Length scales of solid clusters in a two-dimensional circulating fluidized bed of Geldart B particles

D.N. Mondal (Corresponding Author), Sirpa Kallio, H. Saxen

Research output: Contribution to journalArticleScientificpeer-review

14 Citations (Scopus)

Abstract

The flow pattern in a circulating fluidized bed (CFB) is characterized by clusters of particles. The length-scale distribution of solid clusters was analyzed both horizontally and vertically from a number of experiments carried out with Geldart B particles in a two-dimensional circulating fluidized bed. Cluster dimensions were found to be dependent on solid loading, superficial gas velocity and location in the bed. Large length scales were found to be typical for the bottom region, above which more narrow dense clusters are common. The majority of clusters in the upper part of the riser have a width less than 20 mm, which means that in CFD simulations of circulating fluidized beds the mesh resolution should be finer than 5 mm to accurately reproduce the clusters. However, a significant fraction, of the order of 10-15% of the measured cluster widths, was below 2 mm. This is about ten times the particle diameter which is the mesh spacing recommended in the literature for CFD simulation of CFBs. The findings of the study on the width and height distributions of the clusters may also be used as a point of comparison with corresponding measures observed in simulated systems, by which a quantitative validation of CFD results could be made.
Original languageEnglish
Pages (from-to)207-218
JournalPowder Technology
Volume269
DOIs
Publication statusPublished - 2015
MoE publication typeA1 Journal article-refereed

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Fluidized beds
Computational fluid dynamics
Flow patterns
Gases
Experiments

Keywords

  • Circulating fluidized bed
  • Cluster dimensions
  • Length scale
  • Image analysis

Cite this

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title = "Length scales of solid clusters in a two-dimensional circulating fluidized bed of Geldart B particles",
abstract = "The flow pattern in a circulating fluidized bed (CFB) is characterized by clusters of particles. The length-scale distribution of solid clusters was analyzed both horizontally and vertically from a number of experiments carried out with Geldart B particles in a two-dimensional circulating fluidized bed. Cluster dimensions were found to be dependent on solid loading, superficial gas velocity and location in the bed. Large length scales were found to be typical for the bottom region, above which more narrow dense clusters are common. The majority of clusters in the upper part of the riser have a width less than 20 mm, which means that in CFD simulations of circulating fluidized beds the mesh resolution should be finer than 5 mm to accurately reproduce the clusters. However, a significant fraction, of the order of 10-15{\%} of the measured cluster widths, was below 2 mm. This is about ten times the particle diameter which is the mesh spacing recommended in the literature for CFD simulation of CFBs. The findings of the study on the width and height distributions of the clusters may also be used as a point of comparison with corresponding measures observed in simulated systems, by which a quantitative validation of CFD results could be made.",
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Length scales of solid clusters in a two-dimensional circulating fluidized bed of Geldart B particles. / Mondal, D.N. (Corresponding Author); Kallio, Sirpa; Saxen, H.

In: Powder Technology, Vol. 269, 2015, p. 207-218.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Length scales of solid clusters in a two-dimensional circulating fluidized bed of Geldart B particles

AU - Mondal, D.N.

AU - Kallio, Sirpa

AU - Saxen, H.

N1 - Project code: 73052

PY - 2015

Y1 - 2015

N2 - The flow pattern in a circulating fluidized bed (CFB) is characterized by clusters of particles. The length-scale distribution of solid clusters was analyzed both horizontally and vertically from a number of experiments carried out with Geldart B particles in a two-dimensional circulating fluidized bed. Cluster dimensions were found to be dependent on solid loading, superficial gas velocity and location in the bed. Large length scales were found to be typical for the bottom region, above which more narrow dense clusters are common. The majority of clusters in the upper part of the riser have a width less than 20 mm, which means that in CFD simulations of circulating fluidized beds the mesh resolution should be finer than 5 mm to accurately reproduce the clusters. However, a significant fraction, of the order of 10-15% of the measured cluster widths, was below 2 mm. This is about ten times the particle diameter which is the mesh spacing recommended in the literature for CFD simulation of CFBs. The findings of the study on the width and height distributions of the clusters may also be used as a point of comparison with corresponding measures observed in simulated systems, by which a quantitative validation of CFD results could be made.

AB - The flow pattern in a circulating fluidized bed (CFB) is characterized by clusters of particles. The length-scale distribution of solid clusters was analyzed both horizontally and vertically from a number of experiments carried out with Geldart B particles in a two-dimensional circulating fluidized bed. Cluster dimensions were found to be dependent on solid loading, superficial gas velocity and location in the bed. Large length scales were found to be typical for the bottom region, above which more narrow dense clusters are common. The majority of clusters in the upper part of the riser have a width less than 20 mm, which means that in CFD simulations of circulating fluidized beds the mesh resolution should be finer than 5 mm to accurately reproduce the clusters. However, a significant fraction, of the order of 10-15% of the measured cluster widths, was below 2 mm. This is about ten times the particle diameter which is the mesh spacing recommended in the literature for CFD simulation of CFBs. The findings of the study on the width and height distributions of the clusters may also be used as a point of comparison with corresponding measures observed in simulated systems, by which a quantitative validation of CFD results could be made.

KW - Circulating fluidized bed

KW - Cluster dimensions

KW - Length scale

KW - Image analysis

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M3 - Article

VL - 269

SP - 207

EP - 218

JO - Powder Technology

JF - Powder Technology

SN - 0032-5910

ER -