scholarly journals 0D KINETIC MODEL: APPLIED TO SF6

2021 ◽  
Vol 7 (3) ◽  
pp. 52-58
Author(s):  
A. Harry Solo ◽  
P. Freton ◽  
J.-J. Gonzalez ◽  
M. Benmouffok
Keyword(s):  
Cooling Rate ◽  
Constant Pressure ◽  
Local Thermodynamic Equilibrium ◽  
Mass Density ◽  
Kinetic Scheme ◽  
Constant Mass ◽  
Dimensional Model ◽  
Circuit Breakers ◽  
Kinetics Modelling ◽  
Temperature Decay

This work is related to the chemical kinetics modelling of plasma during extinction. A zero-dimensional model (0D) has been developed. Two hypotheses were used: (A) a constant pressure or (B) a constant mass density. Three initial data categories are generally required for the model: (1) the chemical reactions that govern the kinetic scheme, (2) the chemical composition at the local thermodynamic equilibrium (LTE) and (3) a law of temperature decay as a function of time representing the cooling rate. The developed model is presented and applied to SF6, gas commonly used in high voltage circuit breakers (HVCB), in order to be validated. We present the evolution of the species during the temperature decay for several cooling rates. The results give the evolution of species densities and the departures from equilibrium according to the cooling rate. Consideration of SFx molecules is essential in order to avoid erroneous interpretations.

scholarly journals State of Art and Challenges for the Calculation of Radiative and Transport Properties of Thermal Plasmas in HVCB

2019 ◽  
Vol 6 (2) ◽  
pp. 208-216 ◽  
Author(s):  
Y. Cressault ◽  
Ph. Teulet ◽  
X. Baumann ◽  
G. Vanhulle ◽  
F. Reichert ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
High Voltage ◽  
Thermophysical Properties ◽  
Local Thermodynamic Equilibrium ◽  
State Of The Art ◽  
Thermal Plasmas ◽  
Radiative Properties ◽  
Circuit Breakers ◽  
Non Local ◽  
State Of Art

This paper is focused on the state-of-the-art and challenges concerning the thermophysical properties of thermal plasmas used in numerical modelling devoted to high voltage circuit breakers. <br />For Local Thermodynamic Equilibrium (LTE) and Non-Local Thermodynamic (NLTE) and/or Chemical Equilibrium (NLCE) plasmas, the methods used to calculate the composition, thermodynamic, transport and radiative properties are presented. <br />A review of these last data is proposed and some comparisons are given for illustrations.

scholarly journals Evolution of supernovae-driven superbubbles with conduction and cooling

2019 ◽  
Vol 490 (2) ◽  
pp. 1961-1990 ◽  
Author(s):  
Kareem El-Badry ◽  
Eve C Ostriker ◽  
Chang-Goo Kim ◽  
Eliot Quataert ◽  
Daniel R Weisz
Keyword(s):  
Cooling Rate ◽  
Evaporation Rate ◽  
Mass Density ◽  
Dynamical Evolution ◽  
Effective Diffusivity ◽  
Blast Waves ◽  
Conductive Heat ◽  
Hydrodynamic Simulations ◽  
Non Linear ◽  
Order Of Magnitude

ABSTRACT We use spherically symmetric hydrodynamic simulations to study the dynamical evolution and internal structure of superbubbles (SBs) driven by clustered supernovae (SNe), focusing on the effects of thermal conduction and cooling in the interface between the hot bubble interior and cooled shell. Our simulations employ an effective diffusivity to account for turbulent mixing from non-linear instabilities that are not captured in 1D. The conductive heat flux into the shell is balanced by a combination of cooling in the interface and evaporation of shell gas into the bubble interior. This evaporation increases the density, and decreases the temperature, of the SB interior by more than an order of magnitude relative to simulations without conduction. However, most of the energy conducted into the interface is immediately lost to cooling, reducing the evaporative mass flux required to balance conduction. As a result, the evaporation rate is typically a factor of ∼3–30 lower than predicted by the classical similarity solution of (Weaver et al. 1977), which neglects cooling. Blast waves from the first ∼30 SNe remain supersonic in the SB interior because reduced evaporation from the interface lowers the mass they sweep up in the hot interior. Updating the Weaver solution to include cooling, we construct a new analytic model to predict the cooling rate, evaporation rate, and temporal evolution of SBs. The cooling rate, and hence the hot gas mass, momentum, and energy delivered by SBs, is set by the ambient interstellar mass density and the efficiency of non-linear mixing at the bubble–shell interface.

