scholarly journals CFD Modelling of Global Mixing Parameters in a Peirce-Smith Converter with Comparison to Physical Modelling

2011 ◽  
Vol 6 (1) ◽  
Author(s):  
Deside K Chibwe ◽  
Guven Akdogan ◽  
Chris Aldrich ◽  
Rauf H Eric
Keyword(s):  
Flow Rate ◽  
Volume Fraction ◽  
Mixing Time ◽  
Volumetric Flow Rate ◽  
Numerical Code ◽  
Mixing Efficiency ◽  
Phase System ◽  
Cfd Modelling ◽  
Cold Model ◽  
Peirce Smith Converter

The flow pattern and mixing in an industrial Peirce-Smith converter (PSC) has been experimentally and numerically studied using cold model simulations. The effects of air volumetric flow rate and presence of overlaying slag phase on matte on the flow structure and mixing were investigated. The 2-D and 3-D simulations of the three phase system were carried out using volume of fluid (VOF) and realizable k - ɛ turbulence model to account for the multiphase and turbulence nature of the flow respectively. These models were implemented using commercial Computational Fluid Dynamics (CFD) numerical code FLUENT. The cold model for physical simulations was a 1:5 horizontal cylindrical container made of Perspex with seven tuyeres on one side of the cylinder typifying a Peirce-Smith converter. Compressed air was blown into the cylinder through the tuyeres, simulating air or oxygen enriched air injection into the PSC. The matte and slag phases were simulated with water and kerosene respectively in this study. The influence of varying blowing conditions and simulated slag quantities on the bulk mixing was studied with five different air volumetric flow rates and five levels of simulated slag thickness. Mixing time results were evaluated in terms of total specific mixing power and two mixing time correlations were proposed for estimating mixing times in the model of PSC for low slag and high slag volumes. Both numerical and experimental simulations were in good agreement to predict the variation characteristics of the system in relation to global flow field variables set up in the converter through mathematical calculation of relevant integrated quantities of turbulence, Volume Fraction (VF) and velocity magnitudes. The findings revealed that both air volumetric flow rate and presence of the overlaying slag layer have profound effects on the mixing efficiency of the converter.

scholarly journals Modeling of mixing for stirred bioreactors: 3. Mixing time for aerated simulated broths

2002 ◽  
Vol 56 (12) ◽  
pp. 506-513 ◽  
Author(s):  
Dan Cascaval ◽  
Corneliu Oniscu ◽  
Anca-Irina Galaction ◽  
Fiorina Ungureanu
Keyword(s):  
Flow Rate ◽  
Rotation Speed ◽  
Mixing Time ◽  
Volumetric Flow Rate ◽  
Mixing Efficiency ◽  
Complex Flow ◽  
Average Deviation ◽  
Stirred Bioreactor ◽  
Stirred Bioreactors ◽  
Turbine Impeller

This paper presents the experiments on mixing efficiency for aerated media for a laboratory stirred bioreactor with a double turbine impeller. The effects of stirrer rotation speed, air volumetric flow rate and stirrer position on the shaft on mixing time for aerated water and simulated broths (CMCNa solutions) were analyzed. Compared to non-aerated broths, the results indicated that the variation of mixing time with the considered parameters is very different, due to the complex flow mechanism of the gas-liquid dispersion, a mechanism which is changed by changing the broth properties or fermentation conditions. Using the Statistics Toolbox of MATLAB some correlations between the mixing time and rotation speed, air volumetric flow rate and stirrer position on the shaft were established. The proposed equations agree well with the experiments, the average deviation being ?9.02%.

