Correlation For Mass Transfer Coefficient Research Articles

New Impeller for Viscous Fermentation: Power Input and Mass Transfer Coefficient Correlations

To mix viscous fermentation broths more efficiently, a new close-clearance impeller, the rotational reciprocating plate impeller (RRPI), was designed to partly mimic the axial reciprocating plate impeller (ARPI). Akin to the axial movement of a reciprocating plate impeller, this new RRPI rotates back and forth driven by a three-arm linkage system. Its power consumption and overall mass transfer coefficient (KLa) were determined in a 22 L laboratory scale bioreactor using model fluids of different viscosities. Results obtained with this new impeller were compared to those of a triple Rushton impeller (TRI) and an ARPI. In water, results were the same as those of the TRI. However, the ARPI gave significantly lower KLa than the other two impellers for the same power input per unit volume. In highly viscous non-Newtonian carboxymethyl cellulose (CMC) solutions, the new impeller showed similar performance as the ARPI, whereas the TRI was not able to provide acceptable mixing due to the presence of stagnant zon...

Correlations of Mass Transfer Coefficients in a Rotating Packed Bed

The usefulness of a rotating packed bed (RPB) in the absorption and stripping of ammonia and volatile organic compounds (VOCs) has been examined, and numerous correlations of the overall mass transfer coefficient (KGa) have been proposed in the literature. However, these correlations do not provide acceptable predictions concerning other experimental systems. In this study, a local gas-side mass transfer coefficient (kGa) in an RPB is calculated and an empirical correlation is proposed, based on 430 experimental KGa data gathered from the literature. Results showed that, with the aid of the two-film theory and the correlation of the local liquid-side mass transfer coefficient (kLa) reported in our previous work (Chen, Lin et al. 2006), most of the experimental KGa data could be reasonably predicted. The effects of gas flow rate, liquid flow rate, liquid viscosity, and centrifugal acceleration on KGa were found to depend on the ratio of the mass transfer resistances in the gas phase and the liquid phase.

Mass transfer and separation criteria for high‐speed countercurrent chromatography

AbstractHigh‐speed countercurrent chromatography (HSCCC) is a versatile technique for preparative separations of a wide variety of solutes. For optimization of operating conditions, prediction of separations, and scale‐up study, a model is needed to describe the effluent concentration profile, which determines the separation efficiency (mass transfer, mixing, and partitioning) and the resolution between peaks. A transfer‐dispersive model is proposed to describe the effluent profile based on the assumption that the retention of a peak is caused by partitioning over two phases, and peak broadening is caused by axial dispersion and mass transfer limitation. In this work, mass transfer was investigated by comparing model simulations to experimental data. One generalized correlation of overall mass transfer coefficients was derived. Based on the correlations of axial dispersion coefficients in our previous work and mass transfer coefficients in this study, the model predicts the elution concentration profile well. Furthermore, separation criteria were proposed to predict the separation of two adjacent solutes, and they were verified using literature data. © 2010 American Institute of Chemical Engineers AIChE J, 2011

Removal of Nitrogen Dioxide and Sulfur Dioxide from Air Streams by Absorption in Urea Solution

The study focuses on the absorption rates of NO2, SO2 and a mixture of these two acid gases into urea solution in packed bed column. The absorption rate was studied as a function of absorbent temperature, urea concentration and acid gas concentration. The influence of liquid temperature between 10 - 40?C, urea concentration between 0.1 - 0.5 M and acid gas concentration NO2 between 100 - 1000 ppm (191 - 1910 mg/m3), SO2 between 500 - 2500 ppm (1310 - 6530 mg/m3) were investigated. The mass gas flow rate of 20.646 (kg/m2.min) at 25?C and the absorption rate were determined by measuring the NO2 and SO2 concentrations in the inlet and outlet streams of the absorptioncolumn. The absorption rate of SO2 increases with the decrease of temperature of absorbent (urea solution) and with the increase of the urea concentration. The presence of NO2 in the effluent gas stream lowers the absorption rate of SO2 in urea solution due to the fast reaction of NO2 with urea as compared with SO2. The absorption rate of NO2 decreases as the urea concentration exceeds 0.4 mol/l and for NO2 gas concentration of 100 ppm due to the decrease the diffusivity of the gas. The experimental data were analyzed using dimensionless analysis to find the correlation of mass transfer coefficient in the packed column Sh (H / dp)1.2 = 4.19*10–2 *(G' dp / μg)0.87 (μg / ρg DAB)0.60 The results confirmed the hypothesis that the absorption is accompanied with chemical reaction. Also it is found the increasing the temperature of absorbent solution the absorption rate of two gases is decreases. The mass transfer coefficient models are in good agreements with the Kramer’s equation.

