Analysis of capillary flows in non-uniform cross-sectional capillaries

Young, Wen-Bin

doi:10.1016/j.colsurfa.2003.12.007

Cited by 64 publications

(42 citation statements)

References 12 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: 76%

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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: 76%

“…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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“…The equivalent pore size must be smaller than the average pore size, since the pore size varies along its length due to changing filament configurations. For a given average pore diameter, the flow in nonuniform capillary is much smaller compared with that in uniform capillary (Young, 2004).…”

Section: Vertical Wicking In Nonwovensmentioning

confidence: 93%

Liquid sorption behaviour of nonwovens

Rengasamy

Kothari

Bele

et al. 2011

The Journal of The Textile Institute

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In this paper, spunbond, meltblown and spunbond-meltblown-spunbond (SMS) nonwovens made from polypropylene are analysed for liquid transport behaviour. The thickness, grams per square metre (GSM), porosity, fibre diameter, fibre orientation distribution and water contact angles of these nonwovens are measured. Vertical wicking with decane using tensiometry and water absorbency and spreading using gravimetric absorbency tester are reported. The equivalent pore radii of the nonwovens are deduced from the vertical sorption experiments using tensiometry. The sorption rate under vertical wicking and water spreading rates are faster along machine direction compared with that in cross-direction due to preferential fibre orientation. The thickness of the nonwoven, fibre diameter and porosity play a vital role in transporting liquid. Thin nonwovens have poor vertical wicking and spreading rate. SMS web has poor absorbency behaviour mainly due to the inability of its top S-layer to pull the liquid from the middle M-layer. The measured water spreading lengths with respect to time are compared to the theoretical ones using a model developed by earlier researchers. This model reasonably predicts the spreading behaviour of nonwovens.

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“…More recently, Reyssat et al (2008) studied imbibition in capillary channels with axial variations and demonstrated that the imbibition dynamics is closely related to the details of the geometry of the capillary channel at long times. Various shapes have also been considered, including stepped capillary tubes (Erickson et al 2002;Polzin & Choueiri 2003;Young 2004), V-shaped open grooves (Romero & Yost 1996;Rye, Mann & Yost 1996;Weislogel & Litcher 1998;Dussaud, Adler & Lips 2003;Warren 2004), assemblies of parallel cylinders (Princen 1969) or corner flows (Higuera, Medina & Linan 2008;Ponomarenko, Quéré & Clanet 2011). To our knowledge, none of these studies were aimed at optimizing geometry for fast transport.…”

Section: Introductionmentioning

confidence: 98%

Rise in optimized capillary channels

Figliuzzi

Buie

2013

J. Fluid Mech.

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Many technological applications rely on the phenomenon of wicking flow induced by capillarity. However, despite a continuing interest in the subject, the influence of the capillary geometry on the wicking dynamics remains underexploited. In numerous applications, the ability to promote wicking in a capillary is a key issue. In this article, a model describing the capillary rise of a liquid in a capillary of varying circular crosssection is presented. The wicking dynamics is described by an ordinary differential equation with a term dependent upon the shape of the capillary channel. Using optimal control theory, we were able to design optimized capillaries which promote faster wicking than uniform cylinders. Numerical simulations show that the height of the rising liquid was up to 50 % greater with the optimized shapes than with a uniform cylinder of optimal radius. Experiments on specially designed capillaries with silicone oil show a good agreement with the theory. The methods presented can be useful in the design and optimization of systems employing capillary-driven transport including micro-heat pipes or oil extracting devices.

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Analysis of capillary flows in non-uniform cross-sectional capillaries

Cited by 64 publications

References 12 publications

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Liquid sorption behaviour of nonwovens

Rise in optimized capillary channels

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