Technical Transactions iss. 24. Chemistry iss. 2-Ch

Technical Transactions iss. 24. Chemistry iss. 2-Ch

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Collection items (19)


Prediction of turbulent fluid mixing in corrugated static mixers

Montante, Giuseppina, Coroneo, Mirella, Magelli, Franco, Paglianti, Alessandro
Article
2014
This work deals with the analysis of the turbulent flow of Newtonian fluids in pipelines equipped with corrugated plate static mixers. The investigation is carried out by Computational Fluid Dynamics simulations based on the numerical solution of the Reynolds Averaged continuity, momentum and scalar transport equations coupled with the standard k‒ε turbulence model. The mixing characteristics of the SMV mixer in blending two miscible liquids having equal or different density are presented and the effects of different operating conditions are discussed. Finally, the effectiveness of the simulation results to provide guidelines for the optimization of the static mixing operating conditions and design are highlighted.

Power characteristics of unsteadily rotating Rushton turbine in aerated vessel

Woziwodzki, Szymon, Broniarz-Press, Lubomira
Article
2014
The paper presents an analysis of power requirements for unsteadily rotating Rushton turbine in an aerated vessel. The experiments have shown that the presence of gas phase in liquid results in reduction of power requirements. The effect of oscillation frequency on power requirements for F1 mixing mode was not observed while for FR mode power requirement was inversely proportional to oscillation frequency. The lowest relative power demand (RPD) was equal to 0.49, and the overall power requirements for unsteady mixing modes were higher in comparison to standard unidirectional mixing mode.

Modelling and experimantal validation of fluid velocity and tracer concentration in jet reactors

Wojtas, Krzysztof, Makowski, Łukasz, Orciuch, Wojciech
Article
2014
The paper presents a collection of experimental data from particle image velocimetry and planar laser induced fluorescence methods containing local microstructures of fluid velocity and inert tracer concentration in jet reactors. The results of experiments, performed with resolution of the level of several microns, can be used for direct validation of CFD models, especially for timedependent mixing model used in large eddy simulations.

Analysis of a mixing process induced by a rotating magnetic field by means of the dimensional analysis

Story, Grzegorz, Kordas, Marian, Rakoczy, Rafał
Article
2014
The main objective of this work is to study the effect of rotating magnetic field (RMF) on the hydrodynamic conditions in the mixed liquid. The dimensional analysis of Navier-Stokes equations including the Lorenz force allows describing the analyzed process by using the relationships basing on the dimensionless numbers. The comparison between the obtained results and the experimental investigations is carried out. It was found a strong correlation between the velocity field and the magnetic induction or electrical conductivity of fluid.

PIV measurements of the velocity field of a newtonian fluid in a stirred tank equipped with the PMT type impeller

Story, Anna, Jaworski, Zdzisław, Simmons, Mark, Nowak, Emilia
Article
2014
The paper presents the results of Particle Image Velocimetry (PIV) measurements of the velocity field of a Newtonian fluid in a mixing tank equipped with a PMT type impeller. The results are presented in the form of the velocity vectors, profiles and maps and compared with available data in the literature for the corresponding system, obtained from Laser Doppler Anemometry (LDA) measurements. A good qualitative agreement of the results was found. In the flow one primary and two secondary circulation loops were observed. The PMT type impeller produced a typical axial-radial circulation of the liquid in the vessel. The value of the circulation flow number, KC, was calculated.

Effect of the numerical grid density on the modelling of fluid flow in a stirred tank with a PMT impeller

Story, Anna, Jaworski, Zdzisław
Article
2014
The paper present the results of numerical simulations performed for a stirred tank equipped with a PMT type impeller, filled up with a Newtonian fluid. The effects of the grid density and mesh quality and also of the simulation mode on the modelling of fluid flow in a stirred tank were studied. The results are compared with literature data obtained from LDA measurements. It was found that denser numerical grids give more detailed information about generated flow field near the impeller blades. Additionally, better compatibility of predicting and experimental results was obtained in the case of the transient mode simulation, what also demonstrates a significant effect of the angular position of the impeller against baffles on the generated velocity field.

Mixing characteristics for gas-liquid system in an external-loop air-lift column

Musiał, Monika, Bitenc, Marcelina, Karcz, Joanna
Article
2014
This paper presents the results of the experimental investigations of hydrodynamics for an external-loop air-lift column. Process characteristics (gas hold-up, liquid velocities, liquid circulation time and mixing time) were analyzed as a function of the modified Froude number. The obtained results were presented graphically and in the form of the quantitative correlations.

Large eddy simulation of precipitation process carried out in jet reactors

Makowski, Łukasz, Wojtas, Krzysztof, Orciuch, Wojciech, Bałdyga, Jerzy
Article
2014
The paper presents an application of large eddy simulations to predict a course of precipitation process carried out in selected types of jet reactors. In the first part of this work the simulations results were validated using PIV and PLIF techniques and also by comparing model predictions with experimental data for fast parallel chemical test reactions. In the second part of this work predictions of modeling are compared with experimental data for BaSO4 precipitation. Precipitation model is tested in this part also by comparing predictions of the model based on LES with results obtained using the multiple-time-scale mixing model combined with the k‒ɛ model.

An effect of different factors on heat transfer process in an agitated vessel

Major-Godlewska, Marta
Article
2014
Heat transfer process depends on many different factors. The type of heating/cooling surface area has an effect on the intensity of the heat transfer process. In the agitated vessel, a jacket or a coil can be used as heating/cooling surface area. When using coil as a heating/cooling surface area, its shape (helical or vertical) and its location in the vessel should be taken into account. The size of the vessel and the type of the agitator and its diameter also have the influence on heat transfer process. Moreover, except for geometrical factors, the fluid type and its physical properties are important in heat transfer process. The aim of the study presented in the paper was to compare intensity of heat transfer process as a function of different factors for the agitated vessel equipped with jacket or coil. This analysis was carried out on the basis of the own experimental results and literature data.

CFD simulation of turbulent velocity field in the discharge streem from a standard Rushton turbine impeller

Kysela, Bohuš, Fořt, Ivan, Konfršt, Jiří
Article
2014
The velocity field around the standard Rushton turbine was investigated by the Computational Fluid Dynamics (CFD) calculations and compared with results obtained from the Laser Doppler Anemometry (LDA) measured in a pilot plant baffled cylindrical vessel. For calculations the Large Eddy Simulation (LES) approach was employed. The impeller motion was modeled using the Sliding Mesh technique (SM). The mean ensemble-averaged velocity profiles and root mean square values of fluctuations were compared in the radial discharge jet from the standard Rushton turbine under turbulent regime of flow of agitated liquid. There were found two subregions in the discharge stream and the values of the axial profiles of the radial component of the fluctuating velocity are rather same determined from the LES calculations and from the LDA measurements in the second one ZEF (zone of established flow) of the impeller discharge stream, but they differ in the first region ZFE (zone of flow establishment) in the impeller vicinity, although they exhibit the same shape. The impeller power number derived from calculations shows also good agreement with values introduced in literature with a significant influence of the thickness of the impeller disc.