scholarly journals Demulsification of Kerosene/Water Emulsion in the Transparent Asymmetric Plate-Type Micro-Channel

Micromachines ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 680 ◽  
Author(s):  
Da Ruan ◽  
Diliyaer Hamiti ◽  
Zheng-Dong Ma ◽  
Ya-Dong Pu ◽  
Xiao Chen
Keyword(s):  
Optical Microscope ◽  
Channel Height ◽  
Micro Channel ◽  
Oil Droplets ◽  
Water Emulsion ◽  
Micro Channels ◽  
Demulsification Process ◽  
Surface Modified ◽  
Plate Type ◽  
Demulsification Efficiency

Asymmetric plate-type micro-channels (APM) have one hydrophobic wall and one hydrophilic wall. By flowing through APM, a kerosene-in-water emulsion can be de-emulsified in one second. To date, however, the demulsification process in the APM is still a black box. In order to observe the demulsification process directly, transparent asymmetric plate-type micro-channels (TAPM) were fabricated with two surface-modified glass plates. Emulsions with oil contents of 10%, 30%, and 50% were pumped through TAPM with heights of 39.2 μm and 159.5 μm. The movement and coalescence of oil droplets (the dispersed phase of a kerosene-in-water emulsion) in the TAPM were observed directly with an optical microscope. By analyzing videos and photographs, it was found that the demulsification process included three steps: oil droplets flowed against and were adsorbed on the hydrophobic wall, then oil droplets coalesced to form larger droplets, whereupon the oil phase was separated. The experimental results showed that the demulsification efficiency was approximately proportional to the oil content (30–50%) of the emulsions and increased when the micro-channel height was reduced.

Fabrication of Micro-Channels in PMMA by Tip-Based Microfabrication Technique: Depth and Friction Analysis

2017 ◽  
Author(s):  
Felicia Stan ◽  
Catalin Fetecau ◽  
Nicoleta V. Stanciu
Keyword(s):  
Normal Load ◽  
Finite Depth ◽  
Channel Height ◽  
Micro Channel ◽  
Channel Depth ◽  
Channel Geometry ◽  
Single Pass ◽  
Micro Channels ◽  
Microfabrication Technique ◽  
Logarithmic Relationship

In this paper, millimeter-scale straight parallel micro-channels were fabricated in PMMA (Polymethyl-methacrylate) using the tip-based micro-fabrication method. The dimensional characteristics (channel width, channel depth and pile-up height) of micro-channels were evaluated and the effects of normal load and speed on the micro-channel geometry and friction were examined. A logarithmic relationship between the normal load and micro-channel depth was identified. The experimental results indicate that the selection of the normal load is critical to achieve a desired micro-channel geometry using a single pass scratching. To machine a micro-channel with a finite depth in PMMA, the normal load must be higher than 4.5 N. Within the range of the tested normal loads, about 70% of the channel height was elastically recovered after a single pass, and pile-ups as high as 50–60% of the depth were observed along the micro-channel sides.

Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels

2003 ◽  
Author(s):  
Weilin Qu ◽  
Seok-Mann Yoon ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase ◽  
Micro Channels

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406 × 2.032 mm cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal that the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Annual flow is identified as the dominant flow pattern for conditions relevant to two-phase micro-channel heat sinks, and forms the basis for development of a theoretical model for both pressure drop and heat transfer in micro-channels. Features unique to two-phase micro-channel flow, such as laminar liquid and gas flows, smooth liquid-gas interface, and strong entrainment and deposition effects are incorporated into the model. The model shows good agreement with experimental data for water-cooled heat sinks.

Flow Characteristics of Pressure-Driven Water in Serpentine Micro-Channels

2006 ◽  
Author(s):  
Renqiang Xiong ◽  
J. N. Chung
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Flow Characteristics ◽  
Flow Structures ◽  
Micro Channel ◽  
Pressure Drops ◽  
Micro Particle Image Velocimetry ◽  
Image Velocimetry ◽  
Micro Channels ◽  
Shape And Size

Flow structures and pressure drops were investigated in rectangular serpentine micro-channels with miter bends which had hydraulic diameters of 0.209mm, 0.395mm and 0.549mm respectively. To evaluate the bend effect, the additional pressure drop due to the miter bend must be obtained. Three groups of micro-channels were fabricated to remove the inlet and outlet losses. A validated micro-particle image velocimetry (μPIV) system was used to achieve the flow structure in a serpentine micro-channel with hydraulic diameter of 0.173mm. The experimental results show the vortices around the outer and inner walls of the bend do not form when Re<100. Those vortices appear and continue to develop with the Re number when Re> 100-300, and the shape and size of the vortices almost remain constant when Re>1000. The bend loss coefficient Kb was observed to be related with the Re number when Re<100, with the Re number and channel size when Re>100. It almost keeps constant and changes in the range of ± 10% When Re is larger than some value in 1300-1500. And a size effect on Kb was also observed.

