Direct Measurement of Contact Angle Change in Capillary Rise

Kim, Hanul; Lim, Jae‐Hong; Lee, Kyoungmun; Choi, Siyoung Q.

doi:10.1021/acs.langmuir.0c02372

Cited by 14 publications

(11 citation statements)

References 57 publications

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“…Even though there is evidence that in some cases meniscus formation and capillary rise may occur concurrently, it assumed here that they are two distinct stages. First, the meniscus fully forms, and then, the liquid rises in the tube.…”

Section: Theorymentioning

confidence: 92%

“…Since that time, many aspects of capillary rise have been experimentally measured and theoretically modeled for various types of tubes and liquids. Capillary rise has been examined in the absence of gravity, − in tilted tubes, , in noncircular tubes, − in tapered tubes, , in rough tubes, ,, between two tubes, in chemically heterogeneous tubes with wetting gradients, in tubes where viscous forces control the rate at which liquid rises, − in tubes where the inertial forces of the liquid dominated over viscous forces, , and in tubes where the contact angle ,− or viscosity , depended on the rate of liquid rise.…”

Section: Introductionmentioning

confidence: 99%

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Meniscus Formation in a Vertical Capillary Tube

Extrand¹

2022

Langmuir

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In this theoretical work, the energies associated with the formation of a meniscus in a small diameter capillary tube are analyzed. A mechanism for meniscus creation and an associated energy balance are proposed. Equations for work of wetting, surface energy, gravitational energy, and dissipation are derived. The relative magnitude of these quantities is compared, first to each other and then to energies from capillary rise. In capillary rise, the energy released as work of wetting is evenly split between gravitational energy stored in the liquid column and heat dissipated there. The analysis performed here suggests that meniscus formation is energetically distinct and more complex than capillary rise. In meniscus formation, most of the energy released as work of wetting is stored in the stretched air–liquid interface or dissipated in the bulk liquid; their relative distribution depends on the properties of the liquid and the tube.

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Section: Theorymentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Meniscus Formation in a Vertical Capillary Tube

Extrand¹

2022

Langmuir

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“…The following designs are proposed and compared by the model to quantify the gas and liquid flow resistance within MEA. The capillary pressure of micro-meter-size pores is much higher than the liquid flow resistance, and the time scale for contact angle dynamics is on the order of 1-10 ms [26]. Therefore, the design principle is to reduce the liquid connection between the CL and the fuel channel.…”

Section: Designs Of Membrane Electrode Assembly Structures Tomentioning

confidence: 99%

Understanding Carbon Dioxide Transfer in Direct Methanol Fuel Cells Using a Pore-Scale Model

Metzger

Sekar

et al. 2021

Journal of Electrochemical Energy Conversion and Storage

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The gas flow of carbon dioxide from the catalyst layer (CL) through the micro porous layer (MPL) and gas diffusion layer (GDL) has great impacts on the water and fuel management in direct methanol fuel cells (DMFCs). This work has developed a liquid-vapor two-phase model considering the counter flow of carbon dioxide gas, methanol, and water liquid solution in porous electrodes of DMFC. The model simulation includes the capillary pressure as well as the pressure drop due to flow resistance through the fuel cell components. The pressure drop of carbon dioxide flow is found to be about 2-3 orders of magnitude higher than the pressure drop of the liquid flow. The big difference between liquid and gas pressure drops can be explained by two reasons: volume flow rate of gas is three orders of magnitude higher than that of liquid; only a small fraction of pores (< 5%) in hydrophilic fuel cell components are available for gas flow. Model results indicate that the gas pressure and the mass transfer resistance of liquid and gas are more sensitive to the pore size distribution than the thickness of porous components. To build up high gas pressure and high mass transfer resistance of liquid, the MPL and CL should avoid micro cracks during manufacture. Distributions of pore size and wettability of the GDL and MPL have been designed to reduce the methanol crossover and improve fuel efficiency. The model results provide design guidance to obtain superior DMFC performance using highly concentrated methanol solutions or even pure methanol.

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“…However, this has recently been questioned in light of experimental results indicating that the contact angle is affected by the velocity of the contact line . Even though some authors ,, reported that, for several liquids, the predicted deviations from the classical Lucas–Washburn equation due to velocity-dependent contact angles are very small, several experimental studies ,− and theoretical investigations supported by numerical and experimental data , reported better agreement with models that included this effect than with Lucas–Washburn approaches. In the literature, different dynamic contact angle models can be found to predict the dynamic contact angle effects in the capillary imbibition process.…”

Section: Introductionmentioning

confidence: 99%

Capillary Flow Dynamics in Composite Rectangular Microchannels with Rough Walls

2022

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In this article, we consider rectangular microchannels composed of glass and thin polymeric walls with different roughness in which opposed walls are of the same material but adjacent walls are not. We propose a model for fluid capillary transport into these rectangular microchannels when horizontally positioned and focus our research on how the microchannel aspect ratio modifies the motion during the initial viscous regimes. The model relies on an effective static contact angle and an effective friction coefficient that averages local magnitudes in the cross section. An extensive experimental investigation with different microchannels enabled us to obtain these coefficients for different aspect ratios. While for low aspect ratios, the effective contact angle presents the smallest values, the effective friction coefficient shows the larger ones. With rough surfaces, the spontaneous occurrence of pinning and depinning events associated with sharp wall defects notably reduces the effective static contact angle even when high aspect ratios are used. The obtained values of the effective friction coefficient show good agreement with previous literature investigations for rough and smooth lateral wall surfaces. Finally, we propose a nondimensional time to establish when contact angle effects dominate the dynamics. We found that for the materials and fluid properties used in this work, these effects become negligible for times larger than t ∼ 1 s.

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Direct Measurement of Contact Angle Change in Capillary Rise

Cited by 14 publications

References 57 publications

Meniscus Formation in a Vertical Capillary Tube

Meniscus Formation in a Vertical Capillary Tube

Understanding Carbon Dioxide Transfer in Direct Methanol Fuel Cells Using a Pore-Scale Model

Capillary Flow Dynamics in Composite Rectangular Microchannels with Rough Walls

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