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Journal ArticleDOI

A correlation for interfacial area in co-current gas-liquid downflow through packed beds

01 Feb 1994-Bioprocess Engineering (Springer-Verlag)-Vol. 10, Iss: 2, pp 53-59

AbstractInterfacial area in cocurrent gas-liquid downflow through packed beds is correlated taking into consideration the physical properties of the fluids and the power dissipation in the system. The correlation is tested with the experimental data covering a wide range in system variables including low and high porosity packings, the flow rates of the phases and their physical properties.

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Citations
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Journal ArticleDOI
Abstract: Conventional and emerging processes that require the application of multiphase reactors are reviewed with an emphasis on catalytic processes. In the past, catalyst discovery and development preceded and drove the selection and development of an appropriate multiphase reactor type. This sequential approach is increasingly being replaced by a parallel approach to catalyst and reactor selection. Either approach requires quantitative models for the flow patterns, phase contacting, and transport in various multiphase reactor types. This review focuses on these physical parameters for various multiphase reactors. First, fixed-bed reactors are reviewed for gas-phase catalyzed processes with an emphasis on unsteady state operation. Fixed-bed reactors with two-phase flow are treated next. The similarities and differences are outlined between trickle beds with cocurrent gas–liquid downflow, trickle-beds with countercurrent gas–liquid flow, and packed-bubble columns where gas and liquid are contacted in coc...

313 citations

Journal ArticleDOI
Abstract: A double-slit model developed can predict the frictional two-phase pressure drop, external liquid holdup, pellet-scale external wetting efficiency, and gas–liquid interfacial area in cocurrent downflow trickle-bed reactors operated under partially wetted conditions in the trickle flow regime. The model, an extension of the Holub et al. (1992, 1993) mechanistic pore-scale phenomenological approach, was designed to mimic the actual bed void by two inclined and interconnected slits: wet and dry slit. The external wetting efficiency is linked to both the pressure drop and external liquid holdup. The model also predicts gas–liquid interfacial areas in partially wetted conditions. An extensive trickle-flow regime database including over 1,200 measurements of two-phase pressure drop, liquid holdup, gas–liquid interfacial area and wetting efficiency, published in 1974–1998 on the partial-wetted conditions, was used to validate the modeling approach. Two new improved slip-factor functions were also developed using dimensional analysis and artificial neural networks. High-pressure and -temperature wetting efficiency, liquid holdup, pressure drop, and gas–liquid interfacial area data from the literature on the trickle-flow regime using conventional monosized beds and catalyst bed-dilution conditions were successfully forecasted by the model.

86 citations

Journal ArticleDOI
Abstract: The state-of-the-art of the gas-liquid mass transfer characteristics in trickle-bed reactors was summarized and its quantification methods were reevaluated based on a wide-ranging data base of some 3200 measurements. A set of three unified whole-flow-regime dimensionless correlations for volumetric liquid- and gas-side mass transfer coefficients, and gas–liquid interfacial area, each of which spanned four-order-of-magnitude intervals, were derived. The correlations involved combination of artificial neural networks and dimensional analysis. The dimensionless interfacial area, ShL and ShG were expressed as a function of the most pertinent dimensionless groups: ReL, ReG, WeL, WeG, ScL, ScG, StL, XG, MoL, FrL, Eom, Sb.

77 citations

Journal ArticleDOI
Abstract: Meticulous inspection of the literature has unveiled the weakness of several empirical methods for predicting the macroscopic mass- and heat-transfer characteristics relevant to gas−liquid cocurrent downflow and upflow packed-bed reactors. In response, using a wide experimental database consisting of 5279 measurements for trickle beds (downflow) and 1974 measurements for packed bubble columns (upflow), a set of reliable correlations has been recommended for the prediction of the gas−liquid interfacial area (agl), the volumetric liquid- (kla) and gas-side (kga) mass-transfer coefficients, the wall (ηeklw) and bed (ηekls) liquid−solid mass-transfer coefficients, the wall heat-transfer coefficient (hw), the bed effective radial thermal conductivity (λe), and the particle-to-fluid heat-transfer coefficient (hp). Some of these correlations are from the literature, and others have been developed by combining artificial neural networks and dimensional analysis. The accuracy of the proposed correlations surpasses...

58 citations

Journal ArticleDOI
Abstract: A phenomenological description and a semiempirical two-zone model are proposed for the gas−liquid interfacial areas and the volumetric liquid-side mass-transfer coefficients in cocurrent downflow t...

