-coupled device (CCD) camera. Gas generated at the bottom of the cell in the biologically active zone moved upwards in discrete fingers, so that gas phase saturations (gas-filled fraction of void space) in the biologically active zone at the bottom of the cell did not exceed 40-50%, while gas accumulation at the top of the cell produced gas phase saturations as high as 80%. Macroscopic invasion percolation (MIP) at near pore scale[Glass, et al., 2001; Kueper and McWhorter, 1992]was used to model gas bubbles growth in porous media. The nonwetting phase migration pathway can be yielded directly by MIP. MIP was adopted to simulate the expansion, fragmentation, and mobilization of gas clusters in the cell. The production of gas, and gas phash saturations were simulated by a continuum model - compositional simulator (COMPSIM) [Sleep and Sykes, 1993]. So a combination of a continuum model and a MIP model was used to simulate the formation, fragmentation and migration of biogenic gas bubbles. Key words: biogenic gas; two dimensional; porous media; MIP; COMPSIM
Development of a gas systems analysis model (GSAM)
Energy Technology Data Exchange (ETDEWEB)
Godec, M.L. [IFC Resources Inc., Fairfax, VA (United States)
1995-04-01
The objectives of developing a Gas Systems Analysis Model (GSAM) are to create a comprehensive, non-proprietary, PC based model of domestic gas industry activity. The system is capable of assessing the impacts of various changes in the natural gas system within North America. The individual and collective impacts due to changes in technology and economic conditions are explicitly modeled in GSAM. Major gas resources are all modeled, including conventional, tight, Devonian Shale, coalbed methane, and low-quality gas sources. The modeling system asseses all key components of the gas industry, including available resources, exploration, drilling, completion, production, and processing practices, both for now and in the future. The model similarly assesses the distribution, storage, and utilization of natural gas in a dynamic market-based analytical structure. GSAM is designed to provide METC managers with a tool to project the impacts of future research, development, and demonstration (RD&D) benefits in order to determine priorities in a rapidly changing, market-driven gas industry.
Modelling of Rotor-gas bearings for Feedback Controller Design
DEFF Research Database (Denmark)
Theisen, Lukas Roy Svane; Niemann, Hans Henrik
2014-01-01
Controllable rotor-gas bearings are popular oering adaptability, high speed operation, low friction and clean operation. Rotor-gas bearings are however highly sensitive to disturbances due to the low friction of the injected gas. These undesirable damping properties call for controllers, which can...... be designed from suitable models describing the relation from actuator input to measured shaft position. Current state of the art models of controllable gas bearings however do not provide such relation, which calls for alternative strategies. The present contribution discusses the challenges for feedback...... controller design using the state of the art method, and an alternative data driven modelling approach is pursued based on Grey-Box system identication. The method allows development of models of the rotor-gas bearing suitable for controller design, which can be identied from data over the range of operation...
Energy Technology Data Exchange (ETDEWEB)
Gomes, Leonardo Vinicius; Mendes, Pedro Paulo C. [Escola Federal de Engenharia de Itajuba, MG (Brazil). Dept. de Eletrotecnica; Ferreira, Claudio [Agencia Nacional de Energia Eletrica (ANEEL), Brasilia, DF (Brazil)
1999-07-01
This paper presents the development and analysis of various mathematical models for gas turbine which can be incorporated to dynamic stability or to electric power systems. The work provides answers for questions such as: the dynamic behaviour of gas turbine driven generator unities, the influence of those equipment in the other elements and the best operational conditions for the equipment.
Forecasting China's natural gas consumption based on a combination model
Institute of Scientific and Technical Information of China (English)
Gang Xu; Weiguo Wang
2010-01-01
Ensuring a sufficient energy supply is essential to a country.Natural gas constitutes a vital part in energy supply and therefore forecasting natural gas consumption reliably and accurately is an essential part of a country's energy policy.Over the years,studies have shown that a combinative model gives better projected results compared to a single model.In this study,we used Polynomial Curve and Moving Average Combination Projection (PCMACP) model to estimate the future natural gas consumption in China from 2009 to 2015.The new proposed PCMACP model shows more reliable and accurate results:its Mean Absolute Percentage Error (MAPE) is less than those of any previous models within the investigated range.According to the PCMACP model,the average annual growth rate will increase for the next 7 years and the amount of natural gas consumption will reach 171600 million cubic meters in 2015 in China.
Bertei, A.; Nicolella, C.
2015-04-01
The paper shows as two assumptions typically made in modeling gas transport in solid oxide fuel cell electrodes, i.e., a) uniform pressure in the dusty-gas model, and b) validity of the Bosanquet formula in the Fick model, may lead to serious inconsistencies (such as molar fractions that do not sum up to one or fluxes that do not obey reaction stoichiometry), thus nullifying the efforts of the mechanistic modeling of transport phenomena. The nature of the inconsistent use of the models is explained with clear examples, then the correct implementation of the gas transport models is discussed. The study aims to promote a coherent physically-based modeling of gas transport phenomena in porous electrodes in order to assist their rational design.
Data Processing Model of Coalmine Gas Early-Warning System
Institute of Scientific and Technical Information of China (English)
QIAN Jian-sheng; YIN Hong-sheng; LIU Xiu-rong; HUA Gang; XU Yong-gang
2007-01-01
The data processing mode is vital to the performance of an entire coalmine gas early-warning system, especially in real-time performance. Our objective was to present the structural features of coalmine gas data, so that the data could be processed at different priority levels in C language. Two different data processing models, one with priority and the other without priority, were built based on queuing theory. Their theoretical formulas were determined via a M/M/1 model in order to calculate average occupation time of each measuring point in an early-warning program. We validated the model with the gas early-warning system of the Huaibei Coalmine Group Corp. The results indicate that the average occupation time for gas data processing by using the queuing system model with priority is nearly 1/30 of that of the model without priority..
Natural gas distribution network modelling and leak minimization
Westering, W.H.P. van; Hellendoorn, H.; Brasjen, B.J.; Linden, R.J.P. van der
2014-01-01
A gas network model has been constructed based on the steady-state Weymouth equation. A fast and robust solution algorithm is proposed and subsequently used to calculate all flows and pressures in a gas network with over 40,000 pipes. The obtained result is mathematically accurate within 0.1% and ha
Modification of TOUGH2 to Include the Dusty Gas Model for Gas Diffusion; TOPICAL
International Nuclear Information System (INIS)
The GEO-SEQ Project is investigating methods for geological sequestration of CO(sub 2). This project, which is directed by LBNL and includes a number of other industrial, university, and national laboratory partners, is evaluating computer simulation methods including TOUGH2 for this problem. The TOUGH2 code, which is a widely used code for flow and transport in porous and fractured media, includes simplified methods for gas diffusion based on a direct application of Fick's law. As shown by Webb (1998) and others, the Dusty Gas Model (DGM) is better than Fick's Law for modeling gas-phase diffusion in porous media. In order to improve gas-phase diffusion modeling for the GEO-SEQ Project, the EOS7R module in the TOUGH2 code has been modified to include the Dusty Gas Model as documented in this report. In addition, the liquid diffusion model has been changed from a mass-based formulation to a mole-based model. Modifications for separate and coupled diffusion in the gas and liquid phases have also been completed. The results from the DGM are compared to the Fick's law behavior for TCE and PCE diffusion across a capillary fringe. The differences are small due to the relatively high permeability (k= 10(sup -11) m(sup 2)) of the problem and the small mole fraction of the gases. Additional comparisons for lower permeabilities and higher mole fractions may be useful
Gas Deliverability Model with Different Vertical Wells Properties
Directory of Open Access Journals (Sweden)
L. Mucharam
2003-11-01
Full Text Available We present here a gas deliverability computational model for single reservoir with multi wells. The questions of how long the gas delivery can be sustained and how to estimate the plateau time are discussed here. In order to answer such a question, in this case, a coupling method which consists of material balance method and gas flow equation method is developed by assuming no water influx in the reservoir. Given the rate and the minimum pressure of gas at the processing plant, the gas pressure at the wellhead and at the bottom hole can be obtained. From here, the estimation of the gas deliverability can be done. In this paper we obtain a computational method which gives direct computation for pressure drop from the processing plant to the wells, taking into account different well behavior. Here AOF technique is used for obtaining gas rate in each well. Further Tian & Adewumi correlation is applied for pressure drop model along vertical and horizontal pipes and Runge-Kutta method is chosen to compute the well head and bottom hole pressures in each well which then being used to estimate the plateau times. We obtain here direct computational scheme of gas deliverability from reservoir to processing plant for single reservoir with multi-wells properties. Computational results give different profiles (i.e. gas rate, plateau and production time, etc for each well. Further by selecting proper flow rate reduction, the flow distribution after plateau time to sustain the delivery is computed for each well.
Optimising Gas Quenching Technology through Modelling of Heat Transfer
Institute of Scientific and Technical Information of China (English)
Florent Chaffotte; Linda L(e)fevre; Didier Domergue; Aymeric Goldsteinas; Xavier Doussot; Qingfei Zhang
2004-01-01
Gas Quenching represents an environmentally friendly alternative to more commonly-used oil quenching. Yet,the performances of this technology remain limited in terms of cooling rates reached compared to oil quenching. Distortion and process homogeneity also have to be controlled carefully. The efficiency of the gas quenching process fully depends on the heat transfer between the gas and the quenched parts. The goal of this study is the optimisation of the gas quenching process efficiency through a better understanding of the heat transfer phenomena involved. The study has been performed with modelling means and validated by an experimental approach. The configuration of the gas flow has a major influence on the heat transfer phenomena between the gas and the parts. The fluid dynamics modelling approach performed in this study allows to optimise the heat transfer phenomena. New gas quenching processes allowing enhanced gas quenching performance through higher cooling rates can be thereby identified. The new solutions have been validated in experimental and industrial conditions. Results obtained allow to expect significant improvement of high pressure gas quenching technology.
Optimising Gas Quenching Technology through Modelling of Heat Transfer
Institute of Scientific and Technical Information of China (English)
FiorentChaffotte; LindaLefevre; DidierDomergue; AymericGoidsteinas; XavierDoussot; QingfeiZhang
2004-01-01
Gas Quenching represents an environmentally friendly alternative to more commonly-used oil quenching. Yet,the performances of this technology remain limited in terms of cooling rates reached compared to oil quenching. Distortion and process homogeneity also have to be controlled carefully. The efficiency of the gas quenching process fully depends on the heat transfer between the gas and the quenched parts. The goal of this study is the optimisation of the gas quenching process efficiency through a better understanding of the heat transfer phenomena involved. The study has been performed with modelling means and validated by an experimental approach. ThE configuration of the gas flow has a major influence on the heat transfer phenomena between the gas and the parts. The fluid dynamics modelling approach performed in this study allows to optimise the heat transfer phenomena. New gas quenching processes allowing enhanced gas quenching performance through higher cooling rates can be thereby identified. The new solutions have been validated in experimental and industrial conditions. Results obtained allow to expect significant improvement of high pressure gas quenching technology.
Modelling of Rotor-gas bearings for Feedback Controller Design
International Nuclear Information System (INIS)
Controllable rotor-gas bearings are popular offering adaptability, high speed operation, low friction and clean operation. Rotor-gas bearings are however highly sensitive to disturbances due to the low friction of the injected gas. These undesirable damping properties call for controllers, which can be designed from suitable models describing the relation from actuator input to measured shaft position. Current state of the art models of controllable gas bearings however do not provide such relation, which calls for alternative strategies. The present contribution discusses the challenges for feedback controller design using the state of the art method, and an alternative data driven modelling approach is pursued based on Grey- Box system identification. The method allows development of models of the rotor-gas bearing suitable for controller design, which can be identified from data over the range of operation and are shown to accurately describe the dynamical behaviour of the rotor-gas bearing. Design of a controller using the identified models is treated and experiments verify the improvement of the damping properties of the rotor-gas bearing
Superconformal models and the supersymmetric coulomb gas
International Nuclear Information System (INIS)
The obtention of the supersymmetric 19-vertex model from an inhomogeneous 6-vertex model, is discussed. The 19-vertex model is considered the underlying theory and applied to calculate the partition function of the torus. A similar scheme to that for the critical models obtention, concerning the restriction procedure at special points of the gaussian line (of the 6-vertex model) is used. The critical line, in the supersymmetric model, is described by a free superfield and related to the XY model. The ''fused'' lattice models are outlined. It is shown that the results can be generalized to the models obtained by SU(2) coset construction
Thermodynamic Modeling of Natural Gas Systems Containing Water
DEFF Research Database (Denmark)
Karakatsani, Eirini K.; Kontogeorgis, Georgios M.
2013-01-01
with a heavy phase were previously obtained using cubic plus association (CPA) coupled with a solid phase model in the case of hydrates, for the binary systems of water–methane and water–nitrogen and a few natural gas mixtures. In this work, CPA is being validated against new experimental data, both water......As the need for dew point specifications remains very urgent in the natural gas industry, the development of accurate thermodynamic models, which will match experimental data and will allow reliable extrapolations, is needed. Accurate predictions of the gas phase water content in equilibrium...... content and phase equilibrium data, and solid model parameters are being estimated for four natural gas main components (methane, ethane, propane, and carbon dioxide). Different tests for the solid model parameters are reported, including vapor-hydrate-equilibria (VHE) and liquid-hydrate-equilibria (LHE...
Computational modeling of Krypton Gas Puffs on Z
Jennings, Christopher
2014-10-01
Large diameter multi-shell gas puffs rapidly imploded by high current (~20 MA, ~100 ns) on the Z generator of Sandia National Laboratories are able to produce high-intensity K-shell radiation. Experiments are currently underway to produce Krypton K-shell emission at ~13 keV, from double annular shell gas puffs imploded from a 12 cm diameter onto a central gas jet. Efficiently radiating at these high photon energies represents a significant challenge which necessitates the careful design and optimization of the gas distribution. To facilitate this we hydro-dynamically model the gas flow out of the nozzle, before imploding that mass distribution using a 3-dimensional resistive, radiative MHD code (GORGON). We present details of how modeled gas profiles are validated against 2-dimensional interferometric measurements of the initial gas distribution, and MHD calculations are validated against power, yield, spectral and imaging diagnostics of the experiments. This approach has enabled us to iterate between modeling the implosion and gas flow from the nozzle to optimize radiative output from this combined system. Guided by our implosion calculations we have designed and implemented gas profiles that help mitigate disruption from Magneto-Rayleigh-Taylor implosion instabilities, while preserving sufficient kinetic energy to thermalize to the high temperatures required for K-shell emission. Predicted increases in yield from introducing a relief feature into the inner gas nozzle to create a radially increasing density distribution were recovered in experiment. K-shell yield is predicted to further increase by the introduction of an on-axis gas jet, although the mass of this jet must be carefully selected with respect to the delivered current to avoid reducing the yield. For Kr gas puffs the predicted K-shell yield increase from addition of a light central jet was realized in the experiments, considerably increasing the yield over previous results. Further confidence in our
Validation of spectral gas radiation models under oxyfuel conditions
Energy Technology Data Exchange (ETDEWEB)
Becher, Johann Valentin
2013-05-15
Combustion of hydrocarbon fuels with pure oxygen results in a different flue gas composition than combustion with air. Standard computational-fluid-dynamics (CFD) spectral gas radiation models for air combustion are therefore out of their validity range in oxyfuel combustion. This thesis provides a common spectral basis for the validation of new spectral models. A literature review about fundamental gas radiation theory, spectral modeling and experimental methods provides the reader with a basic understanding of the topic. In the first results section, this thesis validates detailed spectral models with high resolution spectral measurements in a gas cell with the aim of recommending one model as the best benchmark model. In the second results section, spectral measurements from a turbulent natural gas flame - as an example for a technical combustion process - are compared to simulated spectra based on measured gas atmospheres. The third results section compares simplified spectral models to the benchmark model recommended in the first results section and gives a ranking of the proposed models based on their accuracy. A concluding section gives recommendations for the selection and further development of simplified spectral radiation models. Gas cell transmissivity spectra in the spectral range of 2.4 - 5.4 {mu}m of water vapor and carbon dioxide in the temperature range from 727 C to 1500 C and at different concentrations were compared in the first results section at a nominal resolution of 32 cm{sup -1} to line-by-line models from different databases, two statistical-narrow-band models and the exponential-wide-band model. The two statistical-narrow-band models EM2C and RADCAL showed good agreement with a maximal band transmissivity deviation of 3 %. The exponential-wide-band model showed a deviation of 6 %. The new line-by-line database HITEMP2010 had the lowest band transmissivity deviation of 2.2% and was therefore recommended as a reference model for the
A mathematical model of pulmonary gas exchange under inflammatory stress
Reynolds, Angela; Ermentrout, G. Bard; Clermont, Gilles
2010-01-01
During a severe local or systemic inflammatory response, immune mediators target lung tissue. This process may lead to acute lung injury and impaired diffusion of gas molecules. Although several mathematical models of gas exchange have been described, none simulate acute lung injury following inflammatory stress. In view of recent laboratory and clinical progress in the understanding of the pathophysiology of acute lung injury, such a mathematical model would be useful. We first derived a par...
Modelling and interpretation of gas detection using remote laser pointers.
Hodgkinson, Jane; van Well, Ben; Padgett, Miles; Pride, Russ D.
2006-01-01
We have developed a quantitative model of the performance of laser pointer style gas leak detectors, which are based on remote detection of backscattered radiation. The model incorporates instrumental noise limits, the reflectivity of the target background surface and a mathematical description of gas leak dispersion in constant wind speed and turbulence conditions. We have investigated optimum instrument performance and limits of detection in simulated leak detection situations. We predict t...
Gas Atomization of Aluminium Melts: Comparison of Analytical Models
Directory of Open Access Journals (Sweden)
Georgios Antipas
2012-06-01
Full Text Available A number of analytical models predicting the size distribution of particles during atomization of Al-based alloys by N2, He and Ar gases were compared. Simulations of liquid break up in a close coupled atomizer revealed that the finer particles are located near the center of the spray cone. Increasing gas injection pressures led to an overall reduction of particle diameters and caused a migration of the larger powder particles towards the outer boundary of the flow. At sufficiently high gas pressures the spray became monodisperse. The models also indicated that there is a minimum achievable mean diameter for any melt/gas system.
Reliability modelling - PETROBRAS 2010 integrated gas supply chain
Energy Technology Data Exchange (ETDEWEB)
Faertes, Denise; Heil, Luciana; Saker, Leonardo; Vieira, Flavia; Risi, Francisco; Domingues, Joaquim; Alvarenga, Tobias; Carvalho, Eduardo; Mussel, Patricia
2010-09-15
The purpose of this paper is to present the innovative reliability modeling of Petrobras 2010 integrated gas supply chain. The model represents a challenge in terms of complexity and software robustness. It was jointly developed by PETROBRAS Gas and Power Department and Det Norske Veritas. It was carried out with the objective of evaluating security of supply of 2010 gas network design that was conceived to connect Brazilian Northeast and Southeast regions. To provide best in class analysis, state of the art software was used to quantify the availability and the efficiency of the overall network and its individual components.
Nawaz AHMAD
2009-01-01
The thesis work aims at devising analytical thermodynamic model and numerical modeling of the compressor of a small gas turbine to be operated on producer gas with lower heating contents. The turbine will serve as a component of “EXPLORE-Biomass Based Polygeneration” project to meet the internal electrical power requirements of 2-5 KW. The gas turbine engine is of radial type (one stage radial compressor, one stage radial turbine). Small gas turbines give less electrical efficiencies especial...
Modeling and forecasting natural gas demand in Bangladesh
International Nuclear Information System (INIS)
Natural gas is the major indigenous source of energy in Bangladesh and accounts for almost one-half of all primary energy used in the country. Per capita and total energy use in Bangladesh is still very small, and it is important to understand how energy, and natural gas demand will evolve in the future. We develop a dynamic econometric model to understand the natural gas demand in Bangladesh, both in the national level, and also for a few sub-sectors. Our demand model shows large long run income elasticity - around 1.5 - for aggregate demand for natural gas. Forecasts into the future also show a larger demand in the future than predicted by various national and multilateral organizations. Even then, it is possible that our forecasts could still be at the lower end of the future energy demand. Price response was statistically not different from zero, indicating that prices are possibly too low and that there is a large suppressed demand for natural gas in the country. - Highlights: → Natural gas demand is modeled using dynamic econometric methods, first of its kind in Bangladesh. → Income elasticity for aggregate natural gas demand in Bangladesh is large-around 1.5. → Demand is price insensitive, indicating too low prices and/or presence of large suppressed demand. → Demand forecasts reveal large divergence from previous estimates, which is important for planning. → Attempts to model demand for end-use sectors were successful only for the industrial sector.
Atomistic Modeling of Gas Adsorption in Nanocarbons
Directory of Open Access Journals (Sweden)
G. Zollo
2012-01-01
Full Text Available Carbon nanostructures are currently under investigation as possible ideal media for gas storage and mesoporous materials for gas sensors. The recent scientific literature concerning gas adsorption in nanocarbons, however, is affected by a significant variation in the experimental data, mainly due to the different characteristics of the investigated samples arising from the variety of the synthesis techniques used and their reproducibility. Atomistic simulations have turned out to be sometimes crucial to study the properties of these systems in order to support the experiments, to indicate the physical limits inherent in the investigated structures, and to suggest possible new routes for application purposes. In consideration of the extent of the theme, we have chosen to treat in this paper the results obtained within some of the most popular atomistic theoretical frameworks without any purpose of completeness. A significant part of this paper is dedicated to the hydrogen adsorption on C-based nanostructures for its obvious importance and the exceptional efforts devoted to it by the scientific community.
Marković Jelena; Omorjan Radovan
2007-01-01
The transport of gaseous components through porous media could be described according to the well-known Fick model and its modifications. It is also known that Fick’s law is not suitable for predicting the fluxes in multicomponent gas mixtures, excluding binary mixtures. This model is still frequently used in chemical engineering because of its simplicity. Unfortunately, besides the Fick’s model there is no generally accepted model for mass transport through porous media (membranes, catalysts...
2010-08-31
... of LNG vapor-gas dispersion models. The FPRF subsequently contracted with the Health & Safety... validation stage is * * * to quantify the performance of a model by comparison of its predictions with... boundary conditions, including the boundary condition specifications available (e.g., wall functions,...
Modelling of gas generation in radioactive waste repositories
International Nuclear Information System (INIS)
The paper describes a gas generation model, GAMMON (GAs generation from Microbial degradation and Metal corrosiON). The model addresses gas generation within a repository containing both low-level and intermediate-level radioactive waste by the coupled processes of microbial degradation of cellulosic waste, and metal corrosion. The microbial degradation model simulates the activities of eight different microbial populations that are maintained as functions of the concentrations of particular chemical species, whereas the metal corrosion model incorporates a three-phase process encompassing both the aerobic and anaerobic corrosion regimes. In order to display the flexibility of the model, two sets of results are presented pertaining to two different repository environments an aerobic, unsaturated environment and an anaerobic, fully resaturated environment. 2 figs
A lattice gas model on a tangled chain
International Nuclear Information System (INIS)
We have used a model of a lattice gas defined on a tangled chain to study the enzyme kinetics by a modified transfer matrix method. By using a simple iterative algorithm we have obtained different kinds of saturation curves for different configurations of the tangled chain and different types of the additional interactions. In some special cases of configurations and interactions we have found the same equations for the saturation curves, which we have obtained before studying the lattice gas model with nearest neighbor interactions or the lattice gas model with alternate nearest neighbor interactions, using different techniques as the correlated walks' theory, the partition point technique or the transfer matrix model. This more general model and the new results could be useful for the experimental investigations. (author). 20 refs, 6 figs
International Nuclear Information System (INIS)
The Natural Gas Transmission and Distribution Model (NGTDM) of the National Energy Modeling System is developed and maintained by the Energy Information Administration (EIA), Office of Integrated Analysis and Forecasting. This report documents the archived version of the NGTDM that was used to produce the natural gas forecasts presented in the Annual Energy Outlook 1996, (DOE/EIA-0383(96)). The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic approach, and provides detail on the methodology employed. Previously this report represented Volume I of a two-volume set. Volume II reported on model performance, detailing convergence criteria and properties, results of sensitivity testing, comparison of model outputs with the literature and/or other model results, and major unresolved issues
Energy Technology Data Exchange (ETDEWEB)
NONE
1996-02-26
The Natural Gas Transmission and Distribution Model (NGTDM) of the National Energy Modeling System is developed and maintained by the Energy Information Administration (EIA), Office of Integrated Analysis and Forecasting. This report documents the archived version of the NGTDM that was used to produce the natural gas forecasts presented in the Annual Energy Outlook 1996, (DOE/EIA-0383(96)). The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic approach, and provides detail on the methodology employed. Previously this report represented Volume I of a two-volume set. Volume II reported on model performance, detailing convergence criteria and properties, results of sensitivity testing, comparison of model outputs with the literature and/or other model results, and major unresolved issues.
Estimating Predictive Variance for Statistical Gas Distribution Modelling
Lilienthal, Achim J.; Asadi, Sahar; Reggente, Matteo
2009-05-01
Recent publications in statistical gas distribution modelling have proposed algorithms that model mean and variance of a distribution. This paper argues that estimating the predictive concentration variance entails not only a gradual improvement but is rather a significant step to advance the field. This is, first, since the models much better fit the particular structure of gas distributions, which exhibit strong fluctuations with considerable spatial variations as a result of the intermittent character of gas dispersal. Second, because estimating the predictive variance allows to evaluate the model quality in terms of the data likelihood. This offers a solution to the problem of ground truth evaluation, which has always been a critical issue for gas distribution modelling. It also enables solid comparisons of different modelling approaches, and provides the means to learn meta parameters of the model, to determine when the model should be updated or re-initialised, or to suggest new measurement locations based on the current model. We also point out directions of related ongoing or potential future research work.
The World gas model. A multi-period mixed complementarity model for the global natural gas market
International Nuclear Information System (INIS)
We provide the description, mathematical formulation and illustrative results of the World Gas Model, a multi-period complementarity model for the global natural gas market with explicit consideration of market power in the upstream market. Market players include producers, traders, pipeline and storage operators, LNG (liquefied natural gas) liquefiers and regasifiers as well as marketers. The model data set contains more than 80 countries and regions and covers 98% of world wide natural gas production and consumption. We also include a detailed representation of cross-border natural gas pipelines and constraints imposed by long-term contracts in the LNG market. The model is calibrated to match production and consumption projections from the PRIMES [EC. European energy and transport: trends to 2030-update 2007. Brussels: European Commission; 2008] and POLES models [EC. World energy technology outlook - 2050 (WETO-H2). Brussels: European Commission; 2006] up to 2030. The results of our numerical simulations illustrate how the supply shares of pipeline and LNG in various regions in the world develop very differently over time. LNG will continue to play a major role in the Asian market, also for new importers like China and India. Europe will expand its pipeline import capacities benefiting from its relative proximity to major gas suppliers. (author)
The World gas model. A multi-period mixed complementarity model for the global natural gas market
Energy Technology Data Exchange (ETDEWEB)
Egging, Ruud [Dept of Civil and Environmental Engineering, University of Maryland, 1143 Glenn L. Martin Hall, College Park, MD 20742 (United States); Holz, Franziska [DIW Berlin, Mohrenstr. 58, 10117 Berlin (Germany); Gabriel, Steven A. [Dept of Civil and Environmental Engineering, University of Maryland, 1143 Glenn L. Martin Hall, College Park, MD 20742 (United States); DIW Berlin, Mohrenstr. 58, 10117 Berlin (Germany)
2010-10-15
We provide the description, mathematical formulation and illustrative results of the World Gas Model, a multi-period complementarity model for the global natural gas market with explicit consideration of market power in the upstream market. Market players include producers, traders, pipeline and storage operators, LNG (liquefied natural gas) liquefiers and regasifiers as well as marketers. The model data set contains more than 80 countries and regions and covers 98% of world wide natural gas production and consumption. We also include a detailed representation of cross-border natural gas pipelines and constraints imposed by long-term contracts in the LNG market. The model is calibrated to match production and consumption projections from the PRIMES [EC. European energy and transport: trends to 2030-update 2007. Brussels: European Commission; 2008] and POLES models [EC. World energy technology outlook - 2050 (WETO-H2). Brussels: European Commission; 2006] up to 2030. The results of our numerical simulations illustrate how the supply shares of pipeline and LNG in various regions in the world develop very differently over time. LNG will continue to play a major role in the Asian market, also for new importers like China and India. Europe will expand its pipeline import capacities benefiting from its relative proximity to major gas suppliers. (author)
Hot Gas in Clusters of Galaxies the Punctuated Equilibria Model
Cavaliere, A; Tozzi, P
1998-01-01
We develop a model to describe the evolution of the intra-cluster X-ray emitting baryons. These are included in the potential wells of galaxy clusters evolving through subsequent merging events in the framework of hierarchical clustering. The gas is assumed to re-adjusts to a new hydrostatic equilibrium after each merging event. Before merging it is gravitationally heated at the local virial temperature when bound in subclusters; at early $z$ the gas is preheated by supernova activity following star formation. In detail, we compute analytically the following steps: the dynamic histories of dark matter halos with their merging events; the associated infall of gas into a halo, with compressions and shocks estabilishing the conditions at the cluster boundary; the updated disposition of the gas in the potential well matching such conditions; the statistical convolution of the key quantities over the merging histories. The model predicts the density and surface brightness profiles with no free parameters; the so-c...
Modeling of Hybrid Permanent Magnetic-Gas Bearings
DEFF Research Database (Denmark)
Morosi, Stefano; Santos, Ilmar
2009-01-01
of the gas bearing is balanced by the properties of the passive magnetic one. At high speeds the dynamic characteristics of the gas bearing are improved by offsetting the stator ring of the permanent magnetic bearing. Furthermore this design shows a kind of redundancy, which offers soft failure properties....... In the present paper, a detailed mathematical modeling of the gas bearing based on the compressible form of the Reynolds equation is presented. Perturbation theory is applied in order to identify the dynamic characteristic of the bearing. Due to the simple design of the magnetic bearings elements - being...
Numerical modeling of gas hydrate emplacements in oceanic sediments
Schnurle, Philippe; Liu, Char-Shine
2011-01-01
We have implemented a 2-dimensional numerical model for simulating gas hydrate and free gas accumulation in marine sediments. The starting equations are those of the conservation of the transport of momentum, energy, and mass, as well as those of the thermodynamics of methane hydrate stability and methane solubility in the pore-fluid. These constitutive equations are then integrated into a finite element in space, finite-difference in time scheme. We are then able to examine the formation and...
A numerical model of gas-fluidized beds
Kuipers, J.A.M.; Duin, van K.J.; Beckum, van F.P.H.; Swaaij, van W.P.M.
1992-01-01
A first-principles model for gas-fluidized bed based on the so-called "two-fluid model" (TFM) has been developed. In the TFM approach, both phases are considered to be continuous and fully interpenetrating. The equations of mass, momentum and thermal energy conservation, supplemented with the necess
Geomechanical Modeling of Gas Hydrate Bearing Sediments
Sanchez, M. J.; Gai, X., Sr.
2015-12-01
This contribution focuses on an advance geomechanical model for methane hydrate-bearing soils based on concepts of elasto-plasticity for strain hardening/softening soils and incorporates bonding and damage effects. The core of the proposed model includes: a hierarchical single surface critical state framework, sub-loading concepts for modeling the plastic strains generally observed inside the yield surface and a hydrate enhancement factor to account for the cementing effects provided by the presence of hydrates in sediments. The proposed framework has been validated against recently published experiments involving both, synthetic and natural hydrate soils, as well as different sediments types (i.e., different hydrate saturations, and different hydrates morphologies) and confinement conditions. The performance of the model in these different case studies was very satisfactory.
Modeling Propagation of Gas Path Damage
National Aeronautics and Space Administration — This paper describes how damage propagation can be tracked and modeled for a range of fault modes in some modules of commercial high bypass aircraft engines. To...
An Equilibrium-Based Model of Gas Reaction and Detonation
International Nuclear Information System (INIS)
During gaseous diffusion plant operations, conditions leading to the formation of flammable gas mixtures may occasionally arise. Currently, these could consist of the evaporative coolant CFC-114 and fluorinating agents such as F2 and ClF3. Replacement of CFC-114 with a non-ozone-depleting substitute is planned. Consequently, in the future, the substitute coolant must also be considered as a potential fuel in flammable gas mixtures. Two questions of practical interest arise: (1) can a particular mixture sustain and propagate a flame if ignited, and (2) what is the maximum pressure that can be generated by the burning (and possibly exploding) gas mixture, should it ignite? Experimental data on these systems, particularly for the newer coolant candidates, are limited. To assist in answering these questions, a mathematical model was developed to serve as a tool for predicting the potential detonation pressures and for estimating the composition limits of flammability for these systems based on empirical correlations between gas mixture thermodynamics and flammability for known systems. The present model uses the thermodynamic equilibrium to determine the reaction endpoint of a reactive gas mixture and uses detonation theory to estimate an upper bound to the pressure that could be generated upon ignition. The model described and documented in this report is an extended version of related models developed in 1992 and 1999
Experimental Grey Box Model Identification of an Active Gas Bearing
DEFF Research Database (Denmark)
Theisen, Lukas Roy Svane; Pierart Vásquez, Fabián Gonzalo; Niemann, Hans Henrik;
2014-01-01
Gas bearings have inherent dynamics that gives rise to low damping and potential instability at certain rotational speeds. Required damping and stabilization properties can be achieved by active ow control if bearing parameters are known. This paper deals with identifacation of parameters...... in a dynamic model of an active gas bearing and subsequent control loop design. A grey box model is determined based on experiments where piezo actuated valves are used to perturb the journal and hence excite the rotor-bearing system. Such modelling from actuator to output is shown to effciently support...... controller design, in contrast to impact models that focus on resonance dynamics. The identified model is able to accurately reproduce the lateral dynamics of the rotor-bearing system in a desired operating range, in this case around the first two natural frequencies. The identified models are validated...
Development of a natural Gas Systems Analysis Model (GSAM)
International Nuclear Information System (INIS)
Lacking a detailed characterization of the resource base and a comprehensive borehole-to-burnertip evaluation model of the North American natural gas system, past R ampersand D, tax and regulatory policies have been formulated without a full understanding of their likely direct and indirect impacts on future gas supply and demand. The recent disappearance of the deliverability surplus, pipeline deregulation, and current policy debates about regulatory initiatives in taxation, environmental compliance and leasing make the need for a comprehensive gas evaluation system critical. Traditional econometric or highly aggregated energy models are increasingly regarded as unable to incorporate available geologic detail and explicit technology performance and costing algorithms necessary to evaluate resource-technology-economic interactions in a market context. The objective of this research is to create a comprehensive, non-proprietary, microcomputer model of the North American natural gas system. GSAM explicitly evaluates the key components of the natural gas system, including resource base, exploration and development, extraction technology performance and costs, transportation and storage and end use. The primary focus is the detailed characterization of the resource base at the reservoir and sub-reservoir level and the impact of alternative extraction technologies on well productivity and economics. GSAM evaluates the complex interactions of current and alternative future technology and policy initiatives in the context of the evolving gas markets. Scheduled for completion in 1995, a prototype is planned for early 1994. ICF Resources reviewed relevant natural gas upstream, downstream and market models to identify appropriate analytic capabilities to incorporate into GSAM. We have reviewed extraction technologies to better characterize performance and costs in terms of GSAM parameters
A Vision for the EU Gas Target Model: the MECO-S Model
Glachant, Jean-Michel
2011-01-01
A previous version of this paper was replaced on 14/09/2011. The discussion on a target model for European gas network access started at the 18th Madrid Forum in 2010. This model shall provide a unifying vision on the future layout of the European gas market architecture. That vision shall assist all stakeholders in implementing the 3rd EU energy market package on the internal gas market in a consistent way. Here is my proposal for the European gas target model termed MECO-S Mo...
Gas-grain models for interstellar anion chemistry
Cordiner, M. A.; Charnley, S. B.
2012-01-01
Long-chain hydrocarbon anions CnH- (n=4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances ...
Prediction of gas compressibility factor using intelligent models
Directory of Open Access Journals (Sweden)
Mohamad Mohamadi-Baghmolaei
2015-10-01
Full Text Available The gas compressibility factor, also known as Z-factor, plays the determinative role for obtaining thermodynamic properties of gas reservoir. Typically, empirical correlations have been applied to determine this important property. However, weak performance and some limitations of these correlations have persuaded the researchers to use intelligent models instead. In this work, prediction of Z-factor is aimed using different popular intelligent models in order to find the accurate one. The developed intelligent models are including Artificial Neural Network (ANN, Fuzzy Interface System (FIS and Adaptive Neuro-Fuzzy System (ANFIS. Also optimization of equation of state (EOS by Genetic Algorithm (GA is done as well. The validity of developed intelligent models was tested using 1038 series of published data points in literature. It was observed that the accuracy of intelligent predicting models for Z-factor is significantly better than conventional empirical models. Also, results showed the improvement of optimized EOS predictions when coupled with GA optimization. Moreover, of the three intelligent models, ANN model outperforms other models considering all data and 263 field data points of an Iranian offshore gas condensate with R2 of 0.9999, while the R2 for best empirical correlation was about 0.8334.
Validation of spectral gas radiation models under oxyfuel conditions. Part A: Gas cell experiments
DEFF Research Database (Denmark)
Becher, Valentin; Clausen, Sønnik; Fateev, Alexander;
2011-01-01
for the validation of new developed models. In part A of the series gas cell transmissivity spectra in the spectral range of 2.4–5.4μm of water vapor and carbon dioxide in the temperature range from 727 to 1500° C and at different concentrations were compared at a nominal resolution of 32cm−1 to line-by-line models...
Modelling and identification for control of gas bearings
Theisen, Lukas R. S.; Niemann, Hans H.; Santos, Ilmar F.; Galeazzi, Roberto; Blanke, Mogens
2016-03-01
Gas bearings are popular for their high speed capabilities, low friction and clean operation, but suffer from poor damping, which poses challenges for safe operation in presence of disturbances. Feedback control can achieve enhanced damping but requires low complexity models of the dominant dynamics over its entire operating range. Models from first principles are complex and sensitive to parameter uncertainty. This paper presents an experimental technique for "in situ" identification of a low complexity model of a rotor-bearing-actuator system and demonstrates identification over relevant ranges of rotational speed and gas injection pressure. This is obtained using parameter-varying linear models that are found to capture the dominant dynamics. The approach is shown to be easily applied and to suit subsequent control design. Based on the identified models, decentralised proportional control is designed and shown to obtain the required damping in theory and in a laboratory test rig.
Energy Technology Data Exchange (ETDEWEB)
NONE
1994-02-24
The Natural Gas Transmission and Distribution Model (NGTDM) is a component of the National Energy Modeling System (NEMS) used to represent the domestic natural gas transmission and distribution system. NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the Energy Information Administration (EIA) and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. This report documents the archived version of NGTDM that was used to produce the natural gas forecasts used in support of the Annual Energy Outlook 1994, DOE/EIA-0383(94). The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic design, provides detail on the methodology employed, and describes the model inputs, outputs, and key assumptions. It is intended to fulfill the legal obligation of the EIA to provide adequate documentation in support of its models (Public Law 94-385, Section 57.b.2). This report represents Volume 1 of a two-volume set. (Volume 2 will report on model performance, detailing convergence criteria and properties, results of sensitivity testing, comparison of model outputs with the literature and/or other model results, and major unresolved issues.) Subsequent chapters of this report provide: (1) an overview of the NGTDM (Chapter 2); (2) a description of the interface between the National Energy Modeling System (NEMS) and the NGTDM (Chapter 3); (3) an overview of the solution methodology of the NGTDM (Chapter 4); (4) the solution methodology for the Annual Flow Module (Chapter 5); (5) the solution methodology for the Distributor Tariff Module (Chapter 6); (6) the solution methodology for the Capacity Expansion Module (Chapter 7); (7) the solution methodology for the Pipeline Tariff Module (Chapter 8); and (8) a description of model assumptions, inputs, and outputs (Chapter 9).
