Influence of spectral particle properties on radiative heat transfer in optically thin and thick media of fluidized bed combustors

Date

2017-12-01

Author

Ates, Cihan
Sen, Ozge
Selçuk, Nevin
Külah, Görkem

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

220
views

0
downloads

In this study, influence of spectral particle properties on radiative heat transfer in the freeboard/dilute zone of fluidized bed combustors (FBCs) is investigated. The aim is to identify how important it is to involve spectral particle properties and to determine the predictive accuracy of gray Mie and gray Geometric Optics (GOA) approximations in optically thin and thick media by benchmarking their predictions against spectral solutions. For that purpose, input data required for modelling radiative heat transfer and validating its predictions are provided from three combustion tests carried out in lignite fired 300 kWt Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) and 150 kWt Circulating Fluidized Bed Combustor (CFBC) test rigs. The results show that gray particle assumption leads to accurate radiative heat flux predictions with one order of magnitude less CPU time for both optically thin and thick media while it gives acceptable accuracy in source term predictions for only optically thin medium and the error becomes significant as the optical thickness increases. Assessment of GOA in FBCs, on the other hand, 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. If the majority of cumulative cross sectional area is constituted by large particles which fall into geometric optics limit, gray GOA yields satisfactory results compared to spectral solution even if the medium is optically thick without going through cumbersome spectral calculations. (C) 2017 Elsevier Masson SAS. All rights reserved.

Subject Keywords

Nongray Particle Radiation, Spectral Solution of RTE, Geometric Optics Approximation, Particle Size Distribution, Phase Function, Fluidized Bed Combustors

URI

https://hdl.handle.net/11511/32639

Journal

INTERNATIONAL JOURNAL OF THERMAL SCIENCES

DOI

https://doi.org/10.1016/j.ijthermalsci.2017.08.023

Collections

Graduate School of Natural and Applied Sciences, Article

Suggestions

OpenMETU
Core

Influence of soot on radiative heat transfer in bubbling fluidized bed combustors Yaşar, Mehmet Soner; Selçuk, Nevin; Külah, Görkem (2021-08-01) The effect of soot particles and aggregates on radiative heat transfer in bubbling fluidized bed combustors is investigated. For this purpose, a soot radiative property model based on Rayleigh scattering theory is coupled with in-house developed 1-D gray and spectral radiation codes and a 3-D spectral radiation code based on method of lines solution of discrete ordinates method for the application of (i) a 1-D slab problem involving combustion gases and soot and (ii) freeboard of a 0.3 MWt atmospheric bubbl...
Significance of particle concentration distribution on radiative heat transfer in circulating fluidized bed combustors Ates, CİHAN; Selçuk, Nevin; Külah, Görkem (2018-02-01) In this study, effect of particle concentration distribution on radiative heat transfer in circulating fluidized bed combustors (CFBCs) is investigated. The aim is to identify how important it is to include axial and radial variations of particle concentration along the splash and dilute zones in radiative heat transfer calculations and to determine the predictive accuracy of simple OD and 1D approximations for particle concentration distribution in the riser by benchmarking their predictions against a semi...
Influence of fly ash composition on non-gray particle radiation in combusting systems Ates, CİHAN; Selçuk, Nevin; Külah, Görkem (2018-08-01) In this study, chemical composition dependency of both radiative properties of ash particles and radiative heat exchange are investigated for conditions typically encountered in industrial coal-fired furnaces. For that purpose, chemical composition dependent / independent complex index of refraction models are utilized to evaluate (i) spectral particle absorption efficiencies, scattering efficiencies and asymmetry factors, (ii) particle cloud properties representing pulverized coal fired furnaces (PC-Fired)...
Influence of bag filter ash to spectral thermal radiation in fluidized bed combustors Co-Fired with biomass Yaşar, Mehmet Soner; Selçuk, Nevin; Külah, Görkem (2021-09-01) Influence of fine particles collected in bag filter on spectral thermal radiation is investigated in the freeboard of a 0.3 MWt atmospheric bubbling fluidized bed combustion test rig where lignite, lignite/olive residue, and lignite/hazelnut shell blends are fired with limestone addition. For this purpose, a 3-D radiation code based on method of lines solution of discrete ordinates method coupled with banded one gas spectral line-based weighted sum of gray gases for spectral gas properties, Mie theory for s...
Escape of photoelectrons and Compton-scattered photons from an HPGe detector Can, Cüneyt (Wiley, 2003-07-01) The response function of a planar HPGe detector due to escape of photoelectrons and Compton-scattered photons was studied for a point source with 59.5 keV energy. It was shown that both mechanisms, in addition to Ge x-ray escape, leading to partial deposition of energy, could be observed in the same experiment. A Monte Carlo program was used to investigate these components of the response function. The results indicate that although the escape of scattered photons and Ge x-rays are of the same magnitude, th...

Citation Formats

C. Ates, O. Sen, N. Selçuk, and G. Külah, “Influence of spectral particle properties on radiative heat transfer in optically thin and thick media of fluidized bed combustors,” INTERNATIONAL JOURNAL OF THERMAL SCIENCES, pp. 266–280, 2017, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/32639.