scholarly journals Vacuum fluctuation inside a star and their consequences for neutron stars, a simple model

2016 ◽  
Vol 25 (04) ◽  
pp. 1650027 ◽  
Author(s):  
G. Caspar ◽  
I. Rodríguez ◽  
P. O. Hess ◽  
W. Greiner
Keyword(s):  
Black Holes ◽  
Simple Model ◽  
Neutron Stars ◽  
Mass Density ◽  
Radial Distance ◽  
Constant Mass ◽  
Vacuum Fluctuations ◽  
Vacuum Fluctuation ◽  
Monopole Approximation ◽  
Classical Quantum

Applying semi-classical quantum mechanics, the vacuum fluctuations within a star are determined, assuming a constant mass density and applying a monopole approximation. It is found that the density for the vacuum fluctuations does not only depend linearly on the mass density, as assumed in a former publication, where neutron stars up to 6 solar masses were obtained. This is used to propose a simple model on the dependence of the dark energy to the mass density, as a function of the radial distance [Formula: see text]. It is shown that stars with up to 200 solar masses can, in principle, be obtained. Though, we use a phenomenological model, it shows that in the presence of vacuum fluctuations stars with large masses can be stabilized and probably stars up to any mass can exist, which usually are identified as black holes.

Investigation into the Dynamic Fracture Properties of Large Scale Functionally Graded Materials

2006 ◽  
Vol 324-325 ◽  
pp. 239-242 ◽  
Author(s):  
Xiao Bin Yang ◽  
Zhuo Zhuang ◽  
Xue Feng Yao
Keyword(s):  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Large Scale ◽  
Young's Modulus ◽  
Mass Density ◽  
Poisson's Ratio ◽  
Constant Mass ◽  
Functionally Gradient Materials ◽  
Gradient Materials ◽  
Functionally Gradient

A crack propagation perpendicular to gradient in a large scale functionally gradient materials, which has (1) a linear variation of Young’s modulus with a constant mass density and Poisson’s ratio, and (2) a exponential variation of Young’s modulus with a constant mass density and Poisson’s ratio, is modelled by finite element methods. Based on the experimental result of large scale functionally gradient materials, the dynamic propagation process of the FGMs is modelled and the dynamic parameters, like the energy release rate and crack tip opening angle, are calculated through a generation phase.

Grinding Temperatures for Magnetic Ceramics and Steel

1990 ◽  
Vol 112 (3) ◽  
pp. 535-541 ◽  
Author(s):  
S. Chandrasekar ◽  
T. N. Farris ◽  
B. Bhushan
Keyword(s):  
High Speed ◽  
Grinding Wheel ◽  
Infrared Sensor ◽  
Sliding Velocity ◽  
Dimensional Model ◽  
Workpiece Surface ◽  
Magnetic Ceramics ◽  
Temperature Decay ◽  
Diamond Grain ◽  
Good Agreement

Grinding temperatures are measured using an infrared sensor in ferrite and steel. For reference purposes, temperatures are also measured in a reduced model for grinding which consists of a single diamond grain sliding across the workpiece surface at high speed. The results include temperature as a function of sliding velocity, rate of temperature decay as the grain moves away from contact, and histograms of the frequency that grains on the grinding wheel attain a given temperature. It is found that temperature measurements can be used to detect out-of-roundness in the wheel. Finally, a simplified two-dimensional model based on a heat flux moving with constant velocity gives reasonably good agreement with experiment.

