scholarly journals Slip velosity in pulsed disc and doughnut extraction columns

2011 ◽  
Vol 17 (3) ◽  
pp. 333-339 ◽  
Author(s):  
Meisam Torab-Mostaedi ◽  
Hossein Jalilvand ◽  
Mohammad Outokesh
Keyword(s):  
Slip Velocity ◽  
Energy Input ◽  
Continuous Phase ◽  
Operating Conditions ◽  
Extraction Column ◽  
Empirical Correlations ◽  
Flow Rates ◽  
Operating Variables ◽  
Liquid Systems ◽  
Good Agreement

In the present work, slip velocity has been measured in a 76 mm diameter pulsed disc and doughnut extraction column for four different liquid-liquid systems. The effects of operating variables including pulsation intensity and dispersed and continuous phase flow rates on slip velocity have been investigated. The existence of three different operational regimes, namely mixer-settler, transition, and emulsion regimes, was observed when the energy input was changed. Empirical correlations are derived for prediction of the slip velocity in terms of operating variables, physical properties of the liquid systems, and column geometry for different regimes. Good agreement between prediction and experiments was found for all operating conditions that were investigated.

scholarly journals Dispersed phase hold-up and characteristic velocity in a pulsed packed extraction column

2012 ◽  
Vol 18 (2) ◽  
pp. 255-262 ◽  
Author(s):  
Mehdi Asadollahzadeh ◽  
Jaber Safdari ◽  
Ali Haghighi-Asl ◽  
Meisam Torab-Mostaedi
Keyword(s):  
Physical Properties ◽  
Packed Column ◽  
Operating Conditions ◽  
Empirical Correlation ◽  
Extraction Column ◽  
Dispersed Phase ◽  
Characteristic Velocity ◽  
Operating Variables ◽  
Liquid Systems ◽  
Good Agreement

Dispersed phase hold-up has been measured in a 76.2 mm diameter pulsed packed column for four different liquid-liquid systems. The effects of pulsation intensity, phase ratio, and packing characteristic on the hold-up have been investigated under a variety of operating conditions. The dispersed phase axial hold-up shows a strong non-uniformity, depending on the operating conditions. The results indicated that the characteristic velocity approach is applicable to this type of extraction column for analysis of hold-up. An empirical correlation is derived for prediction of the hold-up in terms of operating variables, physical properties of the systems, and packing geometry. Good agreement between prediction and experiments was observed for all investigated operating conditions.

Numerical Analysis of the Flow Inside a Centrifugal Compressor’s Vaneless Diffuser and Volute

2001 ◽  
Author(s):  
Hooman Rezaei ◽  
Abraham Engeda ◽  
Paul Haley
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Mass Flow ◽  
Operating Conditions ◽  
Vaneless Diffuser ◽  
Flow Angle ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Minimum Medium ◽  
Good Agreement

Abstract The objective of this work was to perform numerical analysis of the flow inside a modified single stage CVHF 1280 Trane centrifugal compressor’s vaneless diffuser and volute. Gambit was utilized to read the casing geometry and generating the vaneless diffuser. An unstructured mesh was generated for the path from vaneless diffuser inlet to conic diffuser outlet. At the same time a meanline analysis was performed corresponding to speeds and mass flow rates of the experimental data in order to obtain the absolute velocity and flow angle leaving the impeller for those operating conditions. These values and experimental data were used as inlet and outlet boundary conditions for the simulations. Simulations were performed in Fluent 5.0 for three speeds of 2000, 3000 and 3497 RPM and mass flow rates of minimum, medium and maximum. Results are in good agreement with the experimental ones and present the flow structures inside the vaneless diffuser and volute.

scholarly journals Visualisation of flow pattern and measurement of liquid distribution in a random packed column using electrical resistance tomography (ERT)

2021 ◽  
Author(s):  
Nazar Aoda
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Electrical Resistance ◽  
Packed Column ◽  
Operating Conditions ◽  
Flow Mode ◽  
Electrical Resistance Tomography ◽  
Liquid Distribution ◽  
Flow Rates ◽  
Good Agreement

