Mass transfer coefficient volumetric, experimental data

In majority of experimental investigations, overall volumetric mass transfer coefficients comprising the true mass transfer coefficient and the interfacial area are reported. To obtain the true mass transfer coefficient from such data, knowledge of the interfacial area is required. There is a wide variation in bubble/drop sizes in a... 

Volumetric Mass-Transfer Coefficients and Kia Experimental determinations of the individual mass-transfer coefficients /cg and /cl and of the effective interfacial area a involve the use of extremely difficult techniques, and therefore such data are not plentiful. More often, column experimental data are reported in terms of overall volumetric coefficients, which normally are defined as follows ... 

Fig. 45.5 Dependence of the volumetric mass transfer coefficient with the speed of agitation for correlations of Eqs. (42) and (43) and comparison with experimental data for (a) a 25 cm3 tank reactor equipped with a four-blade impeller and (b) a 300-cm3 tank reactor equipped with a four-blade gas-inducing turbine.

Obviously, mass transfer coefficient is a topic of general interest. Tamir, Herskowits et at. [59, 106, 107, 109] studied experimentally the absorption of C02 and acetone into water in a two impinging stream absorber operated in various modes with various atomizers. The data they measured for the volumetric mass transfer coefficient are listed in Table 7.2, which are representative among earlier investigations. 

The extraction of toluene and 1,2 dichlorobenzene from shallow packed beds of porous particles was studied both experimentally and theoretically at various operating conditions. Mathematical extraction models, based on the shrinking core concept, were developed for three different particle geometries. These models contain three adjustable parameters an effective diffusivity, a volumetric fluid-to-particle mass transfer coefficient, and an equilibrium solubility or partition coefficient. K as well as Kq were first determined from initial extraction rates. Then, by fitting experimental extraction data, values of the effective diffusivity were obtained. Model predictions compare well with experimental data and the respective value of the tortuosity factor around 2.5 is in excellent agreement with related literature data. 

Gas-liquid interfacial areas, a, and volumetric liquid-side mass transfer coefficients, kLa, are measured in a high pressure trickle-bed reactor. Increase of a and kLa with pressure is explained by the formation of tiny bubbles in the trickling liquid film. By applying Taylor s theory, a model relating the increase in a with the increase in gas hold-up, is developed. The model accounts satisfactorily for the available experimental data. To estimate kLa, contribution due to bubbles in the liquid film has to be added to the corresponding value measured at atmospheric pressure. The mass transfer coefficient from the bubbles to the liquid is calculated as if the bubbles were in a stagnant medium. 

The complete concentration time history is shown in Figure 6.5. The composition trajectories do not compare all that favorably with the experimental data of Krishna et al. (1985). The actual observed equilibration paths and the predictions of the linearized equations are more highly curved (see Fig. 5.3). It must also be pointed out that the effective volumetric mass transfer coefficients should take on equal values (cf. discussion in Section... 

Use experimental breakthrough data to estimate the volumetric overall mass-transfer coefficient for fixed-bed adsorption. 

The dynamics of the fixed-bed affinity adsorption process were simulated using equations (9-59) to (9-63). The value of the overall volumetric mass-transfer coefficient K(.a was selected by trial and error until a good fit to the experimental data was achieved. Figure 9.13 shows that excellent agreement between the experimental resuls of Camperi et al. (2003) and the model predictions was achieved for Kca = 0.024 s-1. 

There is considerable information available in the hterature on the design of ejectors (steam jet ejectors, water jet pumps, air injectors, etc.) supported by extensive experimental data. Most of this information deals with its use as an evacuator and the focus is on ejector optimization for maximizing the gas pumping efficiency. The major advantage of the venturi loop reactor is its relatively very high mass transfer coefficient due to the excellent gas-liquid contact achieved in the ejector section. Therefore, the ejector section needs careful consideration to achieve this aim. The major mass transfer parameter is the volumetric liquid side mass transfer coefficient, k a. The variables that decide k a are (i) the effective gas-hquid interfacial area, a, that is related to the gas holdup, e. The gas induction rate and the shear field generated in the ejector determine the vine of and, consequently, the value of a. (ii) the trae liquid side mass transfer coefficient, k. The mass ratio of the secondary to primary fluid in turn decides both k and a. For the venturi loop reactor the volumetric induction efficiency parameter is more relevant. This definition has a built in energy... 

For relatively slow reactions (

interpreting experimental fmdings. When the concentration of B is measured at various moments in time, both the chemical rate constant and the volumetric mass transfer coefficient can be determined. In principle, two measurements are sufficient, but a series of data will give more accurate results. 

The liquid side volumetric physical mass transfer coefficient was determined from the desorption rate of oxygen. Detailed description of the experimental set up, procedure and analysis of data is given by Tosyali [30]. Methods of estimating the interfacial CO2 concentration, diffusivities of CO2 and OH in the liquid phase, reaction rate constant, which are all required in data analysis, can be found elsewhere [31, 32]. ... 

The mass transfer characteristics obtained on packings are reported in several different ways. At the more fundamental level, we extract volumetric mass transfer coefficients from the experimental performance data. These coefficients, which we have encountered before in Illustrations 2.2 and 2.3, consist of the product of a film coefficient and the nominal specific surface area a of the packing, expressed in units of m per m of packing. If we use the molar concentration-based coefficient or K, which has units of m/s, then the... 

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