Numerical Modeling of Electroosmotically Driven Micro Flows

1999 ◽  
Author(s):  
Prashanta Dutta ◽  
Ali Beskok ◽  
Timothy C. Warburton
Keyword(s):  
Spectral Element ◽  
Double Layers ◽  
Channel Height ◽  
Shear Stresses ◽  
Pressure Gradients ◽  
Pressure Distributions ◽  
Micro Channels ◽  
Micro Flows ◽  
Analytical Relations ◽  
P Type

Abstract Electroosmotically driven flows in micro-channels are analyzed analytically and numerically. Semi-analytical relations for the velocity and pressure distributions in micro channels are obtained for electric double layers that are much smaller than the channel height, by using the Helmholtz Smoluchowski velocity. Analytical relations for wall shear stress and pressure distribution are obtained. Amplification of the normal and shear stresses on the walls are observed and documented. A high-order (h/p type) spectral element method is developed, and verified for numerical simulation of electroosmotic micro fluidic flows. Finally, flow through a step channel geometry is analyzed to document the interaction of the electroosmotic forces with adverse pressure gradients. Significant changes within the separation patterns are observed.

Experimental Study on Roughness Effect for Laminar Micro-Channel Gas Flow

2001 ◽  
Author(s):  
Jih-Hsing Tu ◽  
Fangang Tseng ◽  
Ching-Chang Chieng
Keyword(s):  
Experimental Study ◽  
Surface Roughness ◽  
Friction Factor ◽  
Gas Flow ◽  
Micro Channel ◽  
Micro Machining ◽  
Roughness Effect ◽  
Relative Roughness ◽  
Smooth Channel ◽  
Micro Channels

Abstract Present study investigates the roughness effect on laminar gas flow for microchannels ranging from 40 to 600 μm with various roughness heights (40–82 nm) by systematical experiments. The micro-channels are manufactured by micro-machining technology and KOH anisotropic etching is employed to achieve various roughness patterns. Experimental results shows that higher product levels of Reynolds number (Reh) and friction factor (f) are obtained for microchannels of larger size and smaller relative roughness and friction factor f approaches to laminar flow theory value f0 for very smooth channel but the ratio of (f/f0) decreases as the surface roughness increases.

Experimental Studies of Adiabatic Flow Boiling in Fractal-Like Branching Micro-Channels

2008 ◽  
Author(s):  
Brian J. Daniels ◽  
James A. Liburdy ◽  
Deborah V. Pence
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Flow Boiling ◽  
Experimental Studies ◽  
Channel Length ◽  
Channel Height ◽  
Channel Network ◽  
Adiabatic Flow ◽  
Numerical Predictions ◽  
Micro Channels

Experimental results of adiabatic boiling of water flowing through a fractal-like branching microchannel network are presented and compared to numerical simulations for identical flow conditions. The fractal-like branching channel network had channel length and width ratios between adjacent branching levels of 0.7071, a total flow length of 18 mm, a channel height of 150 μm and a terminal channel width of 100 μm. The channels were DRIE etched into a silicon disk and pyrex was anodically bonded to the silicon to form the channel top and allowed visualization of the flow within the channels. The water flowed from the center of the disk where the inlet was laser cut through the silicon to the periphery of the disc. The flow rates ranged from 100 to 225 g/min and the inlet subcooling levels varied from 0.5 to 6 °C. Pressure drop across the channel as well as void fraction in each branching level were measured for each of the test conditions. The measured pressure drop ranged from 20 to 90 kPa, and the measured void fraction ranged from 0.3 to 0.9. The pressure drop results agree well with the numerical predictions. The measured void fraction results followed the same trends as the numerical results.

scholarly journals SYNTHESIS OF NANOPARTICLE SEMICONDUCTOR CdS IN PHASE TRANSFORMED MICROEMULSION OF WATER/ SDS/ ETANOL/ n-HEXANE SYSTEM

2010 ◽  
Vol 5 (2) ◽  
pp. 92-97
Author(s):  
Fitria Rahmawati ◽  
Abu Masykur ◽  
Heni Worowidiyanti
Keyword(s):  
Sodium Dodecyl Sulphate ◽  
Cluster Size ◽  
Sodium Dodecyl ◽  
Optical Microscope ◽  
Water Type ◽  
Emulsion System ◽  
X Ray Diffraction ◽  
Inversion Point ◽  
Water Emulsion ◽  
Type Transformation

