Differential approximation for radiative transfer in a nongrey gas near equilibrium.

https://isiarticles.com/bundles/Article/pre/pdf/28258.pdf

Thermal performance analysis of porous media receiver with concentrated solar irradiation

In this paper, the problem of unsteady convection with chemical reaction and radiative heat transfer past a flat porous plate moving through a binary mixture in an optically thin environment is presented. The dimensionless governing equations for this investigation are solved numerically by the fourth-order Runge–Kutta integration scheme along with shooting technique. Numerical data for the local skin-friction coefficient, the local Nusselt number and the local Sherwood number have been tabulated for various values of parametric conditions. Graphical results for velocity, temperature and concentration profiles based on the numerical solutions are presented and discussed.

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Unsteady convection with chemical reaction and radiative heat transfer past a flat porous plate moving through a binary mixture

Large eddy simulations of pulverised coal combustion (PCC-LES) stabilised on a laboratory-scale piloted jet burner are carried out. The joint simulation effort of three research groups at Freiberg University (FG), Imperial College (IC) and Stuttgart University (ST) is presented, and the details of the comprehensive coal combustion models and their numerical implementation in three different computer programs are discussed. The (standard) coal sub-models and parameters used by the different groups are unified wherever possible. Differences amongst the groups are a different code basis and an Eulerian treatment of the coal particles by IC, while FG and ST use the Lagrangian framework for particle transport. The flow modelling is first validated for the corresponding non-reacting case and all LES calculations accurately capture the experimental trends. Velocity field statistics for the PCC case are in good accordance with the experimental evidence, but scalar statistics illustrate the complexity of coal combustion modelling. The results show notable differences amongst the groups that cannot only be attributed to the different treatment of the particle phase, and they highlight the difficulty to assess and interpret the quality of specific modelling approaches, and a need for further work by the research community. The present study is the first to compare three originally independent transient coal simulations and a step towards comprehensive PCC-LES.

Towards Comprehensive Coal Combustion Modelling for LES

The exact solution to radiative heat transfer in combusting flows is not possible analytically due to the complex nature of the integro-differential radiative transfer equation (RTE). Many different approximate solution methods for the solution of the RTE in multi-dimensional problems are available. In this paper, two of the principal methods, the spherical harmonics (P1) and the discrete ordinates method (DOM) are used to calculate radiation. The radiative properties of the gases are calculated using a non-gray gas full spectrum k-distribution method and a gray method. Analysis of the effects of numerical quadrature in the DOM and its effect on computation time is performed. Results of different radiative property methods are compared with benchmark statistical narrow band (SNB) data for both cases that simulate air combustion and oxy-fuel combustion. For both cases, results of the non-gray full spectrum k-distribution method are in good agreement with the SNB data. In the case of oxy-fuel simulations with high partial pressures of carbon dioxide, use of gray method for the radiative properties may cause errors and should be avoided.

/pdf/evaluation-of-solution-methods-for-radiative-heat-transfer-2a6uekbn0p.pdf

Evaluation of solution methods for radiative heat transfer in gaseous oxy-fuel combustion environments

: The author first lists the hydrodynamic equations for the three-dimensional time-dependent flow. This is followed by a discussion of the approximate radiationtransport equations. Finally, the linearized equations for two-dimensional steady flow are obtained.

Ping Cheng

Papers

Linearized theory of two-dimensional radiating gas flow by a moment method,