Effective interfacial area in gas-liquid cocurrent downflow through packed beds
TL;DR: In this article, the effective interfacial area in cocurrent gas-liquid downflow through packed beds is analyzed taking into consideration the specific surface of the packing and the interdispersion of the phases.
Abstract: The effective interfacial area in cocurrent gas-liquid downflow through packed beds is analysed taking into consideration the specific surface of the packing and the inter-dispersion of the phases. Predictive equations valid for low and high interaction regimes are developed based on the experimental data of the present study, and are satisfactorily compared with the data of the earlier investigations.
Citations
More filters
TL;DR: In this paper, the development of mathematical models for the problem of bio-dieselization of vegetable oils has been studied in the context of renewable alternative to replace fossil fuels, and mathematical models have been developed.
Abstract: Because of the growing world energy demand, biofuels obtained from the hydrotreatment of vegetable oils represent a renewable alternative to replace fossil fuels. The development of mathematical mo...
19 citations
TL;DR: In this paper, a simple semitheoretical method for calculating the two-phase frictional pressure gradient in porous media using asymptotic analysis is presented, which is expressed in terms of the single-phase FRG for liquid and gas flowing alone.
Abstract: A simple semitheoretical method for calculating the two-phase frictional pressure gradient in porous media using asymptotic analysis is presented. The two-phase frictional pressure gradient is expressed in terms of the asymptotic single-phase frictional pressure gradients for liquid and gas flowing alone. In the present model, the two-phase frictional pressure gradient for x ≅ 0 is nearly identical to the single-phase liquid frictional pressure gradient. Also, the two-phase frictional pressure gradient for x ≅ 1 is nearly identical to the single-phase gas frictional pressure gradient. The proposed model can be transformed into either a two-phase frictional multiplier for liquid flowing alone (φ 2 i ) or a two-phase frictional multiplier for gas flowing alone (φ 2 g ) as a function of the Lockhart-Martinelli parameter X. The advantage of the new model is that it has only one fitting parameter (p), while the other existing correlations, such as the correlation of Larkins et al., Sato et al., and Goto and Gaspillo, have three constants. Therefore, calibration of the new model to the experimental data is greatly simplified. The new model is able to model the existing multiparameter correlations by fitting the single parameter p. Specifically, p = 1/3.25 for the correlation of Midoux et al., p = 1/3.25 for the correlation of Rao et al., p = 1/3.5 for the Tosun correlation, p = 1/3.25 for the correlation of Larkins et al., p = 1/3.75 for the correlation of Sato et al., and p = 1/3.5 for the Goto and Gaspillo correlation.
14 citations
TL;DR: In this article, a comprehensive review of the various studies reported in the literature to date on the mathematical modeling of fixed-bed reactors for the production of fuels by the Fischer-Tropsch synthesis (FTS) was carried out.
Abstract: A comprehensive review of the various studies reported in the literature to date on the mathematical modeling of fixed-bed reactors for the production of fuels by the Fischer–Tropsch synthesis (FTS) was carried out. It is quite clear that most of the proposed models are based on a set of assumptions that allow their wide simplification by reducing the models into forms of low complexity, due to the fact that in most cases the effects of phase equilibrium are neglected, and relatively simple Fischer–Tropsch kinetics of the power law type are used. In addition, most of the proposed modeling schemes neglect the effects of resistances to gas–liquid and liquid–solid mass transfer. On the other hand, few reports consider the energy effects under the consideration of a nonisothermal operation assuming a plug-flow behavior and a gas–liquid system. A generalized model of a fixed-bed FTS reactor is proposed which takes into account all the mass and heat transfer phenomena, as well as hydrodynamics and vapor–liquid ...
13 citations
TL;DR: In this article, the interfacial 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.
Abstract: Interfacial 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.
10 citations
TL;DR: In this article, the dependency of pressure drop and liquid holdup on phase velocities, geometry of the column and packing materials as well as on the physical properties have been analyzed.
Abstract: The dependency of pressure drop and liquid holdup on phase velocities, geometry of the column and packing materials as well as on the physical properties have been analyzed. Our experimental data (825 data points obtained using four liquid systems and three different particles) along with those of the available literature (776 data point from five different sources) were used for the analysis. The applicability and the limitations of the literature correlations were evaluated using the available data. Based on the analysis, new correlations for the estimation of pressure drop and liquid holdup, valid for low and high interaction regimes have been developed using the available data, with a wide range of variables. Copyright © 2005 Society of Chemical Industry
7 citations
References
More filters
225 citations
98 citations
TL;DR: In this article, a macroscopic model based on momentum balance is formulated for the condition of no radial pressure gradients, which includes the effect of bubble formation on the pressure drop and holdup and is compared with the experimental data of earlier investigators and of the present study.
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.
72 citations
TL;DR: In this paper, an empirical equation of liquid holdup and interfacial areas was 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.
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
"Effective interfacial area in gas-l..." refers background or result in this paper
...cylinders). The phenomena, observed also by earlier investigators [3, 6 , 8], may be attributed to the inter-dispersion of the phases as bubbles/droplets in the high interaction regime....
[...]
...While Fukushima and Kusaka [ 6 ] related the interfacial area to the flow rates G. S. Venkata Ratnam and Y. B. G. Varma: Effective interfacial area in gas-liquid cocurrent downflow through packed beds 31...
[...]
...Gianetto et al. [4] and Charpentier [5] related the interracial area to the two phase pressure drop for pulse flow and trickle flow regions, while Fukushima and Kusaka [ 6 ] related it to the gas holdup....
[...]
TL;DR: In this article, a 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.
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
"Effective interfacial area in gas-l..." refers background in this paper
...Different flow patterns for the phases are identified in cocurrent gas-liquid downflow through packed beds [1, 2 ]. At low gas and liquid flow rates (G < 1; L w/G < 4), both the phases are continuous and the flow is broadly termed trickle flow (TF)....
[...]