Flow Characteristics in Rectangular Cross-Sectioned Two-Pass Channels with Different Channel Aspect Ratio (Analysis by Means of POD)

The flow characteristics of water in filleted microchannels were simulated based on CFD method. The flow pressure drop at different aspect ratioandRenumber were rearranged on the simulating results with laminar flow model. The results indicated that the pressure drop enlarges with the increase of in the case of the constant width of the microchannel. Within the range ofRenumber of interest, Poiseuille number of the flow is constant for differentRe, but decreases with increasing aspect ratio. An equation was fitted to describe the relationship betweenPonumber and aspect ratio, i.e. .

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Swirling Flows Characteristics in a Cylinder Under Effect of Buoyancy

Mechanika ◽

10.5755/j02.mech.27975 ◽

2021 ◽

Vol 27 (3) ◽

pp. 201-208

Author(s):

Mustafa FEKHAR ◽

Rachid SACI ◽

Renée GATIGNOL

Keyword(s):

Aspect Ratio ◽

Thermal Stratification ◽

Flow Behavior ◽

Flow Characteristics ◽

Swirling Flows ◽

Viscous Effects ◽

Thermal Buoyancy ◽

State Diagrams ◽

The Core ◽

Flow Stagnation

Thermal buoyancy, induced by injection or by differential heating of a tiny rod is explored to control breakdown in the core of a helical flow driven by the lid rotation of a cylinder. Three main parameters are required to characterize numerically the flow behavior; namely, the rotational Reynolds number Re, the cavity aspect ratio and the Richardson number Ri. Warm injection/rod, Ri > 0, is shown to prevent on-axis flow stagnation while breakdown enhancement is evidenced when Ri < 0. Results revealed that a bubble vortex evolves into a ring type structure which may remain robust, as observed in prior related experiments or, in contrast, disappear over a given range of parameters (Λh, Re, Ri > 0). Besides, the emergence of such a toroidal mode was not found to occur under thermal stratification induced by a differentially heated rod. Moreover, three state diagrams were established which provide detailed flow characteristics under the distinct and combined effects of buoyancy strength, viscous effects and cavity aspect ratio.

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Effects of Packing and Aspect Ratio on Mixing and Heterogeneous Catalysis in Microchannels

Volume 2: Fora, Parts A and B ◽

10.1115/fedsm2007-37442 ◽

2007 ◽

Cited By ~ 1

Author(s):

Robert T. Bailey ◽

Stephen Ryan ◽

Frank Jones ◽

Stephanie Wilson ◽

James Hiestand

Keyword(s):

Heterogeneous Catalysis ◽

Aspect Ratio ◽

Computational Models ◽

Chemical Conversion ◽

Reynolds Numbers ◽

Mixing Efficiency ◽

Substantial Impact ◽

Channel One ◽

Aqueous Streams ◽

Channel Aspect Ratio

Many industrial chemical processes involve the mixing of two or more liquids. By reducing chemical reactors to microscale dimensions, engineers seek to take advantage of decreased diffusion lengths, leading to increased effectiveness (e.g., higher purity of product) over larger process components. In this study, computational models developed using the commercial multiphysics code CFD-ACE+ are used to predict flow within microreactor channels. Two aqueous streams enter a channel—one containing a contaminant and the other devoid of the contaminant. Changes in two geometric attributes are investigated with respect to their effect on mixing of the streams: 1) packing feature layout within the channel and 2) channel aspect ratio. Reynolds numbers (Re) for the simulations range between 0.1 and 100. Results indicate that both packing feature position within the channel and channel aspect ratio can have a substantial impact on mixing. Between Re = 0.1 and Re = 1, mixing efficiency generally decreases with increasing Re; however, as the Re is increased from 1 to 100, fluid flow patterns in the channel are altered, and wake regions and streamline changes created by the packing features lead to improved mixing. Examples showing enhanced chemical conversion during heterogeneous catalysis as a result of better mixing are also presented.

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Influence of channel aspect ratio on the onset of purely-elastic flow instabilities in three-dimensional planar cross-slots

Journal of Non-Newtonian Fluid Mechanics ◽

10.1016/j.jnnfm.2015.11.008 ◽

2016 ◽

Vol 227 ◽

pp. 65-79 ◽

Cited By ~ 14

Author(s):

F.A. Cruz ◽

R.J. Poole ◽

A.M. Afonso ◽

F.T. Pinho ◽

P.J. Oliveira ◽

...

Keyword(s):

Aspect Ratio ◽

Three Dimensional ◽

Flow Instabilities ◽

Channel Aspect Ratio

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Shape and aspect ratio analysis of anisotropic magnetic nanochains based on TEM micrographs

Ceramics International ◽

10.1016/j.ceramint.2018.04.021 ◽

2018 ◽

Vol 44 (11) ◽

pp. 12340-12351 ◽

Cited By ~ 8

Author(s):

Lazar Kopanja ◽

Marin Tadić ◽

Slavko Kralj ◽

Joviša Žunić

Keyword(s):

Aspect Ratio ◽

Ratio Analysis

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The effect of channel aspect ratio on air entrapment during imbibition in soil-on-a-chip micromodels with 2D and 2.5D pore structures

Lab on a Chip ◽

10.1039/d0lc01029d ◽

2021 ◽

Author(s):

Chia-Wen Tsao ◽

Qun-Zhan Huang ◽

Chang-Ye You ◽

Markus Hilpert ◽

Shao-Yiu Hsu ◽

...

