A mechanistic analysis of sieve tray froth height and entrainment

Bennett, Douglas L.; Kao, Alan S.; Wong, Lisa

doi:10.1002/aic.690410907

Cited by 19 publications

(22 citation statements)

References 15 publications

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“…The Murphree efficiency is a function of both the point efficiency and the entrainment. Bennett et al (1995) gave an empirical expression based on numerical results that gives the impact of entrainment recirculation on Murphree efficiency. Their equation is where E is the ratio of the mass flux of entrainment to the mass flux of vapor through the tray, q M V ( E ) and qMv(E = 0) ReLiquid are the Murphree efficiency values with entrainment and the value if there was no entrainment.…”

Section: Methods To Calculate the Point Eficiencymentioning

confidence: 99%

“…We also see a decrease in efficiency at large values of liquid Froude number. This decrease at large values results from entrainment since Bennett et al (1995) show that increasing the hole velocity increases the froth height, which increases the entrainment. Bennett et al (1995) report that the normalized entrainment, E, behaves like Since entrainment is typically a secondary effect, we wish to look at a portion of the data that is well behaved but includes data sets with significant entrainment.…”

Section: Liquid Continuous-only Correlation For the Entire Database mentioning

confidence: 99%

“…This decrease at large values results from entrainment since Bennett et al (1995) show that increasing the hole velocity increases the froth height, which increases the entrainment. Bennett et al (1995) report that the normalized entrainment, E, behaves like Since entrainment is typically a secondary effect, we wish to look at a portion of the data that is well behaved but includes data sets with significant entrainment. The low vapor-density subset satisfies these criteria, and using the point efficiency correlation derived from the low entrainment subset of data we can back-calculate the entrainment values and correlate this vs. T,/h,,.…”

Section: Liquid Continuous-only Correlation For the Entire Database mentioning

confidence: 99%

“…To identify a subset of our database with very little entrainment, consistent with Bennett et al (1995), we will limit this subset to conditions yielding h2+/TS I 0.8. To avoid data sets where significant weeping might be expected, we will, consistent with Lockett and Banik (1984), exclude data if Fr,, I 0.5, where Using Eqs.…”

Section: Liquid-continuous-only Correlation For a Subset Of Data Ignmentioning

confidence: 99%

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New correlation for sieve‐tray point efficiency, entrainmnt, and section efficiency

1997

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A comprehensive composite database for distillation sieve-tray eficiency is used to develop point eficiency and entrainment correlations based on a model that considers the fluid on the distillation tray to be contained in a liquid-continuom region near the tray deck and a vapor-continuous region on top of the liquid-continuous region. This model allows estimates of the portion of the mass transfer that occurs in each region and the mass-transfer resistance that occurs on the liquid side and vapor side of the interface. For most cases, most of the mass transfer occurs within the liquid-continuous region. The liquid side resistance is often significant.The entrainment correlation is consistent with the work of Bennett et al., which relates entrainment to the ratios of the liquid to vapor density and the froth height to the tray spacing. A simple liquid continuous-only mass-transfer model containing only four empirical parameters correlates the point eficiency data to within 6.4%. Despite a twofold change in vapor Schmidt number, no dependency on vapor Schmidt number is seen. Important dimensionless groupings are the Reynolds number based on the hole velocity, effective froth density, ratio of the liquid inventoiy to the perforation diameter, and fraction of the tray area perforated. Mathematically simple and accurate methods allow the prediction of the section eficiency for trays operating in cross or parallel flow. They address vapor and liquid mixing, entrainment and a criterion to avoid significant degradation of the tray eficiency due to weeping.

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Section: Methods To Calculate the Point Eficiencymentioning

confidence: 99%

Section: Liquid Continuous-only Correlation For the Entire Database mentioning

confidence: 99%

Section: Liquid Continuous-only Correlation For the Entire Database mentioning

confidence: 99%

Section: Liquid-continuous-only Correlation For a Subset Of Data Ignmentioning

confidence: 99%

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New correlation for sieve‐tray point efficiency, entrainmnt, and section efficiency

1997

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“…Thus, Hirschberg, et al [10] and Bennett, et al [11] presented an empirical correlation based on the results of numerical solution given by Lockett, et al [5] The Bennett's correlation is simple and convenient to use but the calculated results have a considerable deviation from those of numerical solution in some cases.…”

Section: Introductionmentioning

confidence: 99%

New prediction of Murphree efficiency for distillation tray operating under entrainment condition

2007

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A new empirical correlation has been presented for the effect of entrainment on distillation tray efficiency based on the results of numerical solution given by Lockett, et al. The calculated results are in good agreement with those of the numerical solution given by Lockett, et al. The average deviation is 1.14% and the maximum deviation is 4.76% for the ranges of 0 < P e 1000, 0.40 EOG 1.00, 0.5 λ0 3.0 and e0 0.3. In comparison with the correlation proposed by Bennett et al., the average and maximum deviations of E a MV are 2.17% and 20.49%, respectively. Nomenclature e0-entrainment fraction (e0 = E + /L0) E + -entrainment flow rate (kg·s −1 ) EOG-vapor phase point efficiency EMV-vapor phase tray efficiency in the absence of entrainment E a MV -vapor phase tray efficiency containing effect entrainment E a MV1 -calculated values of E a MV given by Lockett, et al. E a MV2 -calculated values of E a MV from (3) E a MV3 -calculated values of E a MV from (4) L0-flow rate of liquid on tray in the absence of entrainment (kg·s −1 ) m-slope of equilibrium line P e-Peclet number of liquid on tray V -vapor flow rate (kg·s −1 ) λ0-stripping factor (λ0 = mV L 0 )

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Performance analysis and quantitative design of a flow‐guiding sieve tray by computational fluid dynamics

Zhao

et al. 2019

AIChE Journal

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An evolution of the traditional sieve tray, the flow‐guiding sieve tray (FGST), has been utilized in many separation processes, especially for handling viscous systems. The objectives of this work are to optimize the design process of FGSTs and realize the full potential of their separation performance. A computation fluid dynamic (CFD) model that incorporated the modified interphase momentum transfer term was developed. Simulated measures of hydrodynamic performance, such as pressure drop, weeping, entrainment, and clear liquid height agree well with the experimental data, thus verifying the accuracy and reliability of the CFD model established in this work. Furthermore, based on the obtained hydrodynamic parameters, a quantitative model for designing flow‐guiding holes was established and validated by modifying an experimental FGST (diameter 476 mm) and reconstructing an industrial sieve‐tray tower (diameter 1,200 mm). The hydrodynamic parameters and quantitative model are of vital importance for better design and further modification of FGST.

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A mechanistic analysis of sieve tray froth height and entrainment

Abstract: A phenomenologically based model for froth height was developed using the assumption of both vapor-and liquid-continuous

Cited by 19 publications

References 15 publications

New correlation for sieve‐tray point efficiency, entrainmnt, and section efficiency

New correlation for sieve‐tray point efficiency, entrainmnt, and section efficiency

New prediction of Murphree efficiency for distillation tray operating under entrainment condition

Performance analysis and quantitative design of a flow‐guiding sieve tray by computational fluid dynamics

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