Off-gas adsorption model and simulation - OSPREY
International Nuclear Information System (INIS)
A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes is expected to provide substantial cost savings and many technical benefits. To support this capability, a modeling effort focused on the off-gas treatment system of a used nuclear fuel recycling facility is in progress. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed within Multi-physics Object Oriented Simulation Environment (MOOSE) developed at the Idaho National Laboratory (INL). Off-gas Separation and Recovery (OSPREY) models the adsorption of offgas constituents for dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions. Inputs to the model include gas composition, sorbent and column properties, equilibrium and kinetic data, and inlet conditions. The simulation outputs component concentrations along the column length as a function of time from which breakthrough data can be obtained. The breakthrough data can be used to determine bed capacity, which in turn can be used to size columns. In addition to concentration data, the model predicts temperature along the column length as a function of time and pressure drop along the column length. A description of the OSPREY model, results from krypton adsorption modeling and plans for modeling the behavior of iodine, xenon, and tritium will be discussed. (author)
Modelling of massive gas injection for ITER disruption mitigation
International Nuclear Information System (INIS)
In ITER the plasma impact on the wall after disruptions can be mitigated by a preventive massive gas injection (MGI) of a noble gas into the confined plasma. The gas ionises in the core and the contamination of plasma leads to a fast loss of thermal energy by photon radiation. For the MGI modelling a tokamak code TOKES is applied. Two-dimensional simulations for argon MGI into ITER deuterium plasma assuming toroidally symmetric model for a horizontal mid-plane injector are performed. Plasma cooling time and maximal temperatures of a beryllium and tungsten first wall are assessed. One result is that in cases of substantial erosion the beryllium surface can melt. The obtained cooling time is not sensitive in respect to the electron thermal cross-conductivity based on a magnetic field braiding
Modeling CO2 air dispersion from gas driven lake eruptions
Chiodini, Giovanni; Costa, Antonio; Rouwet, Dmitri; Tassi, Franco
2016-04-01
The most tragic event of gas driven lake eruption occurred at Lake Nyos (Cameroon) on 21 August 1986, when a dense cloud of CO2 suffocated more than 1700 people and an uncounted number of animals in just one night. The event stimulated a series of researches aimed to understand gas origins, gas release mechanisms and strategies for gas hazard mitigation. Very few studies have been carried out for describing the transport of dense CO2 clouds in the atmosphere. Although from a theoretical point of view, gas dispersion can be fully studied by solving the complete equations system for mass, momentum and energy transport, in actual practice, different simplified models able to describe only specific phases or aspects have to be used. In order to simulate dispersion of a heavy gas and to assess the consequent hazard we used a model based on a shallow layer approach (TWODEE2). This technique which uses depth-averaged variables to describe the flow behavior of dense gas over complex topography represents a good compromise between the complexity of computational fluid dynamic models and the simpler integral models. Recently the model has been applied for simulating CO2 dispersion from natural gas emissions in Central Italy. The results have shown how the dispersion pattern is strongly affected by the intensity of gas release, the topography and the ambient wind speed. Here for the first time we applied TWODEE2 code to simulate the dispersion of the large CO2 clouds released by limnic eruptions. An application concerns the case of the 1986 event at lake Nyos. Some difficulties for the simulations were related to the lack of quantitative information: gas flux estimations are not well constrained, meteorological conditions are only qualitatively known, the digital model of the terrain is of poor quality. Different scenarios were taken into account in order to reproduce the qualitative observations available for such episode. The observations regard mainly the effects of gas on
Electrodynamic modeling applied to micro-strip gas chambers
Energy Technology Data Exchange (ETDEWEB)
Fang, R
1998-12-31
Gas gain variations as functions of time, counting rate and substrate resistivity have been observed with Micro-Strip Gas Chambers (MSGC). Such a chamber is here treated as a system of 2 dielectrics, gas and substrate, with finite resistivities. Electric charging between their interface results in variations of the electric field and the gas gain. The electrodynamic equations (including time dependence) for such a system are proposed. A Rule of Charge Accumulation (RCA) is then derived which allows to determine the quantity and sign of charges accumulated on the surface at equilibrium. In order to apply the equations and the rule to MSGCs, a model of gas conductance induced by ionizing radiation is proposed, and a differential equation and some formulae are derived to calculate the rms dispersion and the spatial distribution of electrons (ions) in inhomogeneous electric fields. RCA coupled with a precise simulation of the electric fields gives the first quantitative explanation of gas gain variations of MSGCs. Finally an electrodynamic simulation program is made to reproduce the dynamic process of gain variation due to surface charging with an uncertainty of at most 15% relative to experimental data. As a consequence, the methods for stabilizing operation of MSGCs are proposed. (author) 18 refs.
Modeling acid-gas generation from boiling chloride brines
Energy Technology Data Exchange (ETDEWEB)
Zhang, Guoxiang; Spycher, Nicolas; Sonnenthal, Eric; Steefel, Carl
2009-11-16
This study investigates the generation of HCl and other acid gases from boiling calcium chloride dominated waters at atmospheric pressure, primarily using numerical modeling. The main focus of this investigation relates to the long-term geologic disposal of nuclear waste at Yucca Mountain, Nevada, where pore waters around waste-emplacement tunnels are expected to undergo boiling and evaporative concentration as a result of the heat released by spent nuclear fuel. Processes that are modeled include boiling of highly concentrated solutions, gas transport, and gas condensation accompanied by the dissociation of acid gases, causing low-pH condensate. Simple calculations are first carried out to evaluate condensate pH as a function of HCl gas fugacity and condensed water fraction for a vapor equilibrated with saturated calcium chloride brine at 50-150 C and 1 bar. The distillation of a calcium-chloride-dominated brine is then simulated with a reactive transport model using a brine composition representative of partially evaporated calcium-rich pore waters at Yucca Mountain. Results show a significant increase in boiling temperature from evaporative concentration, as well as low pH in condensates, particularly for dynamic systems where partial condensation takes place, which result in enrichment of HCl in condensates. These results are in qualitative agreement with experimental data from other studies. The combination of reactive transport with multicomponent brine chemistry to study evaporation, boiling, and the potential for acid gas generation at the proposed Yucca Mountain repository is seen as an improvement relative to previously applied simpler batch evaporation models. This approach allows the evaluation of thermal, hydrological, and chemical (THC) processes in a coupled manner, and modeling of settings much more relevant to actual field conditions than the distillation experiment considered. The actual and modeled distillation experiments do not represent
Modeling acid-gas generation from boiling chloride brines
Directory of Open Access Journals (Sweden)
Sonnenthal Eric
2009-11-01
Full Text Available Abstract Background This study investigates the generation of HCl and other acid gases from boiling calcium chloride dominated waters at atmospheric pressure, primarily using numerical modeling. The main focus of this investigation relates to the long-term geologic disposal of nuclear waste at Yucca Mountain, Nevada, where pore waters around waste-emplacement tunnels are expected to undergo boiling and evaporative concentration as a result of the heat released by spent nuclear fuel. Processes that are modeled include boiling of highly concentrated solutions, gas transport, and gas condensation accompanied by the dissociation of acid gases, causing low-pH condensate. Results Simple calculations are first carried out to evaluate condensate pH as a function of HCl gas fugacity and condensed water fraction for a vapor equilibrated with saturated calcium chloride brine at 50-150°C and 1 bar. The distillation of a calcium-chloride-dominated brine is then simulated with a reactive transport model using a brine composition representative of partially evaporated calcium-rich pore waters at Yucca Mountain. Results show a significant increase in boiling temperature from evaporative concentration, as well as low pH in condensates, particularly for dynamic systems where partial condensation takes place, which result in enrichment of HCl in condensates. These results are in qualitative agreement with experimental data from other studies. Conclusion The combination of reactive transport with multicomponent brine chemistry to study evaporation, boiling, and the potential for acid gas generation at the proposed Yucca Mountain repository is seen as an improvement relative to previously applied simpler batch evaporation models. This approach allows the evaluation of thermal, hydrological, and chemical (THC processes in a coupled manner, and modeling of settings much more relevant to actual field conditions than the distillation experiment considered. The actual
Natural Gas Transmission and Distribution Model of the National Energy Modeling System. Volume 1
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-01-01
The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. The NGTDM is the model within the NEMS that represents the transmission, distribution, and pricing of natural gas. The model also includes representations of the end-use demand for natural gas, the production of domestic natural gas, and the availability of natural gas traded on the international market based on information received from other NEMS models. The NGTDM determines the flow of natural gas in an aggregate, domestic pipeline network, connecting domestic and foreign supply regions with 12 demand regions. The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic design, provides detail on the methodology employed, and describes the model inputs, outputs, and key assumptions. Subsequent chapters of this report provide: an overview of NGTDM; a description of the interface between the NEMS and NGTDM; an overview of the solution methodology of the NGTDM; the solution methodology for the Annual Flow Module; the solution methodology for the Distributor Tariff Module; the solution methodology for the Capacity Expansion Module; the solution methodology for the Pipeline Tariff Module; and a description of model assumptions, inputs, and outputs.
Real time model based diagnosis of gas turbines
Energy Technology Data Exchange (ETDEWEB)
Trave-Massuyes, L. [Centre National de la Recherche Scientifique (CNRS), 31 - Toulouse (France); Milne, R.
1995-12-31
Exxon petrochemical plant in Scotland requires continuous ethylene supply from offshore site in North Sea. The supply is achieved thanks to compressors driven by a 28 MW gas turbine, whose monitoring is of major importance. The TIGER fault diagnostic system is a knowledge base system containing a prediction model. (D.L.)
Gas Exchange Models for a Flexible Insect Tracheal System.
Simelane, S M; Abelman, S; Duncan, F D
2016-06-01
In this paper two models for movement of respiratory gases in the insect trachea are presented. One model considers the tracheal system as a single flexible compartment while the other model considers the trachea as a single flexible compartment with gas exchange. This work represents an extension of Ben-Tal's work on compartmental gas exchange in human lungs and is applied to the insect tracheal system. The purpose of the work is to study nonlinear phenomena seen in the insect respiratory system. It is assumed that the flow inside the trachea is laminar, and that the air inside the chamber behaves as an ideal gas. Further, with the isothermal assumption, the expressions for the tracheal partial pressures of oxygen and carbon dioxide, rate of volume change, and the rates of change of oxygen concentration and carbon dioxide concentration are derived. The effects of some flow parameters such as diffusion capacities, reaction rates and air concentrations on net flow are studied. Numerical simulations of the tracheal flow characteristics are performed. The models developed provide a mathematical framework to further investigate gas exchange in insects. PMID:27209375
Gas/Aerosol partitioning: a simplified method for global modeling
Metzger, S.M.
2001-01-01
The main focus of this thesis is the development of a simplified method to routinely calculate gas/aerosol partitioning of multicomponent aerosols and aerosol associated water within global atmospheric chemistry and climate models. Atmospheric aerosols are usually multicomponent mixtures, partl
Model-based dynamic control and optimization of gas networks
Energy Technology Data Exchange (ETDEWEB)
Hofsten, Kai
2001-07-01
This work contributes to the research on control, optimization and simulation of gas transmission systems to support the dispatch personnel at gas control centres for the decision makings in the daily operation of the natural gas transportation systems. Different control and optimization strategies have been studied. The focus is on the operation of long distance natural gas transportation systems. Stationary optimization in conjunction with linear model predictive control using state space models is proposed for supply security, the control of quality parameters and minimization of transportation costs for networks offering transportation services. The result from the stationary optimization together with a reformulation of a simplified fluid flow model formulates a linear dynamic optimization model. This model is used in a finite time control and state constrained linear model predictive controller. The deviation from the control and the state reference determined from the stationary optimization is penalized quadratically. Because of the time varying status of infrastructure, the control space is also generally time varying. When the average load is expected to change considerably, a new stationary optimization is performed, giving a new state and control reference together with a new dynamic model that is used for both optimization and state estimation. Another proposed control strategy is a control and output constrained nonlinear model predictive controller for the operation of gas transmission systems. Here, the objective is also the security of the supply, quality control and minimization of transportation costs. An output vector is defined, which together with a control vector are both penalized quadratically from their respective references in the objective function. The nonlinear model predictive controller can be combined with a stationary optimization. At each sampling instant, a non convex nonlinear programming problem is solved giving a local minimum
Gas entrainment in scaled model of pool type LMFBR
Energy Technology Data Exchange (ETDEWEB)
Banerjee, I.; Chandra, L.; Laxman, D.; Kumar, A.; Gopal, C.A.; Shivakumar, N.S.; Padmakumar, G.; Anand Babu, C.; Vaidyanathan, G. [Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu (India)
2007-07-01
The reactor Thermal hydraulics plays an important role for successful operation of Prototype Fast Breeder Reactor (PFBR), which is under construction at Kalpakkam, India. One of the issues to be resolved in PFBR is argon cover gas entrainment problem from free liquid sodium surface. The entrained cover gas may hinder the normal reactor operation. High free surface velocity along with the presence of various immersed components in the hot pool is the cause of gas entrainment from free surface. To reduce the free surface velocity and hence gas entrainment, ring type baffle plates were considered. Initially the optimum geometry of the baffle plate was arrived through numerical analysis using PHOENICS, a commercial computational fluid dynamics tool. Finally the experiments were conducted in a 1/4 scale water model of PFBR primary circuit with selected baffle plate geometry. It was found that a baffle plate with radial width of 125 mm in the model and located above intermediate heat exchanger is very effective to reduce the gas entrainment problem in PFBR. (authors)
Two-dimensional modeling of disruption mitigation by gas injection
International Nuclear Information System (INIS)
In ITER, wall damage after the disruptions can be mitigated using preventive massive gas injection (MGI) of noble gases into confined plasma. In the plasma the injected gas gets ionized and the core contamination results in fast loss of energy by radiation which distributes the wall load in a propitious way. For the modeling of MGI the tokamak code TOKES has been applied. This work reports further development of its models. The simulations earlier limited by the confinement region are expanded over the whole vessel of arbitrary wall shape. A simplified plasma model earlier employed for MGI is replaced by more adequate radiative model with dynamically changing level populations of plasma species. The processes in the plasma such as longitudinal motion, cross thermal conductivity and striking the wall are simulated neglecting wall response. The upgraded code is validated against an argon injection experiment of tokamak DIII-D.
Offer a New Model to Prevent Formation of Hydrate in Gas Pipeline in Gas Refinery
Directory of Open Access Journals (Sweden)
Amir Samimi
2012-12-01
Full Text Available Water molecules by making hydrogen joint with its molecules creates holes in which quest molecules will be trapped and by creating van deer Waals joint with water molecules, hydrates crystals will be produced. Natural gas and crude oil in natural exist in underground reservoirs are in contact with water. Hydration needs condition which consists of having water in pipe line, high pressure (pressure always is high because of reinforcing gas pressure in gas transportation pipe lines, low temperature (temperature is always low in cold seasons of year, and presence of hydrate-making substances like methane, carbon dioxide, and... There are four methods to prevent hydration. This article will focus on analyzing synthetic inhibitors, and their function the task orders are as followed: 1. Synthetic investigation of hydrate formation with and without presence of inhibitor. 2. Using Kashchiev- Firozabad model and experimental data of gas transporting pipe lines for drawing synthetic graphs of gas hydrates formation with presence of synthetic inhibitors.
An integral representation of functions in gas-kinetic models
Perepelitsa, Misha
2016-08-01
Motivated by the theory of kinetic models in gas dynamics, we obtain an integral representation of lower semicontinuous functions on {{{R}}^d,} {d≥1}. We use the representation to study the problem of compactness of a family of the solutions of the discrete time BGK model for the compressible Euler equations. We determine sufficient conditions for strong compactness of moments of kinetic densities, in terms of the measures from their integral representations.
A Lattice Boltzmann model for diffusion of binary gas mixtures
Bennett, Sam
2010-01-01
This thesis describes the development of a Lattice Boltzmann (LB) model for a binary gas mixture. Specifically, channel flow driven by a density gradient with diffusion slip occurring at the wall is studied in depth. The first part of this thesis sets the foundation for the multi-component model used in the subsequent chapters. Commonly used single component LB methods use a non-physical equation of state, in which the relationship between pressure and density varies according to the sca...
Eutectic point in a simple lattice gas model
M. Sandhoff; Pfnuer, H.; Everts, H. U.
1993-01-01
We investigate the phase diagram and the critical properties of the adsorbate system sulphur/ruthenium(0001) in the coverage region $\\frac{1}{4} < \\Theta < \\frac{1}{3}$ by means of Monte-Carlo simulations of a simple lattice gas model on a triangular lattice. The model contains only repulsive nearest and next-nearest neighbor interactions. Combining results obtained by using both Glauber and Kawasaki kinetics in the simulations we identify two tricritical points, three coexistence regions and...
Microeconomics of the ideal gas like market models
Chakrabarti, Anindya S.; Chakrabarti, Bikas K.
2009-10-01
We develop a framework based on microeconomic theory from which the ideal gas like market models can be addressed. A kinetic exchange model based on that framework is proposed and its distributional features have been studied by considering its moments. Next, we derive the moments of the CC model (Eur. Phys. J. B 17 (2000) 167) as well. Some precise solutions are obtained which conform with the solutions obtained earlier. Finally, an output market is introduced with global price determination in the model with some necessary modifications.
Macroscopic fission gas release model applied to Russian fuel
International Nuclear Information System (INIS)
Most models for estimating the rate of fission gas release (FGR) usually maintain the fuel temperature as an independent variable. The FGR model developed by M. Uchida is a modified Booth-type diffusional model with a change from temperature dependence to power dependence. Uchida's model has been checked by Kola-3 and Sofit-1.1 data sets. Very good agreement between calculated and experimental values is observed for Kola-3 and considerable discrepancies were found with Sofit-1.1 data sets. (author)
Asymptotic-preserving Boltzmann model equations for binary gas mixture
Liu, Sha; Liang, Yihua
2016-02-01
An improved system of Boltzmann model equations is developed for binary gas mixture. This system of model equations has a complete asymptotic preserving property that can strictly recover the Navier-Stokes equations in the continuum limit with the correct constitutive relations and the correct viscosity, thermal conduction, diffusion, and thermal diffusion coefficients. In this equation system, the self- and cross-collision terms in Boltzmann equations are replaced by single relaxation terms. In monocomponent case, this system of equations can be reduced to the commonly used Shakhov equation. The conservation property and the H theorem which are important for model equations are also satisfied by this system of model equations.
An integration scheme for stiff solid-gas reactor models
Directory of Open Access Journals (Sweden)
Bjarne A. Foss
2001-04-01
Full Text Available Many dynamic models encounter numerical integration problems because of a large span in the dynamic modes. In this paper we develop a numerical integration scheme for systems that include a gas phase, and solid and liquid phases, such as a gas-solid reactor. The method is based on neglecting fast dynamic modes and exploiting the structure of the algebraic equations. The integration method is suitable for a large class of industrially relevant systems. The methodology has proven remarkably efficient. It has in practice performed excellent and been a key factor for the success of the industrial simulator for electrochemical furnaces for ferro-alloy production.
Multi-dimensional modelling of gas turbine combustion using a flame sheet model in KIVA II
Cheng, W. K.; Lai, M.-C.; Chue, T.-H.
1991-01-01
A flame sheet model for heat release is incorporated into a multi-dimensional fluid mechanical simulation for gas turbine application. The model assumes that the chemical reaction takes place in thin sheets compared to the length scale of mixing, which is valid for the primary combustion zone in a gas turbine combustor. In this paper, the details of the model are described and computational results are discussed.
Energy Technology Data Exchange (ETDEWEB)
Kuuskraa, V.A.; Hammersheimb, E.; Sawyer, W.
1985-05-01
The objective of the work performed under this directive is to assess whether gas hydrates could potentially be technically and economically recoverable. The technical potential and economics of recovering gas from a representative hydrate reservoir will be established using the cyclic thermal injection model, HYDMOD, appropriately modified for this effort, integrated with economics model for gas production on the North Slope of Alaska, and in the deep offshore Atlantic. The results from this effort are presented in this document. In Section 1, the engineering cost and financial analysis model used in performing the economic analysis of gas production from hydrates -- the Hydrates Gas Economics Model (HGEM) -- is described. Section 2 contains a users guide for HGEM. In Section 3, a preliminary economic assessment of the gas production economics of the gas hydrate cyclic thermal injection model is presented. Section 4 contains a summary critique of existing hydrate gas recovery models. Finally, Section 5 summarizes the model modification made to HYDMOD, the cyclic thermal injection model for hydrate gas recovery, in order to perform this analysis.
A Paradigm for Modeling and Computation of Gas Dynamics
Xu, Kun
2016-01-01
In the continuum flow regime, the Navier-Stokes equations are usually used for the description of gas dynamics. On the other hand, the Boltzmann equation is applied for the rarefied gas dynamics. Both equations are constructed from modeling flow physics in different scales. Fortunately, due to the distinct separation of scales, i.e., the hydrodynamic and kinetic ones, both Navier-Stokes equations and the Boltzmann equation are valid in their respectable domains. However, in real physical application, there may not have such a distinctive scale separation. For example, around a hypersonic flying vehicle, the flow physics at different regions may correspond to different regimes, where the local Knudsen number can be changed in several order of magnitudes. With a variation of modeling scale, theoretically a continuous governing equation from kinetic Boltzmann equation to the hydrodynamic Navier-Stokes equations should exist. However, due to the difficulties of a direct modeling of flow physics in the scale betwe...
Grey Smoothing Model for Predicting Mine Gas Emission
Institute of Scientific and Technical Information of China (English)
潘结南; 孟召平; 刘亚川
2003-01-01
A grey smoothing model for predicting mine gas emission was presented by combining the grey system theory with the smoothing prediction technique. First of all, according to the variable sequence, GM(1,1) model was set up to predict the general development trend of variable as first fitted values, then the smoothing prediction technique was used to revise the fitted values so as to improve the accuracy of prediction. The results of application in the No.6 Coal Mine in Pingdingshan mining area show that the grey smoothing model has higher accuracy than that of GM(1,1) in predicting the variable sequence with strong fluctuation. The research provides a new scientific method for predicting mine gas emission.
Neural network models for biological waste-gas treatment systems.
Rene, Eldon R; Estefanía López, M; Veiga, María C; Kennes, Christian
2011-12-15
This paper outlines the procedure for developing artificial neural network (ANN) based models for three bioreactor configurations used for waste-gas treatment. The three bioreactor configurations chosen for this modelling work were: biofilter (BF), continuous stirred tank bioreactor (CSTB) and monolith bioreactor (MB). Using styrene as the model pollutant, this paper also serves as a general database of information pertaining to the bioreactor operation and important factors affecting gas-phase styrene removal in these biological systems. Biological waste-gas treatment systems are considered to be both advantageous and economically effective in treating a stream of polluted air containing low to moderate concentrations of the target contaminant, over a rather wide range of gas-flow rates. The bioreactors were inoculated with the fungus Sporothrix variecibatus, and their performances were evaluated at different empty bed residence times (EBRT), and at different inlet styrene concentrations (C(i)). The experimental data from these bioreactors were modelled to predict the bioreactors performance in terms of their removal efficiency (RE, %), by adequate training and testing of a three-layered back propagation neural network (input layer-hidden layer-output layer). Two models (BIOF1 and BIOF2) were developed for the BF with different combinations of easily measurable BF parameters as the inputs, that is concentration (gm(-3)), unit flow (h(-1)) and pressure drop (cm of H(2)O). The model developed for the CSTB used two inputs (concentration and unit flow), while the model for the MB had three inputs (concentration, G/L (gas/liquid) ratio, and pressure drop). Sensitivity analysis in the form of absolute average sensitivity (AAS) was performed for all the developed ANN models to ascertain the importance of the different input parameters, and to assess their direct effect on the bioreactors performance. The performance of the models was estimated by the regression
MODELING AND AVAILABILITY ANALYZES OF A COMPLEX GAS PIPELINE NETWORK
Energy Technology Data Exchange (ETDEWEB)
Ainouche, A.; Ainouche, H.
2007-07-01
The network reliability, in the way of security of supply of international markets, is proved to be an essential criterion for the conservation of the market shares and the conquest of new customers. In relation with the importance and the existing configurations diversity of gas pipelines networks, the obtaining of a global availability model of a network is difficult to implement by the use of a classic approach based on the analysis of the whole of failure risks, the definition of their probability and the estimation of their impact in term of productivity. This because mainly of the huge dimensions of the phase space that would result from such a conception. To get round this problem we implemented a systemic type approach for the modeling of the availability of a complex gas pipelines network. The approach of modeling is of 'bottom-up' type. The model of coordination is a model of flow maximization whose formalization requires the representation of the gas pipeline network by the graphs theory. The developed tool can also be used as a stand of experimentation and to define by simulation the impact of every decision having the tendency to improve the availability of the network. (auth)
Exact solutions in a model of vertical gas migration
Energy Technology Data Exchange (ETDEWEB)
Silin, Dmitriy B.; Patzek, Tad W.; Benson, Sally M.
2006-06-27
This work is motivated by the growing interest in injectingcarbon dioxide into deep geological formations as a means of avoidingatmospheric emissions of carbon dioxide and consequent global warming.One of the key questions regarding the feasibility of this technology isthe potential rate of leakage out of the primary storage formation. Weseek exact solutions in a model of gas flow driven by a combination ofbuoyancy, viscous and capillary forces. Different combinations of theseforces and characteristic length scales of the processes lead todifferent time scaling and different types of solutions. In the case of athin, tight seal, where the impact of gravity is negligible relative tocapillary and viscous forces, a Ryzhik-type solution implies square-rootof time scaling of plume propagation velocity. In the general case, a gasplume has two stable zones, which can be described by travelling-wavesolutions. The theoretical maximum of the velocity of plume migrationprovides a conservative estimate for the time of vertical migration.Although the top of the plume has low gas saturation, it propagates witha velocity close to the theoretical maximum. The bottom of the plumeflows significantly more slowly at a higher gas saturation. Due to localheterogeneities, the plume can break into parts. Individual plumes alsocan coalesce and from larger plumes. The analytical results are appliedto studying carbon dioxide flow caused by leaks from deep geologicalformations used for CO2 storage. The results are also applicable formodeling flow of natural gas leaking from seasonal gas storage, or formodeling of secondary hydrocarbon migration.
Phenomenologically varying \\Lambda and a toy model for the Universe
Khurshudyan, M; Chubaryan, E; Farahani, H
2014-01-01
We consider a model of the Universe with variable G and {\\Lambda}. Subject of our interest is a phenomenological model for {\\Lambda} proposed and considered in this article first time (up to our knowledge). Modification based on an assumption that ghost dark energy exists and Universe will feel it through {\\Lambda}. In that case we would like to consider possibility that there exist some unusual connections between different components of the fluids existing in Universe. We would like to stress, that this is just an assumption and could be very far from the reality. We are interested by this model as a phenomenological and mathematical and unfortunately, we will not discuss about physical conditions and possibilities of having such modifications. To test our assumption and to observe behavior of the Universe, we will consider toy models filled by a barotropic fluid and modified Chaplyagin gas. To complete the logic of the research we will consider interaction between barotropic fluid or Chaplygin gas with gho...
Off-Gas Adsorption Model Capabilities and Recommendations
Energy Technology Data Exchange (ETDEWEB)
Lyon, Kevin L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Welty, Amy K. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Law, Jack [Idaho National Lab. (INL), Idaho Falls, ID (United States); Ladshaw, Austin [Georgia Inst. of Technology, Atlanta, GA (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2016-03-01
Off-gas treatment is required to reduce emissions from aqueous fuel reprocessing. Evaluating the products of innovative gas adsorption research requires increased computational simulation capability to more effectively transition from fundamental research to operational design. Early modeling efforts produced the Off-Gas SeParation and REcoverY (OSPREY) model that, while efficient in terms of computation time, was of limited value for complex systems. However, the computational and programming lessons learned in development of the initial model were used to develop Discontinuous Galerkin OSPREY (DGOSPREY), a more effective model. Initial comparisons between OSPREY and DGOSPREY show that, while OSPREY does reasonably well to capture the initial breakthrough time, it displays far too much numerical dispersion to accurately capture the real shape of the breakthrough curves. DGOSPREY is a much better tool as it utilizes a more stable set of numerical methods. In addition, DGOSPREY has shown the capability to capture complex, multispecies adsorption behavior, while OSPREY currently only works for a single adsorbing species. This capability makes DGOSPREY ultimately a more practical tool for real world simulations involving many different gas species. While DGOSPREY has initially performed very well, there is still need for improvement. The current state of DGOSPREY does not include any micro-scale adsorption kinetics and therefore assumes instantaneous adsorption. This is a major source of error in predicting water vapor breakthrough because the kinetics of that adsorption mechanism is particularly slow. However, this deficiency can be remedied by building kinetic kernels into DGOSPREY. Another source of error in DGOSPREY stems from data gaps in single species, such as Kr and Xe, isotherms. Since isotherm data for each gas is currently available at a single temperature, the model is unable to predict adsorption at temperatures outside of the set of data currently
Directory of Open Access Journals (Sweden)
Marković Jelena
2007-01-01
Full Text Available The transport of gaseous components through porous media could be described according to the well-known Fick model and its modifications. It is also known that Fick’s law is not suitable for predicting the fluxes in multicomponent gas mixtures, excluding binary mixtures. This model is still frequently used in chemical engineering because of its simplicity. Unfortunately, besides the Fick’s model there is no generally accepted model for mass transport through porous media (membranes, catalysts etc.. Numerous studies on transport through porous media reveal that Dusty Gas Model (DGM is superior in its ability to predict fluxes in multicomponent mixtures. Its wider application is limited by more complicated calculation procedures comparing to Fick’s model. It should be noted that there were efforts to simplify DGM in order to obtain satisfactory accurate results. In this paper linearized DGM, as the simplest form of DGM, is tested under conditions of zero system pressure drop, small pressure drop, and different temperatures. Published experimental data are used in testing the accuracy of the linearized procedure. It is shown that this simplified procedure is accurate enough compared to the standard more complicated calculations.
Stochastic Lattice Gas Model for a Predator-Prey System
Satulovsky, J E; Satulovsky, Javier; Tome, Tania
1994-01-01
We propose a stochastic lattice gas model to describe the dynamics of two animal species population, one being a predator and the other a prey. This model comprehends the mechanisms of the Lotka-Volterra model. Our analysis was performed by using a dynamical mean-field approximation and computer simulations. Our results show that the system exhibits an oscillatory behavior of the population densities of prey and predators. For the sets of parameters used in our computer simulations, these oscillations occur at a local level. Mean-field results predict synchronized collective oscillations.
Mathematical Model of Natural Gas Desulfurization Based on Membrane Absorption
Institute of Scientific and Technical Information of China (English)
Wang Shuli; Ma Jun; Wang Ganyu; Zhou Heng
2014-01-01
Models of mass transfer kinetics combined with mass transfer differential equation and mass transfer resistance equation were established on the basis of double-iflm theory. Mass transfer process of H2S absorption by means of polypro-pylene hydrophobic microporous hollow ifber membrane contactor was simulated using MDEA (N-methyldiethanolamine) as the absorption liquid and corresponding experiments of natural gas desulfurization were performed. The simulation re-sults indicated that the removal rate of hydrogen sulifde showed positive dependence on the absorption liquid concentration and gas pressure. However, the desulfurization rate showed negative dependence on gas lfow. The simulated values were in good agreement with the experimental results. The in-tube concentration of hydrogen sulifde at the same point increased with increase in the gas velocity. Axial concentration of hydrogen sulifde decreased rapidly at the beginning, and the de-crease saw a slowdown during the latter half period. Hydrogen sulifde concentration dropped quickly in the radial direction, and the reduction in the radial direction was weakened with the increase of axial length due to the gradual reduction of hy-drogen sulifde concentration along the tube. The desulfurization rate under given operating conditions can be predicted by this model, and the theoretical basis for membrane module design can also be provided.
Brazilian gas network computational model for reliability analysis
Energy Technology Data Exchange (ETDEWEB)
Carvalho, Thomaz; Bilhim, Thiago; Ferreira, Gustavo P. D.; Pires, Luis F. G. [Dept. Eng. Mecanica, PUC-Rio (Brazil); Faertes, Denise; Saker, Leonardo [PETROBRAS Gas and Energia (Brazil)
2010-07-01
Pipeline thermo-hydraulic simulation is useful to support operation, design development and reliability analysis. PETROBRAS carried reliability programs in the last years. These studies are developed to evaluate gas chain security of supply, pointing out vulnerable points and proposing optimization measures to adopt. Previously, the Brazilian gas network could be modeled using sub-networks because of the physical separation between the Northeast and the Southeast networks, but in 2010 the new GASCAC pipeline will start up and change this. The new simulation models will have to handle this new configuration. The simulations developed by the Pontifice Catholic University of Rio de Janeiro deal with steady state and transient scenarios provided by a PETROBRAS group of experts. This paper discusses the alternatives and strategies used in the thermo-hydraulic simulation of the Brazilian gas pipeline network and analyses the advantages and disadvantages of each approach and the option used to meet the demands of the reliability analysis of the PETROBRAS gas reliability management sector.
Gas Modelling in the Disc of HD 163296
Tilling, I.; Woitke, P.; Meeus, G.; Mora, A.; Montesinos, B.; Riviere-Marichalar, P.; Eiroa, C.; Thi, W. -F.; Isella, A.; Roberge, A.; Martin-Zaidi, C.; Kamp, I.; Pinte, C.; Sandell, G.; Vacca, W. D.; Menard, F.; Mendigutia, I.; Duchene, G.; Dent, W. R. F.; Aresu, G.; Meijerink, R.; Spaans, M.
2011-01-01
We present detailed model fits to observations of the disc around the Herbig Ae star HD 163296. This well-studied object has an age of approx. 4Myr, with evidence of a circumstellar disc extending out to approx. 540AU. We use the radiation thermo-chemical disc code ProDiMo to model the gas and dust in the circumstellar disc of HD 163296, and attempt to determine the disc properties by fitting to observational line and continuum data. These include new Herschel/PACS observations obtained as part of the open-time key program GASPS (Gas in Protoplanetary Systems), consisting of a detection of the [Oi] 63 m line and upper limits for several other far infrared lines. We complement this with continuum data and ground-based observations of the CO-12 3-2, 2-1 and CO-13 J=1-0 line transitions, as well as the H2 S(1) transition. We explore the effects of stellar ultraviolet variability and dust settling on the line emission, and on the derived disc properties. Our fitting efforts lead to derived gas/dust ratios in the range 9-100, depending on the assumptions made. We note that the line fluxes are sensitive in general to the degree of dust settling in the disc, with an increase in line flux for settled models. This is most pronounced in lines which are formed in the warm gas in the inner disc, but the low excitation molecular lines are also affected. This has serious implications for attempts to derive the disc gas mass from line observations. We derive fractional PAH abundances between 0.007 and 0.04 relative to ISM levels. Using a stellar and UV excess input spectrum based on a detailed analysis of observations, we find that the all observations are consistent with the previously assumed disc geometry
Rice husk combustion evolved gas analysis experiments and modelling
International Nuclear Information System (INIS)
Rice husk is a major agricultural waste which could be a major source of fuel for boilers and furnaces if its calorific value could be realized efficiently. The oxidation kinetics of rice husks combustion were investigated using an evolved gas analysis technique. Rice husk samples were heated from 100 °C to 500 °C at a constant rate inside a small pressurised reactor. An oxygen-containing gas was passed through the reactor at a controlled flow rate and the evolved gas was continually analysed for its oxygen, carbon monoxide and carbon dioxide contents after moisture had been removed. A model for the oxidation of the rice husks samples is proposed that considers that the many simultaneous and competing oxidation reactions may be adequately represented by grouping them into three overlapping and competing reaction regimes in which CO2, CO and H2O are the only reaction products. The activation energies, and peak oxygen consumption temperatures were all found to be linear functions of the oxygen partial pressure in the reactor. Increasing the oxygen partial pressure decreased the temperatures at which peak oxygen consumption occurred. The total system pressure had no effect on the combustion behaviour other than through the oxygen partial pressure. At a heating rate of 80 K h−1 and a system pressure of 500 kPa values for E/R for the low temperature, medium temperature and high temperature oxidation reactions are 14.7, 19.2 and 17.4 respectively. - Highlights: • Oxidation kinetics of rice husk waste investigated using evolved gas analysis. • Proposed kinetics model assumes three competing and overlapping reactions occur. • Three oxidation reaction model fits evolved gas analysis well. • Activation energies of reactions are linear functions of O2 partial pressure. • O2 consumption peak temperatures decrease with increasing O2 partial pressure
Gas Generation in Radioactive Wastes - MAGGAS Predictive Life Cycle Model
International Nuclear Information System (INIS)
Gases may form from radioactive waste in quantities posing different potential hazards throughout the waste package life cycle. The latter includes surface storage, transport, placing in an operating repository, storage in the repository prior to backfill, closure and the post-closure stage. Potentially hazardous situations involving gas include fire, flood, dropped packages, blocked package vents and disruption to a sealed repository. The MAGGAS (Magnox Gas generation) model was developed to assess gas formation for safety assessments during all stages of the waste package life cycle. This is a requirement of the U.K. regulatory authorities and Nirex and progress in this context is discussed. The processes represented in the model include: Corrosion, microbial degradation, radiolysis, solid-state diffusion, chemico-physical degradation and pressurisation. The calculation was split into three time periods. First the 'aerobic phase' is used to model the periods of surface storage, transport and repository operations including storage in the repository prior to backfill. The second and third periods were designated 'anaerobic phase 1' and 'anaerobic phase 2' and used to model the waste packages in the post-closure phase of the repository. The various significant gas production processes are modeled in each phase. MAGGAS (currently Version 8) is mounted on an Excel spreadsheet for ease of use and speed, has 22 worksheets and is operated routinely for assessing waste packages (e.g. for ventilation of stores and pressurisation of containers). Ten operational and decommissioning generic nuclear power station waste streams were defined as initial inputs, which included ion exchange materials, sludges and concentrates, fuel element debris, graphite debris, activated components, contaminated items, desiccants and catalysts. (authors)
Multiscale model reduction for shale gas transport in fractured media
Akkutlu, I Y; Vasilyeva, Maria
2015-01-01
In this paper, we develop a multiscale model reduction technique that describes shale gas transport in fractured media. Due to the pore-scale heterogeneities and processes, we use upscaled models to describe the matrix. We follow our previous work \\cite{aes14}, where we derived an upscaled model in the form of generalized nonlinear diffusion model to describe the effects of kerogen. To model the interaction between the matrix and the fractures, we use Generalized Multiscale Finite Element Method. In this approach, the matrix and the fracture interaction is modeled via local multiscale basis functions. We developed the GMsFEM and applied for linear flows with horizontal or vertical fracture orientations on a Cartesian fine grid. In this paper, we consider arbitrary fracture orientations and use triangular fine grid and developed GMsFEM for nonlinear flows. Moreover, we develop online basis function strategies to adaptively improve the convergence. The number of multiscale basis functions in each coarse region ...
The motion of the 2D hydrodynamic Chaplygin sleigh in the presence of circulation
Fedorov, Yuri N; Vankerschaver, Joris
2012-01-01
We consider the motion of a planar rigid body in a potential flow with circulation and subject to a certain nonholonomic constraint. This model is related to the design of underwater vehicles. The equations of motion admit a reduction to a 2-dimensional nonlinear system, which is integrated explicitly. We show that the reduced system comprises both asymptotic and periodic dynamics separated by a critical value of the energy, and give a complete classification of types of the motion. Then we describe the whole variety of the trajectories of the body on the plane.
Cytochrome C Biosensor—A Model for Gas Sensing
Gabriele Nelles; Nadejda Krasteva; Ingeborg Hospach; Michael Hulko
2011-01-01
This work is about gas biosensing with a cytochrome c biosensor. Emphasis is put on the analysis of the sensing process and a mathematical model to make predictions about the biosensor response. Reliable predictions about biosensor responses can provide valuable information and facilitate biosensor development, particularly at an early development stage. The sensing process comprises several individual steps, such as phase partition equilibrium, intermediate reactions, mass-transport, and rea...
A continuum model for metabolic gas exchange in pear fruit.
Q Tri Ho; Pieter Verboven; Verlinden, Bert E.; Jeroen Lammertyn; Stefan Vandewalle; Nicolaï, Bart M.
2008-01-01
Exchange of O(2) and CO(2) of plants with their environment is essential for metabolic processes such as photosynthesis and respiration. In some fruits such as pears, which are typically stored under a controlled atmosphere with reduced O(2) and increased CO(2) levels to extend their commercial storage life, anoxia may occur, eventually leading to physiological disorders. In this manuscript we have developed a mathematical model to predict the internal gas concentrations, including permeation...
LIQUID-GAS COEXISTENCE EQUILIBRIUM IN A RELAXATION MODEL
Institute of Scientific and Technical Information of China (English)
WANG Ping; TANG Shao-qiang
2005-01-01
Stability of liquid-gas coexistence equilibrium in a relaxation model for isothermal phase transition in a sealed one-dimensional tube was discussed. With matched asymptotic expansion, a linear system for first order perturbations was derived formally. By solving this system analytically, it is shown that small initial perturbations are damped out in general; yet they may maintain at certain level for special cases.Numerical evidence is presented. This manifests the regularization effects of relaxation.
