Isil Ayranci

MOL solution of DOM for transient radiative transfer in 3-D scattering media

Abstract A methodology based on the method of lines solution of discrete ordinates method for solution of the 3-D transient radiative transfer equation is introduced. The method is applied to the prediction of transient and steady state transmittances in a cubical enclosure containing purely scattering medium and validated against Monte Carlo solutions from the literature. The flexibility of the method for implementation of linear spatial differencing schemes, flux limiters and weighted essentially non-oscillatory methods is demonstrated. Van Leer flux limiter is found to provide stable, accurate and efficient solutions.

THE METHOD OF LINES SOLUTION OF THE DISCRETE ORDINATES METHOD FOR RADIATIVE HEAT TRANSFER IN ENCLOSURES CONTAINING SCATTERING MEDIA

A radiation code based on the method of lines (MOL) solution of the discrete ordinates method (DOM) for three-dimensional radiative heat transfer in rectangular enclosures containing gray, absorbing, emitting, isotropically and anisotropically scattering media was developed. Predictive accuracy of the code was evaluated by applying the code to 1-D and 3-,D problems containing scattering media and benchmarking its predictions against exact solutions, the zone method, and Monte Carlo solutions. Favorable comparisons reveal that MOL solution of the DOM provides accurate solutions for modeling radiative heat transfer in 3-D rectangular enclosures containing purely scattering or absorbing, emitting, and scattering media with isotropic or anisotropic scattering properties.

Performance of method of lines solution of discrete ordinates method in the freeboard of a bubbling fluidized bed combustor

Abstract Predictive accuracy of the method of lines (MOL) solution of discrete ordinates method (DOM) is assessed by applying it to the prediction of incident radiative fluxes on the freeboard walls of a bubbling fluidized bed combustor, and comparing its predictions with those of the zone method and measurements. Freeboard is treated as a three-dimensional rectangular enclosure containing gray, absorbing, emitting and isotropically scattering medium. Radiative properties of the medium are calculated by using Leckners correlations for gas and Mie theory for particles. Data for application and validation are generated from METU 0.3 MW t atmospheric bubbling fluidized bed combustor test rig burning lignite in its own ash. Comparisons reveal that MOL solution of DOM provides accurate and computationally efficient solutions for wall fluxes in the freeboard of fluidized bed combustors containing particle laden combustion gases. Parametric studies are also carried out to analyze the sensitivity of predicted heat flux profiles to the presence of particles, particle load and anisotropic scattering.

Effect of Recycle on Radiative Heat Transfer in the Freeboard of a Fluidized Bed Combustor

Effect of recycle on radiative heat transfer in the freeboard of a fluidized bed combustor is investigated by applying a previously developed 3-D radiation model to the prediction of incident radiative heat fluxes along the freeboard walls of lignite-fired 0.3 MWt Middle East Technical University (METU) Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) Test Rig and comparing its predictions with measurements. Freeboard is treated as a rectangular enclosure containing gray, absorbing, emitting and isotropically scattering medium bounded by gray and diffuse walls. Radiative properties of the medium are calculated by using Leckner’s correlations for gas and Mie theory for polydisperse particle cloud. Radiative transfer equation for this system is solved by using Method of Lines (MOL) solution of Discrete Ordinates Method (DOM). Experimental data required for application and validation are generated from two runs in which parameters other than recycle ratio was held as nearly constant as possible. Comparisons between predicted incident radiative heat fluxes and measurements with and without recycle reveal that the agreement is excellent and that the effect of recycle on incident radiative heat fluxes is significant. A parametric study is also carried out to investigate the effect of particle load on fluxes. Predictions are found to be relatively insensitive to the particle load but strongly affected by the temperature profile.Copyright