scholarly journals On the mass density distribution of the inner galaxy

1979 ◽  
Vol 84 ◽  
pp. 381-382 ◽  
Author(s):  
T. Maihara
Keyword(s):  
Density Distribution ◽  
Mass Density ◽  
Rotational Velocity ◽  
Axial Ratio ◽  
Specific Model ◽  
Absolute Velocity ◽  
Constant Mass ◽  
The Galaxy ◽  
Inner Region ◽  
Synthetic Models

Based on current 2.4-micron observations of the Galaxy (see Okuda et al. in this Symposium), we have proposed a specific model for the bulge component. This model is a concentric spheroid with an axial ratio of ∼0.5; ρ(a)∞(a2+ac2)−1exp(-(a/ao)2), where ao = 2.5 kpc and ac = 0.14 kpc respectively. A constant mass-to-luminosity ratio M/Lv≃7.6 is assumed, which yields the relevant rotational velocity in the inner region (Figure 1); the absolute velocity is normalized to 250 km s−1. This value of M/Lv is likely to meet with giant-rich synthetic models for the nuclear bulge of M31.

scholarly journals Stochiometry Air − CH4 Mixture: Composition, Thermodynamic Propertiess and Transport Coefficients

2020 ◽  
Vol 7 (1) ◽  
pp. 21-29
Author(s):  
A. Harry Solo ◽  
M. Benmouffok ◽  
P. Freton ◽  
J.-J. Gonzalez
Keyword(s):  
Chemical Composition ◽  
Local Thermodynamic Equilibrium ◽  
Mass Density ◽  
Transport Coefficients ◽  
Equation System ◽  
Mass Action ◽  
Particle Interactions ◽  
First Order ◽  
Mass Action Law

This work is related to the determination of the local thermodynamic equilibrium (LTE) data of 90.5% air and 9.5% CH4 mixture. The results of chemical composition, thermodynamic properties and transport coefficients are presented for temperatures (300 K to 30 kK) and pressure (1 and 10 bars) or mass density (0.1481 and 1.111 kg.m<sup>−3</sup>). The chemical composition is determined using the mass action law. Input data come from the NIST and JANAF sites. For pressure equation, Debye-Huckel’s first order and virial’s second order corrections are used in the equation system to take into account the different particle interactions. For the considered mixture (90.5% air and 9.5% CH4) the properties are compared to those of pure air.

cooling in primordial gas

2006 ◽  
Vol 364 (1848) ◽  
pp. 3107-3112 ◽  
Author(s):  
Simon Glover ◽  
Daniel Wolf Savin
Keyword(s):  
Cooling Rate ◽  
Local Thermodynamic Equilibrium ◽  
Critical Density ◽  
Dynamical Evolution ◽  
Planetary Atmospheres ◽  
The Other ◽  
Emission Lines ◽  
Low Density ◽  
Interesting Candidate ◽  
Approximate Treatment

Simulations of the thermal and dynamical evolution of primordial gas typically focus on the role played by H 2 cooling. H 2 is the dominant coolant in low-density primordial gas and it is usually assumed that it remains dominant at high densities. However, H 2 is not an effective coolant at high densities, owing to the low critical density at which it reaches local thermodynamic equilibrium and to the large opacities that develop in its emission lines. It is therefore important to quantify the contribution made to the cooling rate by emission from the other molecules and ions present in the gas. A particularly interesting candidate is the ion, which is known to be an effective coolant at high densities in planetary atmospheres. In this paper, we present results from simulations of the thermal and chemical evolution of gravitationally collapsing primordial gas, which include a detailed treatment of chemistry and an approximate treatment of cooling. We show that in most cases, the contribution from is too small to be important, but if a sufficiently strong ionizing background is present, then cooling may become significant.

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