A generalized analysis of capillary flows in channels

Yan, Xiao; Yang, Fei; Pitchumani, R.

doi:10.1016/j.jcis.2006.01.005

Cited by 64 publications

(67 citation statements)

References 15 publications

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“…Some of our experimental observations are supported by reports in the literature (e.g., water absorption and water transport by the bricks [16][17][18] ), but others are not explainable on the basis of present knowledge (e.g., by capillary flow within the bricks 5,19,20 ). This is probably because some reports regard organised systems, while others regard single elements.…”

Section: Our Results Show Thatsupporting

confidence: 80%

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Signanini¹,

Santis²,

Fazio³

et al. 2014

WATER

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Significant and persistent decreases in temperature have been observed in very porous materials when they are partially immersed in water at room temperature. As the sample sizes were much smaller than the maximum height of the typical capillary rise, this represents a far-from-equilibrium system. We attribute this thermal decrease to two concurrent actions: (i) the highly porous property of the material used; and (ii) a transition-phase-like process of the water. Thus, the water not only cools down the material surface through evaporation at the sample-air interface, but it also expands within the material, causing a further internal decrease in temperature that cannot be explained solely through evaporation. This latter process is persistent enough to maintain the decrease in temperature over time. This unexpected characteristic of water and its persistence when diffusing inside an extremely porous medium are the most original results of this study. Our results seem in agreement with the recent model on the fourth phase of water

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Section: Our Results Show Thatsupporting

confidence: 80%

“…Let us keep in mind that, although there are different models of capillary rise -capillary rate in the literature 16,19,20 , we believe in the validity of a particular innovative model 25 , at least with respect to our main goal, maximum cooling, which means that the amount of power generated by the material during the process is of interest.…”

mentioning

confidence: 99%

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Signanini¹,

Santis²,

Fazio³

et al. 2014

WATER

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“…Newer papers account also parallel-plate and rectangular capillaries [9,11]. A generalized theoretical analysis [12] gives the results which agree very well with experimental results for different geometries, dimensions and fluids. Despite the fact that the effect of the capillary rise seems a very well understood subject, to our knowledge, there is no analysis on the temporal evolution of the height of rise for the case when DEP forces exist together with capillary forces.…”

Section: Introductionsupporting

confidence: 61%

Experimental analysis of the dielectrophoretic forces influence on height of rise of fluid in a capillary system for boiling control in microchannel

Lackowski

Karwacki

2017

ZN PRz Mechanika

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Flow control in microchannels is one of the key issues in many areas of modern technology, such as medicine, bio-engineering, chemistry and, in recent years, also in problems of thermodynamic processes control. This paper presents the results of experimental studies on the dynamics of liquid movement between the walls of a microchannel, which is the effect of the electric field applied to the walls (the dielectrophoresis phenomenon). The presented results fill a gap in the literature, being also an important material for the determination of the device key parameters, such as the height of the microchannel electrodes, frequency and amplitude of applied voltage, the selection of periods with and without voltage, all of which affect the operation of the device.

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“…These include a possible dynamic contact angle effect during flow (Siebold et al, 2000;Hamdaoui and Nylander;2002Chebbi 2007Xiao et al, 2006;Xue et al 2006), and a possible retardation coefficient arising from an increased frictional dissipation of the moving liquid front (Hamdaoui and Nylander, 2002). A number of different models for how cos e in the capillary term b in eq.…”

Section: Resultsmentioning

confidence: 99%

Wetting considerations in capillary rise and imbibition in closed square tubes and open rectangular cross-section channels

Ouali

McHale

Javed

et al. 2013

Microfluid Nanofluid

149

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The spontaneous capillary-driven filling of microchannels is important for a wide range of applications. These channels are often rectangular in cross-section, can be closed or open, and horizontal or vertically orientated. In this work, we develop the theory for capillary imbibition and rise in channels of rectangular cross-section, taking into account rigidified and non-rigidified boundary conditions for the liquid-air interfaces and the effects of surface topography assuming Wenzel or Cassie-Baxter states. We provide simple interpolation formulae for the viscous friction associated with flow through rectangular cross-section channels as a function of aspect ratio. We derive a dimensionless cross-over time, T c , below which the exact numerical solution can be approximated by the Bousanquet solution and above which by the visco-gravitational solution. For capillary rise heights significantly below the equilibrium height, this cross-over time is T c  (3X e /2) 2/3 and has an associated dimensionless crossover rise height X c  (3X e /2) 1/3 , where X e =1/G is the dimensionless equilibrium rise height and G is a dimensionless form of the acceleration due to gravity. We also show from wetting considerations that for rectangular channels, fingers of a wetting liquid can be expected to imbibe in advance of the main meniscus along the corners of the channel walls. We test the theory via capillary rise experiments using polydimethylsiloxane oils of viscosity 96.0, 48.0, 19.2 and 4.8 mPa s within a range of closed square tubes and open rectangular cross-section channels with SU-8 walls. We show that the capillary rise heights can be fitted using the exact numerical solution and that these are similar to fits using the analytical visco-gravitational solution. The viscous friction contribution was found to be slightly higher than predicted by theory assuming a non-rigidified liquid-air boundary, but far below that for a rigidified boundary, which was recently reported for imbibition into horizontally mounted open microchannels. In these experiments we also observed fingers of liquid spreading along the internal edges of the channels in advance of the main body of liquid consistent with wetting expectations. We briefly discuss the implications of these observations for the design of microfluidic systems.

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A generalized analysis of capillary flows in channels

Cited by 64 publications

References 15 publications

Untitled

Untitled

Experimental analysis of the dielectrophoretic forces influence on height of rise of fluid in a capillary system for boiling control in microchannel

Wetting considerations in capillary rise and imbibition in closed square tubes and open rectangular cross-section channels

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