Homogeneous gas phase models of relaxation kinetics in neon afterglow
Directory of Open Access Journals (Sweden)
Marković Vidosav Lj.
2007-01-01
Full Text Available The homogeneous gas phase models of relaxation kinetics (application of the gas phase effective coefficients to represent surface losses are applied for the study of charged and neutral active particles decay in neon afterglow. The experimental data obtained by the breakdown time delay measurements as a function of the relaxation time td (τ (memory curve is modeled in early, as well as in late afterglow. The number density decay of metastable states can explain neither the early, nor the late afterglow kinetics (memory effect, because their effective lifetimes are of the order of milliseconds and are determined by numerous collision quenching processes. The afterglow kinetics up to hundreds of milliseconds is dominated by the decay of molecular neon Ne2 + and nitrogen ions N2 + (present as impurities and the approximate value of N2 + ambipolar diffusion coefficient is determined. After the charged particle decay, the secondary emitted electrons from the surface catalyzed excitation of nitrogen atoms on the cathode determine the breakdown time delay down to the cosmic rays and natural radioactivity level. Due to the neglecting of number density spatial profiles, the homogeneous gas phase models give only the approximate values of the corresponding coefficients, but reproduce correctly other characteristics of afterglow kinetics from simple fits to the experimental data.
Planning the network of gas pipelines through modeling tools
Energy Technology Data Exchange (ETDEWEB)
Sucupira, Marcos L.L.; Lutif Filho, Raimundo B. [Companhia de Gas do Ceara (CEGAS), Fortaleza, CE (Brazil)
2009-07-01
Natural gas is a source of non-renewable energy used by different sectors of the economy of Ceara. Its use may be industrial, residential, commercial, as a source of automotive fuel, as a co-generation of energy and as a source for generating electricity from heat. For its practicality this energy has a strong market acceptance and provides a broad list of clients to fit their use, which makes it possible to reach diverse parts of the city. Its distribution requires a complex network of pipelines that branches throughout the city to meet all potential clients interested in this source of energy. To facilitate the design, analysis, expansion and location of bottlenecks and breaks in the distribution network, a modeling software is used that allows the network manager of the net to manage the various information about the network. This paper presents the advantages of modeling the gas distribution network of natural gas companies in Ceara, showing the tool used, the steps necessary for the implementation of the models, the advantages of using the software and the findings obtained with its use. (author)
Dense Molecular Gas: A Sensitive Probe of Stellar Feedback Models
Hopkins, Philip F; Murray, Norman; Quataert, Eliot
2012-01-01
We show that the mass fraction of GMC gas (n>100 cm^-3) in dense (n>>10^4 cm^-3) star-forming clumps, observable in dense molecular tracers (L_HCN/L_CO(1-0)), is a sensitive probe of the strength and mechanism(s) of stellar feedback. Using high-resolution galaxy-scale simulations with pc-scale resolution and explicit models for feedback from radiation pressure, photoionization heating, stellar winds, and supernovae (SNe), we make predictions for the dense molecular gas tracers as a function of GMC and galaxy properties and the efficiency of stellar feedback. In models with weak/no feedback, much of the mass in GMCs collapses into dense sub-units, predicting L_HCN/L_CO(1-0) ratios order-of-magnitude larger than observed. By contrast, models with feedback properties taken directly from stellar evolution calculations predict dense gas tracers in good agreement with observations. Changing the strength or timing of SNe tends to move systems along, rather than off, the L_HCN-L_CO relation (because SNe heat lower-de...
Material point method modeling in oil and gas reservoirs
Energy Technology Data Exchange (ETDEWEB)
Vanderheyden, William Brian; Zhang, Duan
2016-06-28
A computer system and method of simulating the behavior of an oil and gas reservoir including changes in the margins of frangible solids. A system of equations including state equations such as momentum, and conservation laws such as mass conservation and volume fraction continuity, are defined and discretized for at least two phases in a modeled volume, one of which corresponds to frangible material. A material point model technique for numerically solving the system of discretized equations, to derive fluid flow at each of a plurality of mesh nodes in the modeled volume, and the velocity of at each of a plurality of particles representing the frangible material in the modeled volume. A time-splitting technique improves the computational efficiency of the simulation while maintaining accuracy on the deformation scale. The method can be applied to derive accurate upscaled model equations for larger volume scale simulations.
Testing dark energy models with $H(z)$ data
Qi, Jing-Zhao; Liu, Wen-Biao
2016-01-01
$Om(z)$ is a diagnostic approach to distinguish dark energy models. However, there are few articles to discuss what is the distinguishing criterion. In this paper, firstly we smooth the latest observational $H(z)$ data using a model-independent method -- Gaussian processes, and then reconstruct the $Om(z)$ and its fist order derivative $\\mathcal{L}^{(1)}_m$. Such reconstructions not only could be the distinguishing criteria, but also could be used to estimate the authenticity of models. We choose some popular models to study, such as $\\Lambda$CDM, generalized Chaplygin gas (GCG) model, Chevallier-Polarski-Linder (CPL) parametrization and Jassal-Bagla-Padmanabhan (JBP) parametrization. We plot the trajectories of $Om(z)$ and $\\mathcal{L}^{(1)}_m$ with $1 \\sigma$ confidence level of these models, and compare them to the reconstruction from $H(z)$ data set. The result indicates that the $H(z)$ data does not favor the CPL and JBP models at $1 \\sigma$ confidence level. Strangely, in high redshift range, the recons...
Semiphenomenological model for gas-liquid phase transitions.
Benilov, E S; Benilov, M S
2016-03-01
We examine a rarefied gas with inter-molecular attraction. It is argued that the attraction force amplifies random density fluctuations by pulling molecules from lower-density regions into high-density regions and thus may give rise to an instability. To describe this effect, we use a kinetic equation where the attraction force is taken into account in a way similar to how electromagnetic forces in plasma are treated in the Vlasov model. It is demonstrated that the instability occurs when the temperature T is lower than a certain threshold value T(s) depending on the gas density. It is further shown that, even if T is only marginally lower than T(s), the instability generates clusters with density much higher than that of the gas. These results suggest that the instability should be interpreted as a gas-liquid phase transition, with T(s) being the temperature of saturated vapor and the high-density clusters representing liquid droplets.
Directory of Open Access Journals (Sweden)
M. Saternus
2015-01-01
Full Text Available Today there are many reactors used in refining of primary and secondary aluminium. Continuous reactor URC-7000 is one of them. The model of such reactor was built at 1:3 scale. The physical modelling research was conducted taking into account the flow rate of refining gas and its influence of the dispersion level. There are two nozzles introducing a gas. The carried out tests included the different flow rate of a gas through the nozzles (from 5 to 15 dm3/min. Additionally, the mixing characteristics were measured and discussed for different flow rate of an inert gas.
Lattice gas cellular automata and lattice Boltzmann models an introduction
Wolf-Gladrow, Dieter A
2000-01-01
Lattice-gas cellular automata (LGCA) and lattice Boltzmann models (LBM) are relatively new and promising methods for the numerical solution of nonlinear partial differential equations. The book provides an introduction for graduate students and researchers. Working knowledge of calculus is required and experience in PDEs and fluid dynamics is recommended. Some peculiarities of cellular automata are outlined in Chapter 2. The properties of various LGCA and special coding techniques are discussed in Chapter 3. Concepts from statistical mechanics (Chapter 4) provide the necessary theoretical background for LGCA and LBM. The properties of lattice Boltzmann models and a method for their construction are presented in Chapter 5.
Applications of vortex gas models to tornadogenesis and maintenance
Bělík, Pavel; Potvin, Corey K; Scholz, Kurt; Shvartsman, Mikhail M
2016-01-01
Two-dimensional and three-dimensional vortex gas models are discussed and proposed in this paper as potential models for tornadogenesis and tornado maintenance. The idea of maximization of entropy is utilized which gives rise to negative-temperature systems, in such systems energy is transferred from smaller to larger scales resulting in an inverse energy cascade. In this paper, the smaller scales are represented by intense, supercritical vortices, which transfer energy to the larger-scale tornadic flows. We address the formation of these vortices as a result of the interaction of the flow with the surface and a boundary layer.
The modeling of carbon isotope kinetics and its application to the evaluation of natural gas
Institute of Scientific and Technical Information of China (English)
Xianqing LI; Xianming XIAO; Yongchun TANG; Hui TIAN; Qiang ZHOU; Yunfeng YANG; Peng DONG; Yan WANG; Zhihong SONG
2008-01-01
The modeling of carbon isotope kinetics of natural gas is an issue driving pioneering research in the oil and gas geochemistry in China and internationally.Combined with the sedimentary burial history and basin geothermal history,the modeling of carbon isotope kinetics provides a new and effective means for the determination of the origin and accumulation history of natural gas pools.In this paper,we introduce the modeling of carbon isotope kinetics of natural gas formation and its applications to the assessment of natural gas maturity,the determination of the gas source,the history of gas accumulation,and the oil-gas ratio.It is shown that this approach is of great value for these applications.The carbon isotopic characteristics of natural gas are not only affected by the gas source and maturity of the source rock,but also are related to the accumulation condition and geothermal gradient in a basin.There are obvious differences in the characteristics of carbon isotope ratios between instantaneous gas and cumulative gas.Different basins have different kinetic models of carbon isotope fractionation,which depends on the gas source condition,the accumulation history and the sedimentary-tectonic history.Since the origin of natural gas in the superimposed basin in China is very complicated,and the natural gas pool is characterized by multiphase and variable gas-sources,this paper may provide a new perspective on the study and evaluation of natural gas.
Study and mathematical model of ultra-low gas burner
International Nuclear Information System (INIS)
The main objective of this project is prediction and reduction of NOx and CO2 emissions under levels recommended from European standards for gas combustion processes. A mathematical model of burner and combustion chamber is developed based on interacting fluid dynamics processes: turbulent flow, gas phase chemical reactions, heat and radiation transfer The NOx prediction model for prompt and thermal NOx is developed. The validation of CFD (Computer fluid-dynamics) simulations corresponds to 5 MWI burner type - TEA, installed on CASPER boiler. This burner is three-stream air distribution burner with swirl effect, designed by ENEL to meet future NOx emission standards. For performing combustion computer modelling, FLUENT CFD code is preferred, because of its capabilities to provide accurately description of large number of rapid interacting processes: turbulent flow, phase chemical reactions and heat transfer and for its possibilities to present wide range of calculation and graphical output reporting data The computational tool used in this study is FLUENT version 5.4.1, installed on fs 8200 UNIX systems The work includes: study the effectiveness of low-NOx concepts and understand the impact of combustion and swirl air distribution and flue gas recirculation on peak flame temperatures, flame structure and fuel/air mixing. A finite rate combustion model: Eddy-Dissipation (Magnussen-Hjertager) Chemical Model for 1, 2 step Chemical reactions of bi-dimensional (2D) grid is developed along with NOx and CO2 predictions. The experimental part of the project consists of participation at combustion tests on experimental facilities located in Livorno. The results of the experiments are used, to obtain better vision for combustion process on small-scaled design and to collect the necessary input data for further Fluent simulations
Sorption Modeling and Verification for Off-Gas Treatment
Energy Technology Data Exchange (ETDEWEB)
Tavlarides, Lawrence L. [Syracuse Univ., NY (United States); Lin, Ronghong [Syracuse Univ., NY (United States); Nan, Yue [Syracuse Univ., NY (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Georgia Inst. of Technology, Atlanta, GA (United States); Ladshaw, Austin [Georgia Inst. of Technology, Atlanta, GA (United States); Sharma, Ketki [Georgia Inst. of Technology, Atlanta, GA (United States); Gabitto, Jorge [Prairie View A & M Univ., Prairie View, TX (United States); DePaoli, David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2015-04-29
The project has made progress toward developing a comprehensive modeling capability for the capture of target species in off gas evolved during the reprocessing of nuclear fuel. The effort has integrated experimentation, model development, and computer code development for adsorption and absorption processes. For adsorption, a modeling library has been initiated to include (a) equilibrium models for uptake of off-gas components by adsorbents, (b) mass transfer models to describe mass transfer to a particle, diffusion through the pores of the particle and adsorption on the active sites of the particle, and (c) interconnection of these models to fixed bed adsorption modeling which includes advection through the bed. For single-component equilibria, a Generalized Statistical Thermodynamic Adsorption (GSTA) code was developed to represent experimental data from a broad range of isotherm types; this is equivalent to a Langmuir isotherm in the two-parameter case, and was demonstrated for Kr on INL-engineered sorbent HZ PAN, water sorption on molecular sieve A sorbent material (MS3A), and Kr and Xe capture on metal-organic framework (MOF) materials. The GSTA isotherm was extended to multicomponent systems through application of a modified spreading pressure surface activity model and generalized predictive adsorbed solution theory; the result is the capability to estimate multicomponent adsorption equilibria from single-component isotherms. This advance, which enhances the capability to simulate systems related to off-gas treatment, has been demonstrated for a range of real-gas systems in the literature and is ready for testing with data currently being collected for multicomponent systems of interest, including iodine and water on MS3A. A diffusion kinetic model for sorbent pellets involving pore and surface diffusion as well as external mass transfer has been established, and a methodology was developed for determining unknown diffusivity parameters from transient
Sorption Modeling and Verification for Off-Gas Treatment
International Nuclear Information System (INIS)
The project has made progress toward developing a comprehensive modeling capability for the capture of target species in off gas evolved during the reprocessing of nuclear fuel. The effort has integrated experimentation, model development, and computer code development for adsorption and absorption processes. For adsorption, a modeling library has been initiated to include (a) equilibrium models for uptake of off-gas components by adsorbents, (b) mass transfer models to describe mass transfer to a particle, diffusion through the pores of the particle and adsorption on the active sites of the particle, and (c) interconnection of these models to fixed bed adsorption modeling which includes advection through the bed. For single-component equilibria, a Generalized Statistical Thermodynamic Adsorption (GSTA) code was developed to represent experimental data from a broad range of isotherm types; this is equivalent to a Langmuir isotherm in the two-parameter case, and was demonstrated for Kr on INL-engineered sorbent HZ PAN, water sorption on molecular sieve A sorbent material (MS3A), and Kr and Xe capture on metal-organic framework (MOF) materials. The GSTA isotherm was extended to multicomponent systems through application of a modified spreading pressure surface activity model and generalized predictive adsorbed solution theory; the result is the capability to estimate multicomponent adsorption equilibria from single-component isotherms. This advance, which enhances the capability to simulate systems related to off-gas treatment, has been demonstrated for a range of real-gas systems in the literature and is ready for testing with data currently being collected for multicomponent systems of interest, including iodine and water on MS3A. A diffusion kinetic model for sorbent pellets involving pore and surface diffusion as well as external mass transfer has been established, and a methodology was developed for determining unknown diffusivity parameters from transient
Natural gas production problems : solutions, methodologies, and modeling.
Energy Technology Data Exchange (ETDEWEB)
Rautman, Christopher Arthur; Herrin, James M.; Cooper, Scott Patrick; Basinski, Paul M. (El Paso Production Company, Houston, TX); Olsson, William Arthur; Arnold, Bill Walter; Broadhead, Ronald F. (New Mexico Bureau of Geology and Mineral Resources, Socorro, NM); Knight, Connie D. (Consulting Geologist, Golden, CO); Keefe, Russell G.; McKinney, Curt (Devon Energy Corporation, Oklahoma City, OK); Holm, Gus (Vermejo Park Ranch, Raton, NM); Holland, John F.; Larson, Rich (Vermejo Park Ranch, Raton, NM); Engler, Thomas W. (New Mexico Institute of Mining and Technology, Socorro, NM); Lorenz, John Clay
2004-10-01
Natural gas is a clean fuel that will be the most important domestic energy resource for the first half the 21st centtuy. Ensuring a stable supply is essential for our national energy security. The research we have undertaken will maximize the extractable volume of gas while minimizing the environmental impact of surface disturbances associated with drilling and production. This report describes a methodology for comprehensive evaluation and modeling of the total gas system within a basin focusing on problematic horizontal fluid flow variability. This has been accomplished through extensive use of geophysical, core (rock sample) and outcrop data to interpret and predict directional flow and production trends. Side benefits include reduced environmental impact of drilling due to reduced number of required wells for resource extraction. These results have been accomplished through a cooperative and integrated systems approach involving industry, government, academia and a multi-organizational team within Sandia National Laboratories. Industry has provided essential in-kind support to this project in the forms of extensive core data, production data, maps, seismic data, production analyses, engineering studies, plus equipment and staff for obtaining geophysical data. This approach provides innovative ideas and technologies to bring new resources to market and to reduce the overall environmental impact of drilling. More importantly, the products of this research are not be location specific but can be extended to other areas of gas production throughout the Rocky Mountain area. Thus this project is designed to solve problems associated with natural gas production at developing sites, or at old sites under redevelopment.
EXPERIMENTAL STUDY AND COMPUTATIONAL MODELLING OF GAS FIRED PULSE COMBUSTION
Directory of Open Access Journals (Sweden)
I. Smajevic
2010-06-01
Full Text Available The paper presents some results of computational modelling of a gas-fired pulse combustor with aerodynamic valves. The development of the model followed experimental investigations during which the combustor geometry and operating conditions were defined. A simple 'tank and tube' approach was adopted by decomposing the combustor into several elements which were modelled separately, together with the interconnecting processes. The solution was obtained by marching integration in time over several cycles. The model reproduced reasonably well the recorded time history and averaged values of all basic parameters and is expected to complement the experiments aiming to develop a pulse combustor as a device for to cleaning the outer sides of power plants’ boiler heating surfaces during operation.
Extended models of nonlinear waves in liquid with gas bubbles
Kudryashov, Nikolay A
2016-01-01
In this work we generalize the models for nonlinear waves in a gas--liquid mixture taking into account an interphase heat transfer, a surface tension and a weak liquid compressibility simultaneously at the derivation of the equations for nonlinear waves. We also take into consideration high order terms with respect to the small parameter. Two new nonlinear differential equations are derived for long weakly nonlinear waves in a liquid with gas bubbles by the reductive perturbation method considering both high order terms with respect to the small parameter and the above mentioned physical properties. One of these equations is the perturbation of the Burgers equation and corresponds to main influence of dissipation on nonlinear waves propagation. The other equation is the perturbation of the Burgers--Korteweg--de Vries equation and corresponds to main influence of dispersion on nonlinear waves propagation.
The magnetic field of Mars - Implications from gas dynamic modeling
Russell, C. T.; Luhmann, J. G.; Spreiter, J. R.; Stahara, S. S.
1984-01-01
On January 21, 1972, the Mars 3 spacecraft observed a variation in the magnetic field during its periapsis passage over the dayside of Mars that was suggestive of entry into a Martian magnetosphere. Original data and trajectory of the spacecraft have been obtained (Dolginov, 1983) and an attempt is made to simulate the observed variation of the magnetic field by using a gas dynamic simulation. In the gas dynamic model a flow field is generated and this flow field is used to carry the interplanetary magnetic field through the Martian magnetosheath. The independence of the flow field and magnetic field calculation makes it possible to converge rapidly on an IMF orientation that would result in a magnetic variation similar to that observed by Mars 3. There appears to be no need to invoke an entry into a Martian magnetosphere to explain these observations.
A Model for Predicting Laminar Gas Flow Through Micropassages
Institute of Scientific and Technical Information of China (English)
Jun－MingLi; Bu－XuanWang; 等
1997-01-01
An theoretical investigation was conducted to detect the gas-solid interface effect on laminar flow characteristics for gas flowing through micropassages.In the wall-adjacent region,the change in viscosity of fluid vs the distance from the wall surface,as derived from the dkinetic theory of gases result in significant influence on the flow characteristics in micropassages.A model was proposed to account for the wall effect.Analytical expressions for velocity profiles and pressure drop were derived,respectively,for laminar flow of gases in microtubes and in extremely narrow parallel plaes.The Knudsen number,Kn,as a criterion,that the flow can be treated reasonably as flow in macrochannels,is discussed.
Energy Technology Data Exchange (ETDEWEB)
Venson, Giuliano Gardolinski [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Mecanica], e-mail: venson@ufmg.br; Barros, Jose Eduardo Mautone; Pereira, Josemar Figueiredo [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET-MG), Belo Horizonte, MG (Brazil)], e-mail: mautone@des.cefetmg.br, e-mail: josemar_cefet@yahoo.com.br
2006-07-01
This work presents the modeling of a gas microturbine power generator. The microturbine consists in a small thermo-electrical power unit, design for combined heat and power generation. The unit has an electric generator, coaxially connected with a turbocharger, which one is driven by a fuel burner. The system also incorporates an air regenerator, used for pre-heat the combustion air, and a heat exchanger, used for water heating. The objective of the modeling is the attainment of the electrical performance and the operational limits for the microturbine in function of the subsystems operational conditions. The modeling is based on the first law of the thermodynamic, using specific models for each component. In the combustion chamber is used a model that takes the fuel injection properties, as absolute pressure and temperature. A semi-empirical model, based in the modified Euler equation, is used in the turbocharger. In the air regenerator and heat exchanger, the method of mean logarithmic temperature difference is used. Through the modeling of a commercial microturbine, reference values obtained were used in some subsystems of a new microturbine. The results for this new microturbine in development, based in automotive turbochargers, indicate a nominal electrical power of 38 kW with electrical efficiency of 33% and global efficiency of 73%. (author)
Gas-Grain Models for Interstellar Anion Chemistry
Cordiner, M. A.; Charnely, S. B.
2012-01-01
Long-chain hydrocarbon anions C(sub n) H(-) (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with n(sub H2) approx > / cubic cm). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C6H(-) anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C6O, C7O, HC6O, and HC7O, the abundances of which depend on the assumed branching ratios for associative electron detachment
GAS-GRAIN MODELS FOR INTERSTELLAR ANION CHEMISTRY
International Nuclear Information System (INIS)
Long-chain hydrocarbon anions CnH– (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with nH2∼>105 cm–3). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C6H– anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C6O, C7O, HC6O, and HC7O, the abundances of which depend on the assumed branching ratios for associative electron detachment.
GAS-GRAIN MODELS FOR INTERSTELLAR ANION CHEMISTRY
Energy Technology Data Exchange (ETDEWEB)
Cordiner, M. A. [Also at Institute for Astrophysics and Computational Sciences, Catholic University of America, Washington, DC 20064 (United States); Charnley, S. B., E-mail: martin.cordiner@nasa.gov [Astrochemistry Laboratory and Goddard Center for Astrobiology, Mailstop 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20770 (United States)
2012-04-20
Long-chain hydrocarbon anions C{sub n}H{sup -} (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with n{sub H{sub 2}}{approx}>10{sup 5} cm{sup -3}). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C{sub 6}H{sup -} anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C{sub 6}O, C{sub 7}O, HC{sub 6}O, and HC{sub 7}O, the abundances of which depend on the assumed branching ratios for associative electron detachment.
The Geopolitical Impact of Shale Gas: The Modelling Approach
Auping, W.L.; De Jong, S.; Pruyt, E.; Kwakkel, J.H.
2014-01-01
The US’ shale gas revolution, a spectacular increase in natural gas extraction from previously unconventional sources, has led to considerable lower gas prices in North America. This study focusses on consequences of the shale gas revolution on state stability of traditional oil and gas exporting co
Gas turbine cooling modeling - Thermodynamic analysis and cycle simulations
Energy Technology Data Exchange (ETDEWEB)
Jordal, Kristin
1999-02-01
Considering that blade and vane cooling are a vital point in the studies of modern gas turbines, there are many ways to include cooling in gas turbine models. Thermodynamic methods for doing this are reviewed in this report, and, based on some of these methods, a number of model requirements are set up and a Cooled Gas Turbine Model (CGTM) for design-point calculations of cooled gas turbines is established. Thereafter, it is shown that it is possible to simulate existing gas turbines with the CGTM. Knowledge of at least one temperature in the hot part of the turbine (TET, TRIT or possibly TIT) is found to be vital for a complete heat balance over the turbine. The losses, which are caused by the mixing of coolant and main flow, are in the CGTM considered through a polytropic efficiency reduction factor S. Through the study of S, it can be demonstrated that there is more to gain from coolant reduction in a small and/or old turbine with poor aerodynamics, than there is to gain in a large, modern turbine, where the losses due to interaction between coolant and main flow are, relatively speaking, small. It is demonstrated, at the design point (TET=1360 deg C, {pi}=20) for the simple-cycle gas turbine, that heat exchanging between coolant and fuel proves to have a large positive impact on cycle efficiency, with an increase of 0.9 percentage points if all of the coolant passes through the heat exchanger. The corresponding improvement for humidified coolant is 0.8 percentage points. A design-point study for the HAT cycle shows that if all of the coolant is extracted after the humidification tower, there is a decrease in coolant requirements of 7.16 percentage points, from 19.58% to 12.52% of the compressed air, and an increase in thermal efficiency of 0.46 percentage points, from 53.46% to 53.92%. Furthermore, it is demonstrated with a TET-parameter variation, that the cooling of a simple-cycle gas turbine with humid air can have a positive effect on thermal efficiency
Modeling cast IN-738 superalloy gas tungsten arc welds
Energy Technology Data Exchange (ETDEWEB)
Bonifaz, E.A. [Department of Mechanical and Manufacturing Engineering, University of Manitoba, E2-327F EITC, Winnipeg, Man., R3T 5V6 (Canada); Universidad San Francisco de Quito, Casilla Postal: 17-12-841 Circulo de Cumbaya, Quito (Ecuador)], E-mail: bonifaz@cc.umanitoba.ca; Richards, N.L. [Department of Mechanical and Manufacturing Engineering, University of Manitoba, E2-327F EITC, Winnipeg, Man., R3T 5V6 (Canada)], E-mail: nrichar@cc.umanitoba.ca
2009-04-15
A three-dimensional finite-element thermal model has been developed to generate weld profiles, and to analyze transient heat flow, thermal gradients and thermal cycles in cast IN-738 superalloy gas tungsten arc welds. Outputs of the model (cooling rates, the thermal gradient G and the growth rate R) were used to describe solidification structures found around the weld pool for three different welding speeds at constant heat input. Calculations around the weld pool indicate that the cooling rate increases from the fusion line to the centerline at all welding speeds. It was also observed that the cooling rate (G x R) and the ratio G/R fall with welding speed. For instance, as the welding speed is increased, the cooling rates at the centerline, fusion line and penetration depth decrease. Moreover, it was observed that as the power and welding speed both increase (but keeping the heat input constant), the weld pool becomes wider and more elongated, shifting from circular to elliptical shaped. The calculations were performed using ABAQUS FE code on the basis of a time-increment Lagrangian formulation. The heat source represented by a moving Gaussian power density distribution is applied over the top surface of the specimen during a period of time that depends on the welding speed. Temperature-dependent material properties and the effect of forced convection due to the flow of the shielding gas are included in the model. Numerically predicted sizes of the melt-pool zone and dendrite secondary arm spacing induced by the gas tungsten arc welding process are also given.
A strategic model of European gas supply (GASMOD)
International Nuclear Information System (INIS)
This paper presents a model of the European natural gas supply, GASMOD, which is structured as a two-stage-game of successive natural gas exports to Europe (upstream market) and wholesale trade within Europe (downstream market) and which explicitly includes infrastructure capacities. We compare three possible market scenarios: Cournot competition in both markets, perfect competition in both markets, and perfect competition in the downstream with Cournot competition in the upstream market (EU liberalization). We find that Cournot competition in both markets is the most accurate representation of today's European natural gas market, where suppliers at both stages generate a mark-up at the expense of the final customer (double marginalization). Our results yield a diversified supply portfolio with newly emerging (LNG) exporters gaining market shares. Enforcing competition in the European downstream market would lead to lower prices and higher quantities by avoiding the welfare-reducing effects of double marginalization. Binding infrastructure capacity restrictions strongly influence the results, and we identify bottlenecks mainly for intra-European trade relations whereas transport capacity in the upstream market is globally sufficient in the Cournot scenario. (author)
Modelling Circumbinary Gas Flows in Close T Tauri Binaries
de Val-Borro, M; Stempels, H C; Pepliński, A
2011-01-01
Young close binaries open central gaps in the surrounding circumbinary accretion disc, but the stellar components may still gain mass from gas crossing through the gap. It is not well understood how this process operates and how the stellar components are affected by such inflows. Our main goal is to investigate how gas accretion takes place and evolves in close T Tauri binary systems. In particular, we model the accretion flows around two close T Tauri binaries, V4046 Sgr and DQ Tau, both showing periodic changes in emission lines, although their orbital characteristics are very different. In order to derive the density and velocity maps of the circumbinary material, we employ two-dimensional hydrodynamic simulations with a locally isothermal equation of state. The flow patterns become quasi-stable after a few orbits in the frame co-rotating with the system. Gas flows across the circumbinary gap through the co-rotating Lagrangian points, and local circumstellar discs develop around both components. Spiral de...
Externally Fired micro-Gas Turbine: Modelling and experimental performance
Energy Technology Data Exchange (ETDEWEB)
Traverso, Alberto; Massardo, Aristide F. [Thermochemical Power Group, Dipartimento di Macchine, Sistemi Energetici e Trasporti, Universita di Genova, Genova (Italy); Scarpellini, Riccardo [Ansaldo Ricerche s.r.l., Genova (Italy)
2006-11-15
This work presents the steady-state and transient performance obtained by an Externally Fired micro-Gas Turbine (EFmGT) demonstration plant. The plant was designed by Ansaldo Ricerche (ARI) s.r.l. and the Thermochemical Power Group (TPG) of the Universita di Genova, using the in-house TPG codes TEMP (Thermoeconomic Modular Program) and TRANSEO. The plant was based on a recuperated 80kW micro-gas turbine (Elliott TA-80R), which was integrated with the externally fired cycle at the ARI laboratory. The first goal of the plant construction was the demonstration of the EFmGT control system. The performance obtained in the field can be improved in the near future using high-temperature heat exchangers and apt external combustors, which should allow the system to operate at the actual micro-gas turbine inlet temperature (900-950{sup o}C). This paper presents the plant layout and the control system employed for regulating the microturbine power and rotational speed. The experimental results obtained by the pilot plant in early 2004 are shown: the feasibility of such a plant configuration has been demonstrated, and the control system has successfully regulated the shaft speed in all the tests performed. Finally, the plant model in TRANSEO, which was formerly used to design the control system, is shown to accurately simulate the plant behaviour both at steady-state and transient conditions. (author)
Strategies simulation model for the gas business chain MEGAS
International Nuclear Information System (INIS)
MEGAS is a simulation model representing fundamental parameters of Corpoven's natural gas and NGL production, handling, processing, transportation and distribution systems in the Venezuelan mid-east, as well as its financial implications. Various strategies regarding development, prices, costs, new business opportunities, production scenarios, demand and energy policies can be evaluated through this model in order to determine, after analyzing the economics results, a set of strategies to follow in the mid and long term. MEGAS could be also used to make risk analysis studies, considering that probabilistic parameters and variables like gas quality, production, demand, plant shutdowns and others are to be represented by their distinctive function. It is possible to set up a probabilistic function for each economic indicator or operating variables with an appropriate experiment design. MEGAS is based on a dynamic simulation language, which facilitates both the real system components representation and the main variables statistical data accumulation. It also allows graphical representation of results and the simulation animation. Demand and price forecasts, new projects, costs and capabilities of the systems are some of the model input data. MEGAS should be considered as a tool that eases the strategic planning of the business, making it possible for the Corporation to foresee changes, both in the domestic and international market, to predict how these changes could affect its business affairs and to visualize different return scenarios
A dynamic model of active mode locking in gas lasers
Energy Technology Data Exchange (ETDEWEB)
Mel' nikov, L.A.; Tatarkov, G.N. (Saratovskii Gosudarstvennyi Universitet, Saratov (USSR))
1990-09-01
A dynamic model is proposed for describing active mode locking in gas lasers with inhomogeneous broadening. Different dynamic modes of operation are examined as a function of the loss modulation depth. It is demonstrated that the destruction of mode locking is accompanied by the appearance of more complex dynamic states which can be either regular or chaotic. It is also shown that each individual pulse has a complex multihump structure resulting from the coherent character of the interaction between the electromagnetic field and the active medium. 14 refs.
Institute of Scientific and Technical Information of China (English)
陈建彬; 吕小强
2011-01-01
Aiming at the fact that the energy and mass exchange phenomena exist between barrel and gas-operated device of the automatic weapon, for describing its interior ballistics and dynamic characteristics of the gas-operated device accurately, a new variable-mass thermodynamics model is built. It is used to calculate the automatic mechanism velocity of a certain automatic weapon, the calculation results coincide with the experimental results better, and thus the model is validated. The influences of structure parameters on gas-operated device＇ s dynamic characteristics are discussed. It shows that the model is valuable for design and accurate performance prediction of gas-operated automatic weapon.
An electricity price model with consideration to load and gas price effects
Institute of Scientific and Technical Information of China (English)
黄民翔; 陶小虎; 韩祯祥
2003-01-01
Some characteristics of the electricity load and prices are studied, and the relationship between electricity prices and gas (fuel) prices is analyzed in this paper. Because electricity prices are strongly dependent on load and gas prices, the authors constructed a model for electricity prices based on the effects of these two factors; and used the Geometric Mean Reversion Brownian Motion (GMRBM) model to describe the electricity load process, and a Geometric Brownian Motion(GBM) model to describe the gas prices; deduced the price stochastic process model based on the above load model and gas price model. This paper also presents methods for parameters estimation, and proposes some methods to solve the model.
Comparison of dark energy models:A perspective from the latest observational data
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
We compare some popular dark energy models under the assumption of a flat universe by using the latest observational data including the type Ia supernovae Constitution compilation,the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey,the cosmic microwave background measurement given by the seven-year Wilkinson Microwave Anisotropy Probe observations and the determination of H0 from the Hubble Space Telescope.Model comparison statistics such as the Bayesian and Akaike information criteria are applied to assess the worth of the models.These statistics favor models that give a good fit with fewer parameters.Based on this analysis,we find that the simplest cosmological constant model that has only one free parameter is still preferred by the current data.For other dynamical dark energy models,we find that some of them,such as the αdark energy,constant w,generalized Chaplygin gas,Chevalliear-Polarski-Linder parametrization,and holographic dark energy models,can provide good fits to the current data,and three of them,namely,the Ricci dark energy,agegraphic dark energy,and Dvali-Gabadadze-Porrati models,are clearly disfavored by the data.
Natural gas transmission and distribution model of the National Energy Modeling System
International Nuclear Information System (INIS)
The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of Integrated Analysis and Forecasting of the Energy Information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. From 1982 through 1993, the Intermediate Future Forecasting System (IFFS) was used by the EIA for its analyses, and the Gas Analysis Modeling System (GAMS) was used within IFFS to represent natural gas markets. Prior to 1982, the Midterm Energy Forecasting System (MEFS), also referred to as the Project Independence Evaluation System (PIES), was employed. NEMS was developed to enhance and update EIA's modeling capability by internally incorporating models of energy markets that had previously been analyzed off-line. In addition, greater structural detail in NEMS permits the analysis of a broader range of energy issues. The time horizon of NEMS is the midterm period (i.e., through 2015). In order to represent the regional differences in energy markets, the component models of NEMS function at regional levels appropriate for the markets represented, with subsequent aggregation/disaggregation to the Census Division level for reporting purposes
Natural gas transmission and distribution model of the National Energy Modeling System
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-02-01
The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of Integrated Analysis and Forecasting of the Energy Information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. From 1982 through 1993, the Intermediate Future Forecasting System (IFFS) was used by the EIA for its analyses, and the Gas Analysis Modeling System (GAMS) was used within IFFS to represent natural gas markets. Prior to 1982, the Midterm Energy Forecasting System (MEFS), also referred to as the Project Independence Evaluation System (PIES), was employed. NEMS was developed to enhance and update EIA`s modeling capability by internally incorporating models of energy markets that had previously been analyzed off-line. In addition, greater structural detail in NEMS permits the analysis of a broader range of energy issues. The time horizon of NEMS is the midterm period (i.e., through 2015). In order to represent the regional differences in energy markets, the component models of NEMS function at regional levels appropriate for the markets represented, with subsequent aggregation/disaggregation to the Census Division level for reporting purposes.
Advanced modeling of oxy-fuel combustion of natural gas
Energy Technology Data Exchange (ETDEWEB)
Chungen Yin
2011-01-15
The main goal of this small-scale project is to investigate oxy-combustion of natural gas (NG) through advanced modeling, in which radiation, chemistry and mixing will be reasonably resolved. 1) A state-of-the-art review was given regarding the latest R and D achievements and status of oxy-fuel technology. The modeling and simulation status and achievements in the field of oxy-fuel combustion were also summarized; 2) A computer code in standard c++, using the exponential wide band model (EWBM) to evaluate the emissivity and absorptivity of any gas mixture at any condition, was developed and validated in detail against data in literature. A new, complete, and accurate WSGGM, applicable to both air-fuel and oxy-fuel combustion modeling and applicable to both gray and non-gray calculation, was successfully derived, by using the validated EWBM code as the reference mode. The new WSGGM was implemented in CFD modeling of two different oxy-fuel furnaces, through which its great, unique advantages over the currently most widely used WSGGM were demonstrated. 3) Chemical equilibrium calculations were performed for oxy-NG flame and air-NG flame, in which dissociation effects were considered to different degrees. Remarkable differences in oxy-fuel and air-fuel combustion were revealed, and main intermediate species that play key roles in oxy-fuel flames were identified. Different combustion mechanisms are compared, e.g., the most widely used 2-step global mechanism, refined 4-step global mechanism, a global mechanism developed for oxy-fuel using detailed chemical kinetic modeling (CHEMKIN) as reference. 4) Over 15 CFD simulations were done for oxy-NG combustion, in which radiation, chemistry, mixing, turbulence-chemistry interactions, and so on were thoroughly investigated. Among all the simulations, RANS combined with 2-step and refined 4-step mechanism, RANS combined with CHEMKIN-based new global mechanism for oxy-fuel modeling, and LES combined with different combustion
A permeation-diffusion-reaction model of gas transport in cellular tissue of plant materials
Ho, Quang Tri; Verlinden, Bert; Verboven, Pieter; Vandewalle, Stefan; Nicolai, Bart
2006-01-01
Gas transport in fruit tissue is governed by both diffusion and permeation. The latter phenomenon is caused by overall pressure gradients which may develop due to the large difference in O-2 and CO2 diffusivity during controlled atmosphere storage of the fruit. A measurement set-up for tissue permeation based on unsteady-state gas exchange was developed. The gas permeability of pear tissue was determined based on an analytical gas transport model. The overall gas transport in pear tissue samp...
SIMMER-III modeling of gas cooled fast reactor
International Nuclear Information System (INIS)
This paper deals with extension and application of the SIMMER-III code for safety studies of a gas cooled fast reactor. The equation of state of the helium gas and its thermal physical properties have been prepared and implemented in the code. The geometric, thermal hydraulic and neutronic models have been set up for the ALLEGERO reactor. The code and the associated model are verified by comparing steady state and unprotected loss of flow 20% remained flow rate (ULOF-20%) results with those done by other project partners. Reasonable or good agreements have been achieved for major physical variables. The unprotected loss of coolant accident (ULOCA) case is a severe transient case with core melting and degradation that was emulated only by SIMMER, in the project. In the initiating phase the clad becomes molten, this triggers the first power excursion. Then the fuel becomes more mobile and further power excursions take place, which lead to core melting and degradation. The fuel is ejected by power excursion and then moves relatively slowly to the lower part of vessel. Finally there are only a few kilograms of fuel escaping to the vessel outside (into reactor container) and the released thermal energy is about 6 GJ within a period of one minute. The final power stays below one MW and the reactor is in a deep sub-criticality state, since 1/2 fuel becomes noneffective. (author)
A complementarity model for solving stochastic natural gas market equilibria
International Nuclear Information System (INIS)
This paper presents a stochastic equilibrium model for deregulated natural gas markets. Each market participant (pipeline operators, producers, etc.) solves a stochastic optimization problem whose optimality conditions, when combined with market-clearing conditions give rise to a certain mixed complementarity problem (MiCP). The stochastic aspects are depicted by a recourse problem for each player in which the first-stage decisions relate to long-term contracts and the second-stage decisions relate to spot market activities for three seasons. Besides showing that such a market model is an instance of a MiCP, we provide theoretical results concerning long-term and spot market prices and solve the resulting MiCP for a small yet representative market. We also note an interesting observation for the value of the stochastic solution for non-optimization problems
Phonon Gas Model (PGM) workflow in the VLab Science Gateway
da Silveira, P.; Zhang, D.; Wentzcovitch, R. M.
