Evaporating Meniscus of Ethanol and Ethanol-Based Nanofluids in Single Micro-Channels

2013 ◽  
Vol 390 ◽  
pp. 685-690
Author(s):  
Yuan Wang ◽  
Khellil Sefiane ◽  
Zhen Guo Wang
Keyword(s):  
Heat Flux ◽  
Aspect Ratio ◽  
Evaporation Rate ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Particle Volume ◽  
Cross Sectional ◽  
Stick Slip ◽  
Micro Channels ◽  
Sink Effect

Evaporating meniscus of ethanol and ethanol-based nanofluids (0.01vol.%) in micro-channels were experimentally studied. Visualisation and thermographic results of the stationary meniscus confined in high-aspect-ratio rectangular micro-channels (hydraulic diameters are 571 μm, 727 μm and 1454 μm, channel cross sectional aspect ratio is 20, 20, 10 respectively) were obtained. It was found that interface evaporation rate increases with heat flux. The meniscus interface becomes deformed when the evaporation rate increases. The use of nanofluids largely enhances the interface stability even though the particle volume fraction is at a very low level. Besides, a stick-slip and back-jump behaviour of the nanofluids meniscus was captured during the transition from stable to deformed interface. Moreover, sink effect at the liquid-vapour interface was discussed based on the IR results.

Cross-Sectional Measurement of Micro Particles Volume Fraction in a Microchannel by Using Capacitance Tomography Sensing

2012 ◽  
Author(s):  
Nur Tantiyani Ali Othman ◽  
Hiromichi Obara ◽  
Je-Eun Choi ◽  
Masahiro Takei
Keyword(s):  
Cross Section ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Electrode Pair ◽  
Particle Volume ◽  
Cross Sectional ◽  
Adjacent Pair ◽  
Micro Particles ◽  
Sectional Measurement ◽  
Capacitance Tomography

In this study, a cross-sectional capacitance is measured in a microchannel with 12 multi-layered electrodes. The cross-sectional capacitance of polystyrene particles and deionized water is measured at upstream and downstream microchannel. Based on the measured cross-sectional capacitance, the particle volume fraction is calculated at three area measurements with different electrode pair. The three area measurements are at the adjacent pair, horizontal pair and vertical pair. The particle volume fraction at the adjacent pair area is almost same and higher at upstream and downstream cross-section. While at the vertical and horizontal pair areas, the particle volume fraction increased from upstream to downstream cross-section around 1.0–9.3% at electrode pair near the walls whilst decreased 0.4–0.96% at electrode pair near the center streamlines. It shows the particles are more attracted to migrate to the equilibrium position at near to the walls. The particles migration induced by inertial lift forces is reflected to Serge-Silberberg phenomenon where the particles are distributed and transverse from the center streamlines of fluid flowing to the area near the walls.

Experimental study of the sedimentation of dilute and semi-dilute suspensions of fibres

1999 ◽  
Vol 384 ◽  
pp. 133-158 ◽  
Author(s):  
BENJAMIN HERZHAFT ◽  
ÉLISABETH GUAZZELLI
Keyword(s):  
Aspect Ratio ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Complex Function ◽  
Orientation Distribution ◽  
Particle Volume ◽  
Mean Velocity ◽  
Aspect Ratios ◽  
Dilute Suspensions ◽  
Orientation Distributions

Steady-state velocity and orientation distributions of sedimenting fibres were measured as a function of particle concentration and aspect ratio. Two different regimes of sedimentation were clearly identified. For dilute suspensions, the fibres tend to align in the direction of gravity with occasional flipping and clump together to form packets. In this regime, the vertical mean sedimentation speed is not hindered and can be larger than the Stokes' velocity of an isolated vertical fibre. Its scaling is a complex function of particle volume fraction and aspect ratio. As the concentration is increased, the fibres still tend to orient in the direction of gravity. The mean velocity becomes hindered and scales with particle volume fraction. The velocity fluctuations were found to be large and anisotropic. They were found to increase with increasing volume fraction. A similar substantial anisotropy of the orientation distribution was observed for all particle concentrations and aspect ratios studied.

scholarly journals Inertial Migration of Neutrally Buoyant Spherical Particles in Square Channels at Moderate and High Reynolds Numbers

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 198
Author(s):  
Yanfeng Gao ◽  
Pascale Magaud ◽  
Lucien Baldas ◽  
Yanping Wang
Keyword(s):  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Reynolds Numbers ◽  
Spherical Particles ◽  
Particle Volume ◽  
Inertial Focusing ◽  
Inertial Migration ◽  
High Reynolds Numbers ◽  
Micro Channels ◽  
High Reynolds

