Improvements of radiative transfer calculation for SF6 thermal plasmas

International audienceWe present a comparison between an exact calculation of radiative transfer in SF 6 thermal plasma based on a fine description of the spectrum with 300 000 spectral points for each temperature value, for simplified conditions (1D and 2D geometries with imposed symmetrical temperature profiles and Local Thermodynamic Equilibrium) and two kinds of approximated calculations. The first is the classical Net Emission Coefficient largely used in arc modelling. The second one is based on a very simplified spectral description with only seven intervals assuming a grey body condition within each interval and using the Planck and the Rosseland averaging for deducing the mean absorption coefficient. At high temperature the use of the Rosseland averaging is not satisfactory. The other two approximated methods (Net emission and the Planck averaging) are acceptable but the radiative flux is in general not very accurate. The radiative transfer calculation can be improved following three ways: a better knowledge of the basic processes and in particular of the absorption coefficients for diatomic and polyatomic molecules ; the use of different definitions of mean absorption coefficients (Planck averaging at high temperature and mean natural value at low temperature) ; a careful choice of the spectral intervals

Computational Approaches to Zeolite-Based Adsorption Processes

Computational methods to calculate the properties of zeolites in gas adsorption and separation have proven to be a valuable complement to experimental work. Molecular simulation provides a molecular understanding of the mechanisms involved in the adsorption, desorption, and transport. The accuracy and reliability of the predictions depend on the models used for adsorbates and adsorbents, the force fields that describe the interaction, and the computational methods to calculate the properties. The selection of force fields and methods depends on the properties of the systems and on characteristics such as the flexibility of the framework, the hydrophobicity/hydrophilicity of the zeolite, the chirality, the silicon atom substitutions, the nature and concentration of extra framework cations, the composition of the guest gases, the measured property, etc. In this chapter, a brief description of the state of the art of molecular simulation applied to porous materials is provided, as well as a discussion of current challenges in the field.</p