Fabrication of Microfluidic Rapid Micromixer

2011 ◽  
Vol 467-469 ◽  
pp. 2013-2017
Author(s):  
Hsiang Chen Hsu ◽  
Hsi Chien Liu ◽  
Cheng Jiun Han
Keyword(s):  
Flow Rate ◽  
Fluid Velocity ◽  
Volumetric Flow Rate ◽  
Mixing Efficiency ◽  
Mixing Index ◽  
Micro Pump ◽  
Chaotic Convection ◽  
Wide Range ◽  
Parametric Studies ◽  
Junction Type

A microfluidic multi-cylindric rapid micromixer is fabricated in the present paper. The key features in the presented MEMS-based microchannel design are (1) micro pump (2) Y-junction type channel (3) cylindric obstacle (4) notch with the edge of sharp teeth. Two different fluids (DI water and red ink) were pumped and injected into Y-type channel, and the fluids were broken-up by a cylindric obstacle in the center of tapered microchannel. The chaotic convection occurs in the mixing channel behind the cylindric obstacle. The mixing index is defined to qualify the mixing efficiency, which demonstrates the outlet notch with sharp teeth along the sidewall plays an important role for mixing effects. The developed micromixer can enhance mixing using the mechanisms of diffusion and convection for wide range of Reynolds number (0.01<Re<100). Parametric studies for volumetric flow rate include the number of cylindric obstacles, the number of notches with sharp-teeth and the width of microchannel. Preliminary results demonstrate that the mixing index reaches the desired effect (<0.1) within 0.08 second when the inlet fluid velocity is 0.49992m/s, i.e. volumetric flow rate is 1200μl /min. The presented device is faster than most of reported micromixers.

scholarly journals CFD simulation of the hydrodynamics and mixing time in a stirred tank

2010 ◽  
Vol 16 (4) ◽  
pp. 379-386 ◽  
Author(s):  
Aoyi Ochieng ◽  
Maurice Onyango
Keyword(s):  
Cfd Simulation ◽  
Draft Tube ◽  
Mixing Time ◽  
Operating Cost ◽  
Flow Fields ◽  
Stirred Tank ◽  
Mixing Efficiency ◽  
Phase System ◽  
Rushton Turbine ◽  
Power Draw

Hydrodynamics and mixing efficiency in stirred tanks influence power draw and are therefore important for the design of many industrial processes. In the present study, both experimental and simulation methods were employed to determine the flow fields in different mixing tank configurations in single phase system. The laser Doppler velocimetry (LDV) and computational fluid dynamics (CFD) techniques were used to determine the flow fields in systems with and without a draft tube. There was a reasonable agreement between the simulation and experimental results. It was shown that the use of a draft tube with the Rushton turbine and hydrofoil impeller resulted in a reduction in the homogenization energy by 19.2% and 17.7%, respectively. This indicates that a reduction in the operating cost can be achieved with the use of a draft tube in a stirred tank and there would be a greater cost reduction in a system stirred by the Rushton turbine compared to that stirred by a propeller.

scholarly journals An Experimental and Simulated Study on Gas-Liquid Flow and Mixing Behavior in an ISASMELT Furnace

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 565 ◽  
Author(s):  
Hongliang Zhao ◽  
Tingting Lu ◽  
Pan Yin ◽  
Liangzhao Mu ◽  
Fengqin Liu
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Turbulent Viscosity ◽  
Mixing Time ◽  
Water Model ◽  
Mixing Efficiency ◽  
Gas Flow Rate ◽  
Factors Affecting ◽  
Sufficient Energy ◽  
Gas Liquid Flow

In this study, a water-model experiment and numerical simulation were carried out in a pilot ISASMELT furnace to study the factors affecting mixing time. The experimental results were compared to the simulation results to test the accuracy of the latter. To study the internal factors that affect the mixing time, the turbulent viscosity and flow field were calculated using simulation. In addition, following previous research, external factors that influence the mixing time including the depth of the submerged lance, lance diameter, gas flow rate, and the presence of a swirler were studied to investigate their effect on the flow regime. The results indicated that the mixing time is controlled by the turbulent viscosity and velocity vector. In addition, it was found that the lance diameter should not exceed 3.55 cm to maintain sufficient energy for stirring the bath. Finally, the optimal gas flow rate that offers the best mixing efficiency was found to be 50 Nm3/h.