Dynamic Simulation of Continuous-Contact Separation Processes with the Moment Transformation Method

A model for the simulation of continuous-contact separation processes, based on heat and energy balances, multicomponent mass transfer, and chemical engineering correlations for mass and heat transfer coefficients and liquid holdup is developed and solved with the moment transformation method. Polynomials are used to approximate the concentration and flow rate profiles within the packing. The moment transformation method is used to transform the partial differential equations into a system of differential-algebraic equations that is solved with Newton’s method. The model can be used for both steady-state and dynamic simulation, and it can also be used for systems with axial dispersion. The features of the model are demonstrated with an example of ternary distillation.

Experimental analysis of mass transfer in adiabatic structured packing dehumidifier/regenerator with liquid desiccant

Mass-transfer characteristics of a structured packing dehumidifier/regenerator were studied using a lithium chloride solution as the desiccant. Experiments included air dehumidification and desiccant regeneration in typical operating ranges of air-conditioning applications. When the air velocity increased from 0.5 to 1.5 m/s, the overall mass-transfer coefficient in the structured packing dehumidifier and regenerator varied from 4.0 to 8.5 g/m 2 s and from 2.0 to 4.5 g/m 2 s, respectively. Higher solution temperature resulted in lower overall mass-transfer coefficients. Dimensionless overall mass-transfer coefficient correlations were developed for the dehumidifier and regenerator. Deviations between predicted values and experimental values were within ±20%.

Hybrid Modeling of Modified Mathematical Model for Gas Phase Olefine in Fluidized Bed Catalyst Reactors Using Artificial Neural Networks

The complex flow patterns induced in fluidized bed catalytic reactors and the competing parameters affecting the mass and heat transfer characteristics makes the design of such reactors a challenging task to accomplish. The models of such a process rely heavily on predictive empirical correlations for mass and heat transfer coefficients. Unfortunately, published empirical based correlations have the common shortcoming of low-prediction efficiency compared with experimental data. In this work, an artificial neural network approach is used to capture the reactor characteristics in terms of heat and mass transfer based on published experimental data. The developed ANN-based heat and mass transfer coefficients relations were used in a conventional FCR model and simulated under industrial operating conditions. The hybrid model predictions of the melt-flow index and the emulsion temperature were compared to industrial measurements as well as published models. The predictive quality of the hybrid model was superior to other models. This modeling approach can be used as an alternative to conventional modeling methods.

Convective heat and mass transfer coefficient measurements and correlations for particle beds using temperature and humidity step changes with air flow through a test bed

In this paper, transient responses of a porous urea particle bed subject to a step change in the inlet temperature or humidity for a forced convective air flow through the particle bed are investigated to determine the convective heat and mass transfer coefficients inversely by comparing the measured time constant with the predicted characteristic time constant, which is a function of the convection coefficients and Reynolds number. The experimental results show, that although both the time constants for temperature and humidity step changes are dependent on Reynolds number, the temperature response time constant (35–1300 s) is much larger than the humidity response time constant (4–25 s) for the Reynolds number range of 300–5. The surface adsorption of water vapor is very rapid but the absorption inside the porous urea particle is slowed by a very low internal effective diffusion coefficient within the particles whereas the very low Biot number for heat transfer in the particles implies a complete thermal interaction with the air flow throughout each particle and a much larger time constant. Empirical correlations of the Chilton–Colburn j-factor and Nusselt number versus Reynolds number are compared with the correlations of other researchers. These new correlations, which include an uncertainty analysis, imply much lower convective coefficients than those reported previously in the literature.