2013-12-01
This contribution describes a scientific workflow for first principles computations of free energy of crystalline solids using the phonon gas model (PGM). This model was recently implemented as a hybrid method combining molecular dynamics and phonon normal mode analysis to extract temperature dependent phonon frequencies and life times beyond perturbation theory. This is a demanding high throughout workflow and is currently being implemented in VLab Cyberinfrastructure [da Silveira et al., 2008], which has recently been integrated to the XSEDE. First we review the underlying PGM, its practical implementation, and calculation requirements. We then describe the workflow management and its general method for handling actions. We illustrate the PGM application with a calculation of MgSiO3-perovskite's anharmonic phonons. We conclude with an outlook of workflows to compute other material's properties that will use the PGM workflow. Research supported by NSF award EAR-1019853.
On The Modelling Of Hybrid Aerostatic - Gas Journal Bearings
DEFF Research Database (Denmark)
Morosi, Stefano; Santos, Ilmar
2011-01-01
Gas journal bearing have been increasingly adopted in modern turbo-machinery applications, as they meet the demands of operation at higher rotational speeds, in clean environment and great efficiency. Due to the fact that gaseous lubricants, typically air, have much lower viscosity than more...... modeling for hybrid lubrication of a compressible fluid film journal bearing. Additional forces are generated by injecting pressurized air into the bearing gap through orifices located on the bearing walls. A modified form of the compressible Reynolds equation for active lubrication is derived. By solving...... this equation, stiffness and damping coefficients can be determined. A multibody dynamics model of a global system comprised of rotor and hybrid journal bearing is built in order to study the lateral dynamics of the system. Campbell diagrams and stability maps are presented, showing the main advantages...
Factorial Moments in a Generalized Lattice Gas Model
Wettig, T
1994-01-01
We construct a simple multicomponent lattice gas model in one dimension in which each site can either be empty or occupied by at most one particle of any one of $D$ species. Particles interact with a nearest neighbor interaction which depends on the species involved. This model is capable of reproducing the relations between factorial moments observed in high--energy scattering experiments for moderate values of $D$. The factorial moments of the negative binomial distribution can be obtained exactly in the limit as $D$ becomes large, and two suitable prescriptions involving randomly drawn nearest neighbor interactions are given. These results indicate the need for considerable care in any attempt to extract information regarding possible critical phenomena from empirical factorial moments.
Transient multiphase flow modeling of gas well liquid loading
Veeken, K.; Hu, B.; Schiferli, W.
2009-01-01
Gas well liquid loading occurs when gas production becomes insufficient to lift the associated liquids to surface. When that happens gas production first turns intermittent and eventually stops. Hence in depleting gas reservoirs the technical abandonment pressure and ultimate recovery are typically
Operational modeling of a sustainable gas supply chain
Bekkering, Jan; Broekhuis, Ton A.; Gemert, Wim J.T. van
2010-01-01
Biogas production from codigestion of cattle manure and biomass can have a significant contribution to a sustainable gas supply when this gas is upgraded to specifications prescribed for injection into the national gas grid and injected into this grid. In this study, we analyzed such a gas supply ch
BIODEGRADATION AND GAS-EXCHANGE OF GASEOUS ALKANES IN MODEL ESTUARINE ECOSYSTEMS
Gas exchange-biodegradation experiments conducted in model estuarine ecosystems indicate that the ease of degradation of gaseious normal alkanes increases with chain length. The behavior of gaseous perhalogenated alkanes can be explained by gas exchange alone with no degradation....
Adapting a weather forecast model for greenhouse gas simulation
Polavarapu, S. M.; Neish, M.; Tanguay, M.; Girard, C.; de Grandpré, J.; Gravel, S.; Semeniuk, K.; Chan, D.
2015-12-01
The ability to simulate greenhouse gases on the global domain is useful for providing boundary conditions for regional flux inversions, as well as for providing reference data for bias correction of satellite measurements. Given the existence of operational weather and environmental prediction models and assimilation systems at Environment Canada, it makes sense to use these tools for greenhouse gas simulations. In this work, we describe the adaptations needed to reasonably simulate CO2 with a weather forecast model. The main challenges were the implementation of a mass conserving advection scheme, and the careful implementation of a mixing ratio defined with respect to dry air. The transport of tracers through convection was also added, and the vertical mixing through the boundary layer was slightly modified. With all these changes, the model conserves CO2 mass well on the annual time scale, and the high resolution (0.9 degree grid spacing) permits a good description of synoptic scale transport. The use of a coupled meteorological/tracer transport model also permits an assessment of approximations needed in offline transport model approaches, such as the neglect of water vapour mass when computing a tracer mixing ratio with respect to dry air.
Anyonic behavior of an intermediate-statistics fermion gas model.
Algin, Abdullah; Irk, Dursun; Topcu, Gozde
2015-06-01
We study the high-temperature behavior of an intermediate-statistics fermionic gas model whose quantum statistical properties enable us to effectively deduce the details about both the interaction among deformed (quasi)particles and their anyonic behavior. Starting with a deformed fermionic grand partition function, we calculate, in the thermodynamical limit, several thermostatistical functions of the model such as the internal energy and the entropy by means of a formalism of the fermionic q calculus. For high temperatures, a virial expansion of the equation of state for the system is obtained in two and three dimensions and the first five virial coefficients are derived in terms of the model deformation parameter q. From the results obtained by the effect of fermionic deformation, it is found that the model parameter q interpolates completely between bosonlike and fermionic systems via the behaviors of the third and fifth virial coefficients in both two and three spatial dimensions and in addition it characterizes effectively the interaction among quasifermions. Our results reveal that the present deformed (quasi)fermion model could be very efficient and effective in accounting for the nonlinear behaviors in interacting composite particle systems.
Modelling gas migration in compacted bentonite: GAMBIT Club Phase 2. Final report
International Nuclear Information System (INIS)
This report describes the second phase of a programme of work to develop a computational model of gas migration through highly compacted bentonite. Experimental data that have appeared since the earlier report are reviewed for the additional information they might provide on the mechanism of gas migration in bentonite. Experiments carried out by Horseman and Harrigton (British Geological Survey) continued to provide the main data sets used in model evaluation. The earlier work (POSIVA Report 98-08) had resulted in a preliminary model of gas migration whose main features are gas invasion by microcrack propagation, and dilation of the pathways formed with increasing gas pressure. New work was carried out to further explore the capabilities of this model. In addition, a feature was added to the model to simulate gas pathway creation by water displacement rather than crack propagation. The development of a new alternative gas migration model is described. This is based on a volume-averaged representation of gas migration rather than on a description of flow in discrete pathways. Evaluation of this alternative model showed that it can produce similar agreement with experimental results to the other models examined. The implications of flow geometry, confining conditions and flow boundary conditions on gas migration behaviour in bentonite are reviewed. Proposals are made for the development of the new model into a tool for simulating gas migration through a bentonite buffer around a waste canister, and for possible enhancements to the model that might remove some of its currently perceived deficiencies. (orig.)
Modelling long run strategic behaviour on the liberalised European gas market
International Nuclear Information System (INIS)
In gas markets, intertemporal constraints are of particular importance due to the finiteness of gas resources. In particular in the UK and the Netherlands, gas resources are expected to dry up on the medium term, giving rise to a positive resource rent of the gas. On shorter time scales, decisions on investments in production, transmission, storage and LNG terminal capacities affect short term output decisions in following years, while within the year prices across seasons are related through storage decisions. We develop a model of strategic behaviour on the European gas markets that incorporates such intertemporal relations. We take into account interactions between strategic producers of gas, price-taking transmission companies, and traders arbitraging the markets by transporting gas across borders, storing gas across seasons, and importing LNG. As a case study, we use the model to explore the impacts on producer behaviour and infrastructure investments of a cap on production from a large gas field in the Netherlands. (Author)
Development and application of an efficient gas extraction model for low-rank high-gas coal beds
Institute of Scientific and Technical Information of China (English)
Baiquan Lin; He Li; Desheng Yuan; Ziwen Li
2015-01-01
To promote gas extraction in low-rank high-gas coal beds, the pore structure characteristics of the coal and their effect on gas desorption were studied. The results show that micropores are relatively rare in low-rank coal;mesopores are usually semi-open and inkpot-shaped whereas macropores are usually slit-shaped. Gas desorption is relatively easy at high-pressure stages, whereas it is difficult at low-pressure stages because of the‘bottleneck effect’ of the semi-open inkpot-shaped mesopores. A ‘two-three-two’ gas extraction model was established following experimental analysis and engi-neering practice applied in the Binchang mining area. In this model, gas extraction is divided into three periods:a planning period, a transitional period and a production period. In each period, surface extraction and underground extraction are performed simultaneously, and pressure-relief extraction and conventional extraction are coupled to each other. After applying this model, the gas extraction rate rose to 78.8%.
Modeling California policy impacts on greenhouse gas emissions
International Nuclear Information System (INIS)
This paper examines policy and technology scenarios in California, emphasizing greenhouse gas (GHG) emissions in 2020 and 2030. Using CALGAPS, a new, validated model simulating GHG and criteria pollutant emissions in California from 2010 to 2050, four scenarios were developed: Committed Policies (S1), Uncommitted Policies (S2), Potential Policy and Technology Futures (S3), and Counterfactual (S0), which omits all GHG policies. Forty-nine individual policies were represented. For S1–S3, GHG emissions fall below the AB 32 policy 2020 target [427 million metric tons CO2 equivalent (MtCO2e) yr−1], indicating that committed policies may be sufficient to meet mandated reductions. In 2030, emissions span 211–428 MtCO2e yr−1, suggesting that policy choices made today can strongly affect outcomes over the next two decades. Long-term (2050) emissions were all well above the target set by Executive Order S-3-05 (85 MtCO2e yr−1); additional policies or technology development (beyond the study scope) are likely needed to achieve this objective. Cumulative emissions suggest a different outcome, however: due to early emissions reductions, S3 achieves lower cumulative emissions in 2050 than a pathway that linearly reduces emissions between 2020 and 2050 policy targets. Sensitivity analysis provided quantification of individual policy GHG emissions reduction benefits. - Highlights: • Developed CALGAPS, a new California greenhouse gas (GHG) policy evaluation model. • Three scenarios (plus counterfactual) developed, modeling 49 state/federal policies. • All scenarios achieve 2020 target; GHG emissions through 2030 span a factor of two. • No scenario achieves 2050 target, but cumulative emissions can be very low. • GHG impact of each policy (plus combinations) quantified in sensitivity analysis
Greenhouse Gas Source Attribution: Measurements Modeling and Uncertainty Quantification.
Energy Technology Data Exchange (ETDEWEB)
Liu, Zhen; Safta, Cosmin; Sargsyan, Khachik; Najm, Habib N.; van Bloemen Waanders, Bart Gustaaf; LaFranchi, Brian; Ivey, Mark D.; Schrader, Paul E.; Michelsen, Hope A.; Bambha, Ray
2014-09-01
In this project we have developed atmospheric measurement capabilities and a suite of atmospheric modeling and analysis tools that are well suited for verifying emissions of green- house gases (GHGs) on an urban-through-regional scale. We have for the first time applied the Community Multiscale Air Quality (CMAQ) model to simulate atmospheric CO 2 . This will allow for the examination of regional-scale transport and distribution of CO 2 along with air pollutants traditionally studied using CMAQ at relatively high spatial and temporal resolution with the goal of leveraging emissions verification efforts for both air quality and climate. We have developed a bias-enhanced Bayesian inference approach that can remedy the well-known problem of transport model errors in atmospheric CO 2 inversions. We have tested the approach using data and model outputs from the TransCom3 global CO 2 inversion comparison project. We have also performed two prototyping studies on inversion approaches in the generalized convection-diffusion context. One of these studies employed Polynomial Chaos Expansion to accelerate the evaluation of a regional transport model and enable efficient Markov Chain Monte Carlo sampling of the posterior for Bayesian inference. The other approach uses de- terministic inversion of a convection-diffusion-reaction system in the presence of uncertainty. These approaches should, in principle, be applicable to realistic atmospheric problems with moderate adaptation. We outline a regional greenhouse gas source inference system that integrates (1) two ap- proaches of atmospheric dispersion simulation and (2) a class of Bayesian inference and un- certainty quantification algorithms. We use two different and complementary approaches to simulate atmospheric dispersion. Specifically, we use a Eulerian chemical transport model CMAQ and a Lagrangian Particle Dispersion Model - FLEXPART-WRF. These two models share the same WRF assimilated meteorology fields, making it
Greenhouse Gas Source Attribution: Measurements Modeling and Uncertainty Quantification
Energy Technology Data Exchange (ETDEWEB)
Liu, Zhen [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Safta, Cosmin [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sargsyan, Khachik [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Najm, Habib N. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); van Bloemen Waanders, Bart Gustaaf [Sandia National Lab. (SNL-CA), Livermore, CA (United States); LaFranchi, Brian W. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Ivey, Mark D. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Schrader, Paul E. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Michelsen, Hope A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Bambha, Ray P. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)
2014-09-01
In this project we have developed atmospheric measurement capabilities and a suite of atmospheric modeling and analysis tools that are well suited for verifying emissions of green- house gases (GHGs) on an urban-through-regional scale. We have for the first time applied the Community Multiscale Air Quality (CMAQ) model to simulate atmospheric CO_{2} . This will allow for the examination of regional-scale transport and distribution of CO_{2} along with air pollutants traditionally studied using CMAQ at relatively high spatial and temporal resolution with the goal of leveraging emissions verification efforts for both air quality and climate. We have developed a bias-enhanced Bayesian inference approach that can remedy the well-known problem of transport model errors in atmospheric CO_{2} inversions. We have tested the approach using data and model outputs from the TransCom3 global CO_{2} inversion comparison project. We have also performed two prototyping studies on inversion approaches in the generalized convection-diffusion context. One of these studies employed Polynomial Chaos Expansion to accelerate the evaluation of a regional transport model and enable efficient Markov Chain Monte Carlo sampling of the posterior for Bayesian inference. The other approach uses de- terministic inversion of a convection-diffusion-reaction system in the presence of uncertainty. These approaches should, in principle, be applicable to realistic atmospheric problems with moderate adaptation. We outline a regional greenhouse gas source inference system that integrates (1) two ap- proaches of atmospheric dispersion simulation and (2) a class of Bayesian inference and un- certainty quantification algorithms. We use two different and complementary approaches to simulate atmospheric dispersion. Specifically, we use a Eulerian chemical transport model CMAQ and a Lagrangian Particle Dispersion Model - FLEXPART-WRF. These two models share the same WRF
Ammonia concentration modeling based on retained gas sampler data
Energy Technology Data Exchange (ETDEWEB)
Terrones, G.; Palmer, B.J.; Cuta, J.M.
1997-09-01
The vertical ammonia concentration distributions determined by the retained gas sampler (RGS) apparatus were modeled for double-shell tanks (DSTs) AW-101, AN-103, AN-104, and AN-105 and single-shell tanks (SSTs) A-101, S-106, and U-103. One the vertical transport of ammonia in the tanks were used for the modeling. Transport in the non-convective settled solids and floating solids layers is assumed to occur primarily via some type of diffusion process, while transport in the convective liquid layers is incorporated into the model via mass transfer coefficients based on empirical correlations. Mass transfer between the top of the waste and the tank headspace and the effects of ventilation of the headspace are also included in the models. The resulting models contain a large number of parameters, but many of them can be determined from known properties of the waste configuration or can be estimated within reasonable bounds from data on the waste samples themselves. The models are used to extract effective diffusion coefficients for transport in the nonconvective layers based on the measured values of ammonia from the RGS apparatus. The modeling indicates that the higher concentrations of ammonia seen in bubbles trapped inside the waste relative to the ammonia concentrations in the tank headspace can be explained by a combination of slow transport of ammonia via diffusion in the nonconvective layers and ventilation of the tank headspace by either passive or active means. Slow transport by diffusion causes a higher concentration of ammonia to build up deep within the waste until the concentration gradients between the interior and top of the waste are sufficient to allow ammonia to escape at the same rate at which it is being generated in the waste.
Viscosity in the excluded volume hadron gas model
Gorenstein, M I; Moroz, O N
2007-01-01
The shear viscosity $\\eta$ in the van der Waals excluded volume hadron-resonance gas model is considered. For the shear viscosity the result of the non-relativistic gas of hard-core particles is extended to the mixture of particles with different masses, but equal values of hard-core radius r. The relativistic corrections to hadron average momenta in thermal equilibrium are also taken into account. The ratio of the viscosity $\\eta$ to the entropy density s is studied. It monotonously decreases along the chemical freeze-out line in nucleus-nucleus collisions with increasing collision energy. As a function of hard-core radius r, a broad minimum of the ratio $\\eta/s\\approx 0.3$ near $r \\approx 0.5$ fm is found at high collision energies. For the charge-neutral system at $T=T_c=180$ MeV, a minimum of the ratio $\\eta/s\\cong 0.24$ is reached for $r\\cong 0.53$ fm. To justify a hydrodynamic approach to nucleus-nucleus collisions within the hadron phase the restriction from below, $r~ \\ge ~0.2$ fm, on the hard-core ha...
Constraining Intracluster Gas Models with AMiBA13
Molnar, Sandor M.; Umetsu, Keiichi; Birkinshaw, Mark; Bryan, Greg; Haiman, Zoltán; Hearn, Nathan; Shang, Cien; Ho, Paul T. P.; Locutus Huang, Chih-Wei; Koch, Patrick M.; Liao, Yu-Wei Victor; Lin, Kai-Yang; Liu, Guo-Chin; Nishioka, Hiroaki; Wang, Fu-Cheng; Proty Wu, Jiun-Huei
2010-11-01
Clusters of galaxies have been extensively used to determine cosmological parameters. A major difficulty in making the best use of Sunyaev-Zel'dovich (SZ) and X-ray observations of clusters for cosmology is that using X-ray observations it is difficult to measure the temperature distribution and therefore determine the density distribution in individual clusters of galaxies out to the virial radius. Observations with the new generation of SZ instruments are a promising alternative approach. We use clusters of galaxies drawn from high-resolution adaptive mesh refinement cosmological simulations to study how well we should be able to constrain the large-scale distribution of the intracluster gas (ICG) in individual massive relaxed clusters using AMiBA in its configuration with 13 1.2 m diameter dishes (AMiBA13) along with X-ray observations. We show that non-isothermal β models provide a good description of the ICG in our simulated relaxed clusters. We use simulated X-ray observations to estimate the quality of constraints on the distribution of gas density, and simulated SZ visibilities (AMiBA13 observations) for constraints on the large-scale temperature distribution of the ICG. We find that AMiBA13 visibilities should constrain the scale radius of the temperature distribution to about 50% accuracy. We conclude that the upgraded AMiBA, AMiBA13, should be a powerful instrument to constrain the large-scale distribution of the ICG.
Multiscale model reduction for shale gas transport in fractured media
Akkutlu, I. Y.
2016-05-18
In this paper, we develop a multiscale model reduction technique that describes shale gas transport in fractured media. Due to the pore-scale heterogeneities and processes, we use upscaled models to describe the matrix. We follow our previous work (Akkutlu et al. Transp. Porous Media 107(1), 235–260, 2015), where we derived an upscaled model in the form of generalized nonlinear diffusion model to describe the effects of kerogen. To model the interaction between the matrix and the fractures, we use Generalized Multiscale Finite Element Method (Efendiev et al. J. Comput. Phys. 251, 116–135, 2013, 2015). In this approach, the matrix and the fracture interaction is modeled via local multiscale basis functions. In Efendiev et al. (2015), we developed the GMsFEM and applied for linear flows with horizontal or vertical fracture orientations aligned with a Cartesian fine grid. The approach in Efendiev et al. (2015) does not allow handling arbitrary fracture distributions. In this paper, we (1) consider arbitrary fracture distributions on an unstructured grid; (2) develop GMsFEM for nonlinear flows; and (3) develop online basis function strategies to adaptively improve the convergence. The number of multiscale basis functions in each coarse region represents the degrees of freedom needed to achieve a certain error threshold. Our approach is adaptive in a sense that the multiscale basis functions can be added in the regions of interest. Numerical results for two-dimensional problem are presented to demonstrate the efficiency of proposed approach. © 2016 Springer International Publishing Switzerland
New models for success emerge for US natural gas industry
International Nuclear Information System (INIS)
Very few companies in the US natural gas industry are confident in their ability to compete effectively in the brave new world of deregulation. Boston Consulting Group recently conducted an internal study to help the industry think about its future and identify models for success in this new environment. The authors examined the historical performance of 800 companies using several shareholder-value indicators, including cash-flow returns on investment, a measure of cash returns on cash invested that correlates closely to share price. Based on that review and discussions with investment managers and industry analysts, the authors were able to focus on a handful of companies that actually have thrived and created value against the difficult landscape of the past decade. Interviews with their senior executives provided important strategic and operational insights
Pseudo-particle modeling for gas flow in microchannels
Institute of Scientific and Technical Information of China (English)
WANG LiMin; GE Wei; CHEN FeiGuo
2007-01-01
The velocity profiles and temperature distributions of gas flow in microchannels, for Knudsen numbers ranging from 0.01 to 0.20, are investigated with pseudo-particle modeling (PPM). It has been found that the velocity profiles are mainly affected by Knudsen number and the external force fields applied. When Knudsen number was increased, the slip velocities on the walls increased at the beginning, and then decreased. The temperature distributions were also significantly affected by the external force. The Darcy friction factor increased with increasing Knudsen number, and its variation with Mach number under increased Knudsen number was similar to the so-called premature laminar-turbulent transition observed in experiments.
Stochastic method for modeling of the rarefied gas transport coefficients
Rudyak, V. Ya; Lezhnev, E. V.
2016-08-01
In this paper, we propose an algorithm for computation of the transport coefficients of rarefied gas, which is based on stochastic modeling of phase trajectories considered molecular system. The hard spheres potential is used. The number of operations is proportional to the number of used molecules. Naturally in this algorithm the conservation laws are performed. The efficiency of the algorithm is demonstrated by the calculation of the viscosity and diffusion coefficients of several noble gases (argon, neon, xenon, krypton). It was shown that the algorithm accuracy of the order of 1-2% can be obtained by using a relatively small number of molecules. The accuracy dependence on the number of used molecules, statistics (number of the used phase trajectories) and calculation time was analyzed.
On The Modeling Of Hybrid Aerostatic - Gas Journal Bearings
DEFF Research Database (Denmark)
Morosi, Stefano; Santos, Ilmar
2010-01-01
Gas journal bearing have been increasingly adopted in modern turbo-machinery applications, as they meet the demands of operation at higher rotational speeds, in clean environment and great efficiency. Due to the fact that gaseous lubricants, typically air, have much lower viscosity than more...... of a compressible fluid film journal bearing. Control forces are generated by injecting pressurized air into the bearing gap through orifices located on the bearing walls. A modified form of the compressible Reynolds equation for active lubrication is derived. By solving this equation, stiffness and damping...... conventional oil bearings, carrying capacity and dynamic characteristics of passive systems are generally poorer. In order to enhance these characteristics, one solution is to employ active control strategies. The present contribution presents a detailed mathematical modeling for active lubrication...
Modelling internal air systems in gas turbine engines
Institute of Scientific and Technical Information of China (English)
J Michael Owen
2007-01-01
Rotating-disc systems can be used to model,experimentally and computationally,the flow and heat transfer that occur inside the internal cooling-air systems of gas turbine engines.These rotating-disc systems have been used successfully to simplify and understand some of the complex flows that occur in internal-air systems,and designers have used this insight to improve the cooling effectiveness,thereby increasing the engine efficiency and reducing the emissions.In this review paper,three important cases are considered:hot-gas ingress;the pre-swirl system;and buoyancy-induced flow.Ingress,or ingestion,occurs when hot gas from the mainstream gas path is ingested into the wheel-space between the turbine disc and its adjacent casing.Rim seals are fitted at the periphery of the system,and sealing flow is used to reduce or prevent ingress.However,too much sealing air reduces the engine efficiency,and too little can cause serious overheating,resulting in damage to the turbine rim and blade roots.Although the flow is three-dimensional and unsteady,there are encouraging signs that simple 'orifice models' could be used to estimate the amount of ingress into the wheel-space.In a pre-swirl system,the cooling air for the gas-turbine blades is swirled by stationary nozzles,and the air is delivered to the blades via receiver holes in the rotating turbine disc.Swirling the air reduces its temperature relative to the rotating blades,and the designer needs to calculate the air temperature and pressure drop in the system.The designer also needs to calculate the effect of this swirling flow on the heat transfer from the turbine disc to the air,as this has a significant effect on the temperature distribution and stresses in the disc.Recent experimental and computational studies have given a better understanding of the flow and heat transfer in these systems.Buoyancy-induced flow occurs in the cavity between two co-rotating compressor discs when the temperature of the discs is higher
Evaluation of gas radiation models in CFD modeling of oxy-combustion
International Nuclear Information System (INIS)
Highlights: • CFD modeling of a typical industrial water tube boiler is conducted. • Different combustion processes were considered including air and oxy-fuel combustion. • SGG, EWBM, Leckner, Perry and WSGG radiation models were considered in the study. • EWBM is the most accurate model and it’s considered to be the benchmark model. • Characteristics of oxy-fuel combustion are compared to those of air–fuel combustion. - Abstract: Proper determination of the radiation energy is very important for proper predictions of the combustion characteristics inside combustion devices using CFD modeling. For this purpose, different gas radiation models were developed and applied in the present work. These radiation models vary in their accuracy and complexity according to the application. In this work, a CFD model for a typical industrial water tube boiler was developed, considering three different combustion environments. The combustion environments are air–fuel combustion (21% O2 and 79% N2), oxy-fuel combustion (21% O2 and 79% CO2) and oxy-fuel combustion (27% O2 and 73% CO2). Simple grey gas (SGG), exponential wide band model (EWBM), Leckner, Perry and weighted sum of grey gases (WSGG) radiation models were examined and their influences on the combustion characteristics were evaluated. Among those radiation models, the EWBM was found to provide close results to the experimental data for the present boiler combustion application. The oxy-fuel combustion characteristics were analyzed and compared with those of air–fuel combustion
Coupled multiphysics modeling of gas hydrate bearing sediments
Sanchez, Marcelo; Gai, Xuerui; Santamarina, J. Carlos
2014-01-01
Gas hydrates are crystalline clathrate compounds made of water and a low molecular gas like methane (Sloan 1998). Gas hydrates are generally present in oil-producing areas and in permafrost regions. Methane hydrate deposits can lead to large-scale submarine slope failures, blowouts, platform foundation failures, and -borehole instability. Gas hydrates constitute also an attractive source of energy as they are estimated to contain very large reserves of methane. Hydrate formation, dissociation...
Monte Carlo model for electron degradation in xenon gas
Mukundan, Vrinda
2016-01-01
We have developed a Monte Carlo model for studying the local degradation of electrons in the energy range 9-10000 eV in xenon gas. Analytically fitted form of electron impact cross sections for elastic and various inelastic processes are fed as input data to the model. Two dimensional numerical yield spectrum, which gives information on the number of energy loss events occurring in a particular energy interval, is obtained as output of the model. Numerical yield spectrum is fitted analytically, thus obtaining analytical yield spectrum. The analytical yield spectrum can be used to calculate electron fluxes, which can be further employed for the calculation of volume production rates. Using yield spectrum, mean energy per ion pair and efficiencies of inelastic processes are calculated. The value for mean energy per ion pair for Xe is 22 eV at 10 keV. Ionization dominates for incident energies greater than 50 eV and is found to have an efficiency of 65% at 10 keV. The efficiency for the excitation process is 30%...
Kinetic model on coke oven gas with steam reforming
Institute of Scientific and Technical Information of China (English)
ZHANG Jia-yuan; ZHOU Jie-min; YAN Hong-jie
2008-01-01
The effects of factors such as the molar ratio of H2O to CH4 (n(H2O)/n(CH4)), methane conversion temperature and time on methane conversion rate were investigated to build kinetic model for reforming of coke-oven gas with steam. The results of experiments show that the optimal conditions for methane conversion are that the molar ratio of H2O to CH4 varies from 1.1 to 1.3and the conversion temperature varies from 1 223 to 1 273 K. The methane conversion rate is more than 95% when the molar ratio ofH2O to CH4 is 1.2, the conversion temperature is above 1 223 K and the conversion time is longer than 0.75 s. Kinetic model of methane conversion was proposed. All results demonstrate that the calculated values by the kinetic model accord with the experimental data well, and the error is less than 1.5%.
Hydrodynamic and Heat Transfer Model of a Gas-Liquid Microreactor
Křišťál, Jiří
2012-01-01
In this contribution we present a hydrodynamic and heat transfer model of a microreactor for a gas-liquid reaction. In the course of formulation of the model, we considered the characteristic features of the studied system – the gas-liquid flow pattern and the change in physical properties induced by pressure and temperature variation along the microreactor. Based on the input information (gas and liquid flow rates, compositions, temperatures), the model calculates the two-phase pressure dr...
Orlic, B.; Wassing, B.B.T.; Geel, C.R.
2013-01-01
A geomechanical modeling study was conducted to investigate stability of major faults during past gas production and future underground gas storage operations in a depleted gas field in the Netherlands. The field experienced induced seismicity during gas production, which was most likely caused by t
Offer a New Model to Prevent Formation of Hydrate in Gas Pipeline in Gas Refinery
Amir Samimi
2012-01-01
Water molecules by making hydrogen joint with its molecules creates holes in which quest molecules will be trapped and by creating van deer Waals joint with water molecules, hydrates crystals will be produced. Natural gas and crude oil in natural exist in underground reservoirs are in contact with water. Hydration needs condition which consists of having water in pipe line, high pressure (pressure always is high because of reinforcing gas pressure in gas transportation pipe lines), low temper...
Rudra, Prabir; Biswas, Ritabrata(Indian Institute of Engineering Sceince and Technology Shibpur (Formerly, Bengal Engineering and Science University Shibpur), 711 013, Howrah, West Bengal, India); Debnath, Ujjal
2012-01-01
In this work the collapsing process of a spherically symmetric star, made of dust cloud, in the background of dark energy is studied for two different gravity theories separately, i.e., DGP Brane gravity and Loop Quantum gravity. Two types of dark energy fluids, namely, Modified Chaplygin gas and Generalised Cosmic Chaplygin gas are considered for each model. Graphs are drawn to characterize the nature and the probable outcome of gravitational collapse. A comparative study is done between the...
Modelling and Numerical Simulation of Gas Migration in a Nuclear Waste Repository
Bourgeat, Alain; Smai, Farid
2010-01-01
We present a compositional compressible two-phase, liquid and gas, flow model for numerical simulations of hydrogen migration in deep geological radioactive waste repository. This model includes capillary effects and the gas diffusivity. The choice of the main variables in this model, Total or Dissolved Hydrogen Mass Concentration and Liquid Pressure, leads to a unique and consistent formulation of the gas phase appearance and disappearance. After introducing this model, we show computational evidences of its adequacy to simulate gas phase appearance and disappearance in different situations typical of underground radioactive waste repository.
Makashev, N. K.; Buzykin, O. G.; Asmolov, E. S.
1996-03-01
The gas flow in the system of nozzle-cut is investigated for the case of gas-assisted laser cutting of materials. The direct measurement of pressure fields is used with geometrically similar models which simulate the configuration forming during the laser cutting of metal sheet. The effect of geometric parameters of the system on the flow pattern in the kerf and on its features responsible for the cutting quality is analyzed. The choice and proper implementation of the assisting gas blowing to the cut front zone if of great importance for the gas-assisted laser cutting. There exist many various methods and facilities for the gas delivery. Nozzle configurations of many kinds and the peculiarities of free jet streams formed by them was the subject of extensive exploration. The efficiency of the nozzle under investigation was evaluated empirically or by the pressure exerted to the flat plate in the stagnation point of normally impinging jet. Recently the attention of investigators has been redirected to the details of the gas flow in the cut kerf. This activity is connected with the development of the theoretical models of gas-assisted laser cutting which serves to appreciate the role of the gas flow parameters in the phenomena responsible for the cutting efficiency. The efficiency of the gas delivery which is characterized by the cutting speed, the maximum thickness of the cut material, or the quality parameters of cut edges depends mainly on the flow features in the cut kerf. In the present paper these features are discussed closely. The results of the investigation provide the ability to choose purposefully the geometrical parameters of the nozzle facilities for laser cutter.
Thermodynamic Model for Updraft Gasifier with External Recirculation of Pyrolysis Gas
Directory of Open Access Journals (Sweden)
Fajri Vidian
2016-01-01
Full Text Available Most of the thermodynamic modeling of gasification for updraft gasifier uses one process of decomposition (decomposition of fuel. In the present study, a thermodynamic model which uses two processes of decomposition (decomposition of fuel and char is used. The model is implemented in modification of updraft gasifier with external recirculation of pyrolysis gas to the combustion zone and the gas flowing out from the side stream (reduction zone in the updraft gasifier. The goal of the model obtains the influences of amount of recirculation pyrolysis gas fraction to combustion zone on combustible gas and tar. The significant results of modification updraft are that the increases amount of recirculation of pyrolysis gas will increase the composition of H2 and reduce the composition of tar; then the composition of CO and CH4 is dependent on equivalence ratio. The results of the model for combustible gas composition are compared with previous study.
Polyakov loop and the hadron resonance gas model.
Megías, E; Arriola, E Ruiz; Salcedo, L L
2012-10-12
The Polyakov loop has been used repeatedly as an order parameter in the deconfinement phase transition in QCD. We argue that, in the confined phase, its expectation value can be represented in terms of hadronic states, similarly to the hadron resonance gas model for the pressure. Specifically, L(T)≈1/2[∑(α)g(α)e(-Δ(α)/T), where g(α) are the degeneracies and Δ(α) are the masses of hadrons with exactly one heavy quark (the mass of the heavy quark itself being subtracted). We show that this approximate sum rule gives a fair description of available lattice data with N(f)=2+1 for temperatures in the range 150 MeV
Energy Technology Data Exchange (ETDEWEB)
Al Mamon, Abdulla; Das, Sudipta [Visva-Bharati, Department of Physics, Santiniketan (India)
2015-06-15
In this present work, we try to build up a cosmological model using a non-canonical scalar field within the framework of a spatially flat FRW space-time. In this context, we have considered four different parametrizations of the equation of state parameter of the non-canonical scalar field. Under this scenario, analytical solutions for various cosmological parameters have been found out. It has been found that the deceleration parameter shows a smooth transition from a positive value to some negative value which indicates that the universe was undergoing an early deceleration followed by late time acceleration which is essential for the structure formation of the universe. With these four parametrizations, the future evolution of the models are also discussed. It has been found that one of the models (Generalized Chaplygin gas model, GCG) mimics the concordance ΛCDM in the near future, whereas two other models (CPL and JBP) diverge due to future singularity. Finally, we have studied these theoretical models with the latest datasets from SN Ia + H(z) + BAO/CMB. (orig.)
Hu, Shenyang; Burkes, Douglas E.; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie
2016-10-01
Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the formation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was developed. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn't cause the gas bubble alignment, and fast 1-D migration of interstitials along directions in the body-centered cubic U matrix causes the gas bubble alignment along directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.
Energy Technology Data Exchange (ETDEWEB)
Hu, Shenyang Y.; Burkes, Douglas; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie
2016-07-08
Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the for- mation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was devel- oped. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn’t cause the gas bubble alignment, and fast 1-D migration of interstitials along 〈110〉 directions in the body-centered cubic U matrix causes the gas bubble alignment along 〈110〉 directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.
TESTING NONSTANDARD COSMOLOGICAL MODELS WITH SNLS3 SUPERNOVA DATA AND OTHER COSMOLOGICAL PROBES
Energy Technology Data Exchange (ETDEWEB)
Li Zhengxiang; Yu Hongwei [Department of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of the Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Wu Puxun, E-mail: hwyu@hunnu.edu.cn [Center of Nonlinear Science and Department of Physics, Ningbo University, Ningbo, Zhejiang 315211 (China)
2012-01-10
We investigate the implications for some nonstandard cosmological models using data from the first three years of the Supernova Legacy Survey (SNLS3), assuming a spatially flat universe. A comparison between the constraints from the SNLS3 and those from other SN Ia samples, such as the ESSENCE, Union2, SDSS-II, and Constitution samples, is given and the effects of different light-curve fitters are considered. We find that analyzing SNe Ia with SALT2 or SALT or SiFTO can give consistent results and the tensions between different data sets and different light-curve fitters are obvious for fewer-free-parameters models. At the same time, we also study the constraints from SNLS3 along with data from the cosmic microwave background and the baryonic acoustic oscillations (CMB/BAO), and the latest Hubble parameter versus redshift (H(z)). Using model selection criteria such as {chi}{sup 2}/dof, goodness of fit, Akaike information criterion, and Bayesian information criterion, we find that, among all the cosmological models considered here ({Lambda}CDM, constant w, varying w, Dvali-Gabadadze-Porrati (DGP), modified polytropic Cardassian, and the generalized Chaplygin gas), the flat DGP is favored by SNLS3 alone. However, when additional CMB/BAO or H(z) constraints are included, this is no longer the case, and the flat {Lambda}CDM becomes preferred.
Defect trap model of gas behaviour in UO2 fuel during irradiation
International Nuclear Information System (INIS)
Fission gas behaviour is one of the central concern in the fuel design, performance and hypothetical accident analysis. The report 'Defect trap model of gas behaviour in UO2 fuel during irradiation' is the worldwide literature review of problems studied, experimental results and solutions proposed in related topics. Some of them were described in details in the report chapters. They are: anomalies in the experimental results; fission gas retention in the UO2 fuel; microstructure of the UO2 fuel after irradiation; fission gas release models; defect trap model of fission gas behaviour; fission gas release from UO2 single crystal during low temperature irradiation in terms of a defect trap model; analysis of dynamic release of fission gases from single crystal UO2 during low temperature irradiation in terms of defect trap model; behaviour of fission gas products in single crystal UO2 during intermediate temperature irradiation in terms of a defect trap model; modification of re-crystallization temperature of UO2 in function of burnup and its impact on fission gas release; apparent diffusion coefficient; formation of nanostructures in UO2 fuel at high burnup; applications of the defect trap model to the gas leaking fuel elements number assessment in the nuclear power station (VVER-PWR)
Modeling lateral gas transport in soil adjacent to an old landfill
DEFF Research Database (Denmark)
Poulsen, T.G.; Christophersen, Mette; Moldrup, P.;
2001-01-01
. An empirical expression for calculating methane oxidation rate as a function of soil temperature was developed using site-specific measurements of methane oxidation rate. The transport and degradation parameter expressions were incorporated into a numerical model for simulating landfill gas transport, using...... the gas transport model using methane oxidation rate, landfill gas pressure, and wind-induced dispersion as fitting parameters. The model was subsequently tested against independent concentration and flux data (not used in the model calibration). This yielded a prediction accuracy similar to that found......Lateral migration of landfill gases in soils surrounding old (closed) municipal landfills can lead to explosion hazards and damage to vegetation. Landfill gas production and migration is controlled by microbial activity and soil physical properties such as gas (air) permeability, gas diffusivity...
Clennell, M.B.; Hovland, M.; Booth, J.S.; Henry, P.; Winters, W.J.
