Search results for "Baffle"
showing 10 items of 44 documents
The Effect of Baffles on Heat Transfer
2019
For a long time technicians and engineers have used geometric changes of objects for the purpose of enhancement of heat transfer. The discovery and use of nanofluids and their unique properties lead to a new revolution on the heat transfer. This paper presents the simulation of Ansis software applied to the flow tube with a constant flux, also studies the effect of baffles and the use of nano particles on heat transfer.
Top-covered unbaffled stirred tanks: experiments and numerical simulations
2015
In this work computational fluid dynamics was employed to predict the flow field of an unbaffled stirred tank from steady to turbulent conditions
Experimental Study of Central Baffle Flume
2019
In this paper, the hydraulics of a central baffle flume (CBF) were experimentally studied. Extensive experimental runs were carried out to highlight the effects of different geometrical parameters such as baffle length, contraction ratio, and the length of upstream and downstream guide walls. Two different approaches, i.e., the Π theorem of dimensional analysis coupled with the incomplete self-similarity theory and the energy balance equation, were applied to deduce the stage–discharge formula of a CBF characterized by different geometrical parameters. The stage–discharge relationship deduced by the dimensional analysis approach was more accurate than that obtained by the energy approach. F…
Mixing dynamics in uncovered unbaffled stirred tanks
2014
Abstract The present work is aimed at providing experimental information on mixing rates in an unbaffled vessel under free surface vortexing conditions. The planar laser induced fluorescence (PLIF) technique was used for measuring the dispersion dynamics of a passive tracer over a vertical section of the vessel. In agreement with the quite scant literature information available for these systems, results confirm the existence of two well defined, partially segregated, zones that give rise to a double mixing dynamics behavior. A suitable mixing time definition is proposed and applied to a number of experimental runs with different stirrer geometries and agitation speeds. Results confirm that…
On the assessment of power consumption and critical impeller speed in vortexing unbaffled stirred tanks
2017
Abstract Unbaffled stirred tanks are increasingly recognized as a viable alternative to common baffled tanks for a number of processes and bio-processes where the presence of baffles is undesirable. Notwithstanding the increasing industrial interest towards unbaffled tanks, available experimental information on their behaviour is still very poor, even for important parameters such as mechanical power drawn and critical impeller speed (Ncr) at which the transition between non-aerated (sub-critical regime) and aerated (super-critical regime) conditions occurs. In this work the influence of Reynolds and Froude numbers on power consumption characteristics of unbaffled stirred tanks is presented…
Oscillation dynamics of free vortex surface in uncovered unbaffled stirred vessels
2016
Abstract The main feature of unbaffled stirred tanks is the highly swirling liquid motion, which leads to the formation of a central vortex on the liquid free surface, when the vessel is operated without top-cover (Uncovered Unbaffled Stirred Tanks, UUST). One of the main drawbacks of such vessels, that limits their industrial applicability, is the possible onset of low-frequency sloshing of the free surface. In this work, original data on oscillation dynamics in UUST are presented. In particular, data focus on the oscillation amplitude as well as on their frequency. Data were obtained by means of a novel experimental technique based on digital image analysis. The effect of impeller geometr…
Particle distribution in dilute solid liquid unbaffled tanks via a novel laser sheet and image analysis based technique
2013
The availability of experimental information on particle distribution inside stirred tanks is a topic of great importance for many industrial applications such as catalysis and polymerization. The measurement of solid particle distribution is not simple and the development of suitable measuring techniques is still an open problem in chemical engineering research. In this work, a non-intrusive optical technique for measuring particle concentration fields in solid–liquid systems is discussed. The “Laser Sheet Image Analysis” (LSIA) technique described here makes use of a laser sheet, a digital camera for image acquisition and a suitable procedure for post-processing. It is able to provide sol…
Free-surface shape in unbaffled stirred vessels: Experimental study via digital image analysis
2013
There is a growing interest in using unbaffled stirred tanks for addressing a number of processing needs such as low shear damage (sensitive biocultures), low attrition (solid–liquid applications), deep-cleaning/sterilization (pharmaceutical applications). The main feature of uncovered, unbaffled stirred tanks is highly swirling motion of the fluid that results in a deformation of the free liquid surface. At sufficiently high agitation speeds the resulting whirlpool reaches the impeller and gives rise to a gas–liquid dispersion, so leading to the formation of a dispersion without the use of gas-sparger; the so-called self-inducing operation of the vessel. In this work, digital image analysi…
Large-Eddy Simulation of Turbulent Flow in an Unbaffled Stirred Tank Driven by a Rushton Turbine
2005
The turbulent flow fieldgeneratedin an unbaffledstirredtank by a Rushton turbine was computedby large-eddy simulation (LES). The Smagorinsky model was used to model the unresolved, or sub-grid, scales. A general purpose CFD code was appropriately modified in order to allow the computation of the sub-gridviscosity andto perform statistics on the computedresults. The numerical predictions were comparedwith the literature results for comparable configurations andwith experimental data obtainedusing particle image velocimetry. A very goodagreement was foundas regards both time-averagedresolv edfield s andturb ulence quantities. 2004 Elsevier Ltd. All rights reserved.
Enhancement of heat exchanger thermal hydraulic performance using aluminum foam
2018
Abstract This paper deals with an experimental study of a turbulent forced convection in a rectangular channel partly fitted with aluminum metallic foam blocks. Experiments were carried out on samples having a constant porosity of 93.8%, different grades of 5, 20 and 40 PPI, and three different height ratios of 0.6, 0.8 and 1. The blocks were arranged in a baffle like configuration. A constant heat flux of 2 W/cm2 was applied on the bottom wall of the test section, while air velocity was varied from 1 to 5 m·s−1. Temperatures of the wall along the flow direction as well as those of the inlet and outlet sections have been measured. Additionally, pressure drop measurements across the aluminum…