Empirical correlation of volumetric mass transfer coefficient for a rectangular internal-loop airlift bioreactor

An empirical correlation of volumetric mass transfer coefficient was developed for a pilot-scale internal-loop rectangular airlift bioreactor that was designed for biotechnology. The empirical correlation combines classic turbulence theory, Kolmogorov’s isotropic turbulence theory with Higbie’s penetration theory. The simulation results based on the correlation suggested that the loading of polyethylene granules (for microbial colony support) in the bioreactor had little effect on the mass transfer coefficient of oxygen gas in the reactor, however, the gas superficial velocity was shown to affect the mass transfer coefficient substantially. These simulation results are comparable to the experimental results from a similar, albeit smaller in volume, three-phase internal-loop rectangular reactor in the literature.

Performance analysis of a new sustainable evaporative cooling pad made from coconut coir

This paper reports a performance analysis for a new sustainable engineering application to beneficially reuse an abundant agricultural waste, coconut coir (Cocos nucifera), in evaporative cooling pads. Two small coconut coir pads of different configurations were fabricated and tested using a laboratory‐scale experimental arrangement. The air supply velocity was controlled and varied between 1.88 and 2.79 m s−1. Heat and mass transfer coefficients, evaporative cooling efficiency and pressure drop across the two types of coconut coir pad were analysed and compared with those of a commercial rigid media paper pad. Results show that the cooling efficiency of the manufactured coconut coir evaporative cooling pad was fairly good (about 50%) and close to that of the commercial paper pad (about 47%). The average pressure drop across the two coconut coir pads was 1.5 and 5.1 Pa respectively. Correlations for heat and mass transfer coefficients expressed using Nusselt and Sherwood numbers are also reported. In addition, the cooling potential of the coconut coir pads was analysed using the average climatic conditions of the central region in Thailand throughout the year. The analysis showed that the air temperature leaving the coconut coir pad varied from 23 to 28°C. Commercial development appears feasible given the coconut coir pad's good performance, lower cost and its availability throughout the country.

NAPLS: SOCIAL FUNCTIONING FOUND TO BE A STABLE TRAIT AND A PREDICTOR OF PSYCHOSIS

Pollutants in the form of non-aqueous phase liquids (NAPLs), such as petroleum products, pose a serious threat to the soil and groundwater. A mathematical model was derived to study the unsteady pollutant concentrations through water saturated contaminated soil under air sparging conditions for different NAPLs and soil properties. The comparison between the numerical model results and the published experimental results showed acceptable agreement. Furthermore, an experimental study was conducted to remove NAPLs from the contaminated soil using the sparging air technique, considering the sparging air velocity, air temperature, soil grain size and different contaminant properties. This study showed that sparging air at ambient temperature through the contaminated soil can remove NAPLs, however, employing hot air sparging can provide higher contaminant removal efficiency, by about 9%. An empirical correlation for the volatilization mass transfer coefficient was developed from the experimental results. The dimensionless numbers used were Sherwood number (Sh), Peclet number (Pe), Schmidt number (Sc) and several physical-chemical properties of VOCs and porous media. Finally, the estimated volatilization mass transfer coefficient was used for calculation of the influence of heated sparging air on the spreading of the NAPL plume through the contaminated soil.

Mass Transfer Performance in Karr Reciprocating Plate Extraction Columns

A study of the hydrodynamic and mass transfer performance for Karr reciprocating plate extraction columns has been presented for a range of operating conditions and column diameters of 50, 100, and 450 mm. Although the use of Karr columns has been widespread for many years for a range of important applications, the need for more reliable methods for predicting the performance and scale-up of such columns continues to be a matter of significant importance. The present study has examined the hydrodynamic performance in terms of the dispersed phase hold up and droplet size distribution and mass transfer performance which has incorporated the effects of backmixing in the continuous phase. Work was initially carried out in a 50 mm diameter laboratory scale Karr column using the system 10 v/v% tributyl phosphate/kerosene (continuous)−phenol−water (dispersed) where hydrodynamic and mass transfer performance was analyzed for both directions of mass transfer. Using these data, models were investigated and developed to predict performance over a range of operating conditions. An alternative system consisting of an organic solvent (continuous)−phenolic alkaloid−aqueous caustic (dispersed) was also studied, using both 100 and 450 mm diameter Karr columns. These data were used to validate the hydrodynamic and mass transfer performance models developed for the phenol system in the 50 mm diameter column. Dispersed phase holdup data were found to fit the correlation presented by Kumar and Hartland [Ind. Eng. Chem. Res. 1995, 34, 3925−3940], and the drop size distribution also agreed with the relationship presented by Kumar and Hartland [Ind. Eng. Chem. Res. 1996, 35, 2682−2695] within reasonable accuracy. The mass transfer performance results indicated that the continuous phase controlled the mass transfer rate, and thus, column design was simplified by assuming that the overall mass transfer coefficient can be obtained using a standard mass transfer correlation for the continuous phase. The current mass transfer results were found to be best predicted by a refitted form of the overall mass transfer coefficient correlation developed by Harikrishnan et al. [Chem. Eng. J. 1994, 54, 7−16].