1999-01-01
The stability of submarine gas hydrates is largely dictated by pressure and temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of deep marine sediments may also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our conceptual model presumes that gas hydrate behaves in a way analogous to ice in a freezing soil. Hydrate growth is inhibited within fine-grained sediments by a combination of reduced pore water activity in the vicinity of hydrophilic mineral surfaces, and the excess internal energy of small crystals confined in pores. The excess energy can be thought of as a "capillary pressure" in the hydrate crystal, related to the pore size distribution and the state of stress in the sediment framework. The base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature (nearer to the seabed) than would be calculated from bulk thermodynamic equilibrium. Capillary effects or a build up of salt in the system can expand the phase boundary between hydrate and free gas into a divariant field extending over a finite depth range dictated by total methane content and pore-size distribution. Hysteresis between the temperatures of crystallization and dissociation of the clathrate is also predicted. Growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, and lenses in muds; cements in sands) can largely be explained by capillary effects, but kinetics of nucleation and growth are also important. The formation of concentrated gas hydrates in a partially closed system with respect to material transport, or where gas can flush through the system, may lead to water depletion in the host sediment. This "freeze-drying" may be detectable through physical changes to the sediment (low water content and overconsolidation) and/or chemical anomalies in the pore waters and metastable
A sequential Monte Carlo model of the combined GB gas and electricity network
International Nuclear Information System (INIS)
A Monte Carlo model of the combined GB gas and electricity network was developed to determine the reliability of the energy infrastructure. The model integrates the gas and electricity network into a single sequential Monte Carlo simulation. The model minimises the combined costs of the gas and electricity network, these include gas supplies, gas storage operation and electricity generation. The Monte Carlo model calculates reliability indices such as loss of load probability and expected energy unserved for the combined gas and electricity network. The intention of this tool is to facilitate reliability analysis of integrated energy systems. Applications of this tool are demonstrated through a case study that quantifies the impact on the reliability of the GB gas and electricity network given uncertainties such as wind variability, gas supply availability and outages to energy infrastructure assets. Analysis is performed over a typical midwinter week on a hypothesised GB gas and electricity network in 2020 that meets European renewable energy targets. The efficacy of doubling GB gas storage capacity on the reliability of the energy system is assessed. The results highlight the value of greater gas storage facilities in enhancing the reliability of the GB energy system given various energy uncertainties. -- Highlights: •A Monte Carlo model of the combined GB gas and electricity network was developed. •Reliability indices are calculated for the combined GB gas and electricity system. •The efficacy of doubling GB gas storage capacity on reliability of the energy system is assessed. •Integrated reliability indices could be used to assess the impact of investment in energy assets
Neotectonic Model of Formation of Oil and Gas Fields and Mineragenic Role of Geodynamic Active Zones
Directory of Open Access Journals (Sweden)
I. S. Kopylov
2014-03-01
Full Text Available The article considers the importance of role of geodynamic active zones in formation of mineral deposits, their distribution, and mineragenic characteristics. Geodynamic model of formation of the oil and gas fields is developed. It reflects the evolution of formation of oil and gas fields and, after the stage of learning, allows predicting the petroleum potential of local areas. The model building procedure uses the integrated analysis of all the available information and determining the most informative indicators for forecasting the oil and gas reserves. The article presents an example of model worked out for oil and gas fields of the Perm Kray.
V. A. Lapin; V. N. Melkumov; A. N. Kobelev
2009-01-01
The mathematical model of heat transfer in vortex heat exchanger using natural gas energy which is released under decompression in gas-main pipe-lines for consumers of gas supply systems (dwellings, public and industrial buildings).
Directory of Open Access Journals (Sweden)
V. A. Lapin
2009-09-01
Full Text Available The mathematical model of heat transfer in vortex heat exchanger using natural gas energy which is released under decompression in gas-main pipe-lines for consumers of gas supply systems (dwellings, public and industrial buildings.
A Control-Oriented 0D Model of a Turbocharger Gas Stand Including Heat Transfer
Bengtsson, Mikael
2015-01-01
A turbocharger’s performance is measured in a gas stand in order to provide information of the components characteristics. The measurement procedure is a very time consuming process and it is thus desired to make it more time-efficient. To allow for development of an enhanced control strategy used during the measurements, a 0D model of a gas stand is developed. The physical gas stand components are modeled and validated against measurements, all showing a reasonable result. Turbocharger heat ...
Paulus, Sinikka; Jochheim, Hubert; Wirth, Stephan; Maier, Martin
2015-04-01
The apparent gas diffusion coefficient in soil (DS) is an important parameter describing soil aeration. It also links the profiles of soil gas concentration and soil gas flux using Fick's law. Soil gas diffusivity depends mainly on the structure of the pore system and the soil moisture status. There are several standard DS-models available that can easily be used for calculating DS. Another, more laborious option is to calibrate site specific DS models on soil core samples from the respective profile. We tested 4 standard DS models and a site-specific model and compared the resulting soil gas fluxes in two forest soils. Differences between the models were substantial. Another very important effect, however, is that standard DS models are usually derived from a single soil moisture measurement (device), that can result in an substantial offset in soil moisture estimation. The mean soil moisture content at a depth can be addressed more accurately by taking several soil cores. As a consequence, using standard DS models in combination with a single soil moisture measurement is less reliable than using site-specific models based on several soil samples.
Modeling corrosion behavior of gas tungsten arc welded titanium alloy
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The pitting corrosion characteristics of pulse TIG welded Ti-6Al-4V titanium alloy in marine environment were explained.Besides the rapid advance of titanium metallurgy, this is also due to the successful solution of problems associated with the development of titanium alloy welding. The preferred welding process of titanium alloy is frequently gas tungsten arc(GTA) welding due to its comparatively easier applicability and better economy. In the case of single pass GTA welding of thinner section of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current process. The benefit of the process is utilized to obtain better quality titanium weldments. Four factors, five levels, central composite, rotatable design matrix are used to optimize the required number of experiments. The mathematical models have been developed by response surface method(RSM). The results reveal that the titanium alloy can form a protective scale in marine environment and is resistant to pitting corrosion. Experimental results are provided to illustrate the proposed approach.
Simulation and Modeling of Flow in a Gas Compressor
Directory of Open Access Journals (Sweden)
Anna Avramenko
2015-01-01
Full Text Available The presented research demonstrates the results of a series of numerical simulations of gas flow through a single-stage centrifugal compressor with a vaneless diffuser. Numerical results were validated with experiments consisting of eight regimes with different mass flow rates. The steady-state and unsteady simulations were done in ANSYS FLUENT 13.0 and NUMECA FINE/TURBO 8.9.1 for one-period geometry due to periodicity of the problem. First-order discretization is insufficient due to strong dissipation effects. Results obtained with second-order discretization agree with the experiments for the steady-state case in the region of high mass flow rates. In the area of low mass flow rates, nonstationary effects significantly influence the flow leading stationary model to poor prediction. Therefore, the unsteady simulations were performed in the region of low mass flow rates. Results of calculation were compared with experimental data. The numerical simulation method in this paper can be used to predict compressor performance.
Mathematical modelling of the liquid atomization process by cocurrent gas flow
Arkhipov, V. A.; Boiko, V. M.; Goldin, V. D.; Maslov, E. A.; Orlov, S. E.; Poplavskiy, S. V.; Usanina, A. S.; Zharova, I. K.
2016-04-01
This paper focuses on the physical-mathematical model of liquid atomization in the spray pattern of an ejection nozzle. A flow field of a gas phase behind the nozzle section is computed using the Ansys Fluent package. Dynamics of molten metal droplets in the gas phase within a trajectory approach is calculated. Using the presented model, numerical calculation results are given.
Literature search for offsite data to improve the DWPF melter off-gas model
Energy Technology Data Exchange (ETDEWEB)
Daniel, W.E.
2000-05-04
This report documents the literature search performed and any relevant data that may help relax some of the constraints on the DWPF melter off-gas model. The objective of this task was to look for outside sources of technical data to help reduce some of the conservatism built in the DWPF melter off-gas model.
A 3-D microscale model for Co2 GasTransport in tomato leaves during photosynthesis
Ho, Q.T.; Verboven, P.; Herremans, E.; Retta, M.A.; Defraeye, T.; Nicolaï, B.M.; Yin, X.; Thapa, R.K.; Struik, P.C.
2012-01-01
Exchange of CO2 in tomato (Solanum lycopersicum L.) leaves was modelled using combined gas diffusion and photosynthesis kinetics in a real 3-D geometric representation of the cellular microstructure, obtained by synchrotron radiation X-ray microtomography. The microscale model for gas exchange accou
Teaching Pulmonary Gas Exchange Physiology Using Computer Modeling
Kapitan, Kent S.
2008-01-01
Students often have difficulty understanding the relationship of O[subscript 2] consumption, CO[subscript 2] production, cardiac output, and distribution of ventilation-perfusion ratios in the lung to the final arterial blood gas composition. To overcome this difficulty, I have developed an interactive computer simulation of pulmonary gas exchange…
Modeling studies of biological gas desulfurization under haloalkaline conditions
Klok, J.B.M.
2015-01-01
Abstract Biogas, synthesis and natural gas streams often require treatment because of the presence of gaseous hydrogen sulphide (H2S). About 25 years ago, a biotechnological gas treatment process was developed as an alternative to the conventionally applied technologies. This proces
The calculation of gas diffusion from grains in fuel modelling
International Nuclear Information System (INIS)
Further tests have been made on the variational method of calculating gas diffusion from a spherical fuel grain. The effect of varying the junction positions for two trial functions is examined and an improved correction function given. The resultant method is suitable for gas releases of 10-7 to 1.0, with estimated relative errors of < 2%. (author)
Modeling Coma Gas Jets in Comet Hale-Bopp
Lederer, S. M.; Campins, H.
2001-01-01
We present an analysis of OH, CN, and C2 jets observed in Comet Hale-Bopp. The relative contributions from and composition of the coma gas sources, and the parameters describing the active areas responsible for the gas jets will be discussed. Additional information is contained in the original extended abstract.
Modelling of transport phenomena in gas tungsten arc welding
Directory of Open Access Journals (Sweden)
A.H. Kokabi
2007-07-01
Full Text Available Purpose: Since numerical heat transfer and fluid flow models have provided significant insight into welding process and welded materials that could not been achieved otherwise, there has been an important interest in the quantitative representation of transport phenomena in the weld pool. On the other hand, the temperature and velocity distributions of the molten metal as well as the cooling rate after welding operation affect the weld geometry, the microstructure, and the mechanical properties of weld zone. This work demonstrates that the application of numerical transport phenomena can significantly add to the quantitative knowledge in welding and help the welding community in solving practical problems.Design/methodology/approach: The temperature and velocity fields are simulated using the solution of the equations of conversation of mass, energy and momentum in three-dimension and under steady-state heat transfer and fluid flow conditions.Findings: The weld pool geometry and various solidification parameters were calculated. The calculated weld pool geometries were in good agreement with the ones obtained using the experiments. The solidification parameters of G and G/R are determined. It is found that as the welding speed increases, the value of G/R at the weld pool centerline decreases.Research limitations/implications: Welding process used is this study is gas tungsten arc (GTA welding and base metal is commercial pure aluminum. This model can be investigated to simulate other materials and welding processes. Also the results of this study such as the temperature field can be used in the simulation of microstructure, mechanical properties, etc of welding zone.Originality/value: In this research the solidification parameters of G, R and G/R can be used for prediction of the solidification morphology and the scale of the solidification structure.
Energy Technology Data Exchange (ETDEWEB)
Eknes, Monika Loeland
1996-12-31
This Dr. ing. thesis deals with escalation scenarios initiated by gas explosions on offshore installations. Gas explosions is one of the major hazards to such installations. The objectives were to estimate the probability of ignition and frequency of gas explosions for gas leaks on top sides of offshore installations, and to estimate the response and resistance of components that could result in escalation if they failed. Main fields considered cover risk analysis methodology, gas explosions, simplified escalation models, evaluation of structural consequences, case studies, and guidelines. 107 refs., 33 figs., 33 tabs.
Gas generation in deep radioactive waste repositories: a review of processes, controls and models
International Nuclear Information System (INIS)
Gas generation within radioactive waste repositories may produce two general problems: 1) breaching of engineered and natural barriers due to high gas pressures; 2) enhanced radiological risk due to reduced groundwater travel times and/or greater aqueous or gaseous activities reaching the biosphere. As a result of these concerns, HMIP must be aware of the current status of relevant research, together with any associated deficiencies. This report addresses the current status of published research on near-field gas generation from worldwide sources and documents the important gas generating processes, the factors controlling them and models available to simulate them. In the absence of suitable models, outline technical specifications for corrosion and microbial degradation gas generation models are defined and the deficiencies in the current understanding of gas generation are highlighted; a conceptual research programme to correct these deficiencies is presented. (author)
A petroleum system model for gas hydrate deposits in northern Alaska
Lorenson, T.D.; Collett, Timothy S.; Wong, Florence L.
2011-01-01
Gas hydrate deposits are common on the North Slope of Alaska around Prudhoe Bay, however the extent of these deposits is unknown outside of this area. As part of a United States Geological Survey (USGS) and the Bureau of Land Management (BLM) gas hydrate research collaboration, well cutting and mud gas samples have been collected and analyzed from mainly industry-drilled wells on the Alaska North Slope for the purpose of prospecting for gas hydrate deposits. On the Alaska North Slope, gas hydrates are now recognized as an element within a petroleum systems approach or TPS (Total Petroleum System). Since 1979, 35 wells have been samples from as far west as Wainwright to Prudhoe Bay in the east. Geochemical studies of known gas hydrate occurrences on the North Slope have shown a link between gas hydrate and more deeply buried conventional oil and gas deposits. Hydrocarbon gases migrate from depth and charge the reservoir rock within the gas hydrate stability zone. It is likely gases migrated into conventional traps as free gas, and were later converted to gas hydrate in response to climate cooling concurrent with permafrost formation. Gas hydrate is known to occur in one of the sampled wells, likely present in 22 others based gas geochemistry and inferred by equivocal gas geochemistry in 11 wells, and absent in one well. Gas migration routes are common in the North Slope and include faults and widespread, continuous, shallowly dipping permeable sand sections that are potentially in communication with deeper oil and gas sources. The application of this model with the geochemical evidence suggests that gas hydrate deposits may be widespread across the North Slope of Alaska.
A capillary network model for coupled gas and water flow in engineered barriers
International Nuclear Information System (INIS)
A two-dimensional capillary network model for gas migration through a water-saturated medium is presented. The model is an extension of previously developed capillary bundle models, and provides a discrete alternative to classical continuum Darcy models. The need for such an alternative has become apparent from recent experimental results that suggest gas migrates through low permeability water-saturated media via a small number of preferential pathways
Modelling combustion reactions for gas flaring and its resulting emissions
Directory of Open Access Journals (Sweden)
O. Saheed Ismail
2016-07-01
Full Text Available Flaring of associated petroleum gas is an age long environmental concern which remains unabated. Flaring of gas maybe a very efficient combustion process especially steam/air assisted flare and more economical than utilization in some oil fields. However, it has serious implications for the environment. This study considered different reaction types and operating conditions for gas flaring. Six combustion equations were generated using the mass balance concept with varying air and combustion efficiency. These equations were coded with a computer program using 12 natural gas samples of different chemical composition and origin to predict the pattern of emission species from gas flaring. The effect of key parameters on the emission output is also shown. CO2, CO, NO, NO2 and SO2 are the anticipated non-hydrocarbon emissions of environmental concern. Results show that the quantity and pattern of these chemical species depended on percentage excess/deficiency of stoichiometric air, natural gas type, reaction type, carbon mass content, impurities, combustion efficiency of the flare system etc. These emissions degrade the environment and human life, so knowing the emission types, pattern and flaring conditions that this study predicts is of paramount importance to governments, environmental agencies and the oil and gas industry.
Semi-gas kinetics model for performance modeling of flowing chemical oxygen-iodine lasers (COIL)
Institute of Scientific and Technical Information of China (English)
GAO Zhi; HU Limin; SHEN Yiqing
2004-01-01
A semi-gas kinetics (SGK) model for performance analyses of flowing chemical oxygen-iodine laser (COIL) is presented. In this model, the oxygen-iodine reaction gas flow is treated as a continuous medium, and the effect of thermal motions of particles of different laser energy levels on the performances of the COIL is included and the velocity distribution function equations are solved by using the double-parameter perturbational method. For a premixed flow, effects of different chemical reaction systems, different gain saturation models and temperature, pressure, yield of excited oxygen, iodine concentration and frequency-shift on the performances of the COIL are computed, and the calculated output power agrees well with the experimental data. The results indicate that the power extraction of the SGK model considering 21 reactions is close to those when only the reversible pumping reaction is considered, while different gain saturation models and adjustable parameters greatly affect the output power, the optimal threshold gain range, and the length of power extraction.
Analysis of Maisotsenko open gas turbine power cycle with a detailed air saturator model
International Nuclear Information System (INIS)
Highlights: • Developed an accurate air saturator model. • Performed sensitivity analysis for Maisotsenko gas turbine cycle (MGTC). • Performed comparative analysis for MGTC and simple gas turbine with reheat (SGTR) and humid air turbine (HAT). • MGTC has higher efficiency and specific work output with at high compressor pressure ratio. • Optimum air saturator water mass flow rate is calculated. - Abstract: With ever increasing cost of fossil fuels and natural gas, the improvement in gas turbine power cycle efficiency is needed due to the tremendous savings in fuel consumption. Water/steam injection is considered as one of the most popular power augmentation techniques because of its significant impact on the gas turbine performance. One of the recently suggested evaporative gas turbine cycles is the Maisotsenko open cycle for gas turbine power generation. In this paper, detailed thermodynamic analysis of this cycle is investigated with a thorough air saturator model. A comparative analysis is carried out to signify the advantages and disadvantages of Maisotsenko gas turbine cycle (MGTC) as compared with humid air gas turbine cycles. MGTC performance is evaluated based on a simple recuperated gas turbine cycle. In addition, sensitivity analysis is performed to investigate the effect of different operating parameters on the overall cycle performance. Finally, integrating an air saturator instead of a conventional heat exchanger in recuperated gas turbine cycles enhances the power plant performance such that an efficiency enhancement of 7% points and net specific work output augmentation of 44.4% are obtained
An electricity price model with consideration to load and gas price effects
Institute of Scientific and Technical Information of China (English)
黄民翔; 陶小虎; 韩祯祥
2003-01-01
Some characteristics of the electricity load and prices are studied, and the relationship between electricity prices and gas (fnel) prices is analyzed in this paper. Because electricity prices are strongly depen-dent on load and gas prices, the authors constructed a model for electricity prices based on the effects of these two factors; and used the Geometric Mean Reversion Brownian Motion (GMRBM) model to describe the electricity load process, and a Geometric Brownian Motion(GBM) model to describe the gas prices ; deduced the price stochastic process model based on the above load model and gas price model. This paper also presents methods for parameters estimation, and proposes some methods to solve the model.
Predict gas emission quantity of mining coal face with improved Grey Markov model
Energy Technology Data Exchange (ETDEWEB)
Tao, Y.; Xu, J.; Li, S. [Chongqing University, Chongqing (China)
2007-04-15
In order to predict the absolute quantity of gas emission from a mining coal face, the improved grey model GM (1.1) was built based on dealing with the initial data of the gas emission quantity of mining coal face by natural logarithm. The improved Grey Markov prediction mode was built through uniting the improved grey mode (1.1) and the Markov model. This model was used to analyze and predict the gas emission quantity of the first mining coal face in Zhongling Mine, China. The forecast result of the Grey Markov predication model has better fitting precision and correct dependability. It can be generally employed. 6 refs., 5 tabs.
A mathematical model for flow of gas-liquid mixture in a vertical pipe
Dirdal, Inger Karin
2015-01-01
A one-dimensional mathematical model for the ascend velocity to a Taylor bubble consisting of gas in a two-phase flow of gas and liquid in vertical pipes is derived. This model illustrates different effects of two-phase flow in pipes from a numerical approach. The model is based on the conservation laws of mass and momentum for an initial gas slug located on the closed of bottom in a pipe which is filled with stagnant liquid. The model is investigated at laboratory scale where assumpt...
EIA model documentation: Documentation of the Oil and Gas Supply Module (OGSM)
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-01-01
The purpose of this report is to define the objectives of the Oil and Gas Supply Model (OGSM), to describe the model`s basic approach, and to provide detail on how the model works. This report is intended as a reference document for model analysts, users, and the public. Projected production estimates of US crude oil and natural gas are based on supply functions generated endogenously within National Energy Modeling System (NEMS) by the OGSM. OGSM encompasses domestic crude oil and natural gas supply by both conventional and nonconventional recovery techniques. Nonconventional recovery includes enhanced oil recovery (EOR), and unconventional gas recovery (UGR) from tight gas formations, Devonian shale and coalbeds. Crude oil and natural gas projects are further disaggregated by geographic region. OGSM projects US domestic oil and gas supply for six Lower 48 onshore regions, three offshore regions, and Alaska. The general methodology relies on forecasted drilling expenditures and average drilling costs to determine exploratory and developmental drilling levels for each region and fuel type. These projected drilling levels translate into reserve additions, as well as a modification of the production capacity for each region. OGSM also represents foreign trade in natural gas, imports and exports by entry region.
`Gas cushion' model and hydrodynamic boundary conditions for superhydrophobic textures
Nizkaya, Tatiana V; Vinogradova, Olga I
2014-01-01
Superhydrophobic Cassie textures with trapped gas bubbles reduce drag, by generating large effective slip, which is important for a variety of applications that involve a manipulation of liquids at the small scale. Here we discuss how the dissipation in the gas phase of textures modifies their friction properties and effective slip. We propose an operator method, which allows us the mapping of the flow in the gas subphase to a local slip boundary condition at the liquid/gas interface. The determined uniquely local slip length depends on the viscosity contrast and underlying topography, and can be immediately used to evaluate an effective slip of the texture. Beside Cassie surfaces our approach is valid for Wenzel textures, where a liquid follows the surface relief, as well as for rough surfaces impregnated by a low-viscosity `lubricant'. These results provide a framework for the rational design of textured surfaces for numerous applications.
Multicomponent seismic forward modeling of gas hydrates beneath the seafloor
Institute of Scientific and Technical Information of China (English)
Yang Jia-Jia; He Bing-Shou; Zhang Jian-Zhong
2014-01-01
We investigated the effect of microscopic distribution modes of hydrates in porous sediments, and the saturation of hydrates and free gas on the elastic properties of saturated sediments. We simulated the propagation of seismic waves in gas hydrate-bearing sediments beneath the seafloor, and obtained the common receiver gathers of compressional waves (P-waves) and shear waves (S-waves). The numerical results suggest that the interface between sediments containing gas hydrates and free gas produces a large-amplitude bottom-simulating reflector. The analysis of multicomponent common receiver data suggests that ocean-bottom seismometers receive the converted waves of upgoing P-and S-waves, which increases the complexity of the wavefield record.
DEFF Research Database (Denmark)
Pierart Vásquez, Fabián Gonzalo
the critical speeds. In order to overcome such limitations, a mechatronic device has been proposed as a possible solution. This device named "hybrid active radial gas bearing" or simply "active gas bearing", combines an aerodynamic gas journal bearing with piezoelectrically controlled injectors. In the present...... the effect of external pressurization. In order to validate the theoretical model, a test rig is used, which consists of a flexible rotor supported by a ball bearing and the active gas bearing. This thesis has three main focuses and original contributions: Firstly, contribute to improving a existing...... theoretical model for active gas bearings, with special attention to the modelling of the injection system. Secondly, experimentally validate the improved mathematical model in terms of static properties (journal equilibrium position and resulting aerodynamic forces) and dynamic properties (natural...
A planning model for offshore natural gas transmission
Edson K. Iamashita; Frederico Galaxe; José Arica
2008-01-01
This paper aims at new approach to solve complex integrated offshore gas planning problems, defining the best transmission strategy for a system with a large number of platforms interconnected between them and with delivery points through a complex gas pipeline network (which can be cycled). The problem is formulated as a large quadratic mixed-integer problem, where non-convexity and non-differentiability is found. Because the complexity of the problem, it is proposed a heuristic, in the cont...
Hydrogen gas explosions in pipelines - modeling and experimental investigations
Knudsen, Vegeir
2007-01-01
Gas explosions in closed pipes with a single obstacle have been investigated both numerically and experimentally. Most of the work is related to hydrogen and air mixtures, but other fuels have also been used. At the present time there does not exist a software tool or a numerical method that single-handedly can cover the whole range of phenomena in gas explosions. Computational fluid dynamics is also a developing field, even for fluid flow without chemical reactions. The objective of this wor...
Modeling Hydrates and the Gas Hydrate Markup Language
Wang, Weihua; Moridis, George; Wang, Runqiang; Xiao, Yun; Li, Jianhui
2007-01-01
Natural gas hydrates, as an important potential fuels, flow assurance hazards, and possible factors initiating the submarine geo-hazard and global climate change, have attracted the interest of scientists all over the world. After two centuries of hydrate research, a great amount of scientific data on gas hydrates has been accumulated. Therefore the means to manage, share, and exchange these data have become an urgent task. At present, metadata (Markup Language) is recognized as one of the mo...
A Method to Obtain Gas-PDMS Membrane Interaction Parameters for UNIQUAC Model
Institute of Scientific and Technical Information of China (English)
LIN Dongjie; DING Zhongwei; LIU Liying; MA Runyu
2013-01-01
The recovery or capture of one or more components from gas mixture by membrane separation has become a research focus in recent years.This study investigates the gas-membrane solution equilibrium,for which Henry's law is not applicable if the gas phase is a mixture.This problem can be solved by using UNIQUAC model to calculate the activity coefficient of gas dissolved in the membrane.A method was proposed in this study to obtain the gas-membrane interaction parameter for UNIQUAC model.By the experiments of gas permeation through polydimethylsiloxane PDMS membrane,the solubility coefficients of some gases (N2,CO2,CH4) were measured.Through non-linear fitting UNIQUAC model to the experimental results from this study and in literature (H2,O2,C3H8),the gas-membrane interaction parameters for these gases were obtained.Based on these parameters,the activity coefficients of the dissolved gas were calculated by UNIQUAC model,and their values agree well with the experimental data.These results confirm the feasibility and effectiveness of the proposed method,which makes it possible to better predict gas-membrane solution equilibrium.
The water-induced linear reduction gas diffusivity model extended to three pore regions
DEFF Research Database (Denmark)
Chamindu, Deepagoda; De Jonge, Lis Wollesen; Kawamoto, Ken;
2015-01-01
An existing gas diffusivity model developed originally for sieved, repacked soils was extended to characterize gas diffusion in differently structured soils and functional pore networks. A gas diffusivity-derived pore connectivity index was used as a measure of soil structure development....... Characterization of soil functional pore structure is an essential prerequisite to understand key gas transport processes in variably saturated soils in relation to soil ecosystems, climate, and environmental services. In this study, the water-induced linear reduction (WLR) soil gas diffusivity model originally...... developed for sieved, repacked soil was extended to two simple, linear regions to characterize gas diffusion and functional pore-network structure also in intact, structured soil systems. Based on the measurements in soils with markedly different pore regions, we showed that the two linear regions can...
Gas-dynamic modeling of gas flow in semi-closed space including channel surface fluctuation
Petrova, E. N.; Salnikov, A. F.
2016-10-01
In this article frequency interaction conditions, that affect on acoustic stability of solid-propellant rocket engine (SPRE) action, and its influence on level change of pressure fluctuations with longitudinal gas oscillations in the combustion chamber (CC) are considered. Studies of CC in the assessment of the operating rocket engine stability are reported.
Integrated field modelling[Oil and gas fields
Energy Technology Data Exchange (ETDEWEB)
Nazarian, Bamshad
2002-07-01
This research project studies the feasibility of developing and applying an integrated field simulator to simulate the production performance of an entire oil or gas field. It integrates the performance of the reservoir, the wells, the chokes, the gathering system, the surface processing facilities and whenever applicable, gas and water injection systems. The approach adopted for developing the integrated simulator is to couple existing commercial reservoir and process simulators using available linking technologies. The simulators are dynamically linked and customised into a single hybrid application that benefits from the concept of open software architecture. The integrated field simulator is linked to an optimisation routine developed based on the genetic algorithm search strategies. This enables optimisation of the system at field level, from the reservoir to the process. Modelling the wells and the gathering network is achieved by customising the process simulator. This study demonstrated that the integrated simulation improves current capabilities to simulate the performance of the entire field and optimise its design. This is achieved by evaluating design options including spread and layout of the wells and gathering system, processing alternatives, reservoir development schemes and production strategies. Effectiveness of the integrated simulator is demonstrated and tested through several field-level case studies that discuss and investigate technical problems relevant to offshore field development. The case studies cover topics such as process optimisation, optimum tie-in of satellite wells into existing process facilities, optimal well location and field layout assessment of a high pressure high temperature deepwater oil field. Case study results confirm the viability of the total field simulator by demonstrating that the field performance simulation and optimal design were obtained in an automated process with treasonable computation time. No significant
Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation
Institute of Scientific and Technical Information of China (English)
LI; Zhihui; ZHANG; Hanxin; FU; Song
2005-01-01
The gas-kinetic unified algorithm using Boltzmann model equation have been extended and developed to solve the micro-scale gas flows in Poiseuille-like micro-channels from Micro-Electro-Mechanical Systems (MEMS). The numerical modeling of the gas kinetic boundary conditions suitable for micro-scale gas flows is presented. To test the present method, the classical Couette flows with various Knudsen numbers, the gas flows from short microchannels like plane Poiseuille and the pressure-driven gas flows in two-dimensional short microchannels have been simulated and compared with the approximate solutions of the Boltzmann equation, the related DSMC results, the modified N-S solutions with slip-flow boundary theory, the gas-kinetic BGK-Burnett solutions and the experimental data. The comparisons show that the present gas-kinetic numerical algorithm using the mesoscopic Boltzmann simplified velocity distribution function equation can effectively simulate and reveal the gas flows in microchannels. The numerical experience indicates that this method may be a powerful tool in the numerical simulation of micro-scale gas flows from MEMS.
Natural gas generation model and its response in accumulated fluids in the Yinggehai basin
Institute of Scientific and Technical Information of China (English)
郝芳; 邹华耀; 黄保家
2003-01-01
The natural gases found in the Yinggehai basin have nitrogen gas content ranging from 3.5% to 35%, and carbon dioxide content ranging from 0.1% to 93%. The nitrogen and CO2 contents show a wide variation even in the same gas field. The natural gas generation and evolution model has been established based on the relationship among the contents of nitrogen, carbon dioxide and hydrocarbon gases in the discovered gas fields, and the results of simulation experiments. The thickness of the Tertiary and Quaternary in the Yinggehai basin is over 17 km, and gas generation stages from diagenesis (microbial methane) to metamorphism have been developed. Nitrogen in this basin is organic in origin, and has been generated mainly in the catagenetic stage, roughly synchronous with hydrocarbon gases. Carbon dioxide is mainly inorganic in origin, and has been generated from high-temperature decomposition of carbonates in the metamorphic stage. The Dongfang gas field shows strong inter-reservoir compositional heterogeneities, and different gas reservoirs have recorded the products of gas generation at different stages. It has been confirmed that the complexity in natural gas composition in the Yinggehai basin is the combined results of multi-stage natural gas generation and multi-stage gas injection and accumulation.
Simulation of Water Level Fluctuations in a Hydraulic System Using a Coupled Liquid-Gas Model
Directory of Open Access Journals (Sweden)
Chao Wang
2015-08-01
Full Text Available A model for simulating vertical water level fluctuations with coupled liquid and gas phases is presented. The Preissmann implicit scheme is used to linearize the governing equations for one-dimensional transient flow for both liquid and gas phases, and the linear system is solved using the chasing method. Some classical cases for single liquid and gas phase transients in pipelines and networks are studied to verify that the proposed methods are accurate and reliable. The implicit scheme is extended using a dynamic mesh to simulate the water level fluctuations in a U-tube and an open surge tank without consideration of the gas phase. Methods of coupling liquid and gas phases are presented and used for studying the transient process and interaction between the phases, for gas phase limited in a chamber and gas phase transported in a pipeline. In particular, two other simplified models, one neglecting the effect of the gas phase on the liquid phase and the other one coupling the liquid and gas phases asynchronously, are proposed. The numerical results indicate that the asynchronous model performs better, and are finally applied to a hydropower station with surge tanks and air shafts to simulate the water level fluctuations and air speed.
Coupled THCM Modeling of Gas Hydrate Bearing Sediments
Sanchez, M. J.; Gai, X., Sr.; Shastri, A.; Santamarina, J. C.
2014-12-01
Gas hydrates are crystalline clathrate compounds made of water and a low molecular gas, like methane. Gas hydrates are generally present in oil-producing areas and in permafrost regions. Methane hydrate deposits can lead to large-scale submarine slope failures, blowouts, platform foundation failures, and borehole instability. Gas hydrates constitute also an attractive source of energy as they are estimated to contain very large reserves of methane. Hydrate formation, dissociation and methane production from hydrate bearing sediments are coupled Thermo-Hydro-Mechanical (THM) processes that involve, amongst other, exothermic formation and endothermic dissociation of hydrate and ice phases, mixed fluid flow and large changes in fluid pressure. A comprehensive THM formulation is briefly presented here. Momentum balance, mass balance and energy balance equations take into consideration the interaction among all phases (i.e. solid, liquid, gas, hydrates and ice) and mechanical equilibrium. Constitutive equations describe the intrinsic THM behavior of the sediment. Simulation results conducted for hydrate bearing sediments subjected to boundary conditions highlight the complex interaction among THM processes in hydrate bearing sediments.
Modelling of landfill gas adsorption with bottom ash for utilization of renewable energy
Energy Technology Data Exchange (ETDEWEB)
Miao, Chen
2011-10-06
Energy crisis, environment pollution and climate change are the serious challenges to people worldwide. In the 21st century, human being is trend to research new technology of renewable energy, so as to slow down global warming and develop society in an environmentally sustainable method. Landfill gas, produced by biodegradable municipal solid waste in landfill, is a renewable energy source. In this work, landfill gas utilization for energy generation is introduced. Landfill gas is able to produce hydrogen by steam reforming reactions. There is a steam reformer equipment in the fuel cells system. A sewage plant of Cologne in Germany has run the Phosphoric Acid Fuel Cells power station with biogas for more than 50,000 hours successfully. Landfill gas thus may be used as fuel for electricity generation via fuel cells system. For the purpose of explaining the possibility of landfill gas utilization via fuel cells, the thermodynamics of landfill gas steam reforming are discussed by simulations. In practice, the methane-riched gas can be obtained by landfill gas purification and upgrading. This work investigate a new method for upgrading-landfill gas adsorption with bottom ash experimentally. Bottom ash is a by-product of municipal solid waste incineration, some of its physical and chemical properties are analysed in this work. The landfill gas adsorption experimental data show bottom ash can be used as a potential adsorbent for landfill gas adsorption to remove CO{sub 2}. In addition, the alkalinity of bottom ash eluate can be reduced in these adsorption processes. Therefore, the interactions between landfill gas and bottom ash can be explained by series reactions accordingly. Furthermore, a conceptual model involving landfill gas adsorption with bottom ash is developed. In this thesis, the parameters of landfill gas adsorption equilibrium equations can be obtained by fitting experimental data. On the other hand, these functions can be deduced with theoretical approach
Donovan, S M; Bateson, T; Gronow, J R; Voulvoulis, N
2010-03-15
The pretreatment of the biodegradable components of municipal solid waste (MSW) has been suggested as a method of reducing landfill gas emissions. Mechanical biological treatment (MBT) is the technology being developed to provide this reduction in biodegradability, either as an alternative to source segregated collection or for dealing with residual MSW which still contains high levels of biodegradable waste. The compost like outputs (CLOs) from MBT plants can be applied to land as a soil conditioner; treated to produce a solid recovered fuel (SRF) or landfilled. In this study the impact that landfilling of these CLOs will have on gaseous emissions is investigated. It is important that the gas production behaviour of landfilled waste is well understood, especially in European member states where the mitigation of gaseous emissions is a legal requirement. Results of an experiment carried out to characterise the biodegradable components of pretreated biowastes have been used with the GasSim model to predict the long term emissions behaviour of landfills accepting these wastes, in varying quantities. The landfill directive also enforces the mitigation of potential methane emissions from landfills, and the ability of landfill operators to capture gaseous emissions from low emitting landfills of the future is discussed, as well as new techniques that could be used for the mitigation of methane generation. PMID:20092874
An Explosive Range Model Based on the Gas Composition, Temperature, and Pressure during Air Drilling
Directory of Open Access Journals (Sweden)
Xiangyu Fan
2016-01-01
Full Text Available Air drilling is low cost and effectively improves the penetration rate and causes minimal damage to liquid-sensitive pay zones. However, there is a potential downhole explosion when combustible gas mixed with drilling fluid reaches the combustible condition. In this paper, based on the underground combustion mechanism, an explosive range calculation model is established. This model couples the state equation and the empirical formula method, which considers the inert gas content, pressure, mixed gas component, and temperature. The result shows that increase of the inert gas content narrows the explosive range, while increase of the gas temperature and pressure improves the explosive range. A case in Chongqing, China, is used to validate the explosive range calculation model.
Dynamic modeling of fixed-bed adsorption of flue gas using a variable mass transfer model
Energy Technology Data Exchange (ETDEWEB)
Park, Jehun; Lee, Jae W. [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)
2016-02-15
This study introduces a dynamic mass transfer model for the fixed-bed adsorption of a flue gas. The derivation of the variable mass transfer coefficient is based on pore diffusion theory and it is a function of effective porosity, temperature, and pressure as well as the adsorbate composition. Adsorption experiments were done at four different pressures (1.8, 5, 10 and 20 bars) and three different temperatures (30, 50 and 70 .deg. C) with zeolite 13X as the adsorbent. To explain the equilibrium adsorption capacity, the Langmuir-Freundlich isotherm model was adopted, and the parameters of the isotherm equation were fitted to the experimental data for a wide range of pressures and temperatures. Then, dynamic simulations were performed using the system equations for material and energy balance with the equilibrium adsorption isotherm data. The optimal mass transfer and heat transfer coefficients were determined after iterative calculations. As a result, the dynamic variable mass transfer model can estimate the adsorption rate for a wide range of concentrations and precisely simulate the fixed-bed adsorption process of a flue gas mixture of carbon dioxide and nitrogen.
Atmosphere behavior in gas-closed mouse-algal systems - An experimental and modelling study
Averner, M. M.; Moore, B., III; Bartholomew, I.; Wharton, R.
1984-01-01
A NASA-sponsored research program initiated using mathematical modelling and laboratory experimentation aimed at examining the gas-exchange characteristics of artificial animal/plant systems closed to the ambient atmosphere is studied. The development of control techniques and management strategies for maintaining the atmospheric levels of carbon dioxide and oxygen at physiological levels is considered. A mathematical model simulating the behavior of a gas-closed mouse-algal system under varying environmental conditions is described. To verify and validate the model simulations, an analytical system with which algal growth and gas exchange characteristics can be manipulated and measured is designed, fabricated, and tested. The preliminary results are presented.
A Dynamic Model of the Combined Electricity and Natural Gas Markets
DEFF Research Database (Denmark)
Jenkins, Sandra; Annaswamy, Anuradha M.; Hansen, Jacob;
2015-01-01
With the shale gas revolution, coal retirements, environmental regulations, and increasing renewable energy resources, the interdependency of natural gas and electricity has grown significantly. Interdependency challenges, such as mismatched market schedules and disparate market operations, require...... quantitative modeling in order to garner insights into the effectiveness of various solutions. In this paper, a quantitative model with a dynamic market mechanism is proposed to evaluate the effects of the fuel uncertainty of natural gas-fired power plants on Social Welfare. The results of the model show...
A simple model of gas flow in a porous powder compact
Energy Technology Data Exchange (ETDEWEB)
Shugard, Andrew D.; Robinson, David B.
2014-04-01
This report describes a simple model for ideal gas flow from a vessel through a bed of porous material into another vessel. It assumes constant temperature and uniform porosity. Transport is treated as a combination of viscous and molecular flow, with no inertial contribution (low Reynolds number). This model can be used to fit data to obtain permeability values, determine flow rates, understand the relative contributions of viscous and molecular flow, and verify volume calibrations. It draws upon the Dusty Gas Model and other detailed studies of gas flow through porous media.
Field validation of a dynamic model for an MFL ILI tool in gas pipelines
Energy Technology Data Exchange (ETDEWEB)
Botros, K. K. [Nova Chemical Research and Technology Centre, Calgary, Alberta, (Canada); Golshan, H. [TransCanada Pipelines Ltd, Calgary, Alberta, (Canada)
2010-07-01
The pipeline industry uses pigs for numerous operations such as dewatering, cleaning and inspection. Pigs used on gas pipelines are subject to stringent parameters. For example, the inclination in the section of the pipeline affects driving pressure and velocity. The study investigated the behaviour and performance of pigs in gas pipelines. A dynamic model was developed for the movement of pigs in an inclined pipeline section, taking into consideration the effects of gas properties, wall friction, by-pass flow for speed control, differential pressure across the pig, seal efficiency and gap flows. Field data from pigging a 158 km NPS 18 gas pipeline on TransCanada's pipeline system in Alberta are used for field validation of the model. It is found that the developed model is stable. The comparison between field data and model results demonstrated the accuracy of the model, within +/- 8% of St. Deviation.