Numerical Investigation of Flow and Heat Transfer From a Rotating Sphere with Constant Angular Velocity Around Vertical Axis Floating in Stationary Fluid

2021 ◽  
Author(s):  
Sajjad Safarzadeh ◽  
A. B. Rahimi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Flow Rate ◽  
Volume Fraction ◽  
Rotational Velocity ◽  
Water Film ◽  
Volumetric Flow Rate ◽  
Vertical Axis ◽  
Rotating Sphere ◽  
Nusselt Numbers

Abstract Convective heat transfer for a rotating sphere around a vertical axis floating in stationary fluid is studied numerically using the model of volume of fluid (VOF). The effects of the immersion angle and rotating velocity on the streamlines, isotherm and volume fraction contours, mean and local Nusselt numbers, volumetric flow rate, and water film thickness are investigated for the angular rotational velocity, 1500 ≤ Ω ≤ 3500 and the immersion angle, 30° ≤ θi 60°. The results show that the sphere's rotation causes the liquid to be sucked from the lower pole of the sphere, which is thrown out after stopping in the equator. Due to the strong jet flow in the equatorial zone, heat is transferred by forced convection, but diffusion is dominant for heat transfer in other zones. At low rotational velocities, the liquid film is thrown out of the equator in the form of large droplets, but as the rotational velocity increases, its shape changes to a jet. Also, it is found that there is a direct relation between the Reynolds number and mean Nusselt number at different immersion angles so that an average of 27.5% increase for the mean Nusselt number is achieved by increasing the immersion angle from θi = 30° to θi = 60°. In addition, at a constant rotational velocity, the volumetric flow rate increases with increasing immersion angle.

Effect of Additional MnFe2O4 on a Combination of EG-Water Nanofluid and Volumetric Flowrate Variations towards Heat Transfer in Shell and Tube Heat Exchanger System

2020 ◽  
Vol 851 ◽  
pp. 38-46
Author(s):  
Avita Ayu Permanasari ◽  
Fadel Fadillah ◽  
Poppy Puspitasari ◽  
Sukarni Sukarni
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Flow Rate ◽  
Base Fluid ◽  
Volume Fraction ◽  
Volumetric Flow Rate ◽  
Shell And Tube ◽  
Water Base ◽  
Volumetric Flowrate

Nanofluid is an efficient fluid when used in heat exchanger system because of its larger thermal conductivity compared to conventional fluids such as water, oil, and ethylene glycol (EG). This research used MnFe2O4 nanoparticle due to its higher magnetic sensitivity compared to other ferrite nanoparticles and larger thermal conductivity than TiO2. This research used the MnFe2O4 nanoparticle with a combination of EG-Water base fluids in ratios of 40:60, 60:40, and 80:20. MnFe2O4 nanofluid mixed with EG-Water base fluids was made using the two-step method with 0.05% MnFe2O4 volume fraction in each base fluid ratio. This research used shell and tube type heat exchanger with heat temperature of 60°C and cold temperature of 26°C that were carried out at volumetric flowrate in each base fluid ratio for 0.22 l/m, 0.44 l/m, and 0.66 l/m. This research aimed to find the best combination ratio of EG-Water in thermophysical (thermal conductivity, specific heat, density, and viscosity) and to find the effect of volumetric flowrate variations on the heat exchange characteristics (the Reynold number, the Nusselt number, ∆T LMTD, convection coefficient, heat transfer, and overall heat transfer coefficient). The results of this research were that the sample of EG-Water with 40:60 ratio had the best heat transfer characteristics compared to samples with 60:40 and 80:20 ratios. Meanwhile, for the volumetric flow rate, a higher volumetric flow rate resulted in a larger result.