Study on gas–liquid phase mass transfer coefficient of entrained flow reactor

The gas–liquid phase mass transfer coefficient of entrained flow reactor is studied in the paper. The liquid solvent is atomized into the entrained flow reactor after going through a type of pressure nozzle used in the experiment. The isometric decompression technique is used to investigate the mass transfer coefficient of the entrained flow reactor in seven different gas–liquid systems. The effect on mass transfer coefficient of Re and We number of droplet is sufficiently discussed. A mass transfer coefficient correlation model is proposed and the parameters in the model are obtained by nonlinear regression method. The residual shows that the model values are in good agreement with the experiment values.

Impact of mass transfer coefficient correlations on prediction of reactive distillation column behaviour

Abstract A significant part of the safety analysis of a reactive distillation column is the identification of multiple steady states and their stability. A reliable prediction of multiple steady states in a reactive distillation column is influenced by the selection of an adequate mathematical model. For modelling reactive distillation columns, equilibrium (EQ) and nonequilibrium (NEQ) models are available in the literature. The accuracy of the nonequilibrium stage model seems to be limited mainly by the accuracy of the correlations used to estimate the mass transfer coefficient and interfacial area. The binary mass transfer coefficients obtained from empirical correlations are functions of the tray design and layout, or of the packing type and size, as well as of the operational conditions and physical properties of the vapour and liquid mixtures. In this contribution, the nonequilibrium model was used for the simulation of a reactive distillation column. For prediction of the binary mass transfer coefficient for a sieve tray, four correlations were chosen to show their impact on the prediction of the reactive distillation column behaviour. As a model reactive distillation system, the synthesis of methyl tertiary-butyl ether (MTBE) was chosen. The steady-state analysis and the dynamic simulation of the model system were done. Qualitative differences between the steady states were predicted using the chosen correlations.

Hydrodynamics and mass transfer in a draft tube airlift reactor with dilute alcohol solutions

AbstractThe aim of this work was to investigate an influence of different alcohols on the behavior of a draft tube airlift reactor. The main hydrodynamic and mass transfer parameters in 1 wt % aqueous solutions of five aliphatic alcohols were examined. The results showed that alcohol addition enhanced gas holdup and mass transfer coefficient, but led to notable reduction of liquid velocity and hence elongation of circulation time, relative to the values determined for water. By introducing the surface tension gradient as a relevant independent variable, we defined a simple empirical correlation for overall gas holdup, circulation time, and mass transfer coefficient. The proposed empirical correlations have shown a satisfactory agreement between the calculated and the experimental data. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Mass transport correlation for CO 2 absorption in aqueous monoethanolamine in a continuous film contactor

CO 2 absorption in monoethanolamine for the case of counter current gas–liquid flow in a continuous film contactor has been experimentally reported. Attempt has been made to develop an empirical correlation capable of capturing the non-uniformity of liquid flow to estimate the mass transfer effect. The correlation for the gas phase mass transfer coefficient in terms of dimensionless group is represented as: S h G = 0.0387 Re G 0.66 Re L 0.115 S c G 0.5 It was observed that the mass transfer rate strongly depends on gas and liquid flow rates. The proposed relationship gives a simple and direct method of incorporating the enhancement in mass transfer rate due to wavy liquid film. The mean deviation in the Sh G calculated is about 3.9% of the Sh G deduced from the experimental measurements. The study therefore provides test data and a correlation for the mass transfer process that is validated against extensive experimental data.