Uncertainty and sensitivity analysis of fission gas behavior in engineering-scale fuel modeling
International Nuclear Information System (INIS)
The role of uncertainties in fission gas behavior calculations as part of engineering-scale nuclear fuel modeling is investigated using the BISON fuel performance code and a recently implemented physics-based model for the coupled fission gas release and swelling. Through the integration of BISON with the DAKOTA software, a sensitivity analysis of the results to selected model parameters is carried out based on UO2 single-pellet simulations covering different power regimes. The parameters are varied within ranges representative of the relative uncertainties and consistent with the information from the open literature. The study leads to an initial quantitative assessment of the uncertainty in fission gas behavior modeling with the parameter characterization presently available. Also, the relative importance of the single parameters is evaluated. Moreover, a sensitivity analysis is carried out based on simulations of a fuel rod irradiation experiment, pointing out a significant impact of the considered uncertainties on the calculated fission gas release and cladding diametral strain. The results of the study indicate that the commonly accepted deviation between calculated and measured fission gas release by a factor of 2 approximately corresponds to the inherent modeling uncertainty at high fission gas release. Nevertheless, higher deviations may be expected for values around 10% and lower. Implications are discussed in terms of directions of research for the improved modeling of fission gas behavior for engineering purposes
Development and test of an evaluation protocol for heavy gas dispersion models
Duijm, N.J.; Carissimo, B.; Mercer, A.; Bartholome, C.; Giesbrecht, H.
1997-01-01
In order to improve the quality (i.e. fitness-for-purpose) of models used to describe the atmospheric dispersion of heavy gas, an evaluation methodology has been developed and tested through a small evaluation exercise. This activity was carried out by the Heavy Gas Dispersion Expert Group, which wa
MATHEMATIC MODELING IN ANALYSIS OF BIO-GAS PURIFICATION FROM CARBON DIOXIDE
Directory of Open Access Journals (Sweden)
Y. A. Losiouk
2009-01-01
Full Text Available The paper considers a possibility to involve bio-gas generated at testing grounds of hard domestic garbage in power supply system in the Republic of Belarus. An example of optimization using mathematical modeling of plant operation which is used for bio-gas enrichment is given in the paper.
Models for Gas Hydrate-Bearing Sediments Inferred from Hydraulic Permeability and Elastic Velocities
Lee, Myung W.
2008-01-01
Elastic velocities and hydraulic permeability of gas hydrate-bearing sediments strongly depend on how gas hydrate accumulates in pore spaces and various gas hydrate accumulation models are proposed to predict physical property changes due to gas hydrate concentrations. Elastic velocities and permeability predicted from a cementation model differ noticeably from those from a pore-filling model. A nuclear magnetic resonance (NMR) log provides in-situ water-filled porosity and hydraulic permeability of gas hydrate-bearing sediments. To test the two competing models, the NMR log along with conventional logs such as velocity and resistivity logs acquired at the Mallik 5L-38 well, Mackenzie Delta, Canada, were analyzed. When the clay content is less than about 12 percent, the NMR porosity is 'accurate' and the gas hydrate concentrations from the NMR log are comparable to those estimated from an electrical resistivity log. The variation of elastic velocities and relative permeability with respect to the gas hydrate concentration indicates that the dominant effect of gas hydrate in the pore space is the pore-filling characteristic.
Geochemical modelling of hydrogen gas migration in an unsaturated bentonite buffer
Sedighi, M.; Thomas, H.R.; Al Masum, S.; Vardon, P.J.; Nicholson, D.; Chen, Q.
2014-01-01
This paper presents an investigation of the transport and fate of hydrogen gas through compacted bentonite buffer. Various geochemical reactions that may occur in the multiphase and multicomponent system of the unsaturated bentonite buffer are considered. A reactive gas transport model, developed wi
multiscale modelling of gas transport in fruit during controlled atmosphere storage
Ho, Quang Tri
2008-01-01
Contents Acknowledgements iii Nederlandse samenvatting v Abstract ix Contents xiii Symbols and Abbreviations xix 1 General introduction 1 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Respiration and postharvest storage technology . . . . . . . . . . 3 1.3 Gas transport routes in fruit tissue . . . . . . . . . . . . . . . . . 6 1.4 CA storage disorders of fruit . . . . . . . . . . . . . . . . . . . . 8 1.5 Modelling of gas ...
Molecular interpretation of nonclassical gas dynamics of dense vapors under the van der Waals model
Colonna, P.; Guardone, A.
2006-01-01
The van der Waals polytropic gas model is used to investigate the role of attractive and repulsive intermolecular forces and the influence of molecular complexity on the possible nonclassical gas dynamic behavior of vapors near the liquid-vapor saturation curve. The decrease of the sound speed upon
Rodrigues, M.A.M.; Cone, J.W.; Ferreira, L.M.M.; Blok, M.C.; Guedes, C.
2009-01-01
In vitro and in situ studies were conducted to evaluate the influence of different mathematical models, used to fit gas production profiles of 15 feedstuffs, on estimates of nylon bag organic matter (OM) degradation kinetics. The gas production data were fitted to Exponential, Logistic, Gompertz and
MATHEMATIC MODELING IN ANALYSIS OF BIO-GAS PURIFICATION FROM CARBON DIOXIDE
Y. A. Losiouk; Pleskach, A. V.
2014-01-01
The paper considers a possibility to involve bio-gas generated at testing grounds of hard domestic garbage in power supply system in the Republic of Belarus. An example of optimization using mathematical modeling of plant operation which is used for bio-gas enrichment is given in the paper.
Mathematical model of diffusion-limited gas bubble dynamics in unstirred tissue with finite volume.
Srinivasan, R Srini; Gerth, Wayne A; Powell, Michael R
2002-02-01
Models of gas bubble dynamics for studying decompression sickness have been developed by considering the bubble to be immersed in an extravascular tissue with diffusion-limited gas exchange between the bubble and the surrounding unstirred tissue. In previous versions of this two-region model, the tissue volume must be theoretically infinite, which renders the model inapplicable to analysis of bubble growth in a finite-sized tissue. We herein present a new two-region model that is applicable to problems involving finite tissue volumes. By introducing radial deviations to gas tension in the diffusion region surrounding the bubble, the concentration gradient can be zero at a finite distance from the bubble, thus limiting the tissue volume that participates in bubble-tissue gas exchange. It is shown that these deviations account for the effects of heterogeneous perfusion on gas bubble dynamics, and are required for the tissue volume to be finite. The bubble growth results from a difference between the bubble gas pressure and an average gas tension in the surrounding diffusion region that explicitly depends on gas uptake and release by the bubble. For any given decompression, the diffusion region volume must stay above a certain minimum in order to sustain bubble growth.
3D numerical modeling of shale gas stimulation and seisimicity
Shahid, A.S.; Wassing, B.B.T.; Verga, F.; Fokker, P.A.
2013-01-01
The economic production from shale gas reservoir depends on the success of hydraulic stimulation, which is aimed at the creation of a permeable complex fracture network. This is achieved by the reactivation of a natural fracture network; however, the reactivation may be accompanied by unwanted seism
Modelling and Identification for Control of Gas Bearings
DEFF Research Database (Denmark)
Theisen, Lukas Roy Svane; Niemann, Hans Henrik; Santos, Ilmar;
2015-01-01
Gas bearings are popular for their high speed capabilities, low friction and clean operation, but suffer from poor damping, which poses challenges for safe operation in presence of disturbances. Enhanced damping can be achieved through active lubrication techniques using feedback control laws. Su...
Polyakov loop, Hadron Resonance Gas Model and Thermodynamics of QCD
Megias, E.; Arriola, E. Ruiz; Salcedo, L. L.
2013-01-01
We summarize recent results on the hadron resonance gas description of QCD. In particular, we apply this approach to describe the equation of state and the vacuum expectation value of the Polyakov loop in several representations. Ambiguities related to exactly which states should be included are discussed.
Polyakov loop, hadron resonance gas model and thermodynamics of QCD
Energy Technology Data Exchange (ETDEWEB)
Megías, E. [Grup de Física Teòrica and IFAE, Departament de Física, Universitat Autònoma de Barcelona, Bellaterra E-08193 Barcelona (Spain); Arriola, E. Ruiz; Salcedo, L. L. [Departamento de Física Atómica, Molecular y Nuclear and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, E-18071 Granada (Spain)
2014-11-11
We summarize recent results on the hadron resonance gas description of QCD. In particular, we apply this approach to describe the equation of state and the vacuum expectation value of the Polyakov loop in several representations. Ambiguities related to exactly which states should be included are discussed.
Modelling of far-field gas migration from a deep radioactive waste repository
International Nuclear Information System (INIS)
In assessing the post-closure safety of a deep radioactive waste repository, it is necessary to show that gas generated within the repository can migrate away, through the far-field geology, without affecting repository safety. This paper discusses the contribution of various mechanisms to gas migration through the far field; for example, diffusion of dissolved gas versus gas-phase movement, and bubble flow versus formation of a connected gas stream. It outlines different approaches to modelling gas movement from a repository, with simple semi-analytical models furnishing physical insights into the factors controlling gas migration in the absence of directly applicable experimental data, and more comprehensive numerical computations allowing the exploration of more detailed behaviour when appropriate data is obtained. If gas can induce groundwater movement, this could accelerate the transport of water-borne contaminants. Processes by which this could occur are noted, and the current status of work on possible effects of gas migration on groundwater movement in fractured hard rocks is indicated. 14 refs., 4 figs
Uncertainty and sensitivity analysis of fission gas behavior in engineering-scale fuel modeling
Energy Technology Data Exchange (ETDEWEB)
Pastore, Giovanni, E-mail: Giovanni.Pastore@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Swiler, L.P., E-mail: LPSwile@sandia.gov [Optimization and Uncertainty Quantification, Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185-1318 (United States); Hales, J.D., E-mail: Jason.Hales@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Novascone, S.R., E-mail: Stephen.Novascone@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Perez, D.M., E-mail: Danielle.Perez@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Spencer, B.W., E-mail: Benjamin.Spencer@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Luzzi, L., E-mail: Lelio.Luzzi@polimi.it [Politecnico di Milano, Department of Energy, Nuclear Engineering Division, via La Masa 34, I-20156 Milano (Italy); Van Uffelen, P., E-mail: Paul.Van-Uffelen@ec.europa.eu [European Commission, Joint Research Centre, Institute for Transuranium Elements, Hermann-von-Helmholtz-Platz 1, D-76344 Karlsruhe (Germany); Williamson, R.L., E-mail: Richard.Williamson@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States)
2015-01-15
The role of uncertainties in fission gas behavior calculations as part of engineering-scale nuclear fuel modeling is investigated using the BISON fuel performance code with a recently implemented physics-based model for fission gas release and swelling. Through the integration of BISON with the DAKOTA software, a sensitivity analysis of the results to selected model parameters is carried out based on UO{sub 2} single-pellet simulations covering different power regimes. The parameters are varied within ranges representative of the relative uncertainties and consistent with the information in the open literature. The study leads to an initial quantitative assessment of the uncertainty in fission gas behavior predictions with the parameter characterization presently available. Also, the relative importance of the single parameters is evaluated. Moreover, a sensitivity analysis is carried out based on simulations of a fuel rod irradiation experiment, pointing out a significant impact of the considered uncertainties on the calculated fission gas release and cladding diametral strain. The results of the study indicate that the commonly accepted deviation between calculated and measured fission gas release by a factor of 2 approximately corresponds to the inherent modeling uncertainty at high fission gas release. Nevertheless, significantly higher deviations may be expected for values around 10% and lower. Implications are discussed in terms of directions of research for the improved modeling of fission gas behavior for engineering purposes.
DEFF Research Database (Denmark)
Poulsen, T.G.; Christophersen, Mette; Moldrup, P.;
2003-01-01
were applied: (I) State-space analysis was used to identify relations between gas flux and short-term (hourly) variations in atmospheric pressure. (II) A numerical gas transport model was fitted to the data and used to quantify short-term impacts of variations in atmospheric pressure, volumetric soil......-water content, soil gas permeability, soil gas diffusion coefficients, and biological CH4 degradation rate upon landfill gas concentration and fluxes in the soil. Fluxes and concentrations were found to be most sensitive to variations in volumetric soil water content, atmospheric pressure variations and gas...... permeability whereas variations in CH4 oxidation rate and molecular coefficients had less influence. Fluxes appeared to be most sensitive to atmospheric pressure at intermediate distances from the landfill edge. Also overall CH4 fluxes out of the soil over longer periods (years) were largest during periods...
Observations from using models to fit the gas production of varying volume test cells and landfills.
Lamborn, Julia
2012-12-01
Landfill operators are looking for more accurate models to predict waste degradation and landfill gas production. The simple microbial growth and decay models, whilst being easy to use, have been shown to be inaccurate. Many of the newer and more complex (component) models are highly parameter hungry and many of the required parameters have not been collected or measured at full-scale landfills. This paper compares the results of using different models (LANDGEM, HBM, and two Monod models developed by the author) to fit the gas production of laboratory scale, field test cell and full-scale landfills and discusses some observations that can be made regarding the scalability of gas generation rates. The comparison of these results show that the fast degradation rate that occurs at laboratory scale is not replicated at field-test cell and full-scale landfills. At small scale, all the models predict a slower rate of gas generation than actually occurs. At field test cell and full-scale a number of models predict a faster gas generation than actually occurs. Areas for future work have been identified, which include investigations into the capture efficiency of gas extraction systems and into the parameter sensitivity and identification of the critical parameters for field-test cell and full-scale landfill predication.
Territorial and branch associations of the oil and gas complex and the trends in their modeling
Energy Technology Data Exchange (ETDEWEB)
Chudnovskaya, S.N.
1983-01-01
Tendencies in the development of the Western Siberian region are studied on the basis of economic and mathematical modeling. The basic interrelations for an expanded system of the oil and gas complex are examined.
A Physics-Based Starting Model for Gas Turbine Engines Project
National Aeronautics and Space Administration — The objective of this proposal is to demonstrate the feasibility of producing an integrated starting model for gas turbine engines using a new physics-based...
We have conducted numerical simulation studies to assess the potential for injection-induced fault reactivation and notable seismic events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned toward conditions usually encountered in the Marce...
Modified Diffusion Flux Model for Analysis of Turbulent Gas-Particle Two-Phase Flows
Institute of Scientific and Technical Information of China (English)
YANG Ruichang; ZHOU Weiduo; FUKUDA Kenji; JU Zejian; SHANG Zhi
2005-01-01
A modified diffusion flux model (DFM) was developed to analyze turbulent multi-dimensional gas-particle two-phase flows. In the model, the solid particles move in a modified acceleration field, , which includes the effects of various forces on the particles as if all the forces have the same effect on the particles as the gravity. The accelerations due to various forces are then taken into account in the calculation of the diffusion velocities of the solid particles in the gas-particle two-phase flow. The DFM was used to numerically simulate the gas-solid two-phase flow behind a vertical backward-facing step. The numerical simulation compared well with experimental data and numerical results using both the k-ε-Ap and k-ε-kp two-fluid models available in the literature. The comparison shows that the modified diffusion flux model correctly simulates the turbulent gas-particle two-phase flow.
Pizza or Pancake? Formation Models of Gas Escape Biosignatures in Terrestrial and Martian Sediments
Bonaccorsi, R.; Fairen, A. G.; Baker, L.; McKay, C. P.; Willson, D.
2016-05-01
Fine-grained sedimentary hollowed structures were imaged in Gale Crater, but no biomarkers identified to support biology. Our observation-based (gas escape) terrestrial model could inform on possible martian paleoenvironments at time of formation.
Analysis of Stability for Gas-Kinetic Non-Local Traffic Model
Institute of Scientific and Technical Information of China (English)
SUN Xi-Ming; DONG Yu-Jie
2006-01-01
@@ The gas-kinetic non-local traffic model is improved by taking into account the relative velocity of the correlated vehicles. The stability of different relaxation time modes is analytically investigated with the perturbation method.
Lagrangian approach to modeling unsteady gas-liquid flow in a well
Liapidevskii, V. Yu; Tikhonov, V.
2016-06-01
The purpose of this paper is to develop a numerical method of solving the problem of evolution of the finite gas volume that entered in a liquid flow at a set flow rate. The drift- flux model is used as gas-liquid mixture equations. The velocities of both phases, mixture and gas, are related by the Zuber-Findlay equation which coefficients depend on flow regime and gas void fraction. Lagrangian coordinates are used to simplify the initial equations. The numerical solution scheme is proposed. The numerical solution of the Riemann problem is verified by comparison with the exact self-similar solution. The model and numerical method efficiency is illustrated by examples of gas kick calculations in a vertical well.
Modeling of Aerobrake Ballute Stagnation Point Temperature and Heat Transfer to Inflation Gas
Bahrami, Parviz A.
2012-01-01
A trailing Ballute drag device concept for spacecraft aerocapture is considered. A thermal model for calculation of the Ballute membrane temperature and the inflation gas temperature is developed. An algorithm capturing the most salient features of the concept is implemented. In conjunction with the thermal model, trajectory calculations for two candidate missions, Titan Explorer and Neptune Orbiter missions, are used to estimate the stagnation point temperature and the inflation gas temperature. Radiation from both sides of the membrane at the stagnation point and conduction to the inflating gas is included. The results showed that the radiation from the membrane and to a much lesser extent conduction to the inflating gas, are likely to be the controlling heat transfer mechanisms and that the increase in gas temperature due to aerodynamic heating is of secondary importance.
Modeling of gas demand using degree-day concept: case study for Ankara
International Nuclear Information System (INIS)
The demand for natural gas is rapidly increasing in Turkey, as it is in the rest of the world. However, natural gas reserves and production are rather limited in Turkey.The bulk of the Turkish gas demand is met by imports. Russia currently accounts for 69% of Turkey's gas supplies. Physical shortages might occur; supplies for industrial production and household consumption could temporarily run short. Also, fluctuations in consumption might occur due to climatic reasons or peak daily industrial energy demand. Underground gas storage is a necessity in order to regulate these seasonal, daily, and hourly fluctuations. In order to effectively design and utilize underground gas storage, it is necessary to identify the market requirements. In this study, Ankara was chosen as a pilot region due to its strategical importance of being the capital city of Turkey, and a wide range of marketing surveys for the last seven years was performed. All of the factors influencing the gas consumption and the relationships between these factors were analyzed. How does gas demand behave in extremely cold weather? How does the industrial part of the city act in the consumption behavior? What are the plans of the Municipality of Ankara, responsible for the execution of the natural gas distribution project in Ankara? A model was developed based on degree-day (DD) concept, including the annual number of customers, average DDs, and the usage per customer. A history matching study was performed to verify the results of the model with the measured consumption data for the last seven years. Comparisons showed that the calculated consumption by DD model and measured daily consumption were in good agreement. Finally, by using the developed approach, the gas demand was forecasted for Ankara up to 2005. The results of this study can be used to design underground gas storage facility near Ankara. (author)
Security of supply and retail competition in the European gas market. Some model-based insights
International Nuclear Information System (INIS)
In this paper, we analyze the impact of uncertain disruptions in gas supply upon gas retailer contracting behavior and consequent price and welfare implications in a gas market characterized by long-term gas contracts using a static Cournot model. In order to most realistically describe the economical situation, our representation divides the market into two stages: the upstream market that links, by means of long-term contracts, producers in exporting countries (Russia, Algeria, etc.) to local retailers who bring gas to the consuming countries to satisfy local demands in the downstream market. Disruption costs are modeled using short-run demand functions. First we mathematically develop a general model and write the associated KKT conditions, then we propose some case studies, under iso-elasticity assumptions, for the long-short-run inverse-demand curves in order to predict qualitatively and quantitatively the impacts of supply disruptions on Western European gas trade. In the second part, we study in detail the German gas market of the 1980's to explain the supply choices of the German retailer, and we derive interesting conclusions and insights concerning the amounts and prices of natural gas brought to the market. The last part of the paper is dedicated to a study of the Bulgarian gas market, which is greatly dependent on the Russian gas supplies and hence very sensitive to interruption risks. Some interesting conclusions are derived concerning the necessity to economically regulate the market, by means of gas amounts control, if the disruption probability is high enough. (authors)
International Nuclear Information System (INIS)
Innovative applications of natural gas can increase the sale of natural gas, support energy companies in the development of commercial activities, and contribute to energy efficiency measures. The Dutch natural gas trading company Gasunie supports those developments by investigating the market potential of innovative gas appliances. Use is made of the so-called Phase Model for Market Introduction, developed by Kea Consult
Alaska North Slope regional gas hydrate production modeling forecasts
Wilson, S.J.; Hunter, R.B.; Collett, T.S.; Hancock, S.; Boswell, R.; Anderson, B.J.
2011-01-01
A series of gas hydrate development scenarios were created to assess the range of outcomes predicted for the possible development of the "Eileen" gas hydrate accumulation, North Slope, Alaska. Production forecasts for the "reference case" were built using the 2002 Mallik production tests, mechanistic simulation, and geologic studies conducted by the US Geological Survey. Three additional scenarios were considered: A "downside-scenario" which fails to identify viable production, an "upside-scenario" describes results that are better than expected. To capture the full range of possible outcomes and balance the downside case, an "extreme upside scenario" assumes each well is exceptionally productive.Starting with a representative type-well simulation forecasts, field development timing is applied and the sum of individual well forecasts creating the field-wide production forecast. This technique is commonly used to schedule large-scale resource plays where drilling schedules are complex and production forecasts must account for many changing parameters. The complementary forecasts of rig count, capital investment, and cash flow can be used in a pre-appraisal assessment of potential commercial viability.Since no significant gas sales are currently possible on the North Slope of Alaska, typical parameters were used to create downside, reference, and upside case forecasts that predict from 0 to 71??BM3 (2.5??tcf) of gas may be produced in 20 years and nearly 283??BM3 (10??tcf) ultimate recovery after 100 years.Outlining a range of possible outcomes enables decision makers to visualize the pace and milestones that will be required to evaluate gas hydrate resource development in the Eileen accumulation. Critical values of peak production rate, time to meaningful production volumes, and investments required to rule out a downside case are provided. Upside cases identify potential if both depressurization and thermal stimulation yield positive results. An "extreme upside
Atmosphere Behavior in Gas-Closed Mouse-Algal Systems: An Experimental and Modelling Study
Averner, M. M.; Moore, B., III; Bartholomew, I.; Wharton, R.
1985-01-01
A dual approach of mathematical modelling and laboratory experimentation aimed at examining the gas exchange characteristics of artificial animal/plant systems closed to the ambient atmosphere was initiated. The development of control techniques and management strategies for maintaining the atmospheric levels of carbon dioxide and oxygen at physiological levels is examined. A mathematical model simulating the atmospheric behavior in these systems was developed and an experimental gas closed system was constructed. These systems are described and preliminary results are presented.
HFC-134a refrigerant gas hydrate formation process and RIN model
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
In this paper, the macroscopic visualization experiments of HFC-134a refrigerant gas hydrate formation are investigated. According to the macroscopic photos and Mori's microscopic photos of HFC-134a hydrate formation process, the mechanism of gas hydrate formation is analyzed.A random inducement nucleation model is presented to describe the hydrate formation process. The factors affecting the fractal growth dimension in the model, such as step,branch increment and angle, are discussed.``
Thuan, T. X.; Hart, M. H.; Ostriker, J. P.
1975-01-01
The two basic approaches of physical theory required to calculate the evolution of a galactic system are considered, taking into account stellar evolution theory and the dynamics of a gas-star system. Attention is given to intrinsic (stellar) physics, extrinsic (dynamical) physics, and computations concerning the fractionation of an initial mass of gas into stars. The characteristics of a 'standard' model and its variants are discussed along with the results obtained with the aid of these models.
Numerical Analysis of Turbulent Combustion in a Model Swirl Gas Turbine Combustor
Directory of Open Access Journals (Sweden)
Ali Cemal Benim
2016-01-01
Full Text Available Turbulent reacting flows in a generic swirl gas turbine combustor are investigated numerically. Turbulence is modelled by a URANS formulation in combination with the SST turbulence model, as the basic modelling approach. For comparison, URANS is applied also in combination with the RSM turbulence model to one of the investigated cases. For this case, LES is also used for turbulence modelling. For modelling turbulence-chemistry interaction, a laminar flamelet model is used, which is based on the mixture fraction and the reaction progress variable. This model is implemented in the open source CFD code OpenFOAM, which has been used as the basis for the present investigation. For validation purposes, predictions are compared with the measurements for a natural gas flame with external flue gas recirculation. A good agreement with the experimental data is observed. Subsequently, the numerical study is extended to syngas, for comparing its combustion behavior with that of natural gas. Here, the analysis is carried out for cases without external flue gas recirculation. The computational model is observed to provide a fair prediction of the experimental data and predict the increased flashback propensity of syngas.
A New Model for Gas Transfer and Storage in a Permeable Volcanic Edifice
Collinson, A. D.; Neuberg, J.
2011-12-01
There is a marked contrast between the behaviour of a volcano in an open system compared to one which is closed. It is therefore essential to understand degassing, to appreciate how much gas is lost and where. Previous studies by a variety of scientists have led to the accumulation of data via field evidence from both active and fossil volcanoes (Stasiuk et al., 1996), laboratory experiments (Moore et al., 1994) and conceptual modelling, in which Darcy's law has become increasingly applicable (Eichelberger et al., 1986; Edmonds et al., 2003). Of particular interest for this study, is the effect different permeabilities have on the degree and pattern of the gas flux. A new method has been devised to investigate gas transport and storage in a permeable volcanic edifice. The continuity equation and Darcy's law are amalgamated to derive a partial differential equation which is solved using a finite element method to obtain the gas pressure. The associated pressure gradient is then used within Darcy's law to calculate the gas flux. The properties of the gas are described by the ideal gas law. The strength of this method is that it allows the modelling of two and three dimensional structures both in stationary equilibrium and as a time dependent progression. A geometry is created and the pressure and permeabilites incorporated into the model as boundary and domain conditions respectively. The aim of the model is to investigate how variable permeability and pressure gradients influence the gas flux, for example highly permeable cracks in the dome, or impermeable layers within the volcanic structure. We also use this gas model to complement the model of Neuberg et al. (2006) in which brittle failure of the conduit-wall boundary is used as a trigger mechanism of low-frequency earthquakes. The associated behaviour of the gas in response to the brittle failure is simulated in our model by increasing the permeability through a narrow zone at the boundary between the conduit
Modification of Godunov computation method for modeling non-stationary gas-liquid flow
Energy Technology Data Exchange (ETDEWEB)
Kantsyrev, B.L. [Research Institute for Nuclear Power Plant Operation, Moscow (Russian Federation)
2007-07-01
It is proposed to modify the Godunov computation method for modeling the gas-liquid bubble flow. The hydrodynamic equations set for the gas-liquid bubble flow have wave properties which does not conflict with the Zuber-Findley regularity. The equation set belongs to a hyperbolic class and is consistent with Cauchy problem. Within this model a transition from the bubble flow to the gas piston flow is interpreted as a wave process, which corresponds to a transition from the hyperbolic equations set to a parabolic one. A specific solution of a Riemann problem has been obtained.
Modification of Godunov computation method for modeling non-stationary gas-liquid flow
International Nuclear Information System (INIS)
It is proposed to modify the Godunov computation method for modeling the gas-liquid bubble flow. The hydrodynamic equations set for the gas-liquid bubble flow have wave properties which does not conflict with the Zuber-Findley regularity. The equation set belongs to a hyperbolic class and is consistent with Cauchy problem. Within this model a transition from the bubble flow to the gas piston flow is interpreted as a wave process, which corresponds to a transition from the hyperbolic equations set to a parabolic one. A specific solution of a Riemann problem has been obtained
Gas Clumping in Self-Consistent Reionisation Models
Finlator, K; Özel, F; Davé, R
2012-01-01
We use a suite of cosmological hydrodynamic simulations including a self-consistent treatment for inhomogeneous reionisation to study the impact of galactic outflows and photoionisation heating on the volume-averaged recombination rate of the intergalactic medium (IGM). By incorporating an evolving ionising escape fraction and a treatment for self-shielding within Lyman limit systems, we have run the first simulations of "photon-starved" reionisation scenarios that simultaneously reproduce observations of the abundance of galaxies, the optical depth to electron scattering of cosmic microwave background photons \\tau, and the effective optical depth to Lyman\\alpha absorption at z=5. We confirm that an ionising background reduces the clumping factor C by more than 50% by smoothing moderately-overdense (\\Delta=1--100) regions. Meanwhile, outflows increase clumping only modestly. The clumping factor of ionised gas is much lower than the overall baryonic clumping factor because the most overdense gas is self-shield...
Building gas markets. US versus EU, market versus market model
International Nuclear Information System (INIS)
The liberalization process of the gas sector has showed that the reasoning to introduce competition in gas industries separates the services in at least two groups: commodities with relatively low transaction costs, and hence suitable to short-term market coordination, and network services which concentrate most of the specificities related to the physical flows. However, the way to coordinate such network services is still under debate. In this view, in USA specific services are coordinated through long-term contracts, whereas the EU regulatory frame socializes the costs of the network services. In this paper, we develop a general analysis of the major consequences of this fundamental regulatory choice. In addition, we build on such analysis to explain the differences among the current proposals to design the coming European Internal Market.
Gas transfer model to design a ventilator for neonatal total liquid ventilation.
Bonfanti, Mirko; Cammi, Antonio; Bagnoli, Paola
2015-12-01
The study was aimed to optimize the gas transfer in an innovative ventilator for neonatal Total Liquid Ventilation (TLV) that integrates the pumping and oxygenation functions in a non-volumetric pulsatile device made of parallel flat silicone membranes. A computational approach was adopted to evaluate oxygen (O2) and carbon dioxide (CO2) exchanges between the liquid perfluorocarbon (PFC) and the oxygenating gas, as a function of the geometrical parameter of the device. A 2D semi-empirical model was implemented to this purpose using Comsol Multiphysics to study both the fluid dynamics and the gas exchange in the ventilator. Experimental gas exchanges measured with a preliminary prototype were compared to the simulation outcomes to prove the model reliability. Different device configurations were modeled to identify the optimal design able to guarantee the desired gas transfer. Good agreement between experimental and simulation outcomes was obtained, validating the model. The optimal configuration, able to achieve the desired gas exchange (ΔpCO2 = 16.5 mmHg and ΔpO2 = 69 mmHg), is a device comprising 40 modules, 300 mm in length (total exchange area = 2.28 m(2)). With this configuration gas transfer performance is satisfactory for all the simulated settings, proving good adaptability of the device.
Gas transfer model to design a ventilator for neonatal total liquid ventilation.
Bonfanti, Mirko; Cammi, Antonio; Bagnoli, Paola
2015-12-01
The study was aimed to optimize the gas transfer in an innovative ventilator for neonatal Total Liquid Ventilation (TLV) that integrates the pumping and oxygenation functions in a non-volumetric pulsatile device made of parallel flat silicone membranes. A computational approach was adopted to evaluate oxygen (O2) and carbon dioxide (CO2) exchanges between the liquid perfluorocarbon (PFC) and the oxygenating gas, as a function of the geometrical parameter of the device. A 2D semi-empirical model was implemented to this purpose using Comsol Multiphysics to study both the fluid dynamics and the gas exchange in the ventilator. Experimental gas exchanges measured with a preliminary prototype were compared to the simulation outcomes to prove the model reliability. Different device configurations were modeled to identify the optimal design able to guarantee the desired gas transfer. Good agreement between experimental and simulation outcomes was obtained, validating the model. The optimal configuration, able to achieve the desired gas exchange (ΔpCO2 = 16.5 mmHg and ΔpO2 = 69 mmHg), is a device comprising 40 modules, 300 mm in length (total exchange area = 2.28 m(2)). With this configuration gas transfer performance is satisfactory for all the simulated settings, proving good adaptability of the device. PMID:26475493
Mathematical model of diffusion-limited evolution of multiple gas bubbles in tissue.
Srinivasan, R Srini; Gerth, Wayne A; Powell, Michael R
2003-04-01
Models of gas bubble dynamics employed in probabilistic analyses of decompression sickness incidence in man must be theoretically consistent and simple, if they are to yield useful results without requiring excessive computations. They are generally formulated in terms of ordinary differential equations that describe diffusion-limited gas exchange between a gas bubble and the extravascular tissue surrounding it. In our previous model (Ann. Biomed. Eng. 30: 232-246, 2002), we showed that with appropriate representation of sink pressures to account for gas loss or gain due to heterogeneous blood perfusion in the unstirred diffusion region around the bubble, diffusion-limited bubble growth in a tissue of finite volume can be simulated without postulating a boundary layer across which gas flux is discontinuous. However, interactions between two or more bubbles caused by competition for available gas cannot be considered in this model, because the diffusion region has a fixed volume with zero gas flux at its outer boundary. The present work extends the previous model to accommodate interactions among multiple bubbles by allowing the diffusion region volume of each bubble to vary during bubble evolution. For given decompression and tissue volume, bubble growth is sustained only if the bubble number density is below a certain maximum.
Modelling the effect of gas injections on the stability of asphaltene-containing crude oils
Energy Technology Data Exchange (ETDEWEB)
Zhang, X.; Moorwood, T. [Infochem, Munich (Germany); Merino Garcia, D.; Pena Diez, J.L. [Repsol YPF, Madrid (Spain)
2008-07-01
In oil fields where asphaltene deposits occur, they present major remediation problems and can halt production due to flow blockage. Crude oils which precipitate asphaltenes generally contain both asphaltene molecules and lighter resin molecules. Resins are thought to solvate the asphaltene molecules, thus stabilizing the solution, while light gases have the opposite effect. In order to model asphaltene phase behaviour, it is important to understand the impact of adding gas to asphaltene-containing crudes. This study presented several experimental investigations of gas injection into asphaltene-containing crudes. The trends of asphaltene destabilization were discussed. The injection gases ranged from pure gases to a gas condensate. The data were modelled using a conventional equation of state together with an extra term that considered the association between asphaltene molecules and their solvation by resins. Since the model could simultaneously described the gas, oil and asphaltene phases, it was possible to calculate phase stability and phase equilibria. However, a different model had to be used to obtain the gas-oil equilibrium because the use of solubility parameters only allows the stability of the asphaltene phase to be calculated. The model correctly predicted that the gases will promote asphaltene precipitation. In its original form, the model tended to over-predict the trend. The optimal parameter values needed to represent all the available experimental data were determined. The extent to which the effect of gas injection on asphaltenes can be predicted was then discussed.
An integrated transient model for simulating the operation of natural gas transport systems
Pambour, Kwabena Addo; Bolado-Lavin, Ricardo; Dijkema, Gerard P. J.
2016-01-01
This paper presents an integrated transient hydraulic model that describes the dynamic behavior of natural gas transport systems (GTS). The model includes sub models of the most important facilities comprising a GTS, such as pipelines, compressor stations, pressure reduction stations, underground ga
Some insights in novel risk modeling of liquefied natural gas carrier maintenance operations
Nwaoha, T. C.; John, Andrew
2016-06-01
This study discusses the analysis of various modeling approaches and maintenance techniques applicable to the Liquefied Natural Gas (LNG) carrier operations in the maritime environment. Various novel modeling techniques are discussed; including genetic algorithms, fuzzy logic and evidential reasoning. We also identify the usefulness of these algorithms in the LNG carrier industry in the areas of risk assessment and maintenance modeling.
A hybrid model to predict the onset of gas entrainment with surface tension effects
International Nuclear Information System (INIS)
The onset of gas entrainment, in a single downward oriented discharge from a stratified gas-liquid region with was modeled. The assumptions made in the development of the model reduced the problem to that of a potential flow. The discharge was modeled as a point-sink. Through use of the Kelvin-Laplace equation the model included the effects of surface tension. The resulting model required further knowledge of the flow field, specifically the dip radius of curvature prior to the onset of gas entrainment. The dip shape and size was investigated experimentally and correlations were provided to characterize the dip in terms of the discharge Froude number. The experimental correlation was used in conjunction with the theoretical model to predict the critical height. The results showed that by including surface tension effects the predicted critical height showed excellent agreement with experimental data. Surface tension reduces the critical height through the Bond number
Energy Technology Data Exchange (ETDEWEB)
Elsharkawy, A.M.; Foda, S.G. [Kuwait University, Safat (Kuwait). Petroleum Engineering Dept.
1998-03-01
Currently, two approaches are being used to predict the changes in retrograde gas condensate composition and estimate the pressure depletion behavior of gas condensate reservoirs. The first approach uses the equation of states whereas the second uses empirical correlations. Equations of states (EOS) are poor predictive tools for complex hydrocarbon systems. The EOS needs adjustment against phase behavior data of reservoir fluid of known composition. The empirical correlation does not involve numerous numerical computations but their accuracy is limited. This study presents two general regression neural network (GRNN) models. The first model, GRNNM1, is developed to predict dew point pressure and gas compressibility at dew point using initial composition of numerous samples while the second model, GRNNM2, is developed to predict the changes in well stream effluent composition at any stages of pressure depletion. GRNNM2 can also be used to determine the initial reservoir fluid composition using dew point pressure, gas compressibility at dew point, and reservoir temperature. These models are based on analysis of 142 sample of laboratory studies of constant volume depletion (CVD) for gas condensate systems forming a total of 1082 depletion stages. The database represents a wide range of gas condensate systems obtained worldwide. The performance of the GRNN models has been compared to simulation results of the equation of state. The study shows that the proposed general regression neural network models are accurate, valid, and reliable. These models can be used to forecast CVD data needed for many reservoir engineering calculations in case laboratory data is unavailable. The GRNN models save computer time involved in EOS calculations. The study also show that once these models are properly trained they can be used to cut expenses of frequent sampling and laborious experimental CVD tests required for gas condensate reservoirs. 55 refs., 13 figs., 6 tabs.
Development of a natural gas systems analysis model (GSAM). Annual report, July 1994--June 1995
Energy Technology Data Exchange (ETDEWEB)
NONE
1995-07-01
North American natural gas markets have changed dramatically over the past decade. A competitive, cost-conscious production, transportation, and distribution system has emerged from the highly regulated transportation wellhead pricing structure of the 1980`s. Technology advances have played an important role in the evolution of the gas industry, a role likely to expand substantially as alternative fuel price competition and a maturing natural gas resource base force operators to maximize efficiency. Finally, significant changes continue in regional gas demand patterns, industry practices, and infrastructure needs. As the complexity of the gas system grows so does the need to evaluate and plan for alternative future resource, technology, and market scenarios. Traditional gas modeling systems focused solely on the econometric aspects of gas marketing. These systems, developed to assess a regulated industry at a high level of aggregation, rely on simple representation of complex and evolving systems, thereby precluding insight into how the industry will change over time. Credible evaluations of specific policy initiatives and research activities require a different approach. Also, the mounting pressure on energy producers from environmental compliance activities requires development of analysis that incorporates relevant geologic, engineering, and project economic details. The objective of policy, research and development (R&D), and market analysis is to integrate fundamental understanding of natural gas resources, technology, and markets to fully describe the potential of the gas resource under alternative future scenarios. This report summarizes work over the past twelve months on DOE Contract DE-AC21-92MC28138, Development of a Natural Gas Systems Analysis Model (GSAM). The products developed under this project directly support the Morgantown Energy Technology Center (METC) in carrying out its natural gas R&D mission.
Assessment of Condensation Models in SPACE in the Presence of Noncondensable Gas
Energy Technology Data Exchange (ETDEWEB)
Kim, Ji Hun; Yang, Jin Hwa; Park, Goon Cherl [Seoul National University, Seoul (Korea, Republic of)
2011-10-15
The condensation phenomena play an important role in heat removal of reactor coolant system, especially the PRHRS(Passive Residual Heat Removal System) in SMART. During the PRHRS operation, nitrogen gas might be generated because of evaporation in the steam generator. It will act as a noncondensable gas in the condensation heat exchanger. It is known that even a small amount of noncondensable gas can reduce the condensation heat transfer considerably. SPACE adopted condensation models through the experimental studies for those condition. In order to analyze the heat transfer in the steam generator of next generation NPP by using SPACE, verification of its condensation model is essential. In this study, assessment of condensation models in the SPACE in the presence of noncondensable gas is performed by validation with a benchmark experiment
Modelling for Control of Exhaust Gas Recirculation on Large Diesel Engines
DEFF Research Database (Denmark)
Hansen, Jakob Mahler; Zander, Claes-Göran; Pedersen, Nicolai;
2013-01-01
models. While literature is rich on four-stroke automotive engines, this paper considers two-stroke engines and develops a non-linear dynamic model of the exhaust gas system. Parameters are determined by system identication. The paper uses black-box nonlinear model identication and modelling from rst...... principles followed by parameter identication and compares the results of these approaches. The paper performs a validation against experimental data from a test engine and presents a linearised model for EGR control design....
