Transport from a volatile meniscus inside an open microtube

Wang, Hao; Murthy, Jayathi Y.; Garimella, Suresh V.

doi:10.1016/j.ijheatmasstransfer.2007.09.011

Cited by 57 publications

(61 citation statements)

References 22 publications

(40 reference statements)

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“…Very low and unwanted temperature asymmetry around the outlet may also induce a significant asymmetry in the Marangoni flow field (Wang et al 2008). In such cases, the toroidal field is substituted by a single vortex (Wang et al 2008;Braunsfurth and Homsy 1997).…”

Section: Interpretation Of the Experimental Resultsmentioning

confidence: 99%

“…) are characterized by particle image velocimetry (PIV) in vertical micro-channels (Braunsfurth and Homsy 1997;Buffone et al 2004;Kamotani et al 1994). A different flow pattern is observed in horizontal channels (Wang et al 2008;Chamarthy et al 2008) and the toroidal field is substituted by a single vortex in a 400 lm tube because buoyancy breaks the circular symmetry of the experiment. A similar single vortex phenomenon is observed in (Buffone et al 2005).…”

Section: Introductionmentioning

confidence: 99%

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3D visualization of convection patterns in lab-on-chip with open microfluidic outlet

Gazzola

Scarselli

Guerrieri

2009

Microfluid Nanofluid

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Open-outlet microfluidics is getting more and more attention, thanks to the generation of capillarity-driven flows which simplify the connection with the macroworld. It is known that convection flows are generated at the interface with air, i.e., the meniscus. Several works have investigated evaporation-induced convection, but its effect on particle position control in open-outlet biodevices is still not characterized. In this paper, we present the results of 3D measurement of particle traces near the meniscus in an open-outlet vertical 400 lm micro-channel filled with a water-based saline solution. Using a standard optical microscope and a system of mirrors, we observe the 3D position of individual micro-beads floating in the solution, in a way akin to particle image velocimetry technique. A single vortex is generated at the meniscus and occupies the whole region under observation at a distance of 1.5-2.7 mm from the meniscus. The generation of the convection pattern and the vortex rotational speed are described. The convection patterns disappear when evaporation is inhibited, while both the vortex generation and the rotational speed are faster for highly saline solutions. These results are relevant to the design of biochips which require control of the particle position in a fluid since they emphasize that in open-outlet microfluidic systems not only the gravitational fall but also the convection drag must be counteracted.

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Section: Interpretation Of the Experimental Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

3D visualization of convection patterns in lab-on-chip with open microfluidic outlet

Gazzola

Scarselli

Guerrieri

2009

Microfluid Nanofluid

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“…4 Evaporation from liquid menisci in simple wicking geometries has been studied in the literature [9,10] using mathematical models. Wang et al [11] modeled the transport from a volatile meniscus inside an open microtube. This work delineated the structure of fluid flow near an evaporating meniscus, including Marangoni and buoyancy-driven instabilities.…”

Section: Introductionmentioning

confidence: 99%

“…Diffusion-driven evaporation from a liquid-vapor interface in a capillary slot has been modeled by Wang et al [11] and Rice et al [17].…”

Section: Introductionmentioning

confidence: 99%

A microscale model for thin-film evaporation in capillary wick structures

Ranjan

Murthy

Garimella

2011

International Journal of Heat and Mass Transfer

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175

112

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A numerical model is developed for the evaporating liquid meniscus in wick microstructures under saturated vapor conditions. Four different wick geometries representing common wicks used in heat pipes, viz., wire mesh, rectangular grooves, sintered wicks and vertical microwires, are modeled and compared for evaporative performance. The solid-liquid combination considered is copper-water. Steady evaporation is modeled and the liquid-vapor interface shape is assumed to be static during evaporation. Liquid-vapor interface shapes in different geometries are obtained by solving the Young-Laplace equation using Surface Evolver. Mass, momentum and energy equations are solved numerically in the liquid domain, with the vapor assumed to be saturated. Evaporation at the interface is modeled by using heat and mass transfer rates obtained from kinetic theory. Thermocapillary convection due to non-isothermal conditions at the interface is modeled for all geometries and its role in heat transfer enhancement from the interface is quantified for both low and high superheats. More than 80% of the evaporation heat transfer is noted to occur from the thin-film region of the liquid meniscus. The very small Capillary and Weber numbers resulting from the small fluid velocities near the interface for low superheats validate the assumption of a static liquid meniscus shape during evaporation. Solid-liquid contact angle, wick porosity, solid-vapor superheat and liquid level in the wick pore are varied to study their effects on evaporation from the liquid meniscus.

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“…In the present work, the accommodation coefficient, σ is taken as unity, and the equilibrium vapor pressure is taken as the saturation pressure corresponding to the interface temperature, p v_equ (T lv ) = p sat (T lv ) [27]. As mentioned in Section 2, the enclosure leads to approximately saturated conditions in the domain and serves to dampen the concentration gradients.…”

Section: Microregion Mass Transfermentioning

confidence: 99%

Evaporative heat and mass transfer from the free surface of a liquid wicked into a bed of spheres

Migliaccio

Garimella

2011

International Journal of Heat and Mass Transfer

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Evaporation of ethanol from square packed arrays of 3.95 mm diameter copper spheres in a transparent, enclosed chamber is investigated. The enclosure ensures that relatively saturated vapor conditions exist near the free surface. The desired heat flux is imposed on the copper substrate upon which the copper spheres are mounted, and the liquid level in the bed is maintained by wicking from a continuous supply of liquid provided by a syringe pump.Transparent windows in the enclosure allow for visualization of the evaporating liquid meniscus shape, which is recorded for different liquid feeding rates and heat fluxes. Experimentally measured meniscus profiles are compared to analytical results based on surface-energy minimization. A meniscus microregion is defined from the contact line to the length where the liquid thickness reaches 10 μm. An approximate kinetic theory-based analysis estimates that up to ~55% of the total meniscus mass transfer occurs in this microregion.

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Transport from a volatile meniscus inside an open microtube

Cited by 57 publications

References 22 publications

3D visualization of convection patterns in lab-on-chip with open microfluidic outlet

3D visualization of convection patterns in lab-on-chip with open microfluidic outlet

A microscale model for thin-film evaporation in capillary wick structures

Evaporative heat and mass transfer from the free surface of a liquid wicked into a bed of spheres

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