The aim of this research is to use Electrical Resistance Tomography technique (ERT) to measure factors that affect local mass transfer at various axial locations in a random packed column with diameter 0.3m and bed height 150cm filled with 2 cm plastic spheres. These factors are: liquid maldistribution, velocity profiles, and flow pattern. The system was designed to run in a trickling down-flow mode and a full liquid up-flow mode. Experiments were performed at flow rates of 3, 6, and 9 gpm (or 0.27 x 10⁻², 0.54 x 10⁻² and 0.8 x 10⁻² m³/m² s) and under normal operating conditions of 25C° and atmospheric pressure. The liquid maldistribution factors were measured via ERT technique and the conventional liquid collection method. Both measurements were conducted at various fluid flow rates at different bed heights. The results of ERT were in very good agreement with the conventional method. The standard deviation values were 17% and 21% at flow rates 3 and 6 gpm respectively. The numerical values of velocity for full liquid up flow at 3 gpm were 0.83cm/s, 1.2cm/s, 1.2 cm/s and 1.11 cm/s for different heights of 30, 60 and 90 cm respectively and the numerical values of velocity for trickle down flow at 3 gpm were 16.5 cm/s, 22.5 cm/s and 24 cm/ for different heights of 30, 60 and 90 cm respectively. The values of the liquid maldistribution factor for flow rate 3 gpm were 0.43 (30cm), 0.33(60cm) and 0.30 (90cm) and for flow rate 6 gpm were 0.33(30cm), 0.27(60cm) and 0.22 (90cm). By comparison with findings of many studies conducted on liquid distribution in packed bed column, a good agreement was observed on the relation of Mf and flow rates and bed heights.

scholarly journals Visualisation of flow pattern and measurement of liquid distribution in a random packed column using electrical resistance tomography (ERT)

2021 ◽  
Author(s):  
Nazar Aoda
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Electrical Resistance ◽  
Packed Column ◽  
Operating Conditions ◽  
Flow Mode ◽  
Electrical Resistance Tomography ◽  
Liquid Distribution ◽  
Flow Rates ◽  
Good Agreement

The aim of this research is to use Electrical Resistance Tomography technique (ERT) to measure factors that affect local mass transfer at various axial locations in a random packed column with diameter 0.3m and bed height 150cm filled with 2 cm plastic spheres. These factors are: liquid maldistribution, velocity profiles, and flow pattern. The system was designed to run in a trickling down-flow mode and a full liquid up-flow mode. Experiments were performed at flow rates of 3, 6, and 9 gpm (or 0.27 x 10⁻², 0.54 x 10⁻² and 0.8 x 10⁻² m³/m² s) and under normal operating conditions of 25C° and atmospheric pressure. The liquid maldistribution factors were measured via ERT technique and the conventional liquid collection method. Both measurements were conducted at various fluid flow rates at different bed heights. The results of ERT were in very good agreement with the conventional method. The standard deviation values were 17% and 21% at flow rates 3 and 6 gpm respectively. The numerical values of velocity for full liquid up flow at 3 gpm were 0.83cm/s, 1.2cm/s, 1.2 cm/s and 1.11 cm/s for different heights of 30, 60 and 90 cm respectively and the numerical values of velocity for trickle down flow at 3 gpm were 16.5 cm/s, 22.5 cm/s and 24 cm/ for different heights of 30, 60 and 90 cm respectively. The values of the liquid maldistribution factor for flow rate 3 gpm were 0.43 (30cm), 0.33(60cm) and 0.30 (90cm) and for flow rate 6 gpm were 0.33(30cm), 0.27(60cm) and 0.22 (90cm). By comparison with findings of many studies conducted on liquid distribution in packed bed column, a good agreement was observed on the relation of Mf and flow rates and bed heights.

Numerical Investigation of Pressure Pulsation in Vaneless Region of a High Speed Centrifugal Pump

2019 ◽  
Author(s):  
Yongshun Zeng ◽  
Min Yang ◽  
Yuqing Zhai ◽  
Zhifeng Yao ◽  
Fujun Wang ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Pressure Pulsation ◽  
Simulation Method ◽  
Operating Conditions ◽  
Pressure Pulsations ◽  
Flow Rates ◽  
Rotor Stator Interaction ◽  
Frequency Components ◽  
Good Agreement

Abstract The pressure pulsation due to rotor-stator interaction (RSI) is unavoidable for high-speed centrifugal pump when operating under different conditions. The frequency components of pressure pulsation in the vaneless region are the most complex, and the pressure pulsation characteristic plays an important role in pump structural stress analysis. A numerical simulation method is used to obtain the hydraulic performances of a high-speed centrifugal pump with 9857 r/min at the range of flow rates between 48.1 to 155.0 m3/h. The head and efficiency under different operating conditions have good agreement with experimental results, with maximum deviations in 3.82% and 5.37%, respectively. The results show that the level of the pressure pulsation from the inlet to the outlet of the impeller increased gradually, and the pressure pulsations between the short blades are greater than that between the long and short blades. In the diffuser, the pressure pulsation is the highest near the tongue, whereas it is lower in the region between the two tongues, and this region is defined as the vaneless region. The pressure contours in the vaneless region almost have no change, while they near the tongue are densely distributed, revealing the mechanism of uneven pressure pulsation distribution. Moreover, there is a high radial velocity distribution near the tongue in the vaneless region, indicating that there may be a jet-wake pattern occured in this region.