Scale‐up from shake flasks to fermenters in batch and continuous mode with Corynebacterium glutamicum on lactic acid based on oxygen transfer and pH

Scale-up from shake flasks to fermenters has been hampered by the lack of knowledge concerning the influence of operating conditions on mass transfer, hydromechanics, and power input. However, in recent years the properties of shake flasks have been described with empirical models. A practical scale-up strategy for everyday use is introduced for the scale-up of aerobic cultures from shake flasks to fermenters in batch and continuous mode. The strategy is based on empirical correlations of the volumetric mass transfer coefficient (k(L) a) and the pH. The accuracy of the empirical k(L) a correlations and the assumptions required to use these correlations for an arbitrary biological medium are discussed. To determine the optimal pH of the culture medium a simple laboratory method based on titration curves of the medium and a mechanistic pH model, which is solely based on the medium composition, is applied. The effectiveness of the scale-up strategy is demonstrated by comparing the behavior of Corynebacterium glutamicum on lactic acid in shake flasks and fermenters in batch and continuous mode. The maximum growth rate (micro(max) = 0.32 h(-1)) and the oxygen substrate coefficient (Y O2 /S= 0.0174 mol/l) of C. glutamicum on lactic acid were equal for shake flask, fermenter, batch, and continuous cultures. The biomass substrate yield was independent of the scale, but was lower in batch cultures (Y(X/S) = 0.36 g/g) than in continuous cultures (Y(X/S) = 0.45 g/g). The experimental data (biomass, respiration, pH) could be described with a simple biological model combined with a mechanistic pH model.

Correlation of Mass Transfer Coefficients in Supercritical CO2 Separation Process

Weighted least squares and error-in-variable statistical methods were used to minimize variations in the experimental data set obtained from literature, and were used to validate Models I and II, S h′ = 0.0015(R e 1/2 S c 1/3)2.58 and S h′ = 0.00084(R e 0.4299 S c 0.8783), respectively. Published data were used for the empirical estimation of mass transfer coefficients in separation processes in fixed bed systems using supercritical carbon dioxide extraction with low molecular diffusion. Model I gained accuracy when the Schmidt Number Sc is high (> 70) and the molecular diffusion is weak. The exponential ratio of the Re and Sc of Model II differed from the common ratio of 3:2; however, the exponents of the Sc are unique for both Models I and II.

Gas-solid and gas-liquid mass transfer: Effect of turbulent Schmidt number

The scope of this paper is to explain effect of eddy viscosity and turbulent Schmidt number on mass transfer rate. New, theoretically based correlation for gas-liquid mass transfer coefficients are proposed.

A discussion on transport phenomena and three-way kinetics of monolithic converters

A one-dimensional monolithic catalyst model is used to develop a global heterogeneous reaction mechanism for three-way applications. Separate conservation equations for the gas and the solid phase are coupled by the introduction of transport coefficients. Due to the relevance of transport phenomena on the overall conversion efficiency, the adequacy of the considered correlations for heat and mass transfer coefficients is elucidated, prior to the investigation of chemical kinetics. Resolved Nusselt ( Nu) and Sherwood ( Sh) number distributions in a monolith channel at steady-state and transient conditions, including catalytic reactions, are compared to local a priori correlations for constant and non-constant boundary conditions at the wall taken from literature. The reaction rate formulations are modified to achieve acceptable agreement with experimental data of palladium–rhodium catalysts for typical operating conditions of automobile applications. The conversion behavior of the lumped parameter model is validated against a wide range of air/fuel ratios and temperatures. Varying feed gas concentrations ( λ -sweep) and light-off experiments for stoichiometric and lean inlet conditions as well as a typical operating condition for secondary air injection are considered. The reaction mechanism is then used to predict the conversion performance of an aged catalyst. Instead of calibrating the complete kinetic parameter set, the adaption to the aged system is achieved by a physically meaningful reduction of the available reactive surface area only. Finally, the simulation results of an FTP75 drive cycle are compared to experimental data without further tuning.