54 citations


Cites background or result from "A correlation for interfacial area ..."

  • ...Such trends coincide with those already reported for atmospheric conditions (Morsi et al., 1980; Midoux et al., 1984; Wild et al., 1992; Venkata Ratnam et al., 1994)....

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  • ...…were mostly limited to atmospheric pressure (Gianetto et al., 1973; Hirose et al., 1974; Charpentier, 1976; Fukushima and Kusaka, 1977; Bakos et al., 1980; Morsi et al., 1980, 1984; Midoux et al., 1984; Morsi, 1989; Venkata Ratnam and Varma, 1991; Wild et al., 1992; Venkata Ratnam et al., 1994)....

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References
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Journal ArticleDOI
Abstract: Pressure drop and liquid saturation are two important design parameters in cocurrent gas-liquid downflow through packed beds. A macroscopic model based on momentum balance is formulated for the condition of no radial pressure gradients. The model includes the effect of bubble formation on the pressure drop and holdup and is compared with the experimental data of the earlier investigators and of the present study. The model provides a functional form for correlating pressure drop and liquid saturation but some parameters have to be determined by fitting the experimental data.

70 citations

Journal ArticleDOI
Abstract: Liquid holdup and interfacial areas were measured in packed columns with cocurrent downward flow. An empirical equation of liquid holdup Φt is presented in terms of Reynolds numbers of gas Reg(=dsGg/μg) and liquid Rel, surface shape factor of packing φ, void fraction e and ratio of packing to column diameter dp/T, where the ratio is smaller than 0.13. This equation is different for the dispersed bubble flow and other flow regions. The empirical equation of interfacial area ap in the respective flow regions varies as follows: apdp/(1-Φl/e)=ωΦ-mRenlReqg(dp/T)-twhere ω=7.5×10-5, m=Q.2, n=Q.15, q=2/3, t=2.5 for spray flow; ω=2.2×10-4, m=0.3, n=2/3, q=0.2, t=2.5 for pulse flow; ω=3.9×10-3, m=0.1, n=0.4, q=p. t=2 for trickle flow; ω=2.8×10-7, m=0.9, n=1.8, q=0, t=3.3 for dispersed bubble flow. The equation of the boundary in the respective flow regions was found by equating the two of them. The predicted boundaries are in excellent agreement with the literature data given from the analysis of liquid pulse frequencies. The predictions for interfacial areas also agree well with the literature data.

66 citations

Journal ArticleDOI
Abstract: Pressure-drop in cocurrent gas-liquid downflow through packed beds was experimentally measured for nonfoaming, foaming Newtonian, and non-Newtonian liquids. The variables include the column diameter, packing size and shape, flow rates of the phases, and their physical properties. Unified correlations are presented for the data of the present study as well as data available in literature in terms of Lockhart-Martinelli parameters and flow variables and packing characteristics. The data were modeled using a dynamic interaction model.

65 citations

Journal ArticleDOI
Abstract: Flow pattern was visually observed for non-foaming and foaming Newtonian and non-Newtonian liquids under concurrent downflow with air in packed beds using different configurations of column geometry and packins. Flow maps delineating the different flow regions were presented based on the present study as well as that of earlier investigations. The total and dynamic liquid saturation were experimentally measured and correlations were presented in terms of (i) the Lockhart-Martinelli parameter, χ, and (ii) the flow variables. On a observe de maniere visuelle les profils d'ecoulement pour des liquides newtoniens ou non newtoniens, moussants et non moussants, dans le cas d'un acoulement descendant de liquides et d'air dans un lit a garnissage. On a fait varier la gaomatrie de la colonne et le garnissage. Les diagrammes d'ecoulement delimitant les differentes regions d'ecoulement, presentes dans cette etude, s'appuient sur le travail actuel ainsi que sur des recherches anterieures. On a mesure de maniere experimentale la saturation du liquide dynamique et to tale, et les correlations sont presentes en fonction (i) du parametre Lockhart-Martinelli, χ, et (ii) des variables d'ecoulement.

58 citations


"A correlation for interfacial area ..." refers background in this paper

  • ...Trickle flow, spray flow, pulse flow and dispersed bubble flow are the identified flow patterns for non foaming systems in cocurrent gas-liquid downflow through packed beds [1, 2 ]. Foaming flow and foaming pulse flow are additionally identified for foaming systems....

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