scholarly journals Holdup and characteristic velocity in a pulsed packed extraction column

2020 ◽  
Vol 9 (8) ◽  
pp. e674982543
Author(s):  
Jarlon Conceição da Costa ◽  
Luiz Mário Nelson de Góis ◽  
Silvana Mattedi e Silva
Keyword(s):  
Flow Rate ◽  
Water System ◽  
Continuous Phase ◽  
Liquid System ◽  
Operating Conditions ◽  
Extraction Column ◽  
Dispersed Phase ◽  
Internal Diameter ◽  
Phase Flow ◽  
Characteristic Velocity

The present work aims to evaluate the hydrodynamics of a pulsed packed extractor, with an internal diameter of 0.026m and a length of 1.0m, using the liquid butanol-water system. Thus, the basic parameters obtained for the hydrodynamic study of the extraction column in question as dispersed phase, slip velocity, characteristic velocity and flooding point. The methodology used in the work consisted of determining the holdup fraction of the dispersed phase, obtained through tests of simultaneous interruptions in the column feedings. The effects of frequency pulsation, dispersed phase flow rate and continuous phase flow rate investigated in the analysis of these parameters. New empirical correlations derived from the predictions of the parameters studied obtained in terms of operating variables and physical properties of the liquid system involved. The average absolute value of the relative error (AARE) was always below 5.6%. Good agreement between calculated and experimental results observed for all investigated operating conditions.

scholarly journals Comparison Study between Batch and Continuous Processes to Obtain Chitosan-Based High Porous Biomaterial for Biological Applications

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Alina Violeta Ursu ◽  
Diana Furtuna ◽  
Laura Requia ◽  
Safa Larafa ◽  
Hélène de Baynast ◽  
...  
Keyword(s):  
Size Distribution ◽  
Liquid Flow ◽  
Porous Scaffold ◽  
Continuous Process ◽  
Continuous Phase ◽  
Operating Conditions ◽  
Mixture Flow ◽  
Flow Rates ◽  
Foaming Process ◽  
Freeze Dried

Foaming process can be monitored under batch or continuous flows conditions. In the batch process, foaming is time-dependent and the foaming efficiency is controlled by the operator. On the other hand, in the continuous process, the foaming efficiency is only monitored by gas and liquid flow rates. The aim of this work is to compare the two technologies to perform porous scaffold biomaterial based on chitosan (a biocompatible polysaccharide) as well as calcium (Ca2+) and silica (SiO2) (two osteogenesis compounds). Diverse recipes using chitosan (CS) solution (2% (w/v)) in acetic acid (1% (v/v in distilled water)) mixed with whey protein isolate (WPI) (2% (w/v)) as natural surfactant were studied. They were supplemented or not by hydroxyapatite powder (HAp) and tetraethyl orthosilicate (TEOS). A jacketed narrow annular gap unit (NAGU) was used to perform the continuous foaming process. For all experimentations, the mixture flow rate was maintained at 30 mL min-1. The influence of operating conditions such as gas and liquid flow rates was studied to obtain foams and final scaffold material with different densities and porosities. Some other recipes followed foaming under batch conditions. Generally, the recipes were placed in a vessel under mixing allowing the gas phase to come from the roof of the vessel. In this case, it becomes very difficult to control the density and the size distribution of bubbles in the final product. In both cases, liquid foams were analysed (density, bubble size distribution) and then freeze-dried for mechanical and porosity investigations using the dynamic mechanical analysis (DMA) system and scanning electron microscopy (SEM). It has been shown that the controlled injected gas affected the continuous phase, resulting in a lighter and higher porous structure, a more homogeneous appearance, and a more uniform distribution of osteogenesis components compared to one obtained using batch operation. The obtained porous materials exhibited good properties (porosity, interconnectivity, and good HAp and silica distribution) and potential for future bone regeneration applications.

