On time-averaged CFD modeling of circulating fluidized beds

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

Abstract

CFD simulations of single-phase flows are regularly performed as steady-state utilizing closure models of varying complexity. On the contrary, multiphase flows are usually computed as time dependent. Multiphase simulations commonly require a small time step and a fine mesh resulting in costly and time-consuming computations. In case of large industrial circulating fluidized beds (CFB), steady-state CFD modeling would be an attractive alternative for the transient simulations if reliable closure models for the time-averaged transport equations were available. The multiphase closure models developed for time-dependent CFB computations are not as such applicable to the steady-state approach. For instance, the fraction of the momentum transfer expressed by the velocities is significantly smaller in the steady-state models than in the transient ones. Therefore, the steady-state simulations rely more on the closure relations and especially on the models for inter-phase momentum transfer and for the Reynolds stress terms. Several attempts to develop closure models for coarse-mesh and steady-state simulations have been presented in the literature. In this paper, a novel steady-state simulation approach for a CFB process and a corresponding CFD model are introduced. A successful steady-state simulation for a test case is presented. Compared to the time-dependent simulations, the computing time is reduced by a factor of an order of 1000.
Original languageEnglish
Title of host publicationProceedings
Subtitle of host publication12th International Conference on Multiphase flow in Industrial Plants, MFIP 2012
Place of PublicationNapoli, Italy
Number of pages7
Publication statusPublished - 2011
MoE publication typeA4 Article in a conference publication
Event12th International Conference on Multiphase flow in Industrial Plants, MFIP12 - Ischia, Italy
Duration: 21 Sep 201123 Sep 2011

Conference

Conference12th International Conference on Multiphase flow in Industrial Plants, MFIP12
Abbreviated titleMFIP 2012
CountryItaly
CityIschia
Period21/09/1123/09/11

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Fluidized beds
Computational fluid dynamics
Momentum transfer
Fluidized bed process
Multiphase flow

Cite this

Taivassalo, V., Kallio, S., & Peltola, J. (2011). On time-averaged CFD modeling of circulating fluidized beds. In Proceedings: 12th International Conference on Multiphase flow in Industrial Plants, MFIP 2012 Napoli, Italy.
Taivassalo, Veikko ; Kallio, Sirpa ; Peltola, Juho. / On time-averaged CFD modeling of circulating fluidized beds. Proceedings: 12th International Conference on Multiphase flow in Industrial Plants, MFIP 2012. Napoli, Italy, 2011.
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Taivassalo, V, Kallio, S & Peltola, J 2011, On time-averaged CFD modeling of circulating fluidized beds. in Proceedings: 12th International Conference on Multiphase flow in Industrial Plants, MFIP 2012. Napoli, Italy, 12th International Conference on Multiphase flow in Industrial Plants, MFIP12, Ischia, Italy, 21/09/11.

On time-averaged CFD modeling of circulating fluidized beds. / Taivassalo, Veikko; Kallio, Sirpa; Peltola, Juho.

Proceedings: 12th International Conference on Multiphase flow in Industrial Plants, MFIP 2012. Napoli, Italy, 2011.

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

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AU - Kallio, Sirpa

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N2 - CFD simulations of single-phase flows are regularly performed as steady-state utilizing closure models of varying complexity. On the contrary, multiphase flows are usually computed as time dependent. Multiphase simulations commonly require a small time step and a fine mesh resulting in costly and time-consuming computations. In case of large industrial circulating fluidized beds (CFB), steady-state CFD modeling would be an attractive alternative for the transient simulations if reliable closure models for the time-averaged transport equations were available. The multiphase closure models developed for time-dependent CFB computations are not as such applicable to the steady-state approach. For instance, the fraction of the momentum transfer expressed by the velocities is significantly smaller in the steady-state models than in the transient ones. Therefore, the steady-state simulations rely more on the closure relations and especially on the models for inter-phase momentum transfer and for the Reynolds stress terms. Several attempts to develop closure models for coarse-mesh and steady-state simulations have been presented in the literature. In this paper, a novel steady-state simulation approach for a CFB process and a corresponding CFD model are introduced. A successful steady-state simulation for a test case is presented. Compared to the time-dependent simulations, the computing time is reduced by a factor of an order of 1000.

AB - CFD simulations of single-phase flows are regularly performed as steady-state utilizing closure models of varying complexity. On the contrary, multiphase flows are usually computed as time dependent. Multiphase simulations commonly require a small time step and a fine mesh resulting in costly and time-consuming computations. In case of large industrial circulating fluidized beds (CFB), steady-state CFD modeling would be an attractive alternative for the transient simulations if reliable closure models for the time-averaged transport equations were available. The multiphase closure models developed for time-dependent CFB computations are not as such applicable to the steady-state approach. For instance, the fraction of the momentum transfer expressed by the velocities is significantly smaller in the steady-state models than in the transient ones. Therefore, the steady-state simulations rely more on the closure relations and especially on the models for inter-phase momentum transfer and for the Reynolds stress terms. Several attempts to develop closure models for coarse-mesh and steady-state simulations have been presented in the literature. In this paper, a novel steady-state simulation approach for a CFB process and a corresponding CFD model are introduced. A successful steady-state simulation for a test case is presented. Compared to the time-dependent simulations, the computing time is reduced by a factor of an order of 1000.

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Taivassalo V, Kallio S, Peltola J. On time-averaged CFD modeling of circulating fluidized beds. In Proceedings: 12th International Conference on Multiphase flow in Industrial Plants, MFIP 2012. Napoli, Italy. 2011