Modeling of radiative heat transfer in strongly forward scattering media of bubbling fluidized bed combustor with and without recycle

Download

index.pdf

Date

2017

Author

Şen, Özge

Metadata

Show full item record

Item Usage Stats

183
views

82
downloads

Predictive accuracy and CPU efficiency of geometric optics approximation (GOA) and scattering phase function simplifications in the freeboard of lignite-fired METU 0.3 MWt ABFBC Test Rig were tested by applying them to the modeling of radiative heat transfer and comparing their predictions against measurements and benchmark solutions. The freeboard was treated as 3-D rectangular enclosure containing grey, absorbing, emitting gas with grey, absorbing, emitting, non/isotropically/anisotropically scattering particles surrounded by diffuse grey/black walls. A three-dimensional radiation model based on Method of Lines (MOL) solution of Discrete Ordinates Method (DOM) coupled with Grey Gas (GG) for gases and Mie theory / GOA for fly ash particles in rectangular coordinates was extended for incorporation of anisotropic scattering by using normalized Henyey-Greenstein (HG) for the phase function. The input data required for the model and its validation were provided from the experimental data, which was previously taken from METU 0.3 MWt ABFBC Test Rig operating with and without recycle of fine particles. Assessment of GOA in terms of predictive accuracy reveals that applicability limit of GOA should be based on cumulative cross sectional area distribution rather than surface mean diameter or cumulative weight distribution of particles. From the viewpoints of computational economy, GOA was found to improve CPU efficiency of the solution with increasing optical thickness. Predictive accuracy and computational efficiency of scattering phase function simplifications were tested by comparing their predictions with those of forward scattering with HG. Comparisons reveal that phase function simplifications have insignificant effect on incident heat fluxes whereas source terms were found to be sensitive to phase function simplifications and the sensitivity increases with increasing optical thickness. Improvement in CPU efficiency of phase function simplifications is observed in only combusting systems involving high particle loads; however, in those systems, accurate representation of particle scattering that is forward scattering is vital.

Subject Keywords

Heat, Fluidized-bed combustion., Heat, Anisotropy.

URI

http://etd.lib.metu.edu.tr/upload/12621210/index.pdf
https://hdl.handle.net/11511/26633

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Investigation of tightly coupled arrays for wideband applications Arda, Kaan; Dural Ünver, Mevlüde Gülbin; Department of Electrical and Electronics Engineering (2020-10) This thesis aims to provide in depth research on tightly coupled dipole arrays to be used in ultrawideband apertures applications. First, operation principles of tightly coupled dipole arrays are investigated. Starting from the Wheeler’s current sheet aperture concept, some calculations on bandwidth and impedance concepts are conducted. B.A. Munk’s addition to the concept, use of capacitive elements between adjacent dipoles, are introduced. Array unit cell is modeled using equivalent circuit approach,...
Measurement of differential top-quark-pair production cross sections in pp collisions at root s=7 TeV Chatrchyan, S.; et. al. (Springer Science and Business Media LLC, 2013-03-01) Normalised differential top-quark-pair production cross sections are measured in pp collisions at a centre-of-mass energy of 7 TeV at the LHC with the CMS detector using data recorded in 2011 corresponding to an integrated luminosity of 5.0 fb(-1). The measurements are performed in the lepton + jets decay channels (e + jets and mu + jets) and the dilepton decay channels (e(+)e(-), mu(+)mu(-), and mu(+/-)e(-/+)). The t (t) over bar differential cross section is measured as a function of kinematic properties ...
Modeling and sensitivity analysis of high temperature PEM fuel cells by using Comsol Multiphysics Sezgin, Berna; Caglayan, Dilara Gulcin; DEVRİM, YILSER; Steenberg, Thomas; Eroğlu, İnci (2016-06-22) The objective of this study is to observe the effect of the critical design parameters, velocities of inlet gases (hydrogen and air) and the conductivity of polymer membrane, on the performance of a high temperature PEM fuel cell. A consistent and systematic mathematical model is developed in order to study the effect of these parameters. The model is applied to an isothermal, steady state, three-dimensional PEM fuel cell in order to observe concentration profiles, current density profiles and polarization ...
Implementation of generalized Harvey-Shack theory in light scattering from rough surfaces Gunoven, M.; Nasser, H.; Ünal, Mustafa; Aytekin, O.; Turan, Raşit; Bek, Alpan (2020-12-01) We present a discrete implementation of generalized Harvey-Shack scalar scattering theory to calculate angular intensity distributions from height profiles of select randomly textured surfaces proposed for use in solar cells and covering a wide range of surface characteristics. We compare these calculations to high-resolution angular intensity distribution measurements. These comparisons suggest that the pupil function does benefit from an additional correction factor for rough surfaces containing lateral f...
Measurement of prompt J/psi pair production in pp collisions at root s = 7 Tev Khachatryan, V.; et. al. (Springer Science and Business Media LLC, 2014-09-01) Production of prompt J/psi meson pairs in proton-proton collisions at root s = 7 TeV is measured with the CMS experiment at the LHC in a data sample corresponding to an integrated luminosity of about 4.7 fb(-1). The two J/psi mesons are fully reconstructed via their decays into mu(+)mu(-) pairs. This observation provides for the first time access to the high-transverse-momentum region of J/psi pair production where model predictions are not yet established. The total and differential cross sections are meas...

Citation Formats

Ö. Şen, “Modeling of radiative heat transfer in strongly forward scattering media of bubbling fluidized bed combustor with and without recycle,” M.S. - Master of Science, Middle East Technical University, 2017.