The objective of this research is to study wheather the emulsion system of water/SDS (Sodium Dodecyl Sulphate)/ethanol/n-hexane can be transformed from S1 (hydrocarbon in water) type to S2 (water in hydrocarbon). CdS can be synthesized in the transformed product of microemulsion medium. The emulsion type transformation from S1 to S2 was conducted by adding n-hexane increment of 5 mL as hydrocarbon phase and stirring at 300 rpm for 2 minutes. The inversion point was defined from the measurement of emulsion conductivity and was supported by data of the droplet view under optical microscope. CdS was synthesized from reaction of Cd(NO3)2.4H2O with Na2S in phase transformed microemulsion medium. CdS cluster size was obtained from its UV-Vis spectrum and was characterized using X-ray diffraction to analyse the crystallinity and crystal system, then the influence of the variation of SDS amount to the CdS cluster size and its UV-Vis spectrum was observed.The result of this research shows that the system of n-hexane/SDS/water emulsion can be transformed from S1 to S2 type. The SDS amount in the microemulsion has influence the CdS cluster size. The larger amount of SDS added, the smaller of CdS cluster size was obtained. XRD data indicated that CdS cluster has been obtained with 40.613 % of purity. Keywords: emulsion system, nanoparticle semiconductor, CdS, sodium dodecyl sulphate

An Investigation on Micro Slip Flows in Micro Channels

2010 ◽  
Author(s):  
Gh. Reza Salehi ◽  
Masoud JalaliBidgoli ◽  
Saeed ZeinaliDanaloo ◽  
Kazem HasanZadeh
Keyword(s):  
Flow Rate ◽  
Pressure Ratio ◽  
Slip Flow ◽  
Accommodation Coefficient ◽  
Flow Rate Ratio ◽  
Numerical Representation ◽  
Micro Channel ◽  
Parallel Plates ◽  
Dimensionless Numbers ◽  
Micro Channels

In this paper, distributions of velocity and flow rate of micro channels are studied. Moreover, the parameters which influence them were also discussed, as well as their effects and relevant curves. In the Analytical study, the governing equation in specific micro flows is obtained. This equation is specifically investigated for slip flow in two micro parallel plates (micro channel).At the next step numerical representation shows the influence of the related parameters in micro channel flow such as Knudsen number, thermal -accommodation coefficient, mass flow rate ratio and pressure ratio (outlet to inlet), Tangential Momentum Accommodation Coefficient with relative curves, and flow rate distribution in slippery state to no slip state has been compared as the another part of this solution. Finally, the results of investigating parameters and dimensionless numbers in micro channels are reviewed.

A Study on the Strength under Pressure of Micro Heat Exchanger

2006 ◽  
Vol 326-328 ◽  
pp. 265-268
Author(s):  
Taek Joon Son ◽  
Young Shin Lee
Keyword(s):  
Stainless Steel ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Structural Analysis ◽  
Thin Plate ◽  
Thin Plates ◽  
Micro Channel ◽  
Design Guideline ◽  
Micro Heat Exchanger ◽  
Micro Channels

The strength of micro heat exchanger under pressure is studied in this paper. Micro heat exchanger is made with brazing technology. It is constructed of stainless steel thin plates with micro channels and in/out port for fluid flow. Micro channels in thin plates are formed by etching and all parts including thin plates are joined by brazing. The study on the strength under pressure is performed by structural analysis. For structural analysis, one layer of micro heat exchanger body is considered. It is composed of thin plate with micro channel and brazing filler which is used to join thin plates. This paper shows the tendency of stress behavior and gives design guideline of micro heat exchanger.

scholarly journals Electrokinetics in Micro-channeled Cantilevers: Extending the Toolbox for Reversible Colloidal Probes and AFM-Based Nanofluidics

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Andreas Mark ◽  
Nicolas Helfricht ◽  
Astrid Rauh ◽  
Jinqiao Xue ◽  
Patrick Knödler ◽  
...  
Keyword(s):  
Essential Element ◽  
The State ◽  
Micro Channel ◽  
Force Measurements ◽  
Ion Conductance ◽  
Nanoparticle Deposition ◽  
Micro Channels ◽  
Wide Range ◽  
Colloidal Probes

AbstractThe combination of atomic force microscopy (AFM) with nanofluidics, also referred to as FluidFM, has facilitated new applications in scanning ion conductance microscopy, direct force measurements, lithography, or controlled nanoparticle deposition. An essential element of this new type of AFMs is its cantilever, which bears an internal micro-channel with a defined aperture at the end. Here, we present a new approach for in-situ characterization of the internal micro-channels, which is non-destructive and based on electrochemical methods. It allows for probing the internal environment of a micro-channeled cantilever and the corresponding aperture, respectively. Acquiring the streaming current in the micro-channel allows to determine not only the state of the aperture over a wide range of ionic strengths but also the surface chemistry of the cantilever’s internal channel. The high practical applicability of this method is demonstrated by detecting the aspiration of polymeric, inorganic and hydrogel particles with diameters ranging from several µm down to 300 nm. By verifying in-situ the state of the aperture, i.e. open versus closed, electrophysiological or nano-deposition experiments will be significantly facilitated. Moreover, our approach is of high significance for direct force measurements by the FluidFM-technique and sub-micron colloidal probes.

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