Transient Flows in Gas Stirred Vessels during Initial and Post Gas Injection Periods.

Mazumdar, Dipak; Seybert, C. D.; Steingart, Daniel Artemus

doi:10.2355/isijinternational.43.132

Cited by 9 publications

(7 citation statements)

References 7 publications

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“…[9,10] Thus, long-term and short-term wandering of the bubble plume, continuous fluctuation of spout, etc. tend to make the associated flow field transient and, accordingly, to influence any measurements.…”

Section: Development Of a Correlation For Mixing Times In Ladles Smentioning

confidence: 98%

“…[5] between the model and full scale system, the ratio between the corresponding 95 pct bulk mixing times can be expressed as [9] Incorporating together with the scaling equation Q mod ϭ 2.5 Q fиs in Eq. [9], it can be readily shown that the ratio between 95 pct bulk mixing times in the model ladle and the full scale system can be correlated explicitly via the geometrical scale factor, , according to [10] *The porous plugs located at the midbath radius position of a perfectly cylindrical-shaped ladle corresponded to 0.58R position for the present marginally tapered vessel. The effect of such small distortion was ignored.…”

Section: F An Assessment Of the Present Correlation And Its Applicabmentioning

confidence: 99%

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Mixing time and correlation for ladles stirred with dual porous plugs

Mandal¹,

Patil

Madan

et al. 2005

Metall Mater Trans B

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Bulk mixing times up to a degree of 95 pct were measured in three different, cylindrical-shaped water model ladles (D ϭ 0.60 m, 0.45 m, and 0.30 m, respectively) in which, water was agitated by air introduced through two tuyeres/nozzles placed diametrically opposite at the base of the vessels at R positions. To this end, the electrical conductivity measurement technique was applied. A range of gas flow rates and liquid depths were investigated (viz. 0.7 Յ L/D Յ 1.2 and 0.002 Յ m (watt/kg) Յ0.01) and these were so chosen to conform to the practical ladle refining conditions. In the beginning, extensive experimental trials were carried out to assess the reliability of the measurement technique. In addition, some experiments were carried out to determine the location of the probe in the vessel such that measured mixing times could be interpreted as the bulk mixing times.It was observed that for smaller gas flow rates (or specific energy input rates), 95 pct bulk mixing times tend to decrease appreciably with increasing gas flow rates (e.g., mix ϱ Q Ϫ0.58 ). However, for relatively higher flow rates, the dependence was found to be less pronounced, mixing times decreasing nearly in proportion to a third power of gas flow rates. Similarly, it was found that there exists a critical gas flow rate for any given vessel beyond which mixing times in dual plug stirred configuration are somewhat shorter than those in equivalent axi-symmetrical systems. A dimensional analysis followed by multiple regression of the experimental data (for m Ն 0.07 W/kg) indicated that mixing times in ladles fitted with dual plugs located diametrically opposite at ϮR/2 locations could be reasonably described via mix, 95 pct ϭ 15Q Ϫ0.38 L Ϫ0.56 R 2.0 in which L is the depth of liquid (m), R is the vessel radius (m), and Q is the ambient flow rate (referenced to mean height and temperature of the liquid). Finally, the adequacy and appropriateness of the correlation was demonstrated with reference to the experimental data derived from a 0.20 scale, tapered cylindrical-shaped water model of a 140 T industrial ladle as well as scaling equations and modeling criteria reported in the literature.

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Section: Development Of a Correlation For Mixing Times In Ladles Smentioning

confidence: 98%

Section: F An Assessment Of the Present Correlation And Its Applicabmentioning

confidence: 99%

Mixing time and correlation for ladles stirred with dual porous plugs

Mandal¹,

Patil

Madan

et al. 2005

Metall Mater Trans B

View full text Add to dashboard Cite

show abstract

“…This is explicitly demonstrated in Figure 3, in which, experimentally measured axial velocity in a water model ladle (D = 0.30 m) via three different techniques, namely, laser doppler velocimeter (LDV), particle image velocimetry (PIV), and video recording is compared with equivalent numerical predictions. [13,25] Thus, it is reasonable to assume that the video recording results of mean flow are sufficiently representative and form a reasonable basis for estimation of dissipation coefficients.…”

Section: Verification With New Set Of Experimental Datamentioning

confidence: 99%

Modeling Energy Dissipation in Slag-Covered Steel Baths in Steelmaking Ladles

Mazumdar

Guthrie

2010

Metall Mater Trans B

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Physical and mathematical modeling of energy dissipation phenomena in a gas-stirred ladle with, and without, an overlying second-phase liquid have been carried out at relatively low gas flow rate and specific energy input rate. Data from the literature are applied to infer the extent of energy dissipation caused by various mechanisms. An analysis reveals that bubble slippage and friction at the vessel walls dominate energy dissipation in such systems, each contributing roughly one third of the input energy. The remainder is dissipated because of turbulence in the bulk of the liquid, the formation of a spout, and interactions between the upper phase and the bulk liquid when an overlying liquid is present. Remarkably, the overlying liquid despite its small volume (~3 pct to 13 pct of the bulk), is found to dissipate about 10 pct of input energy. To understand the way the total input energy is dissipated via the overlying liquid, flow and mixing studies were carried out with different types of upper phase liquids. Tracer dispersion studies conducted with Petroleum ether as the overlying liquid show reasonably intense flow within the upper phase with no noticeable entrainment around the spout. In contrast, a thick layer of highly viscous upper phase liquid such as mustard oil shows extensive deformation of the upper phase around the spout, but no discernable motion within. However, remarkably, the thickness of the upper phase rather than its physical properties was found to influence bath hydrodynamics and mixing most significantly. A mechanism based on the rerouting of the surfacing plume and the attendant reversal of flow in the vicinity of the spout is advocated to explain energy dissipation caused by the overlying liquid. This finding is rationalized with our experimental results on composition adjustment with sealed argon bubbling (CAS) alloy addition procedures reported more than two decades ago, wherein flow reversal caused by the baffle in the immediate vicinity of the surfacing plume was shown to cause significant energy dissipation, leading to much sluggish flow and slower mixing in the bulk of the liquid, in comparison with an equivalent unbaffled situation.

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“… Dependence of average recirculation velocity on the dimensionless gas flow rate; Legend:‐ A: Sheng and Irons 9; B: Johansen and Boysan 10; C: Iguchi al. 11; D: Anagbo and Brimacombe 12; E: Mazumdar et al 13; F: Sahai and Guthrie 14. …”

Section: Resultsmentioning

confidence: 99%

An Analysis of Recirculatory Flow in Gas‐Stirred Ladles

Krishnapisharody

Irons

2010

steel research int.

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The paper is concerned with the fluid mechanics characterizing the bulk flow region in a gas-stirred ladle. A theoretical framework, previously derived for the analysis of the gas-liquid plume region, is extended to include the bulk flow phenomena. In this study, the liquid recirculation and mixing have been quantified in terms of simple dimensionless parameters related to the ladle geometry and gas flow rate. A new correlation for mixing time, consistent with the proper form of the Froude similitude criterion, is presented. The work has implications for the fundamental as well as applied aspects of ladle processing.

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Transient Flows in Gas Stirred Vessels during Initial and Post Gas Injection Periods.

Cited by 9 publications

References 7 publications

Mixing time and correlation for ladles stirred with dual porous plugs

Mixing time and correlation for ladles stirred with dual porous plugs

Modeling Energy Dissipation in Slag-Covered Steel Baths in Steelmaking Ladles

An Analysis of Recirculatory Flow in Gas‐Stirred Ladles

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