The inertial migration of particles in microchannel flows has been deeply investigated in the last two decades. In spite of numerous reports on the inertial focusing patterns in a square channel, the particle inertial focusing and longitudinal ordering processes remain unclear at high Reynolds numbers (>200) in square microchannels smaller than 100 µm in width. Thus, in this work, in situ visualization of particles flowing in square micro-channels at Reynolds numbers Re ranging from 5 to 280 has been conducted and their migration behaviors have been analyzed. The obtained results confirm that new equilibrium positions appear above a critical Re depending on the particle to channel size ratio and the particle volume fraction. It is also shown that, for a given channel length, an optimal Reynolds number can be identified, for which the ratio of particles located on equilibrium positions is maximal. Moreover, the longitudinal ordering process, i.e., the formation of trains of particles on equilibrium positions and the characterization of their length, has also been analyzed for the different flow conditions investigated in this study.

scholarly journals Re-Reflection Effect On Shock Waves in Two-Phase Flows through a Tube of Variable Cross-Section

2018 ◽  
Vol 3 (12) ◽  
pp. 67-73
Author(s):  
Kanti Pandey
Keyword(s):  
Cross Section ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Reflection Effect ◽  
Two Phase Flows ◽  
Particle Volume ◽  
Two Phase ◽  
Cross Sectional

In present paper Re-reflection  effect on  shock –waves in two-phase flows through a tube of variable cross-section is considered when particle  volume fraction appeared as an additional variable .It is concluded that re-reflected effects reduce the cross sectional  area .For two-phase flows when equilibrium is eventually established , presence of particle volume fraction , further reduce  the cross – sectional area. One dimensional area relation for a non – uniform , steady flow ahead of a shock   is obtained and concluded that  all the results are valid for the case   when  direction of the shock motion and the gas flow ahead of the  shock is same  .  In preparation of graphs Mathematica 7 is used .

scholarly journals Heat enhancement analysis of a differentially heated inclined square enclosure filled with Al2O3 nanofluids under three base fluids: Water, water-ethylene glycol mixture & ethylene glycol

2021 ◽  
pp. 269-269
Author(s):  
Lakshmi Gollapudi ◽  
Rohan Senanayake ◽  
Christina Georgantopoulou ◽  
Anil Singh
Keyword(s):  
Heat Flux ◽  
Ethylene Glycol ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Particle Volume ◽  
Left Edge ◽  
Left Wall ◽  
Number Range ◽  
Square Enclosure ◽  
Heater Length

This paper investigates the analysis of natural convection heat enhancement in an inclined square enclosure when filled with water-based nanofluids with left edge wall undergoing heating with consistent heat flux while the the right edge wall being cold and other remaining walls are kept adiabatic. The parameters used in this analysis include: solid fraction volume (range from 0% to 20%), length of the heaters (0.25cm, 0.50cm, and 1.0cm from the left edge), and Rayleigh number (range from 104 to 106). The nanolayer thickness ratio was kept at a constant value of 1.0 throughout the analysis. The heat source is found at the center of the left wall. Polynomial Differential Quadrature (PDQ) equations have been adopted for this analysis for various angles range from 0? to 90?. As the Rayleigh numbers and particle volume fraction got the much-needed raise, the average count of the heat transfer rate improved too. The length of the heat flux heater has become more prominent parameter that has been affecting the calculated temperature and the flow fields. When the heat flux heater length is pushed to an increasing limit, the heat enhancement rate essentially starts to decline. This happens at the smaller inclination angle, though.

scholarly journals Performance improvement of double-tube gas cooler in CO2 refrigeration system using nanofluids

2015 ◽  
Vol 19 (1) ◽  
pp. 109-118 ◽  
Author(s):  
Jahar Sarkar
Keyword(s):  
Performance Improvement ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Cooling Capacity ◽  
Inlet Temperature ◽  
Refrigeration Cycle ◽  
Particle Volume ◽  
Transcritical Carbon Dioxide ◽  
The Given ◽  
Theoretical Analyses

The theoretical analyses of the double-tube gas cooler in transcritical carbon dioxide refrigeration cycle have been performed to study the performance improvement of gas cooler as well as CO2 cycle using Al2O3, TiO2, CuO and Cu nanofluids as coolants. Effects of various operating parameters (nanofluid inlet temperature and mass flow rate, CO2 pressure and particle volume fraction) are studied as well. Use of nanofluid as coolant in double-tube gas cooler of CO2 cycle improves the gas cooler effectiveness, cooling capacity and COP without penalty of pumping power. The CO2 cycle yields best performance using Al2O3-H2O as a coolant in double-tube gas cooler followed by TiO2-H2O, CuO-H2O and Cu-H2O. The maximum cooling COP improvement of transcritical CO2 cycle for Al2O3-H2O is 25.4%, whereas that for TiO2-H2O is 23.8%, for CuO-H2O is 20.2% and for Cu-H2O is 16.2% for the given ranges of study. Study shows that the nanofluid may effectively use as coolant in double-tube gas cooler to improve the performance of transcritical CO2 refrigeration cycle.

A simulation and experimental study on particle volume fraction of PMMA suspension in centrifugal fields

2021 ◽  
Author(s):  
Yosephus Ardean Kurnianto Prayitno ◽  
Tong Zhao ◽  
Yoshiyuki Iso ◽  
Masahiro Takei
Keyword(s):  
Experimental Study ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Particle Volume
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