Papers by Keyword: Dynamic Contact Angle

Abstract: This article analyzes the mechanism of interaction between the ink and paper. The Washburn equation just based on static penetration, while in contact with the ink and paper, freedom infiltration process is a dynamic process. So it is further derived based on a model of the dynamic ink permeability of dynamic contact angle, and mathematical analyzes some of the important parameters of the dynamic model so that can strive a more accurate description of the state of penetration of ink into the paper, thereby theoretically predict the quality control of printed matter.

Abstract: In order to study the effect of surfactants on wettability of quartz surface, the dynamic contact angles of different surfactants on water-wet and oil-wet quartz surfaces were measured. The experimental results showed that the advancing contact angles of cationic surfactants, anionic surfactants and nonionic surfactants on oil-wet quartz surfaces decrease with the increase of surfactant concentrations; the wettability of water-wet quartz plates remains water-wet after treated by all three kinds of surfactants. Surfactants can reverse the wettability from oil-wet to water-wet at low concentrations; The electrostatic force, hydrophobic force and the attraction between surfactant and polar components of crude oil are the key interactions in the wettability alteration process.

Abstract: The droplet impact behaviour provides the particle coating characterization during the coating process of controlled release fertiliser. To have a good coating uniformity around the urea granules, it is necessary to enhance the wettabitily properties between the coating material and urea surface. The biopolymer material is preferred as the coating material because this polymer may degrade and will not cause any environmental impact to the environment. Various compositions of starch/urea /borate/lignin were prepared and evaluated for the wettability properties. The wettability characteristic measured is the dynamic contact angle. The high speed Charged-Couple Device (CCD) camera was used to capture the images of this droplet impact behaviour. Temperature plays an important factor during wetting stage because the coating material must be completely dried in continuous coating process in fluidised bed. From this analysis, it indicates that a composition of starch/urea/ borate (50/15/2.5) with 10% lignin has the best wettability characteristic and thus suitable to be used as a coating material. The ideal temperature for the coating process is 60°C.

Abstract: This paper discusses the modeling of Electrowetting On Dielectric (EWOD) device that moves fluid droplets through surface tension effects and electric force. Instead of using a static contact angle as most papers did, we take the dynamic contact angle into count by using expression proposed by Voinov and Tanner. Firstly, the level set model and its initial values is present. Then the governing equations are discussed, and the diffused format is adopted for density and viscosity varies to smooth over the interface. The detailed expression for surface tension and electric force are also described for Navier–Stokes equations. After presenting the boundary conditions, the steps of numerical implementation are detailed.

Abstract: In China, most of undeveloped oil reserves are low and ultra low permeability reservoirs. The total remaining petroleum reserves of CNPC is about 4.07×107m3, and the low and ultra low permeability reserves is 3.16×107m3, So it is important to reasonable develop the oil reserves to keep the petroleum output stable. Under the low permeability layer condition, it is difficult to inject water to the formation, and the output of oil well is very low. The chemical agent can solve the difficulty of injection water and enhance the oil recovery. The relative permeability experiments shows irreducible oil was reduced by the wettability alteration agents, and the mobile oil saturation increased, which enlarging the range of the two phases co-flowing and enhancing oil recovery. As a result with alteration agents, the cross-point relative permeability moves to right, and the core converts to water-wet. In daqing oil field test, the water injection pressure is reduced by 15%, and the term of validity is more than 10 months.

Abstract: The method of wettability of solid-liquid interface is used to examine the differences of the liquid membranes formed by hydrophilic or hydrophobic membranes with different size and different materials, the influence of the characteristics of membrane modules in the process of desulfurization is studied. The method of accelerating the renewing rate of liquid membrane is proposed. The results show that the hydrophobic liquid membrane leads to higher renewing rate and absorption efficiency of sulfur dioxide and the hollow fiber membrane of polypropylene has higher adsorption efficiency. The dynamic contact angle of the same hollow fiber membrane is increasing with the number of the fibers leading to the increase of the diffusing resistance of liquid between the fibers. In order to accelerate the renewing rate of the liquid membrane, the concentration of the medium should be decreased under the condition of high absorption capacity.