Comparison of axial flow impellers using a laser Doppler anemometer

Ranade, Vivek V.; Mishra, V. P.; Saraph, V. S.; Deshpande, Gunavant; Joshi, Jyeshtharaj B.

doi:10.1021/ie00010a016

Cited by 64 publications

(43 citation statements)

References 5 publications

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“…The flow number for a down-pumping APV-B2 is 0.83, which is higher than that of CHE3, PMT , or propeller (Mishra,1993;Ranade et al, 1992). This indicates that strong flows are generated in the impeller region.…”

Section: Pumping Effectivenessmentioning

confidence: 92%

A study of an up‐ and a down‐pumping wide blade hydrofoil impeller: Part I. LDA measurements

et al. 1998

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A wide blade, high solidity ratio, axial flow hydrofoil impeller has been developed particularly for gas dispersion when used in the upward-pumping mode. It has a low power number so that a relatively low torque is required when using it with a large impeller to tank diameter ratio, a commonly desired aim of retrofitting. As part of the work characterising these impellers, laser Doppler anemometry has been used to study the single phase flow both down-and uppumping, the latter for the first time. Mean and root-mean-square velocities were measured throughout a fully baffled, flat bottomed cylindrical tank. When down-pumping, the discharge flow was almost axial but when up-pumping, it had a strong radial component. Turbulence energy dissipation rates in the impeller region and the discharge stream when uppumping were found to be higher than those when down-pumping. In both modes, the impeller was found to have a high circulation efficiency. In Part 11, the data presented here are used for obtaining computational fluid dynamic solutions of the flow field. Keywords: up-and down-pumping hydrofoils, LDA data, power, flow patterns, turbulence characteristics.or gas-liquid mixing, the main requirements of agitation F are breakage and dispersion of gas bubbles and bulk mixing of all the phases. Rushton turbines, which have traditionally been used have a number of disadvantages, e.g., a significant decrease in aerated power number as compared to a high unaerated power number, which reduces mass transfer potential due to a decrease in the volumetric mass transfer coefficient (Nienow, 1990). Also, radial flow turbines give poor top to bottom mixing in multiple impeller sy\tems, leading to a large increase in mixing time (Otomo et al., 1995). Liquid pumping and gas handling can be improved by the use of large diameter impellers but, the replacement of standard disc turbines with larger ones is not a simple retrofitting operation (Nienow, 1990). As a result, down-pumping axial hydrofoil impellers of high solidity ratio were developed for gas-liquid systems. McFarlane and Nienow ( 1995) have reviewed their performance and concluded that such impellers can be best used at high impeller to tank diameter ratios, especially to give improved bulk blending in multiple impeller configurations (Otomo et al., 1995). However, they produce rather large gassed power fluctuations and in a later review, Nienow (1996) suggested that further improvements could be made by using such hydrofoils in the up-pumping mode.*Author to whom correspondence should be addressed. E-mail address: A.W.Nienow@bham.ac.uk A new impeller design, APV-B2 (Figure 1 a), with smooth and elongated wide blades to give a solidity ratio of I has therefore been developed at The University of Birmingham where this work was conducted. It is especially for use in the up-pumping mode in gassed reactors. Ozcan-Taskin et al. (1995,1996 reported its gassed power characteristics alongside those of two down-pumping impellers, namely the high solidity ratio Lightnin' A-3 15 and a p...

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Section: Pumping Effectivenessmentioning

confidence: 92%

A study of an up‐ and a down‐pumping wide blade hydrofoil impeller: Part I. LDA measurements

et al. 1998

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“…For optimal design of a mixing process, knowledge of the flow field generated by the impeller together with the effect of geometrical properties on the flow pattern is required [11,12]. The use of numerical simulations to investigate mixing dynamics and/or analyze a mixing operation is well established [13].…”

Section: Introductionmentioning

confidence: 99%

Using CFD and Ultrasonic velocimetry to Study the Mixing of Pseudoplastic Fluids with a Helical Ribbon Impeller

Ihejirika

Ein‐Mozaffari

2007

Chem Eng & Technol

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A commercial CFD package was used to simulate the 3D flow field generated in a cylindrical tank by a helical ribbon impeller. The study was carried out using a pseudoplastic fluid with yield stress in the laminar mixing region. Ultrasonic Doppler velocimetry (UDV), a noninvasive fluid flow measurement technique for opaque systems, was used to measure xanthan gum velocity. From flow field calculations and tracer homogenization simulations, power consumption and mixing time results were obtained. The torque and power characteristics remain the same for upward and downward pumping of the impeller, but the mixing times are considerably longer for the downward pumping mode. Overall, the numerical results showed good agreement with experimental results and correlations developed by other researchers. From the power and mixing time results, two efficiency criteria were utilized to determine the best pumping mode of the impeller.

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“…As regards to standard k-modeling, extensive work (Ranade et al, 1992;Jenne and Reuss, 1999;Brucato et al, 1998;Jaworski and Zakrzewska, 2001;Joshi and Patwardhan, 1999;Nere et al, 2001Nere et al, , 2003Aubin et al, 2004) has been reported in the published literature. Hence, the present work reviews the past computational work on the flow generated by DT and PBT using RSM and LES models.…”

Section: Previous Workmentioning

confidence: 99%

Assessment of standard k–ε, RSM and LES turbulence models in a baffled stirred vessel agitated by various impeller designs

Murthy

Joshi

2008

Chemical Engineering Science

186

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Comparison of axial flow impellers using a laser Doppler anemometer

Cited by 64 publications

References 5 publications

A study of an up‐ and a down‐pumping wide blade hydrofoil impeller: Part I. LDA measurements

A study of an up‐ and a down‐pumping wide blade hydrofoil impeller: Part I. LDA measurements

Using CFD and Ultrasonic velocimetry to Study the Mixing of Pseudoplastic Fluids with a Helical Ribbon Impeller

Assessment of standard k–ε, RSM and LES turbulence models in a baffled stirred vessel agitated by various impeller designs

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