Experimental studies and model analysis of noble gas fractionation in porous media
Ding, Xin; Kennedy, B. Mack.; Evans, William C.; Stonestrom, David A.
2016-01-01
The noble gases, which are chemically inert under normal terrestrial conditions but vary systematically across a wide range of atomic mass and diffusivity, offer a multicomponent approach to investigating gas dynamics in unsaturated soil horizons, including transfer of gas between saturated zones, unsaturated zones, and the atmosphere. To evaluate the degree to which fractionation of noble gases in the presence of an advective–diffusive flux agrees with existing theory, a simple laboratory sand column experiment was conducted. Pure CO2 was injected at the base of the column, providing a series of constant CO2 fluxes through the column. At five fixed sampling depths within the system, samples were collected for CO2 and noble gas analyses, and ambient pressures were measured. Both the advection–diffusion and dusty gas models were used to simulate the behavior of CO2 and noble gases under the experimental conditions, and the simulations were compared with the measured depth-dependent concentration profiles of the gases. Given the relatively high permeability of the sand column (5 ´ 10−11 m2), Knudsen diffusion terms were small, and both the dusty gas model and the advection–diffusion model accurately predicted the concentration profiles of the CO2 and atmospheric noble gases across a range of CO2 flux from ?700 to 10,000 g m−2 d−1. The agreement between predicted and measured gas concentrations demonstrated that, when applied to natural systems, the multi-component capability provided by the noble gases can be exploited to constrain component and total gas fluxes of non-conserved (CO2) and conserved (noble gas) species or attributes of the soil column relevant to gas transport, such as porosity, tortuosity, and gas saturation.
Struck, Curtis
2008-01-01
The discovery of partially ionized, diffuse gas and dust clouds at kiloparsec scale distances above the central planes of edge-on galaxy discs was unexpected. Further observations showing that this gas has rotation velocities approximately 10-20% lower than those in the central plane were even more surprising. Simple thermal support and ballistic fountain models have failed to explain these mysteries. Here we present results of hydrodynamic models, with cooling and heating from star formation. We find that in models with star formation generated stochastically across the disc an extraplanar gas layer is generated as long as the star formation is sufficiently strong. However, this gas rotates at nearly the same speed as the mid-plane gas. We then studied models with imposed spiral or bar waves in the disc. EDIG (extended or extraplanar diffuse interstellar gas) layers were also generated in these models, but primarily over the wave regions, not over the entire disc. Because of this partial coverage, the EDIG g...
Kiel, J.H.A.; De Prins, W.; Swaaij, van, W.P.M.
1992-01-01
A one-dimensional, two-phase dispersed plug flow model has been developed to describe the steady-state performance of a relatively new type of reactor, the gas-solid trickle flow reactor (GSTFR). In this reactor, an upward-flowing gas phase is contacted with as downward-flowing dilute solids phase over an inert packing. The model is derived from the separate mass heat balances for both the gas and (porous) solids phases for the case of a non-catalytic gas-solid reaction, which is first-order ...
A planning model for offshore natural gas transmission
Directory of Open Access Journals (Sweden)
Edson K. Iamashita
2008-04-01
Full Text Available This paper aims at new approach to solve complex integrated offshore gas planning problems, defining the best transmission strategy for a system with a large number of platforms interconnected between them and with delivery points through a complex gas pipeline network (which can be cycled. The problem is formulated as a large quadratic mixed-integer problem, where non-convexity and non-differentiability is found. Because the complexity of the problem, it is proposed a heuristic, in the context of genetic technique, for solving it. Several numerical experiments are presented at the end of this work. The results show that the performance of our approach is very good, being its results very close to exact solutions. The algorithm could be used for sizing and optimization designs of gas pipeline networks, as well as for the gas transmission planning of an existing network, seeking for profit maximization.Este trabalho visa apresentar uma nova abordagem para resolver o problema de planejamento integrado de movimentação de gás natural offshore, definindo a melhor estratégia de transmissão para um sistema com um grande número de plataformas interconectadas com pontos de distribuição por meio de uma rede complexa de gasodutos (a qual pode possuir ciclos. O problema formula-se como um modelo misto-inteiro quadrático de grande porte, não convexo e não diferenciável. Devido à complexidade do problema, propõe-se uma heurística com abordagem genética para resolvê-lo. Vários experimentos numéricos se apresentam ao final deste trabalho. Os resultados mostram que o desempenho de nossa abordagem é muito boa, obtendo soluções muito próximas de soluções exatas. O algoritmo genético proposto poderá ser usado para dimensionar e otimizar o planejamento de redes complexas de gasodutos, tanto como para planejamento da transmissão de gás num gasoduto existente, procurando maximizar lucros.
International Nuclear Information System (INIS)
Quickly declining natural gas reserves in some parts of the world, increasing demand in today's major gas consuming regions, the emergence of new demand centres and the globalization of natural gas markets caused by the rising importance of liquefied natural gas (LNG) are changing global gas supply structures and will continue to do so over the next decades. Applying a global gas market model, we produce a forecast for global gas supply to 2030 and determine the supplier-specific long-run average costs of gas supplied to three major consuming regions. Results for the three regions are compared and analysed with a focus on costs, supply diversification and the different roles of LNG. We find that while European and Japanese external gas supply will be less diversified in international comparison, gas can be supplied at relatively low costs due to the regions' favourable locations in geographic proximity to large gas producers. The US market's supply structure on the other hand will significantly change from its current situation. The growing dependency on LNG imports from around the world will lead to significantly higher supply costs but will also increase diversification as gas will originate from an increasing number of LNG exporting countries. (author)
International Nuclear Information System (INIS)
Quickly declining natural gas reserves in some parts of the world, increasing demand in today's major gas consuming regions, the emergence of new demand centres and the globalization of natural gas markets caused by the rising importance of liquefied natural gas (LNG) are changing global gas supply structures and will continue to do so over the next decades. Applying a global gas market model, we produce a forecast for global gas supply to 2030 and determine the supplier-specific long-run average costs of gas supplied to three major consuming regions. Results for the three regions are compared and analysed with a focus on costs, supply diversification and the different roles of LNG. We find that while European and Japanese external gas supply will be less diversified in international comparison, gas can be supplied at relatively low costs due to the regions' favourable locations in geographic proximity to large gas producers. The US market's supply structure on the other hand will significantly change from its current situation. The growing dependency on LNG imports from around the world will lead to significantly higher supply costs but will also increase diversification as gas will originate from an increasing number of LNG exporting countries
Parameter estimation for LLDPE gas-phase reactor models
Directory of Open Access Journals (Sweden)
G. A. Neumann
2007-06-01
Full Text Available Product development and advanced control applications require models with good predictive capability. However, in some cases it is not possible to obtain good quality phenomenological models due to the lack of data or the presence of important unmeasured effects. The use of empirical models requires less investment in modeling, but implies the need for larger amounts of experimental data to generate models with good predictive capability. In this work, nonlinear phenomenological and empirical models were compared with respect to their capability to predict the melt index and polymer yield of a low-density polyethylene production process consisting of two fluidized bed reactors connected in series. To adjust the phenomenological model, the optimization algorithms based on the flexible polyhedron method of Nelder and Mead showed the best efficiency. To adjust the empirical model, the PLS model was more appropriate for polymer yield, and the melt index needed more nonlinearity like the QPLS models. In the comparison between these two types of models better results were obtained for the empirical models.
Flow Measurement Model of Ultrasonic Flowmeter for Gas-Liquid Two-Phase Stratified and Annular Flows
Lanchang Xing; Chenquan Hua; Hao Zhu; Wolfgang Drahm
2014-01-01
An error correction model for ultrasonic gas flowmeter was proposed to explore the potential of an ultrasonic flowmeter for metering gas-liquid stratified and annular flows. The gas and liquid mass flowrates could be obtained provided that the gas quality and physical prosperities were known. A single-path ultrasonic flowmeter was investigated and the error of the apparent volumetric flowrate was considered as mainly resulting from the shrinkage of the gas flow path due to the presence of a l...
Star Formation and Gas Dynamics in Galactic Disks: Physical Processes and Numerical Models
Ostriker, Eve C
2010-01-01
Star formation depends on the available gaseous "fuel" as well as galactic environment, with higher specific star formation rates where gas is predominantly molecular and where stellar (and dark matter) densities are higher. The partition of gas into different thermal components must itself depend on the star formation rate, since a steady state distribution requires a balance between heating (largely from stellar UV for the atomic component) and cooling. In this presentation, I discuss a simple thermal and dynamical equilibrium model for the star formation rate in disk galaxies, where the basic inputs are the total surface density of gas and the volume density of stars and dark matter, averaged over ~kpc scales. Galactic environment is important because the vertical gravity of the stars and dark matter compress gas toward the midplane, helping to establish the pressure, and hence the cooling rate. In equilibrium, the star formation rate must evolve until the gas heating rate is high enough to balance this co...
Institute of Scientific and Technical Information of China (English)
张秀莉; 张卫东; 郝新政; 张慧峰; 张泽廷; 张建春
2003-01-01
Membrane-based separation processes are new technology combined membrane separation with conventional separation. Hydrophobic porous membranes are often used in these processes. The structure of hydrophobic porous membrane has significant effect on mass transfer process. The permeabilities of five kinds of gas, He, N2,O2, CO2 and water vapor, across six polytetrafluoroethylene(PTFE) fiat membranes were tested experimentally.Results indicated that the greater the membrane mean pore size and the wider the pore size distribution are, the higher the gas permeability. A gas permeation model, including the effects of membrane structure parameter and gas properties, was established. A comprehensive characteristic parameter (including porosity, thickness and tortuosity) was found more effective to express the influence of membrane structure in gas permeation process. The predicted permeation coefficients were in good agreement with experimental data.
ORAL ISSUE OF THE JOURNAL "USPEKHI FIZICHESKIKH NAUK": Modeling of gas discharge plasma
Smirnov, Boris M.
2009-06-01
The condition for the self-maintenance of a gas discharge plasma (GDP) is derived from its ionization balance expressed in the Townsend form and may be used as a definition of a gas discharge plasma in its simplest form. The simple example of a gas discharge plasma in the positive column of a cylindrical discharge tube allows demonstrating a wide variety of possible GDP regimes, revealing a contradiction between simple models used to explain gas discharge regimes and the large number of real processes responsible for the self-maintenance of GDP. The variety of GDP processes also results in a stepwise change of plasma parameters and developing some instabilities as the voltage or discharge current is varied. As a consequence, new forms and new applications of gas discharge arise as technology progresses.
Axisymmetric whole pin life modelling of advanced gas-cooled reactor nuclear fuel
International Nuclear Information System (INIS)
Thermo-mechanical contributions to pellet–clad interaction (PCI) in advanced gas-cooled reactors (AGRs) are modelled in the ABAQUS finite element (FE) code. User supplied sub-routines permit the modelling of the non-linear behaviour of AGR fuel through life. Through utilisation of ABAQUS’s well-developed pre- and post-processing ability, the behaviour of the axially constrained steel clad fuel was modelled. The 2D axisymmetric model includes thermo-mechanical behaviour of the fuel with time and condition dependent material properties. Pellet cladding gap dynamics and thermal behaviour are also modelled. The model treats heat up as a fully coupled temperature-displacement study. Dwell time and direct power cycling was applied to model the impact of online refuelling, a key feature of the AGR. The model includes the visco-plastic behaviour of the fuel under the stress and irradiation conditions within an AGR core and a non-linear heat transfer model. A multiscale fission gas release model is applied to compute pin pressure; this model is coupled to the PCI gap model through an explicit fission gas inventory code. Whole pin, whole life, models are able to show the impact of the fuel on all segments of cladding including weld end caps and cladding pellet locking mechanisms (unique to AGR fuel). The development of this model in a commercial FE package shows that the development of a potentially verified and future-proof fuel performance code can be created and used
Chavanis, Pierre-Henri
2013-01-01
We develop a cosmological model based on a quadratic equation of state p/c^2=-(\\alpha+1){\\rho^2}/{\\rho_P}+\\alpha\\rho-(\\alpha+1)\\rho_{\\Lambda} (where \\rho_P is the Planck density and \\rho_{\\Lambda} the cosmological density) "unifying" vacuum energy and dark energy in the spirit of a generalized Chaplygin gas model. For $\\rho\\rightarrow \\rho_P$, it reduces to p=-\\rho c^2 leading to a phase of early accelerated expansion (early inflation) with a constant density equal to the Planck density \\rho_P (vacuum energy). For $\\rho_{\\Lambda}\\ll\\rho\\ll \\rho_P$, we recover the standard linear equation of state p=\\alpha \\rho c^2 describing radiation (\\alpha=1/3) or pressureless matter (\\alpha=0) and leading to an intermediate phase of decelerating expansion. For $\\rho\\rightarrow \\rho_{\\Lambda}$, we get p=-\\rho c^2 leading to a phase of late accelerated expansion (late inflation) with a constant density equal to the cosmological density \\rho_{\\Lambda} (dark energy). We show a nice symmetry between the early universe (vacuum ...
Rajaram, H.; Birdsell, D.; Lackey, G.; Karra, S.; Viswanathan, H. S.; Dempsey, D.
2015-12-01
The dramatic increase in the extraction of unconventional oil and gas resources using horizontal wells and hydraulic fracturing (fracking) technologies has raised concerns about potential environmental impacts. Large volumes of hydraulic fracturing fluids are injected during fracking. Incidents of stray gas occurrence in shallow aquifers overlying shale gas reservoirs have been reported; whether these are in any way related to fracking continues to be debated. Computational models serve as useful tools for evaluating potential environmental impacts. We present modeling studies of hydraulic fracturing fluid and gas migration during the various stages of well operation, production, and subsequent plugging. The fluid migration models account for overpressure in the gas reservoir, density contrast between injected fluids and brine, imbibition into partially saturated shale, and well operations. Our results highlight the importance of representing the different stages of well operation consistently. Most importantly, well suction and imbibition both play a significant role in limiting upward migration of injected fluids, even in the presence of permeable connecting pathways. In an overall assessment, our fluid migration simulations suggest very low risk to groundwater aquifers when the vertical separation from a shale gas reservoir is of the order of 1000' or more. Multi-phase models of gas migration were developed to couple flow and transport in compromised wellbores and subsurface formations. These models are useful for evaluating both short-term and long-term scenarios of stray methane release. We present simulation results to evaluate mechanisms controlling stray gas migration, and explore relationships between bradenhead pressures and the likelihood of methane release and transport.
Study of Gas Flow Characteristics in Tight Porous Media with a Microscale Lattice Boltzmann Model.
Zhao, Jianlin; Yao, Jun; Zhang, Min; Zhang, Lei; Yang, Yongfei; Sun, Hai; An, Senyou; Li, Aifen
2016-01-01
To investigate the gas flow characteristics in tight porous media, a microscale lattice Boltzmann (LB) model with the regularization procedure is firstly adopted to simulate gas flow in three-dimensional (3D) digital rocks. A shale digital rock and a sandstone digital rock are reconstructed to study the effects of pressure, temperature and pore size on microscale gas flow. The simulation results show that because of the microscale effect in tight porous media, the apparent permeability is always higher than the intrinsic permeability, and with the decrease of pressure or pore size, or with the increase of temperature, the difference between apparent permeability and intrinsic permeability increases. In addition, the Knudsen numbers under different conditions are calculated and the results show that gas flow characteristics in the digital rocks under different Knudsen numbers are quite different. With the increase of Knudsen number, gas flow in the digital rocks becomes more uniform and the effect of heterogeneity of the porous media on gas flow decreases. Finally, two commonly used apparent permeability calculation models are evaluated by the simulation results and the Klinkenberg model shows better accuracy. In addition, a better proportionality factor in Klinkenberg model is proposed according to the simulation results. PMID:27587293
An Efficient Hybrid DSMC/MD Algorithm for Accurate Modeling of Micro Gas Flows
Liang, Tengfei
2013-01-01
Aiming at simulating micro gas flows with accurate boundary conditions, an efficient hybrid algorithmis developed by combining themolecular dynamics (MD) method with the direct simulationMonte Carlo (DSMC)method. The efficiency comes from the fact that theMD method is applied only within the gas-wall interaction layer, characterized by the cut-off distance of the gas-solid interaction potential, to resolve accurately the gas-wall interaction process, while the DSMC method is employed in the remaining portion of the flow field to efficiently simulate rarefied gas transport outside the gas-wall interaction layer. A unique feature about the present scheme is that the coupling between the two methods is realized by matching the molecular velocity distribution function at the DSMC/MD interface, hence there is no need for one-toone mapping between a MD gas molecule and a DSMC simulation particle. Further improvement in efficiency is achieved by taking advantage of gas rarefaction inside the gas-wall interaction layer and by employing the "smart-wall model" proposed by Barisik et al. The developed hybrid algorithm is validated on two classical benchmarks namely 1-D Fourier thermal problem and Couette shear flow problem. Both the accuracy and efficiency of the hybrid algorithm are discussed. As an application, the hybrid algorithm is employed to simulate thermal transpiration coefficient in the free-molecule regime for a system with atomically smooth surface. Result is utilized to validate the coefficients calculated from the pure DSMC simulation with Maxwell and Cercignani-Lampis gas-wall interaction models. ©c 2014 Global-Science Press.
Energy Technology Data Exchange (ETDEWEB)
Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert O.; Gao, Fei; Sun, Xin
2012-05-30
Experiments show that inter-granular and intra-granular gas bubbles have different growth kinetics which results in heterogeneous gas bubble microstructures in irradiated nuclear fuels. A science-based model predicting the heterogeneous microstructure evolution kinetics is desired, which enables one to study the effect of thermodynamic and kinetic properties of the system on gas bubble microstructure evolution kinetics and morphology, improve the understanding of the formation mechanisms of heterogeneous gas bubble microstructure, and provide the microstructure to macroscale approaches to study their impact on thermo-mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking. In our previous report 'Mesoscale Benchmark Demonstration, Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing', we developed a phase-field model to simulate the intra-granular gas bubble evolution in a single crystal during post-irradiation thermal annealing. In this work, we enhanced the model by incorporating thermodynamic and kinetic properties at grain boundaries, which can be obtained from atomistic simulations, to simulate fission gas bubble growth kinetics in polycrystalline UO2 fuels. The model takes into account of gas atom and vacancy diffusion, vacancy trapping and emission at defects, gas atom absorption and resolution at gas bubbles, internal pressure in gas bubbles, elastic interaction between defects and gas bubbles, and the difference of thermodynamic and kinetic properties in matrix and grain boundaries. We applied the model to simulate gas atom segregation at grain boundaries and the effect of interfacial energy and gas mobility on gas bubble morphology and growth kinetics in a bi-crystal UO2 during post-irradiation thermal annealing. The preliminary results demonstrate that the model can produce the equilibrium thermodynamic properties and the morphology of gas
General slip regime permeability model for gas flow through porous media
Zhou, Bo; Jiang, Peixue; Xu, Ruina; Ouyang, Xiaolong
2016-07-01
A theoretical effective gas permeability model was developed for rarefied gas flow in porous media, which holds over the entire slip regime with the permeability derived as a function of the Knudsen number. This general slip regime model (GSR model) is derived from the pore-scale Navier-Stokes equations subject to the first-order wall slip boundary condition using the volume-averaging method. The local closure problem for the volume-averaged equations is studied analytically and numerically using a periodic sphere array geometry. The GSR model includes a rational fraction function of the Knudsen number which leads to a limit effective permeability as the Knudsen number increases. The mechanism for this behavior is the viscous fluid inner friction caused by converging-diverging flow channels in porous media. A linearization of the GSR model leads to the Klinkenberg equation for slightly rarefied gas flows. Finite element simulations show that the Klinkenberg model overestimates the effective permeability by as much as 33% when a flow approaches the transition regime. The GSR model reduces to the unified permeability model [F. Civan, "Effective correlation of apparent gas permeability in tight porous media," Transp. Porous Media 82, 375 (2010)] for the flow in the slip regime and clarifies the physical significance of the empirical parameter b in the unified model.
Brown, Paul D.; Charnley, S. B.
1991-01-01
The effects on gas phase chemistry which result from the continuous desorption of methane molecules from grain surfaces are studied. Significant and sustained enhancements in the abundances of several complex hydrocarbon molecules are found, in good agreement with their observed values in TMC-1. The overall agreement is, however, just as good for the case of zero CH4 desorption efficiency. It is thus impossible to determine from the models whether or not the grain-surface production of methane is responsible for the observed abundances of some hydrocarbon molecules.
2D semiclassical model for high harmonic generation from gas
Institute of Scientific and Technical Information of China (English)
陈黎明; 余玮; 张杰; 陈朝阳; 江文勉
2000-01-01
The electron behavior in laser field is described in detail. Based on the 1D semiclassical model, a 20 semiclassical model is proposed analytically using 3D DC-tunneling ionization theory. Lots of harmonic features are explained by this model, including the analytical demonstration of the maximum electron energy 3.17 Up. Finally, some experimental phenomena such as the increase of the cutoff harmonic energy with the decrease of pulse duration and the "anomalous" fluctuations in the cutoff region are explained by this model.
Khaksarfard, R.; Kameshki, M. R.; Paraschivoiu, M.
2010-06-01
Hydrogen is a renewable and clean source of energy, and it is a good replacement for the current fossil fuels. Nevertheless, hydrogen should be stored in high-pressure reservoirs to have sufficient energy. An in-house code is developed to numerically simulate the release of hydrogen from a high-pressure tank into ambient air with more accuracy. Real gas models are used to simulate the flow since high-pressure hydrogen deviates from ideal gas law. Beattie-Bridgeman and Abel Noble equations are applied as real gas equation of state. A transport equation is added to the code to calculate the concentration of the hydrogen-air mixture after release. The uniqueness of the code is to simulate hydrogen in air release with the real gas model. Initial tank pressures of up to 70 MPa are simulated.
Energy transfer process in gas models of Lennard-Jones interactions
Yang, Jinghua; Wang, Jiao; Zhao, Hong
2011-01-01
We perform simulations to investigate how the energy carried by a molecule transfers to others in an equilibrium gas model. For this purpose we consider a microcanonical ensemble of equilibrium gas systems, each of them contains a tagged molecule located at the same position initially. The ensuing transfer process of the energy initially carried by the tagged molecule is then exposed in terms of the ensemble-averaged energy density distribution. In both a 2D and a 3D gas model with Lennard-Jones interactions at room temperature, it is found that the energy carried by a molecule propagates in the gas ballistically, in clear contrast with the Gaussian diffusion widely assumed in previous studies. A possible scheme of experimental study of this issue is also proposed
Directory of Open Access Journals (Sweden)
Tongshan Wang
2011-01-01
Full Text Available The prediction of oil cracked gas resources is necessary and urgent in the gas exploration of these basins at high to over stage in China. A marine crude oil sample was pyrolyzed using sealed gold tubes system in our study. The pyrolysates including gas, liquid, and solid were quantitatively analyzed. Based on the pyrolysis data and kinetic calculation, the yield correlativity among gas, liquid, and solid products was regressed with high correlative coefficients to establish a prediction model suitable for the resource estimation of oil cracked gas. The verification formula for this model was also established on the principle of mass conservation. The affecting factors and the application preconditions of this model were discussed. Finally the model was extrapolated to the prediction of oil cracked gas resources of Feixianguan formation in NE Sichuan basin, SW China. The prediction value of oil cracked resources is about 6.84×1012 m3, and generation intensity of oil cracked gas is about 97.5×108 m3/km2, and the paleo-oil reserves is about 97×108 t. The verifying value for this prediction is approximately equal to 1, indicating the model is reliable in the resource estimation of oil cracked gas.
Langasite Surface Acoustic Wave Gas Sensors: Modeling and Verification
Energy Technology Data Exchange (ETDEWEB)
Zheng, Peng; Greve, David W; Oppenheim, Irving J
2013-01-01
We report finite element simulations of the effect of conductive sensing layers on the surface wave velocity of langasite substrates. The simulations include both the mechanical and electrical influences of the conducting sensing layer. We show that three-dimensional simulations are necessary because of the out-of-plane displacements of the commonly used (0, 138.5, 26.7) Euler angle. Measurements of the transducer input admittance in reflective delay-line devices yield a value for the electromechanical coupling coefficient that is in good agreement with the three-dimensional simulations on bare langasite substrate. The input admittance measurements also show evidence of excitation of an additional wave mode and excess loss due to the finger resistance. The results of these simulations and measurements will be useful in the design of surface acoustic wave gas sensors.
Microscopic reversibility and macroscopic irreversibility: A lattice gas model
Pérez-Cárdenas, Fernando C.; Resca, Lorenzo; Pegg, Ian L.
2016-09-01
We present coarse-grained descriptions and computations of the time evolution of a lattice gas system of indistinguishable particles, whose microscopic laws of motion are exactly reversible, in order to investigate how or what kind of macroscopically irreversible behavior may eventually arise. With increasing coarse-graining and number of particles, relative fluctuations of entropy rapidly decrease and apparently irreversible behavior unfolds. Although that behavior becomes typical in those limits and within a certain range, it is never absolutely irreversible for any individual system with specific initial conditions. Irreversible behavior may arise in various ways. We illustrate one possibility by replacing detailed integer occupation numbers at lattice sites with particle probability densities that evolve diffusively.
CELSS experiment model and design concept of gas recycle system
Nitta, K.; Oguchi, M.; Kanda, S.
1986-01-01
In order to prolong the duration of manned missions around the Earth and to expand the human existing region from the Earth to other planets such as a Lunar Base or a manned Mars flight mission, the controlled ecological life support system (CELSS) becomes an essential factor of the future technology to be developed through utilization of space station. The preliminary system engineering and integration efforts regarding CELSS have been carried out by the Japanese CELSS concept study group for clarifying the feasibility of hardware development for Space station experiments and for getting the time phased mission sets after FY 1992. The results of these studies are briefly summarized and the design and utilization methods of a Gas Recycle System for CELSS experiments are discussed.
Euler-Lagrange CFD modelling of unconfined gas mixing in anaerobic digestion.
Dapelo, Davide; Alberini, Federico; Bridgeman, John
2015-11-15
A novel Euler-Lagrangian (EL) computational fluid dynamics (CFD) finite volume-based model to simulate the gas mixing of sludge for anaerobic digestion is developed and described. Fluid motion is driven by momentum transfer from bubbles to liquid. Model validation is undertaken by assessing the flow field in a labscale model with particle image velocimetry (PIV). Conclusions are drawn about the upscaling and applicability of the model to full-scale problems, and recommendations are given for optimum application.
Gas-liquid flow modeling in columns equipped with structured packing
Soulaine, Cyprien; Horgue, Pierre; Franc, Jacques; Quintard, Michel
2014-01-01
International audience This paper deals with the modeling of gas-liquid flow in distillation columns equipped with structured packing. The devices are seen as bi-structured porous media and a macro-scale model is proposed taking into account this specific geometry. In this model, the two liquid films, one-per-sheet, are treated separately and are allowed to exchange matter at the vicinity of the contact points between corrugated sheets. The model emphasizes mechanisms that lead to the liqu...
MEGAS: modelling and experiments on gas migration in argillaceous host rocks
International Nuclear Information System (INIS)
The primary objective of the MEGAS project is to understand the impact of gas generation on argillaceous host rock and this for various generation rates and different host rock conditions. The importance of the phenomena which might occur is determined. The following phenomena are investigated: -reaction of hydrogen with the host rock (clay); - molecular diffusion; -bubble growth; - pressure build up; - creation of preferential pathways and fractures; - two phase flow. The final objective of the project is the validation of a gas migration model; for that purpose, as in situ gas migration experiment is planned in Boom clay at a representative repository depth. 8 refs., 8 figs
The gas-phase thermal chemistry of tetralin and related model systems
Energy Technology Data Exchange (ETDEWEB)
Malandra, J.
1993-05-01
The thesis is divided into 5 papers: gas-phase thermal decomposition of tetralin; flash vacuum pyrolysis of 3-benzocycloheptenone and 1,3, 4,5-tetrahydro-2-benzothiepin-2,2-dioxide (model systems for gas-phase pyrolysis of tetralin); high-temperature gas-phase reactions of o-allylbenzyl radicals generated by flash vacuum pyrolysis of is(o-allylbenzyl) oxalate; flash vacuum pyrolysis of 1,4-diphenylbutane; and flash vacuum pyrolysis of o-allyltoluene, o-(3-butenyl)toluene and o-(pentenyl)toluene were also used.
Gavrilik, A M
2013-01-01
We consider the deformed Bose gas model with the deformation structure function that is the combination of a q-deformation and a quadratically polynomial deformation. Such a choice of the unifying deformation structure function enables us to describe the interacting gas of composite (two-fermionic or two-bosonic) bosons. Using the relevant generalization of the Jackson derivative, we derive a two-parametric expression for the total number of particles, from which the deformed virial expansion of the equation of state is obtained. The latter is interpreted as the virial expansion for the effective description of a gas of interacting composite bosons with some interaction potential.
Simplified gas sensor model based on AlGaN/GaN heterostructure Schottky diode
Energy Technology Data Exchange (ETDEWEB)
Das, Subhashis, E-mail: subhashis.ds@gmail.com; Majumdar, S.; Kumar, R.; Bag, A. [Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur-721302 (India); Chakraborty, A.; Biswas, D. [Department of Electronics and Electrical communication Engineering, Indian Institute of Technology Kharagpur, Kharagpur-721302 (India)
2015-08-28
Physics based modeling of AlGaN/GaN heterostructure Schottky diode gas sensor has been investigated for high sensitivity and linearity of the device. Here the surface and heterointerface properties are greatly exploited. The dependence of two dimensional electron gas (2DEG) upon the surface charges is mainly utilized. The simulation of Schottky diode has been done in Technology Computer Aided Design (TCAD) tool and I-V curves are generated, from the I-V curves 76% response has been recorded in presence of 500 ppm gas at a biasing voltage of 0.95 Volt.
ANALYSIS OF A COMPRESSIBLE GAS-LIQUID MODEL MOTIVATED BY OIL WELL CONTROL OPERATIONS
Institute of Scientific and Technical Information of China (English)
Steinar Evje; K.H. Karlsen
2012-01-01
We are interested in a viscous two-phase gas-liquid mixture model relevant for modeling of well control operations within the petroleum industry. We focus on a simplified mixture model and provide an existence result within an appropriate class of weak solutions. We demonstrate that upper and lower limits can be obtained for the gas and liquid masses which ensure that transition to single-phase regions do not occur. This is used together with appropriate a prior estimates to obtain convergence to a weak solution for a sequence of approximate solutions corresponding to mollified initial data. Moreover, by imposing an additional regularity condition on the initial masses, a uniqueness result is obtained. The framework herein seems useful for further investigations of more realistic versions of the gas-liquid model that take into account different flow regimes.
DEFF Research Database (Denmark)
Andersen, C.E.; Søgaard-Hansen, J.; Majborn, B.
1994-01-01
A radon test structure has been established at a field site at Riso National Laboratory. Measurements have been made of soil gas entry rates, pressure couplings and radon depletion. The experimental results have been compared with results obtained from measured soil parameters and a two......-dimensional steady-state numerical model of Darcy flow and combined diffusive and advective transport of radon. For most probe locations, the calculated values of the pressure couplings and the radon depletion agree well with the measured values, thus verifying important elements of the Darcy flow approximation......, and the ability of the model to treat combined diffusive and advective transport of radon. However, the model gives an underestimation of the soil gas entry rate. Even if it is assumed that the soil has a permeability equal to the highest of the measured values, the model underestimates the soil gas entry rate...
A predictive model of natural gas mixture combustion in internal combustion engines
Directory of Open Access Journals (Sweden)
Henry Espinoza
2010-04-01
Full Text Available This study shows the development of a predictive natural gas mixture combustion model for conventional com-bustion (ignition engines. The model was based on resolving two areas; one having unburned combustion mixture and another having combustion products. Energy and matter conservation equations were solved for each crankshaft turn angle for each area. Nonlinear differential equations for each phase’s energy (considering compression, combustion and expansion were solved by applying the fourth-order Runge-Kutta method. The model also enabled studying different natural gas components’ composition and evaluating combustion in the presence of dry and humid air. Validation results are shown with experimental data, demonstrating the software’s precision and accuracy in the results so produced. The results showed cylinder pressure, unburned and burned mixture temperature, burned mass fraction and combustion reaction heat for the engine being modelled using a natural gas mixture.
Analysis of GRI North American Regional Gas Supply-Demand Model
International Nuclear Information System (INIS)
This paper summarizes the results from the GRI North American Regional Gas Supply-Demand Model using the four scenarios defined for the Energy Modeling Forum Number 9 (EMF-9) described in EMF-9 Working Paper 9.4 (1987). The analysis is designed both to showcase the GRI North American Regional model as well as to infer meaningful results about the North American natural gas system. The focus of the analysis is not R ampersand D per se; R ampersand D analysis using the model is conducted regularly by GRI and described elsewhere. Rather, the objective is to analyze some of the major uncertainties in the North American gas market, uncertainties that potentially affect all players including GRI. In particular, the authors seek to quantify the overall economic environment in which production, transmission, distribution, consumption, and R ampersand D decisions will be made and how different that overall environment might be under alternative assumptions. An attendant objective of this analysis has been to enlist economists from a range of organizations (producers, regulators, GRI, and consultants) to carefully scrutinize the GRI North American Regional model and results. In particular, the coauthors were assembled from diverse organizations to review and evaluate model outputs, applying their particular experience and perspective. The four EMF-9 scenarios upon which this paper is based are described in detail later in this document. Briefly, scenario one represents a world with a surfeit of gas and a relatively high oil price projection; scenario two considers a lower oil price forecast; scenario three assumes a pessimistic outlook for the gas resource base with the same oil prices as scenario one; and scenario four examines a higher level of demand for gas in the North American gas market. An important objective of this analysis is to illustrate the predictive power of multi-scenario comparisons (as contrasted with detailed analysis of any individual scenario)
Hot-gas cleanup system model development. Volume I. Final report
Energy Technology Data Exchange (ETDEWEB)
Ushimaru, K.; Bennett, A.; Bekowies, P.J.
1982-11-01
This two-volume report summarizes the state of the art in performance modeling of advanced high-temperature, high-pressure (HTHP) gas cleanup devices. Volume I contains the culmination of the research effort carried over the past 12 months and is a summary of research achievements. Volume II is the user's manual for the computer programs developed under the present research project. In this volume, Section 2 presents background information on pressurized, fluidized-bed combustion concepts, a description of the role of the advanced gas cleanup systems, and a list of advanced gas cleanup systems that are currently in development under DOE sponsorship. Section 3 describes the methodology for the software architecture that forms the basis of the well-disciplined and structured computer programs developed under the present project. Section 4 reviews the fundamental theories that are important in analyzing the cleanup performance of HTHP gas filters. Section 5 discusses the effect of alkali agents in HTHP gas cleanup. Section 6 evaluates the advanced HTHP gas cleanup models based on their mathematical integrity, availability of supporting data, and the likelihood of commercialization. As a result of the evaluation procedure detailed in Section 6, five performance models were chosen to be incorporated into the overall system simulation code, ASPEN. These five models (the electrocyclone, ceramic bag filter, moving granular bed filter, electrostatic granular bed filter, and electrostatic precipitator) are described in Section 7. The method of cost projection for these five models is discussed in Section 8. The supporting data and validation of the computer codes are presented in Section 9, and finally the conclusions and recommendations for the HTHP gas cleanup system model development are given in Section 10. 72 references, 19 figures, 25 tables.
GARUSO - Version 1.0. Uncertainty model for multipath ultrasonic transit time gas flow meters
Energy Technology Data Exchange (ETDEWEB)
Lunde, Per; Froeysa, Kjell-Eivind; Vestrheim, Magne
1997-09-01
This report describes an uncertainty model for ultrasonic transit time gas flow meters configured with parallel chords, and a PC program, GARUSO Version 1.0, implemented for calculation of the meter`s relative expanded uncertainty. The program, which is based on the theoretical uncertainty model, is used to carry out a simplified and limited uncertainty analysis for a 12`` 4-path meter, where examples of input and output uncertainties are given. The model predicts a relative expanded uncertainty for the meter at a level which further justifies today`s increasing tendency to use this type of instruments for fiscal metering of natural gas. 52 refs., 15 figs., 11 tabs.
A CFD Model for Fluid Dynamics in a Gas-fluidised Bed
Institute of Scientific and Technical Information of China (English)
ZHANG Kai; Stefano Brandani
2004-01-01
A modified particle bed model derived from the two-fluid momentum balance equations was employed to predict the gas-fluidised bed behaviour. Additional terms are included in both the fluid and the particle momentum balance equations to take into account the effect of the dispersed solid phase. This model has been extended to two-dimensional formulations and has been implemented in the commercial code CFX 4.3. The model correctly simulates the homogeneous fluidisation of Geldart Group A and the bubbling fluidisation of Geldart Group B in gas-solid fluidised beds.
Gas storage valuation and hedging. A quantification of the model risk.
Henaff, Patrick; Laachir, Ismail; Russo, Francesco
2013-01-01
This paper focuses on the valuation and hedging of gas storage facilities, using a spot-based valuation framework coupled with a financial hedging strategy implemented with futures contracts. The first novelty consist in proposing a model that unifies the dynamics of the futures curve and the spot price, which accounts for the main stylized facts of the US natural gas market, such as seasonality and presence of price spikes. The second aspect of the paper is related to the quantification of m...
Directory of Open Access Journals (Sweden)
Леонид Иванович Нефедов
2014-08-01
Full Text Available The extraction and processing and gas transportation have been analyzed in the article. Decomposition of the process of monitoring is introduced based on that; allowing the hierarchical structure of the monitoring system is request. Scientific novelty consists in the fact that developed generalized synthesis quality model monitoring system to extract, processing and gas transportation, which allows solving the problem of synthesis of a unified system and criteria positions.
Interacting polytropic gas model of phantom dark energy in non-flat universe
Energy Technology Data Exchange (ETDEWEB)
Karami, K. [University of Kurdistan, Department of Physics, Sanandaj (Iran); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran); Ghaffari, S.; Fehri, J. [University of Kurdistan, Department of Physics, Sanandaj (Iran)
2009-11-15
By introducing the polytropic gas model of interacting dark energy, we obtain the equation of state for the polytropic gas energy density in a non-flat universe. We show that for an even polytropic index by choosing K>Ba{sup (3)/(n)}, one can obtain {omega}{sub {lambda}}{sup eff}<-1, which corresponds to a universe dominated by phantom dark energy. (orig.)
Struck, Curtis; Smith, Daniel C.
2008-01-01
The existence of partially ionized, diffuse gas and dust clouds at kiloparsec scale distances above the central planes of edge-on, galaxy discs was an unexpected discovery about 20 yrs ago. Subsequent observations showed that this EDIG (extended or extraplanar diffuse interstellar gas) has rotation velocities approximately 10-20% lower than those in the central plane, and have been hard to account for. Here we present results of hydrodynamic models, with radiative cooling and heating from sta...
Modelling of controlled wax deposition and loosening in oil and gas production systems
Ajayi, Oluwatosin Emmanuel
2013-01-01
A large part of worlds remaining oil and gas resources is found in harsh environments such as deep water and arctic conditions. The development of such oil and gas fields requires advanced process and transport solutions. Wax is precipitated out of solution as reservoir fluid cools down during transport. Wax precipitation may cause operational problems when unprocessed well streams are transported in undersea pipelines.The goal of this work is to investigate modelling concept for controlled w...
Molecular interpretation of nonclassical gas dynamics of dense vapors under the van der Waals model
Colonna, P.; Guardone, A.
2006-01-01
The van der Waals polytropic gas model is used to investigate the role of attractive and repulsive intermolecular forces and the influence of molecular complexity on the possible nonclassical gas dynamic behavior of vapors near the liquid-vapor saturation curve. The decrease of the sound speed upon isothermal compression is due to the well-known action of the van der Waals attractive forces and this effect is shown here to be comparatively larger for more complex molecules with a large number...
LIME SPRAY DRYER FLUE GAS DESULFURIZATION COMPUTER MODEL USERS MANUAL
The report describes a lime spray dryer/baghouse (FORTRAN) computer model that simulates SO2 removal and permits study of related impacts on design and economics as functions of design parameters and operating conditions for coal-fired electric generating units. The model allows ...