Keyword(s):

Aspect Ratio ◽

Adhesive Bonding ◽

Film Flow ◽

Ct Images ◽

Cnc Machining ◽

Air Entrapment ◽

Dry Adhesive ◽

X Ray ◽

Piston Displacement ◽

Channel Aspect Ratio

“Soil-on-a-chip” micromodels designed with X-ray CT images were fabricated by tabletop CNC machining and dry adhesive bonding. The competition between film flow and piston displacement causes the air entrapment differences in 2D and 2.5D micromodels.

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Thermohydrodynamic Performance Evaluation of Recharging, Interrupted and Simple Microchannels: A Comparative Study

Journal of Heat Transfer ◽

10.1115/1.4045066 ◽

2019 ◽

Vol 142 (1) ◽

Cited By ~ 1

Author(s):

Sangram Kumar Samal ◽

Manoj Kumar Moharana

Keyword(s):

Heat Transfer ◽

Aspect Ratio ◽

Three Dimensional ◽

High Heat ◽

Heat Sinks ◽

High Heat Flux ◽

Transverse Wall ◽

Performance Factor ◽

Channel Aspect Ratio ◽

Small Channels

Abstract In this study, a three-dimensional numerical investigation on the thermohydrodynamic performance of a recently proposed recharging microchannel (RMC) is carried out. In this design, a straight microchannel is split into more than one smaller length channels (having individual inlet and outlet) placed end to end. This design enhances overall heat transfer and maintains temperature uniformity across the substrate length. The comparison of fluid flow and heat transfer performance of RMC, interrupted microchannel (IMC) and straight microchannel (SMC) with the same hydraulic diameter and substrate length are presented to explore the effect of geometrical configuration on heat transfer enhancement. The parametric variations include the number of channels (n), transverse wall length (Ltw), channel aspect ratio (α), and flow Reynolds number. The results reveal that recharging microchannel shows better thermal performance compared to simple and interrupted microchannel with a maximum performance factor of 1.80. The results also indicate that the performance factor of RMC increases with an increase in the number of small channels, transverse wall length, and channel aspect ratio. The outcome of this study indicates the possible use of recharging microchannel heat sinks for high heat flux removal applications such as electronic cooling.

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Fluid Flow and Entropy Generation Analysis of Al2O3–Water Nanofluid in Microchannel Plate Fin Heat Sinks

Entropy ◽

10.3390/e21080739 ◽

2019 ◽

Vol 21 (8) ◽

pp. 739 ◽

Cited By ~ 6

Author(s):

Hao Ma ◽

Zhipeng Duan ◽

Liangbin Su ◽

Xiaoru Ning ◽

Jiao Bai ◽

...

Keyword(s):

Reynolds Number ◽

Pressure Drop ◽

Aspect Ratio ◽

Entropy Generation ◽

Volume Fraction ◽

Microchannel Plate ◽

Heat Sinks ◽

Entropy Generation Rate ◽

Nanoparticle Volume Fraction ◽

Channel Aspect Ratio

The flow in channels of microdevices is usually in the developing regime. Three-dimensional laminar flow characteristics of a nanofluid in microchannel plate fin heat sinks are investigated numerically in this paper. Deionized water and Al2O3–water nanofluid are employed as the cooling fluid in our work. The effects of the Reynolds number (100 < Re < 1000), channel aspect ratio (0 < ε < 1), and nanoparticle volume fraction (0.5% < Φ < 5%) on pressure drop and entropy generation in microchannel plate fin heat sinks are examined in detail. Herein, the general expression of the entropy generation rate considering entrance effects is developed. The results revealed that the frictional entropy generation and pressure drop increase as nanoparticle volume fraction and Reynolds number increase, while decrease as the channel aspect ratio increases. When the nanoparticle volume fraction increases from 0 to 3% at Re = 500, the pressure drop of microchannel plate fin heat sinks with ε = 0.5 increases by 9%. It is demonstrated that the effect of the entrance region is crucial for evaluating the performance of microchannel plate fin heat sinks. The study may shed some light on the design and optimization of microchannel heat sinks.

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Parametric Study on the Flow Profiles of Vertical Sinter Cooling Bed Using the DEM and Taguchi Method for Waste Heat Recovery

Energies ◽

10.3390/en13195030 ◽

2020 ◽

Vol 13 (19) ◽

pp. 5030

Author(s):

Junpeng Fu ◽

Jiuju Cai

Keyword(s):

Aspect Ratio ◽

Taguchi Method ◽

Waste Heat ◽

Flow Characteristics ◽

Flow Distribution ◽

External Factors ◽

Influential Factor ◽

Geometry Factor ◽

Discharge Velocity ◽

Performance Of Heat Transfer

To comprehensively understand the effectiveness of external factors on flow characteristics and realize particle flow distribution evenly in bulk layers is an essential prerequisite for improving the performance of heat transfer in vertical sinter cooling beds (VSCBs). The numerical discrete element method (DEM) was applied to investigate external geometric and operational factors, such as the aspect ratio, geometry factor, half hopper angle, normalized outlet scale, and discharge velocity. Using the Taguchi method, a statistical analysis of the effect of design factors on response was performed. In this study, we focused more on external factors than granular properties, be remodelling the external factors was more useful and reliable for actual production in industries. The results showed that the most important factor was the aspect ratio, followed by the geometry factor, normalized outlet scale, half hopper angle, and discharge velocity for the dimensionless height of mass flow. In terms of the Froude number, the most influential factor was the normalized outlet scale with a contribution ratio of 33.81%, followed by the aspect ratio (22.86%), geometry factor (17.73%), discharge velocity (17.73%), and half hopper angle (11.83%).

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