Laminar heat transfer enhancement downstream of a backward facing step by using a pulsating flow

Velázquez, A.; Arias, J.R.; Méndez, Beatriz

doi:10.1016/j.ijheatmasstransfer.2007.06.009

Cited by 59 publications

(51 citation statements)

References 37 publications

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“…Assuming that the temperatures at the entrance and at the non-isothermal part of the lower wall are 293 K and 351.6 K respectively, viscosity varíes by afactorof3. Here, some well-knowncorrelations [15] forwaterare used that can be written in terms of the dimensionless temperature, T, as…”

Section: O)mentioning

confidence: 99%

“…However, as shown in [15], it can also be considered a good approximation at the inlet section of the computational domain, which is located at a distance of 10 times the inlet channel height upstream of the step. At the outlet section, x = 15, the flow is also assumed to be fully developed and thus the velocity, pressure gradient, and temperature profiles do not longer depend on the x coordínate, namely…”

Section: O)mentioning

confidence: 99%

“…The CFD computations needed to genérate the snapshots are carried out with the numerical simulation method described in [15], using a Cartesian grid and a pseudo-compressibility approach to solve the time-dependent versions of equations (1)- (4). The snapshots are in fact the steady state solutions to these equations.…”

Section: O)mentioning

confidence: 99%

“…This has been chosen bearing in mind the future prospect of performing an associated experimental study. The máximum Reynolds number (400) is selected to preserve the hypothesis that the flow is two dimensional [15][16][17][18]. The step height is allowed to change in a rather wide range (0.1-0.6), which involves large changes in both the geometry and flow topologies.…”

Section: O)mentioning

confidence: 99%

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Model reduction in the back step fluid–thermal problem with variable geometry

Baché

Vega

Velázquez

2010

International Journal of Thermal Sciences

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ARTICLE INFO ABSTRACT Keywords:Proper orthogonal decomposition Reduced-order model Variable geometry A methodology is presented to undertake the development of reduced-order models (ROMs) in variable geometry ñuid-thermal problems using the method of snapshots. First, some snapshots are calculated in computational domains that vary in both shape and number of grid points. These snapshots are projected onto a so-called virtual grid (defined in a virtual geometry) using a smooth transformation. Proper orthogonal decomposition (POD) modes are obtained from the associated virtual snapshots and projected back onto the original grids, where they are used to define expansions of the flow variables. The associated POD mode amplitudes are obtained minimizing a residual, which is calculated in terms of the reconstructed solution. POD modes are calculated using only a part of the computational domain, which will be called the projection window, and the residual is defined using only a limited number of points of the computational domain. This methodology is illustrated addressing the problem of heat transfer downstream of a backward facing step in the 2-D steady, laminar regime, with three free parameters, namely the Reynolds number, the wall temperature, and the step height.

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Section: O)mentioning

confidence: 99%

Section: O)mentioning

confidence: 99%

Section: O)mentioning

confidence: 99%

Section: O)mentioning

confidence: 99%

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Model reduction in the back step fluid–thermal problem with variable geometry

Baché

Vega

Velázquez

2010

International Journal of Thermal Sciences

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“…Flows in a structured microchannel play an important role in such engineering problems like mixing in microreactors, microelectrochemical systems [1], heat transfer intensification in heat sinks [2] and mitigation of blood flow impact in aneurysms [3].…”

Section: Introductionmentioning

confidence: 99%

Investigation of fluid flow structure in open type cavity under stationary and pulsatile flow conditions

Vilkinis¹,

Valantinavičius²,

Pedišius³

2016

energetika

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A study of fluid flow in structured channels plays an important role in solving most fluid dynamics problems. The knowledge of the flow structure in separate cavities can be used to intensify mixing in microreactors and microelectrochemical systems (MEMS) as well as to increase heat transfer in heat sinks. Besides, knowledge about fluid flow in micro cavities could be useful to mitigate the symptoms of aneurysms. In this study, a 2D micro-particle image velocimetry (µPIV) system was used to investigate water flow in an open-type microcavity located in a straight, square cross-section (0.5 × 0.5 mm 2 ) microchannel. Two identical micro cavities of the same cross-section as the main channel and the depth of 1 mm are oppositely located in the middle part of the channel. Because of symmetry, the flow structure of the primary vortex was investigated in only one cavity. Measurements were carried out in different planes over the entire height of the cavity at Reynolds number in the range from 100 to 3000. The flow in the channel was stationary and pulsating.Results indicate that flow in the cavity is three-dimensional. This is confirmed by velocity profile shape changes in its different transversal planes. In addition, it is determined that flow structure in the cavity depends on flow regime and flow pulsation characteristics. Velocity distribution shows that in the transverse direction there is the minimum velocity zone corresponding to the centre of the primary vortex generated by the channel flow, also the same zone is observed along the cavity in its axial plane. At low Re, such velocity distribution occurs in pulsating flow earlier than in the case of stationary flow. With increasing Re, velocity distribution in pulsating flow flattens out also more. It means that disturbed flow in the channel accelerates the formation of a stable flow structure in the cavity.

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Optimization of semi‐pulsatile liquid‐liquid extraction operations in milli‐channels

2021

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The work in this manuscript presents liquid‐liquid extraction augmentation and optimization due to flow pulsations on a continuous flow. The mass transfer is achieved via a transfer species (acetic acid) that diffuses in the aqueous phase (water), which is in a continuous flow, from the organic phase (toluene), exhibiting pulsed flow pattern. It is observed through experiments that the incorporation of pulsation leads to enhanced extraction/mass transfer compared to continuous flows. Also, an increase of the pulsation parameters, such as amplitude and frequency, increases the mass transfer, but when the process is evaluated in terms of economy, it is found that the rate of extraction per unit power is maximum for moderate frequencies and amplitudes. Based on the experiments, a Linton and Sherwood‐like correlation for determining extracted concentration at the exit of the test section in semi‐pulsatile flow conditions is proposed. During the course of experiments, it is found that the flow pattern changes from dispersed‐type flow pattern of the organic phase to slug and then slug dispersed with an increase of superficial velocity of toluene, at a particular superficial velocity of the water. Also, the total power consumed during the extraction process increases with an increase in the product of amplitude and frequency. With the experimental approach presented in this paper, one will be able to optimize semi‐pulsatile liquid‐liquid mass transfer operations.

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Laminar heat transfer enhancement downstream of a backward facing step by using a pulsating flow

Cited by 59 publications

References 37 publications

Model reduction in the back step fluid–thermal problem with variable geometry

Model reduction in the back step fluid–thermal problem with variable geometry

Investigation of fluid flow structure in open type cavity under stationary and pulsatile flow conditions

Optimization of semi‐pulsatile liquid‐liquid extraction operations in milli‐channels

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