MODELING OF GASEOUSNESS OF PUBLIC PREMISES WITH TOXIC GAS
Directory of Open Access Journals (Sweden)
O. M. Pshinko
2009-03-01
Full Text Available The 2D numerical model to simulate the pollutant dispersion in public compartments is offered. The model is based on the equation of potential flow and the equation of admixture transfer. The results of numerical experiment are presented.
Modelling and analysis of offshore energy systems on North Sea oil and gas platforms
DEFF Research Database (Denmark)
Nguyen, Tuong-Van; Elmegaard, Brian; Pierobon, Leonardo;
2012-01-01
export, and power generation. In this paper, a generic model of a North Sea oil and gas platform is described and the most thermodynamically inefficient processes are identified by performing an exergy analysis. Models and simulations are built and run with the tools Aspen Plus R, DNA and Aspen HYSYS R...
The Cauchy problem for a model of immiscible gas flow with large data
Energy Technology Data Exchange (ETDEWEB)
Sande, Hilde
2008-12-15
The thesis consists of an introduction and two papers; 1. The solution of the Cauchy problem with large data for a model of a mixture of gases. 2. Front tracking for a model of immiscible gas flow with large data. (AG) refs, figs
Modeling methane fluxes in wetlands with gas-transporting plants. 3. Plot scale.
Segers, R.; Leffelaar, P.A.
2001-01-01
A process model based on kinetic principles was developed for methane fluxes from wetlands with gas-transporting plants and a fluctuating water table. Water dynamics are modeled with the 1-D Richards equation. For temperature a standard diffusion equation is used. The depth-dependent dynamics of met
Reconstructing an interacting holographic polytropic gas model in a non-flat FRW universe
Energy Technology Data Exchange (ETDEWEB)
Karami, K; Abdolmaleki, A, E-mail: KKarami@uok.ac.i [Department of Physics, University of Kurdistan, Pasdaran Street, Sanandaj (Iran, Islamic Republic of)
2010-05-01
We study the correspondence between the interacting holographic dark energy and the polytropic gas model of dark energy in a non-flat FRW universe. This correspondence allows one to reconstruct the potential and the dynamics for the scalar field of the polytropic model, which describe accelerated expansion of the universe.
Phase equilibrium modeling of gas hydrate systems for CO_{2} capture
DEFF Research Database (Denmark)
Herslund, Peter Jørgensen; Thomsen, Kaj; Abildskov, Jens;
2012-01-01
Two thermodynamic models capable of describing dissociation pressures of mixed gas clathrate hydrates formed from ternary mixtures of CO2, N2 and liquid water, are presented. Both of the models utilize the Cubic-Plus-Association (CPA) equation of state (EOS) for the thermodynamic description of t...
THE MODELING OF TOXIC GAS DISPERSION IN CONDITIONS OF BUILT-UP AREAS
Directory of Open Access Journals (Sweden)
M. M. Biliaiev
2009-03-01
Full Text Available A numerical model to simulate the process of heavy gas transfer is developed. The numerical simulation is carried out using 3D models of pollutant transfer and potential flow. The implicit finite difference schemes are used. The results of numerical simulation of air pollution are presented.
Optimizing the structure of the natural gas market using an agent-based modeling framework
International Nuclear Information System (INIS)
The overall research question guiding this study is as follows: what is the optimal structure of the natural gas market, considering both the degrees of affordability and supply security resulting from this structure? The sub-questions are: How can the concepts of supply security and affordability be usefully defined? (Chapter 2); What should a modeling framework for analyzing the natural gas market with regard to these concepts look like? (Chapters 3 and 4); What general conclusions can be drawn on the basis of this framework? (Chapter 5); What is the effect of liberalization on the Dutch natural gas market? (Chapter 6); What are the possible effects of current trends unfolding in the Dutch natural gas market? (Chapter 7). The framework constructed in this study implicitly contains the necessary elements for deriving a sustainability indicator too. However, to limit the scope of the study, sustainability will not be analyzed explicitly. Chapter 2 provides an introductory description of the natural gas market. Starting from a description of the natural gas value chain, the process of liberalization is described as a change in the organization of the value chain. In addition, the concepts of affordability and supply security are discussed and appropriate quantitative indicators for both objectives are identified. In Chapter 3, a survey of existing gas market models is performed. On the basis of this survey, a classification system for natural gas market models is developed. Furthermore, the characteristics of a modeling framework fit for the purpose of this study are derived. In Chapter 4, a general, quantitative framework for natural gas market modeling is developed on the basis of agent-based computational economics. The model's structure, its dynamics, output and data requirements are described. Furthermore, the properties of each agent are explored, and the possibilities for model verification and validation are outlined. Chapter 5 provides a number of
Studies on fluid model for numerical simulation of gas discharges in color plasma displays
Institute of Scientific and Technical Information of China (English)
HE Feng; LIU Chun-Liang
2005-01-01
The fluid models of gas discharge in alternating current plasma display panel (AC PDP) cell are discussed.From the Boltzmann equation, the hydrodynamic equations are derived, but this model consumes much computa tional time for simulation. The drift-diffusion approximation model and the local field approximation model are ob tained to simplify the numerical computation, and the approximation conditions of these two models are discussed in detail. The drift-diffusion approximation model gives more satisfactory result for PDP simulation, and the expression of energy balance equation is given completely in this model.
The initial conditions and evolution of isolated galaxy models: effects of the hot gas halo
Hwang, Jeong-Sun; Choi, Jun-Hwan
2013-01-01
We construct several Milky Way-like galaxy models containing a gas halo (as well as gaseous and stellar disks, a dark matter halo, and a stellar bulge) following either an isothermal or an NFW density profile with varying mass and initial spin. In addition, galactic winds associated with star formation are tested in some of the simulations. We evolve these isolated galaxy models using the GADGET-3 $N$-body/hydrodynamic simulation code, paying particular attention to the effects of the gas halo on the evolution. We find that the evolution of the models is strongly affected by the adopted gas halo component. The model without a gas halo shows an increasing star formation rate (SFR) at the beginning of the simulation for some hundreds of millions of years and then a continuously decreasing rate to the end of the run at 3 Gyr. On the other hand, the SFRs in the models with a gas halo emerge to be either relatively flat throughout the simulations or increasing over a gigayear and then decreasing to the end. The mo...
International Nuclear Information System (INIS)
A non-stationary reactive gas dynamics model in a mono-dimensional geometry, including radial mass diffusion, gas temperature variation and chemical kinetics, is developed in this paper. The aim is to analyse the spatio-temporal evolution of the main neutral species involved in a corona discharge used for NO pollution control in polluted air at atmospheric pressure and ambient temperature. The present reactive gas dynamics model takes into account 16 neutral chemical species (including certain metastable species) reacting following 110 selected chemical reactions. The initial concentration of each neutral species is obtained from a 1.5D electrical discharge model. The gas temperature variations are due to direct Joule heating during the discharge phase, and also result from the delayed heating due to the relaxation of the vibrational energy into a random thermal energy during the post-discharge phase. The simulation conditions are those of an existing experimental setup (anode voltage of 10 kV in the case of a point to plane geometry with an interelectrode distance of 10 mm). The obtained results show that the diffusion phenomena and the gas temperature rise affect quite well the gas reactivity and the neutral species evolution. This allows us to better understand the different reaction processes and transport phenomena affecting the NO concentration magnitude inside the discharge channel. (author)
Extending the Modelling Framework for Gas-Particle Systems
DEFF Research Database (Denmark)
Rosendahl, Lasse Aistrup
, with very good results. Single particle combustion has been tested using a number of different particle combustion models applied to coal and straw particles. Comparing the results of these calculations to measurements on straw burnout, the results indicate that for straw, existing heterogeneous combustion...... models perform well, and may be used in high temperature ranges. Finally, the particle tracking and combustion model is applied to an existing coal and straw co- fuelled burner. The results indicate that again, the straw follows very different trajectories than the coal particles, and also that burnout...
Energy Technology Data Exchange (ETDEWEB)
Schossler, Patricia [Fraunhofer WKI, Department of Material Analysis and Indoor Chemistry, Bienroder Weg 54E, D-38108 Braunschweig (Germany); Institute of Environmental and Sustainable Chemistry, Technische Universitaet Braunschweig, Hagenring 30, D-38106 Braunschweig (Germany); Schripp, Tobias, E-mail: tobias.schripp@wki.fraunhofer.de [Fraunhofer WKI, Department of Material Analysis and Indoor Chemistry, Bienroder Weg 54E, D-38108 Braunschweig (Germany); Salthammer, Tunga [Fraunhofer WKI, Department of Material Analysis and Indoor Chemistry, Bienroder Weg 54E, D-38108 Braunschweig (Germany); Bahadir, Muefit [Institute of Environmental and Sustainable Chemistry, Technische Universitaet Braunschweig, Hagenring 30, D-38106 Braunschweig (Germany)
2011-09-01
The ongoing health debate about polymer plasticizers based on the esters of phthalic acid, especially di(2-ethylhexyl) phthalate (DEHP), has caused a trend towards using phthalates of lower volatility such as diisononyl phthalate (DINP) and towards other acid esters, such as adipates, terephthalates, citrates, etc. Probably the most important of these so-called 'alternative' plasticizers is diisononyl cyclohexane-1,2-dicarboxylate (DINCH). In the indoor environment, the continuously growing market share of this compound since its launch in 2002 is inter alia apparent from the increasing concentration of DINCH in settled house dust. From the epidemiological point of view there is considerable interest in identifying how semi-volatile organic compounds (SVOCs) distribute in the indoor environment, especially in air, airborne particles and sedimented house dust. This, however, requires reliable experimental concentration data for the different media and good measurements or estimates of their physical and chemical properties. This paper reports on air concentrations for DINP, DINCH, diisobutyl phthalate (DIBP), diisobutyl adipate (DIBA), diisobutyl succinate (DIBS) and diisobutyl glutarate (DIBG) from emission studies in the Field and Laboratory Emission Cell (FLEC). For DINP and DINCH it took about 50 days to reach the steady-state value: for four months no decay in the concentration could be observed. Moreover, vapor pressures p{sub 0} and octanol-air partitioning coefficients K{sub OA} were obtained for 37 phthalate and non-phthalate plasticizers from two different algorithms: EPI Suite and SPARC. It is shown that calculated gas/particle partition coefficients K{sub p} and fractions can widely differ due to the uncertainty in the predicted p{sub 0} and K{sub OA} values. For most of the investigated compounds reliable experimental vapor pressures are not available. Rough estimates can be obtained from the measured emission rate of the pure compound in a
Studies on scaled models for gas entrainment in the surge tank of LMFBR
Energy Technology Data Exchange (ETDEWEB)
Ramdasu, D.; Shivakumar, N.S.; Padmakumar, G.; Anand Babu, C.; Vaidyanathan, G. [Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Rammohan, S.; Sreekala, S.K.; Manikandan, S.; Saseendran, S. [Fluid Control Research Institute, Palghat (India)
2007-07-01
This paper presents the studies carried out in the different scale models of Surge tank used in the secondary circuit of Liquid metal fast breeder reactor (LMFBR). Surge tank acquires importance because of its ability to take care of pressure surges in case of a sodium water reaction in Steam Generators (SG). The blanket of argon cover gas above the sodium free surface in the surge tank acts as a cushion for the surges. At the same time, argon gas is a source of entrainment into the sodium which is undesirable from the consideration of effective heat transfer in Inter mediate Heat Exchanger and SG, cavitation in pumps and operational problems of continuous feed and bleed of cover gas, thus leading to unfavourable reactor operating conditions. To investigate the phenomenon of gas entrainment in surge tank, hydraulic experiments were conducted in water using 1/38, 1/32, 1/22 and 1/12 scale models with Froude similarity. The minimum height of liquid column required to avoid gas entrainment was determined using different types of internal devices. Experiments were carried out in the 5/8 scale model to confirm the results of the smaller scale models. It was found that free surface height to avoid gas entrainment varies for different scale models. The combination of Pepper pot with ring plate was found to be the most effective in avoiding gas entrainment at H/D equals 1.28 where H is the height of liquid column in the tank from tank bottom and D is the inner diameter of surge tank.
Modeling the influence of the pulmonary pressure-volume curve on gas exchange.
Smith, Bram; Rees, Stephen; Tvorup, Jan; Christensen, Casper; Andreassen, Steen
2005-01-01
Current models of lung mechanics and gas exchange act independently to simulate variations in pressure-volume (PV) and ventilation-perfusion (V/Q) properties in the lungs respectively. However, changes in ventilator pressures can cause alveoli recruitment, collapse or over-distension causing V/Q changes in the lungs that are unaccounted for in these models. A compartmental model of the lungs is presented that is based on a physiological interpretation of lung function and simulates each alveolus individually. By combining this model with currently available lung mechanics and gas exchange models, the effect of changing ventilator settings on gas exchange could be simulated. The model is shown to simulate experimentally measured static PV data from an ARDS patient with an accuracy equivalent to that achieved by the sigmoid function. It could enable quantification of variations in V/Q in the lungs and also gives estimates of other physiological lung properties such as lung density and alveoli compliance. The alveoli model offers a physiologically relevant method of simulating the PV relationship in the lungs and its influence of gas exchange. PMID:17282708
MSW to synthetic natural gas: System modeling and thermodynamics assessment.
Zhu, Lin; Zhang, Le; Fan, Junming; Jiang, Peng; Li, Luling
2016-02-01
To achieve environmental-friendly and energy-efficiency synthetic natural gas (SNG) production routing from municipal solid waste (MSW), a MSW-to-SNG process is unprecedentedly presented in this work, of which the designed configuration is developed and simulated with the aid of Aspen Plus. In addition, sensitivity analyses on major operation parameters, such as equivalence volume ratio (ER), steam-to-MSW mass ratio (S/M) and methanation pressure, are performed with the discussion of process efficiencies and SNG quality. In parallel, the comparison analysis is considered by adopting various MSW material. In this work, the composition of SNG mainly consists of 87.7% CH4, 2.9% CO2, 2.3% H2 and 7.1% N2. And lower heating value (LHV) together with Wobbe index of SNG are separately 31.66MJ/Nm(3) and 45.90MJ/Nm(3). Moreover, the wood-to-SNG, MSW-to-SNG and coal-to-SNG processes are carried out to demonstrate the superiority of the MSW-to-SNG process. The results reveal that the MSW-to-SNG process is a promising option to dispose MSW environmentally, meanwhile converting MSW to the valuable SNG. PMID:26525970
MSW to synthetic natural gas: System modeling and thermodynamics assessment.
Zhu, Lin; Zhang, Le; Fan, Junming; Jiang, Peng; Li, Luling
2016-02-01
To achieve environmental-friendly and energy-efficiency synthetic natural gas (SNG) production routing from municipal solid waste (MSW), a MSW-to-SNG process is unprecedentedly presented in this work, of which the designed configuration is developed and simulated with the aid of Aspen Plus. In addition, sensitivity analyses on major operation parameters, such as equivalence volume ratio (ER), steam-to-MSW mass ratio (S/M) and methanation pressure, are performed with the discussion of process efficiencies and SNG quality. In parallel, the comparison analysis is considered by adopting various MSW material. In this work, the composition of SNG mainly consists of 87.7% CH4, 2.9% CO2, 2.3% H2 and 7.1% N2. And lower heating value (LHV) together with Wobbe index of SNG are separately 31.66MJ/Nm(3) and 45.90MJ/Nm(3). Moreover, the wood-to-SNG, MSW-to-SNG and coal-to-SNG processes are carried out to demonstrate the superiority of the MSW-to-SNG process. The results reveal that the MSW-to-SNG process is a promising option to dispose MSW environmentally, meanwhile converting MSW to the valuable SNG.
Liang, Tengfei
2013-07-16
A systematic study on the performance of two empirical gas-wall interaction models, the Maxwell model and the Cercignani-Lampis (CL) model, in the entire Knudsen range is conducted. The models are evaluated by examining the accuracy of key macroscopic quantities such as temperature, density, and pressure, in three benchmark thermal problems, namely the Fourier thermal problem, the Knudsen force problem, and the thermal transpiration problem. The reference solutions are obtained from a validated hybrid DSMC-MD algorithm developed in-house. It has been found that while both models predict temperature and density reasonably well in the Fourier thermal problem, the pressure profile obtained from Maxwell model exhibits a trend that opposes that from the reference solution. As a consequence, the Maxwell model is unable to predict the orientation change of the Knudsen force acting on a cold cylinder embedded in a hot cylindrical enclosure at a certain Knudsen number. In the simulation of the thermal transpiration coefficient, although all three models overestimate the coefficient, the coefficient obtained from CL model is the closest to the reference solution. The Maxwell model performs the worst. The cause of the overestimated coefficient is investigated and its link to the overly constrained correlation between the tangential momentum accommodation coefficient and the tangential energy accommodation coefficient inherent in the models is pointed out. Directions for further improvement of models are suggested.
A Cloud Microphysics Model for the Gas Giant Planets
Palotai, Csaba J.; Le Beau, Raymond P.; Shankar, Ramanakumar; Flom, Abigail; Lashley, Jacob; McCabe, Tyler
2016-10-01
Recent studies have significantly increased the quality and the number of observed meteorological features on the jovian planets, revealing banded cloud structures and discrete features. Our current understanding of the formation and decay of those clouds also defines the conceptual modes about the underlying atmospheric dynamics. The full interpretation of the new observational data set and the related theories requires modeling these features in a general circulation model (GCM). Here, we present details of our bulk cloud microphysics model that was designed to simulate clouds in the Explicit Planetary Hybrid-Isentropic Coordinate (EPIC) GCM for the jovian planets. The cloud module includes hydrological cycles for each condensable species that consist of interactive vapor, cloud and precipitation phases and it also accounts for latent heating and cooling throughout the transfer processes (Palotai and Dowling, 2008. Icarus, 194, 303–326). Previously, the self-organizing clouds in our simulations successfully reproduced the vertical and horizontal ammonia cloud structure in the vicinity of Jupiter's Great Red Spot and Oval BA (Palotai et al. 2014, Icarus, 232, 141–156). In our recent work, we extended this model to include water clouds on Jupiter and Saturn, ammonia clouds on Saturn, and methane clouds on Uranus and Neptune. Details of our cloud parameterization scheme, our initial results and their comparison with observations will be shown. The latest version of EPIC model is available as open source software from NASA's PDS Atmospheres Node.
Study of coal and gas outbursts by numerical modeling approach
Institute of Scientific and Technical Information of China (English)
LI Sheng; ZHANG Hong-wei
2007-01-01
During mining or road-way development, the distribution of stress and coal pore pressure in the coal face and rib around the new opening will change, under certain conditions, dynamic failure of coal in the form of an outburst can occur. In the modeling studies presented in this paper, an outburst was considered to consist of three distinct stages:preinitiation, initiation and post-initiation, which takes into account the major processes and mechanisms that can influence both outburst-proneness and post-initiation outburst behavior. The model has been applied to simulate the effects of mechanisms in the coal matrix, coal strength, coal damage, geological structures on outbursts. The model constructed using the FLAC software, which were undertaken to research the effects on outbursts of coal strength pressure gradient, and other factors.
A model-based analysis of the implications of shale gas developments for the European gas market
Energy Technology Data Exchange (ETDEWEB)
De Joode, J.; Plomp, A.J.; Ozdemir, O. [ECN Policy Studies, Petten (Netherlands)
2012-04-15
Shale gas in Europe could potentially be a big thing, especially in particular regions. Whereas test drillings need to confirm the technical recoverability of deposits and further research is needed on the environmental and safety aspects of shale gas production, this paper illustrates that shale gas developments may have substantial implications for regional gas balances, gas flows, and infrastructure requirements throughout Europe in the next decades.
How to get cool in the heat: comparing analytic models of halo gas cooling with EAGLE
Stevens, Adam R H; Contreras, Sergio; Croton, Darren J; Padilla, Nelson D; Schaller, Matthieu; Schaye, Joop; Theuns, Tom
2016-01-01
We use the hydrodynamic, cosmological EAGLE simulations to investigate how hot gas in haloes condenses to form and grow galaxies. We select haloes from the simulations that are actively cooling and study the temperature, distribution, and metallicity of their hot, cold, and transitioning `cooling' gas, placing these in context of semi-analytic models. Our selection criteria lead us to focus on Milky Way-like haloes. We find the hot-gas density profiles of the haloes form a progressively stronger core over time, the nature of which can be captured by a beta profile that has a simple dependence on redshift. In contrast, the hot gas that actually cools is broadly consistent with a singular isothermal sphere. We find that cooling gas carries a few times the specific angular momentum of the halo and is offset in spin direction from the rest of the hot gas. The gas loses ~60% of its specific angular momentum during the cooling process, generally remaining greater than that of the halo, and is better aligned with th...
Physical Modeling of Slag `Eye' in an Inert Gas-Shrouded Tundish Using Dimensional Analysis
Chatterjee, Saikat; Chattopadhyay, Kinnor
2016-02-01
The formation of an exposed eye in the gas-stirred metallurgical vessels such as ladle or tundish is a common observation. Although gas stirring results in proper homogenization of melt composition and temperature, the resulting exposed eye leads to higher heat losses, re-oxidation of liquid steel, and formation of inclusions. Most of the previous research related to slag eye were carried out explicitly for ladles. In the present work, a large number of experiments were performed to measure the slag eye area in full scale and one-third scale water models of an inert gas-shrouded tundish under various operating conditions. Based on the polynomial regression of experimental data, and the method of dimensional analysis, correlations for diameter of gas bubbles and plume velocity were developed. Subsequently, these results were used to obtain correlations for the slag eye area, and critical gas flow rate in an inert gas-shrouded tundish in terms of the operational parameters viz., gas flow rate, thickness of the slag and melt baths, along with the physical properties of the liquids viz., kinematic viscosity and density. It was observed that the dimensionless slag eye area can be expressed in terms of dimensionless numbers such as the density ratio, Froude number, and Reynolds number.
Analysis of Neutron Stars Observations Using a Correlated Fermi Gas Model
Hen, O; Piasetzky, E; Weinstein, L B
2016-01-01
Background: The nuclear symmetry energy is a fundamental ingredient in determining the equation of state (EOS) of neutron stars (NS). Recent terrestrial experiments constrain both its value and slope at nuclear saturation density, however, its value at higher densities is unknown. Assuming a Free Fermi-gas (FFG) model for the kinetic symmetry energy, the high-density extrapolation depends on a single parameter, the density dependence of the potential symmetry energy. The Correlated Fermi-gas (CFG) model improves on the FFG model by including the effects of short-range, correlated, high-momentum, nucleons in nuclear matter. Using the CFG model for the kinetic symmetry energy along with constraints from terrestrial measurements leads to a much softer density dependence for the potential symmetry energy. Purpose: Examine the ability of the FFG and CFG models to describe NS observables that are directly sensitive to the symmetry energy at high-density. Specifically, examine the ability of the CFG model, with its ...
French gas industry in transition: breach in the public service model
Energy Technology Data Exchange (ETDEWEB)
Finon, D
2001-08-01
France is generally viewed as the European country that most vigorously resists the pressure to liberalize its national gas markets. The moderate reform which has resulted from the transcription of the European gas directive was voted in 2002 after much delay. The main reason is the robustness of the French public service-model which has shaped the gas industry organisation in the same way as most of the network industries. To explain the institutional stability of the French gas industry, this document analyses its institutional trajectory shaped by the public service model and its strong institutional path dependency, marked by the resistance to change. The central hypothesis of the analysis is that, as long as this model demonstrates economic and social efficiency in the development of gas supply in relation to public services obligation and in the control of the import dependence risk in the gas sector, no reform can be brought about by endogenous factors. The analysis of the French gas industry transition consists of four sections. After a survey of its historical development, the author presents its organisation and regulation under the public service model and its performances in terms of social and economic efficiency. In the third section, the minimalist reform for transcribing the European Directive in the French law is presented, in order to identify its potential effects in terms of competition development and public service erosion. Finally, in the fourth section, the industrial policy option to preserve the existence of a French mono-energy company and its consequences in terms of strategic adaptation are discussed. (A.L.B.)
French gas industry in transition: breach in the public service model
International Nuclear Information System (INIS)
France is generally viewed as the European country that most vigorously resists the pressure to liberalize its national gas markets. The moderate reform which has resulted from the transcription of the European gas directive was voted in 2002 after much delay. The main reason is the robustness of the French public service-model which has shaped the gas industry organisation in the same way as most of the network industries. To explain the institutional stability of the French gas industry, this document analyses its institutional trajectory shaped by the public service model and its strong institutional path dependency, marked by the resistance to change. The central hypothesis of the analysis is that, as long as this model demonstrates economic and social efficiency in the development of gas supply in relation to public services obligation and in the control of the import dependence risk in the gas sector, no reform can be brought about by endogenous factors. The analysis of the French gas industry transition consists of four sections. After a survey of its historical development, the author presents its organisation and regulation under the public service model and its performances in terms of social and economic efficiency. In the third section, the minimalist reform for transcribing the European Directive in the French law is presented, in order to identify its potential effects in terms of competition development and public service erosion. Finally, in the fourth section, the industrial policy option to preserve the existence of a French mono-energy company and its consequences in terms of strategic adaptation are discussed. (A.L.B.)
GASTALE. An oligopolistic model of production and trade in the European gas market
Energy Technology Data Exchange (ETDEWEB)
Boots, M.G.; Rijkers, F.A.M. [ECN Policy Studies, Petten (Netherlands); Hobbs, B.F. [John Hopkins University, Baltimore, Maryland (United States)
2003-08-01
The empirical model GASTALE is described and used to analyse the European natural gas market. These analyses focus primarily on the role of the downstream trading companies and their interaction with gas producers. By default, producers of natural gas are assumed to form an oligopoly in the paper. Meanwhile, downstream within-country traders of gas are represented in different versions of the model as local oligopolists or perfect competitors. The model therefore has a two-level structure, in which producers engage in competition a la Cournot, and each producer is a Stackelberg leader with respect to traders, who may be Cournot oligopolists or perfect competitors. The case of Cournot traders results in a new form of energy model, that of successive oligopoly. The model is formulated as a complementarity problem, and is solved by nonlinear programming. Considering this oligopolistic market structure, several tentative conclusions emerge. First, our model results show that successive oligopoly (so-called 'double marginalisation') yields significantly higher prices and lower consumer welfare than if oligopoly exists only on one level. Second, oligopoly in the trading market (because of the high concentration of traders) results in more distortion than oligopoly in production. Third, the level of traders' profits depends on the possibilities of discrimination on the border prices. If price discrimination by producers is allowed, these producers collect a greater share of the margins on end-use prices. Fourth, when the number of traders increases and assuming an oligopolistic downstream structure, end-use prices converge to prices corresponding with perfect competition. Thus, it is important to prevent (or abolish) monopolistic structures in the downstream gas market. In the case where oligopolistic competition among downstream gas companies cannot be prevented, vertical integration should be supported (or at least not be discouraged), especially if it
Sühring, Roxana; Wolschke, Hendrik; Diamond, Miriam L; Jantunen, Liisa M; Scheringer, Martin
2016-07-01
Gas-particle partitioning is one of the key factors that affect the environmental fate of semivolatile organic chemicals. Many organophosphate esters (OPEs) have been reported to primarily partition to particles in the atmosphere. However, because of the wide range of their physicochemical properties, it is unlikely that OPEs are mainly in the particle phase "as a class". We compared gas-particle partitioning predictions for 32 OPEs made by the commonly used OECD POV and LRTP Screening Tool ("the Tool") with the partitioning models of Junge-Pankow (J-P) and Harner-Bidleman (H-B), as well as recently measured data on OPE gas-particle partitioning. The results indicate that half of the tested OPEs partition into the gas phase. Partitioning into the gas phase seems to be determined by an octanol-air partition coefficient (log KOA) -5 (PL in Pa), as well as the total suspended particle concentration (TSP) in the sampling area. The uncertainty of the physicochemical property data of the OPEs did not change this estimate. Furthermore, the predictions by the Tool, J-P- and H-B-models agreed with recently measured OPE gas-particle partitioning. PMID:27144674
Lattice-fluid model for gas-liquid chromatography.
Tao, Y; Wells, P S; Yi, X; Yun, K S; Parcher, J F
1999-11-01
Lattice-fluid models describe molecular ensembles in terms of the number of lattice sites occupied by molecular species (r-mers) and the interactions between neighboring molecules. The lattice-fluid model proposed by Sanchez and Lacombe (Macromolecules, 1978;11:1145-1156) was used to model specific retention volume data for a series of n-alkane solutes with n-alkane, polystyrene, and poly(dimethylsiloxane) stationary liquid phases. Theoretical equations were derived for the specific retention volume and also for the temperature dependence and limiting (high temperature) values for the specific retention volume. The model was used to predict retention volumes within 10% for the n-alkanes phases; 22% for polystyrene; and from 20 to 70% for PDMS using no adjustable parameters. The temperature derivative (enthalpy) could be calculated within 5% for all of the solutes in nine stationary liquid phases. The limiting value for the specific retention volume at high temperature (entropy controlled state) could be calculated within 10% for all of the systems. The limiting data also provided a new chromatographic method to measure the size parameter, r, for any chromatographic solute using characteristic and size parameters for the stationary phase only. The calculated size parameters of the solutes were consistent, i.e. independent of the stationary phase and agreed within experimental error with the size parameters previously reported from saturated vapor pressure, latent heat of vaporization or density data.
Multi-period natural gas market modeling Applications, stochastic extensions and solution approaches
Egging, Rudolf Gerardus
This dissertation develops deterministic and stochastic multi-period mixed complementarity problems (MCP) for the global natural gas market, as well as solution approaches for large-scale stochastic MCP. The deterministic model is unique in the combination of the level of detail of the actors in the natural gas markets and the transport options, the detailed regional and global coverage, the multi-period approach with endogenous capacity expansions for transportation and storage infrastructure, the seasonal variation in demand and the representation of market power according to Nash-Cournot theory. The model is applied to several scenarios for the natural gas market that cover the formation of a cartel by the members of the Gas Exporting Countries Forum, a low availability of unconventional gas in the United States, and cost reductions in long-distance gas transportation. 1 The results provide insights in how different regions are affected by various developments, in terms of production, consumption, traded volumes, prices and profits of market participants. The stochastic MCP is developed and applied to a global natural gas market problem with four scenarios for a time horizon until 2050 with nineteen regions and containing 78,768 variables. The scenarios vary in the possibility of a gas market cartel formation and varying depletion rates of gas reserves in the major gas importing regions. Outcomes for hedging decisions of market participants show some significant shifts in the timing and location of infrastructure investments, thereby affecting local market situations. A first application of Benders decomposition (BD) is presented to solve a large-scale stochastic MCP for the global gas market with many hundreds of first-stage capacity expansion variables and market players exerting various levels of market power. The largest problem solved successfully using BD contained 47,373 variables of which 763 first-stage variables, however using BD did not result in
International Nuclear Information System (INIS)
This dissertation develops deterministic and stochastic multi-period mixed complementarity problems (MCP) for the global natural gas market, as well as solution approaches for large-scale stochastic MCP. The deterministic model is unique in the combination of the level of detail of the actors in the natural gas markets and the transport options, the detailed regional and global coverage, the multi-period approach with endogenous capacity expansions for transportation and storage infrastructure, the seasonal variation in demand and the representation of market power according to Nash-Cournot theory. The model is applied to several scenarios for the natural gas market that cover the formation of a cartel by the members of the Gas Exporting Countries Forum, a low availability of unconventional gas in the United States, and cost reductions in long-distance gas transportation. The results provide insights in how different regions are affected by various developments, in terms of production, consumption, traded volumes, prices and profits of market participants. The stochastic MCP is developed and applied to a global natural gas market problem with four scenarios for a time horizon until 2050 with nineteen regions and containing 78,768 variables. The scenarios vary in the possibility of a gas market cartel formation and varying depletion rates of gas reserves in the major gas importing regions. Outcomes for hedging decisions of market participants show some significant shifts in the timing and location of infrastructure investments, thereby affecting local market situations. A first application of Benders decomposition (BD) is presented to solve a large-scale stochastic MCP for the global gas market with many hundreds of first-stage capacity expansion variables and market players exerting various levels of market power. The largest problem solved successfully using BD contained 47,373 variables of which 763 first-stage variables, however using BD did not result in
A Graphical Adversarial Risk Analysis Model for Oil and Gas Drilling Cybersecurity
Vieira, Aitor Couce; Houmb, Siv Hilde; Insua, David Rios
2014-01-01
Oil and gas drilling is based, increasingly, on operational technology, whose cybersecurity is complicated by several challenges. We propose a graphical model for cybersecurity risk assessment based on Adversarial Risk Analysis to face those challenges. We also provide an example of the model in the context of an offshore drilling rig. The proposed model provides a more formal and comprehensive analysis of risks, still using the standard business language based on decisions, risks, and value.
New Version of the Universal Modeling for Centrifugal Compressor Gas Dynamic Design
Soldatova, Kristina; Yuri, Galerkin; Aleksandr, Drozdov
2014-01-01
Decades ago at pre – computer era design process consisted of empirically based set of rules application to choose main flow path dimensions. Serious model tests were obligatory before compressor manufacturing to check delivery pressure and efficiency. Better flow physical models and computer progress made possible to develop quickly operating programs to predict gas dynamic performance curves of an arbitrary flow path. TU SPb set of computer programs was named “The Universal modeling method”...
Modeling of NOx emissions in turbulent combustion of natural gas fired industrial furnace
International Nuclear Information System (INIS)
The paper reports the application of three dimensional mathematical model of natural gas combustion in PK-35 steam boiler. Special emphasis is placed on the formation and distribution of the nitric oxide in the combustion chamber. Models for thermal and prompt NO - formation mechanisms are included into the mathematical model. An analysis is made on the bases of comparison between the numerical and experimental data available. Possibilities for reduction of NO - emissions in the furnace are also discussed
A gas bubble-based parallel micro manipulator: conceptual design and kinematics model
International Nuclear Information System (INIS)
The parallel mechanism has become an alternative solution when micro manipulators are demanded in the fields of micro manipulation and micro assembly. In this technical note, a three-degree-of-freedom (3-DOF) parallel micro manipulator is presented, which is directly driven by three micro gas bubbles. Since the micro gas bubbles are generated and maintained due to the surface tension between the gas and liquid media, the proposed novel system can be used in the liquid environment which allows for rotation about the X and Y axes and translation along the Z axis. In this technical note, the conceptual design of micro gas bubble-based parallel manipulator is introduced and the input/output characteristic of the actuator is analyzed in detail. The kinematics model of the parallel micro manipulator is also established, based on which the workspace and the system motion resolution are analyzed as a criterion and reference for future prototype development. (technical note)
Density-Corrected Models for Gas Diffusivity and Air Permeability in Unsaturated Soil
DEFF Research Database (Denmark)
Chamindu, Deepagoda; Møldrup, Per; Schjønning, Per;
2011-01-01
profile data (total of 150 undisturbed soil samples) were used to investigate soil type and density effects on the gas transport parameters and for model development. The measurements were within a given range of matric potentials (-10 to -500 cm H2O) typically representing natural field conditions......Accurate prediction of gas diffusivity (Dp/Do) and air permeability (ka) and their variations with air-filled porosity (e) in soil is critical for simulating subsurface migration and emission of climate gases and organic vapors. Gas diffusivity and air permeability measurements from Danish soil...... in subsurface soil. The data were regrouped into four categories based on compaction (total porosity F 0.4 m3 m-3) and soil texture (volume-based content of clay, silt, and organic matter 15%). The results suggested that soil compaction more than soil type was the major control on gas...
Ning, Youjun; Yang, Jun; Ma, Guowei; Chen, Pengwan
2011-07-01
Explosion gas plays an important role in rock mass fragmentation and cast in rock blasting. In this technical note, the discontinuous deformation analysis method is extended for bench rock blasting by coupling the rock mass failure process and the penetration effect of the explosion gas based on a generalized artificial joint concept to model rock mass fracturing. By tracking the blast chamber evolution dynamically, instant explosion gas pressure is derived from the blast chamber volume using a simple polytropic gas pressure equation of state and loaded on the blast chamber wall. A bench blasting example is carried out. The blast chamber volume and pressure time histories are obtained. The rock failure and movement process in bench rock blasting is reproduced and analysed.
Khalilpour, Rajab
2011-08-12
The modeling and optimal design/operation of gas membranes for postcombustion carbon capture (PCC) is presented. A systematic methodology is presented for analysis of membrane systems considering multicomponent flue gas with CO 2 as target component. Simplifying assumptions is avoided by namely multicomponent flue gas represented by CO 2/N 2 binary mixture or considering the co/countercurrent flow pattern of hollow-fiber membrane system as mixed flow. Optimal regions of flue gas pressures and membrane area were found within which a technoeconomical process system design could be carried out. High selectivity was found to not necessarily have notable impact on PCC membrane performance, rather, a medium selectivity combined with medium or high permeance could be more advantageous. © 2011 American Institute of Chemical Engineers (AIChE).
A Gas Centric Model For Intergalactic Filament Development During the First Gigayear
Harford, A Gayler
2016-01-01
Using a cosmological simulation of the first gigayear of the universe, we find that the mass per unit length of reionizing intergalactic filaments is proportional to the square of the sound speed with a proportionality constant equal to that predicted for a gravitationally bound, isothermal cylinder. These cylinders contain both gas and dark matter, and the dark matter contributes to the gravitational field roughly in proportion to its abundance. The dark matter of each galaxy collapses according to the cycloid predicted for spherically symmetric collapse in an expanding universe. In contrast, the gas collapses more slowly into the centre of the galaxy. After reionization filaments persist and, in some cases, become enriched in either gas or dark matter. We have incorporated these findings into a unified model. A key feature of a gravitationally bound, isothermal cylinder is that the mass per unit length depends only upon the temperature and ionization state of the gas. This property suggests a lower limit on...
Models of evolution of gas and abundances in dwarf irregular galaxies
Gavilan, M; Díaz, A I
2009-01-01
We have developed a grid of chemical evolution models applied to dwarf isolated galaxies, using \\cite{gav05} yields. The input data enclose different star formation efficiencies, galaxy mass and collapse time values. The result is a wide collection of solutions that vary from objects with low metallicity and great amount of gas, to those with little gas and high metallicity. No environmental effects like tidal or galactic winds have been treated, so these objects are expected to be close to field dwarf galaxies, more than cluster ones. We have studied the time evolution of the abundance of oxygen and nitrogen and the amount of gas, related to their star formation history, as well as the possibility of gas losses by SN winds.
Thermodynamic and Process Modelling of Gas Hydrate Systems in CO2 Capture Processes
DEFF Research Database (Denmark)
Herslund, Peter Jørgensen
A novel gas separation technique based on gas hydrate formation (solid precipitation) is investigated by means of thermodynamic modeling and experimental investigations. This process has previously been proposed for application in post-combustion carbon dioxide capture from power station flue gases...... on thermodynamic gas hydrate promotion by hydrate formers stabilising the classical gas clathrate hydrate structures (sI, sII and sH) at low to moderate pressures. Much literature is available on this subject. Both experimental and theoretical studies presented in the literature have pointed out cyclopentane...... and tetrahydrofuran as the two most efficient pressure reducing additives in classical hydrate forming systems. The thermodynamic promoting effects reported in the literature for the two classical sII hydrate formers, tetrahydrofuran and cyclopentane are experimentally confirmed in the present work. Data presented...
Particle-in-cell modeling of gas-confined barrier discharge
Levko, Dmitry; Raja, Laxminarayan L.
2016-04-01
Gas-confined barrier discharge is studied using the one-dimensional Particle-in-Cell Monte Carlo Collisions model for the conditions reported by Guerra-Garcia and Martinez-Sanchez [Appl. Phys. Lett. 106, 041601 (2015)]. Depending on the applied voltage, two modes of discharge are observed. In the first mode, the discharge develops in the entire interelectrode gap. In the second mode, the discharge is ignited and develops only in the gas layer having smaller breakdown voltage. The one-dimensional model shows that for the conditions considered, there is no streamer stage of breakdown as is typical for a traditional dielectric barrier discharge.
Modeling and Simulation for Control of Lean-Burn Gas Engines
Sirum, Jørgen
2009-01-01
In this thesis a lean-burn gas engine, produced by Rolls-Royce is studied. The goal is to make an improved simulation model in Simulink for the Bergen B-gas engine by including turbocharger dynamics. And also test and investigate if an MPC controller can improve the engine's behavior compared to the current controller.First the general internal combustion engine is presented. Then a literature study concerning mathematical modeling of engines is conducted. Further, a mean value engine mo...