Numerical investigation of refrigerant outgassing in the screw pump of a hermetic reciprocating compressor oil supply system

2020 ◽  
pp. 095440892095260
Author(s):  
VM Braga ◽  
JR Barbosa ◽  
CJ Deschamps
Keyword(s):  
Flow Rate ◽  
Volume Fraction ◽  
Variable Mass ◽  
Volumetric Flow Rate ◽  
Supply System ◽  
Lubricating Oil ◽  
Reciprocating Compressor ◽  
Screw Pump ◽  
Oil Supply ◽  
Interfacial Mass Transfer

This paper reports an investigation on the phenomenon of refrigerant outgassing in the screw pump of a hermetic reciprocating compressor oil supply system. The interfacial mass transfer between the refrigerant and the lubricating oil is modelled by means of a cavitation model based on the Rayleigh-Plesset equation, for cases of fixed and variable mass fractions of refrigerant dissolved in the lubricant. The influence of compressor speed and compressor crankcase pressure is evaluated by comparing the lubricant volumetric flow rate and the lubricant volume fraction field for each condition. The results reveal that significant outgassing of refrigerant may take place in the oil pump, reducing the lubricant flow rate supplied by the pump.

scholarly journals Flow and Mixing Behavior in a New Bottom Blown Copper Smelting Furnace

2019 ◽  
Vol 20 (22) ◽  
pp. 5757 ◽  
Author(s):  
Pin Shao ◽  
Lepeng Jiang
Keyword(s):  
Flow Rate ◽  
Liquid Flow ◽  
Gas Flow ◽  
Mixing Time ◽  
Copper Smelting ◽  
Mixing Efficiency ◽  
Smelting Furnace ◽  
Gas Flow Rate ◽  
Mixing Behavior ◽  
Gas Liquid Flow

A mathematical model was developed to describe gas–liquid flow and mixing behavior in a new bottom blown oxygen copper smelting furnace, and the model validation was carried out through a water model experiment. The effects of different nozzle locations, nozzle numbers, and gas flow rates on the gas–liquid flow, gas total volume, and mixing efficiency were investigated. The results show that the gas–liquid two-phase flow and mixing time predicted by the present model agree well with the experimental data. When the nozzles are located near the center of the bath bottom, the gas total volume is larger, but the mixing efficiency is very low. With the increase of nozzle arrangement angle, the mixing time decreased. However, the excessive angle arrangement of nozzles exceeding 21° was found to be detrimental to the bubble residence time and mixing efficiency. With the increase in nozzle numbers from nine to 13, the gas total volume in the furnace increases, and the mixing efficiency does not change greatly. When the number of nozzles is further increased to 18, the mixing efficiency begins to decrease significantly. As the gas flow rate increases from 4.7 m3/h to 14.1 m3/h, the gas total volume in the furnace increases, and the mixing time is rapidly reduced from 314.5 s to 251.5 s. When the gas flow rate exceeds 18.8 m3/h, the gas total volume and mixing efficiency change little.

Computational Fluid Dynamics Investigation of Turbulent Flow Inside a Rotary Double External Gear Pump

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Jafar Ghazanfarian ◽  
D. Ghanbari
Keyword(s):  
Turbulent Flow ◽  
Flow Rate ◽  
Volume Fraction ◽  
Complex Geometry ◽  
Volumetric Flow Rate ◽  
Gear Pump ◽  
Linear Behavior ◽  
Rate Characteristic ◽  
Flow Rate Characteristic ◽  
External Gear Pump

This article presents a numerical investigation of 2D turbulent flow within a double external gear pump. The configuration of the inlet and outlet ports is determined such that the double gear pump acts like the combination of two parallel pumps. The complex geometry of the double gear pump, existence of narrow gaps between rotating and stationary walls, and rapidly deforming flow domain make the numerical solution more complicated. In order to solve the mass, momentum, and energy conservation laws along with the k-ε turbulence model, a second-order finite volume method has been used over a dynamically varying unstructured mesh. The numerical results including pressure contours, velocity vectors, flow patterns inside the suction chamber, leakage paths, and time variation of volumetric flow rate are presented in detail. The flow rate characteristic curves with linear behavior are demonstrated at rotational speeds and outlet pressures in the range of 1500–4000 rpm and 2–80 bar, respectively. The effect of reducing the gear-casing gap-size on the augmentation of the net flow rate has been investigated. It is concluded that the minimum oil pressure within the gear pump occurs at the two places between contacting gears near the inlet ports. The contours of vapor volume fraction are also illustrated.

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