Removing Gas from a Closed-End Small Hole by Irradiating Acoustic Waves with Two Frequencies

Filling microstructures in the air with liquid or removing trapped gases from a surface in a liquid are required in processes such as cleaning, bonding, and painting. However, it is difficult to deform the gas–liquid interface to fill a small hole with liquid when surface tension has closed one end. Therefore, it is necessary to have an efficient method of removing gas from closed-end holes in liquids. Here, we demonstrate the gas-removing method using acoustic waves from small holes. We observed gas column oscillation by changing the hole size, wettability, and liquid surface tension to clarify the mechanism. First, we found that combining two different frequencies enabled complete gas removal in water within 2 s. From high-speed observation, about half of the removal was dominated by droplet or film formation caused by oscillating the gas column. The other half was dominated by approaching and coalescing the divided gas column. We conclude that the natural frequency of both the air column and the bubbles inside the tube are important.

Theoretical background for simulation of physical processes in the interfacial layer “solid-liquid”

The paper shows a modification of the quasi-thermodynamic approach to simulation of the interfacial layer from conditions of its mechanical equilibrium. The anisotropy of the interfacial stress tensor is represented as the sum of the ball and deviator parts, where the ball part defines the pressure in the medium and the deviator part forms the components responsible for the liquid surface tension. Obtaining a closed system of equilibrium equations was possible taking into account evaporation from free surface of liquid. The result is a simple expression for determining the thickness of the interfacial layer.

Synthesis of Comb-Polyurethane-Modified Polycarboxylate at Indoor Temperature and Its Interaction With Portland Cement

According to the principle of radical polymerization reaction, different polycarboxylates with comb structures were synthesized. With the other two commercial polycarboxylates (C-PCE-1 and C-PCE-2), the effects of all the polycarboxylates on adsorption, hydration, zeta potential, liquid surface tension, and flowability in Portland cement were determined. Compared to O-PCE and C-PCEs, the adsorption value of M-PCE increased by 14.1% and the adsorption rate increased by 24% maximum. O-PCE, C-PCE-1, and C-PCE-2 have a delayed effect on the hydration of the cementitious materials, but M-PCE does not. Due to higher adsorption amount, M-PCE with siloxane groups has an excellent comprehensive performance of zeta potential, liquid surface tension, and flowability in cementitious materials.

Investigation of Flow Pattern and Void Fraction of Air and Low Surface Tension Liquid in A 30° Inclined Small Pipe

Two-phase flow in the mini pipe is applied in wide fields. The most common of two-phase flow is a couple of gas and liquid. The essential properties of the liquid are density, viscosity, and surface tension. There are many variations of the flow direction, horizontal, incline, and vertical, in terms of orientation. The two-phase investigation of flow pattern and void fraction of air and low surface tension liquid in a 30° inclined small pipe has been carried out. Dry air was used as a gas phase, while the liquid was the mixture solution of distilled water and 3% (by volume) of butanol. Butanol addition aimed to decrease the surface tension, which became 42.9 millinewton/meter, instead of 71 mN/m when using distilled water. The test section was a 130 mm length, 1.6 mm inner diameter circular glass pipe. The rig used was equipped with the air compressor, pressure tank, high-speed camera, liquid flow meter, and gas flow meter. The liquid was fed to the test section by the pressurized tank, instead of directly pumped, to avoid pulsation. Ranges of gas and liquid superficial velocities were 0.025 – 66.3 m/s and 0.033 – 4,935 m/s, respectively. Flow patterns were obtained from the captured high-speed video. Meanwhile, the void fractions were acquired by image processing of the video. As a result, five distinctive flow patterns were observed: plug, slug-annular, churn, bubbly, and annular. The separated flow was absent. The change of the liquid surface tension affected the shifting of some transition boundary lines in the flow pattern map. The transition line between slug-annular and annular against churn flow was shifted to the lower side or toward lower JL when the liquid surface tension decreased. In short, the churn flow was easier to be formed when the liquid surface tension was lower.

Effects of Tube Radius and Surface Tension on Capillary Rise Dynamics of Water/Butanol Mixtures

Capillary-driven action is an important phenomenon which aids the development of high-performance heat transfer devices, such as microscale heat pipes. This study examines the capillary rise dynamics of n-butanol/water mixture in a single vertical capillary tube with different radii (0.4, 0.6, and 0.85 mm). For liquids, distilled water, n-butanol, and their blends with varying concentrations of butanol (0.3, 0.5, and 0.7 wt.%) were used. The results show that the height and velocity of the capillary rise were dependent on the tube radius and liquid surface tension. The larger the radius and the higher the surface tension, the lower was the equilibrium height (he) and the velocity of rise. The process of capillary rise was segregated into three characteristic regions: purely inertial, inertial + viscous, and purely viscous regions. The early stages (purely inertial and inertial + viscous) represented the characteristic heights h1 and h2, which were dominant in the capillary rise process. There were linear correlations between the characteristic heights (h1, h2, and he), tube radius, and surface tension. Based on these correlations, a linear function was established between each of the three characteristic heights and the consolidated value of tube radius and surface tension (σL/2πr2).