Nitrogen Removal from Anaerobically-Treated Leachate

1984 ◽  
Vol 19 (1) ◽  
pp. 87-100
Author(s):  
D. Prasad ◽  
J.G. Henry ◽  
P. Elefsiniotis
Keyword(s):  
Nitrogen Removal ◽  
Air Flow ◽  
Operating Conditions ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Anaerobic Filter ◽  
Ph Values ◽  
Wide Range ◽  
Ammonia Desorption ◽  
Effects Of Ph

Abstract Laboratory studies were conducted to demonstrate the effectiveness of diffused aeration for the removal of ammonia from the effluent of an anaerobic filter treating leachate. The effects of pH, temperature and air flow on the process were studied. The coefficient of desorption of ammonia, KD for the anaerobic filter effluent (TKN 75 mg/L with NH3-N 88%) was determined at pH values of 9, 10 and 11, temperatures of 10, 15, 20, 30 and 35°C, and air flow rates of 50, 120, and 190 cm3/sec/L. Results indicated that nitrogen removal from the effluent of anaerobic filters by ammonia desorption was feasible. Removals exceeding 90% were obtained with 8 hours aeration at pH of 10, a temperature of 20°C, and an air flow rate of 190 cm3/sec/L. Ammonia desorption coefficients, KD, determined at other temperatures and air flow rates can be used to predict ammonia removals under a wide range of operating conditions.

Cake Formation in Cross-Flow Microfiltration Systems

1992 ◽  
Vol 25 (10) ◽  
pp. 149-162 ◽  
Author(s):  
V. L. Pillay ◽  
C. A. Buckley
Keyword(s):  
Cross Flow ◽  
Operating Conditions ◽  
Waste Waters ◽  
Domestic Waste ◽  
Time Curve ◽  
Good Correspondence ◽  
Operating Variables ◽  
Start Up ◽  
Turbulent Flow Regime ◽  
Cake Formation

Cross-flow microfiltration (CFMF) has potentially wide application in the processing of industrial and domestic waste waters. Optimum design and operation of CFMF systems necessitates a knowledge of the characteristic system behaviour, and an understanding of the mechanisms governing this behaviour. This paper is a contribution towards the elucidation and understanding of the behaviour of a woven fibre CFMF operated in the turbulent flow regime. The characteristic flux-time curve and effects of operating variables on flux are presented for a limestone suspension cross-flow filtered in a 25 mm woven fibre tube. The phenomena contributing to the shape of the flux-time curve are discussed. A model of the mechanisms governing cake growth and limit is presented. Predicted steady-state fluxes show a notably good correspondence with experimentally measured values. It is also found that the flux may not be uniquely defined by the operating conditions, but may also be a function of the operating path taken to reach the operating point. This is of significance in the start-up and operation of CFMF units.

The effect of two-phase flow regime on hydrodynamics and mass transfer in a horizontal-tube gas-liquid reactor

1985 ◽  
Vol 50 (3) ◽  
pp. 745-757 ◽  
Author(s):  
Andreas Zahn ◽  
Lothar Ebner ◽  
Kurt Winkler ◽  
Jan Kratochvíl ◽  
Jindřich Zahradník
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Flow Regime ◽  
Liquid Flow ◽  
Horizontal Tube ◽  
Liquid Holdup ◽  
Two Phase ◽  
Flow Rates ◽  
Type Relation ◽  
Good Agreement

The effect of two-phase flow regime on decisive hydrodynamic and mass transfer characteristics of horizontal-tube gas-liquid reactors (pressure drop, liquid holdup, kLaL) was determined in a cocurrent-flow experimental unit of the length 4.15 m and diameter 0.05 m with air-water system. An adjustable-height weir was installed in the separation chamber at the reactor outlet to simulate the effect of internal baffles on reactor hydrodynamics. Flow regime maps were developed in the whole range of experimental gas and liquid flow rates both for the weirless arrangement and for the weir height 0.05 m, the former being in good agreement with flow-pattern boundaries presented by Mandhane. In the whole range of experi-mental conditions pressure drop data could be well correlated as a function of gas and liquid flow rates by an empirical exponential-type relation with specific sets of coefficients obtained for individual flow regimes from experimental data. Good agreement was observed between values of pressure drop obtained for weirless arrangement and data calculated from the Lockhart-Martinelli correlation while the contribution of weir to the overall pressure drop was well described by a relation proposed for the pressure loss in closed-end tubes. In the region of negligible weir influence values of liquid holdup were again succesfully correlated by the Lockhart-Martinelli relation while the dependence of liquid holdup data on gas and liquid flow rates obtained under conditions of significant weir effect (i.e. at low flow rates of both phases) could be well described by an empirical exponential-type relation. Results of preliminary kLaL measurements confirmed the decisive effect of the rate of energy dissipation on the intensity of interfacial mass transfer in gas-liquid dispersions.

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