Shale gas transport in nanopores with mobile water films and water bridge

Gas flow properties in nanopores are significantly determined by the flow patterns. Slug flow pattern is a potential water–gas two phase flow pattern, in which gas molecules flow in form of gas slugs and water molecules separate gas slugs. Considering water slippage, a portion of water molecules accumulates at the wall with lower mobility, while the remaining water molecules take the shape of a water bridge. Adopting foam apparent viscosity model to represent slug rheological behavior, how water bridge disturbs on gas flow capacity is estimated. The results are compared with the water–gas two phase flow model that assumes annular flow pattern as well as the single gas flow model without the consideration of water. The comparison illustrates that gas molecular movement is significantly hindered by flow space reduction and loss of gas slippage. The impact from water phase of slug flow pattern is more significant than that of annular flow pattern on gas flow capacity. It is discovered that larger nanopores improve gas flow capacity while maintaining bulk water layer thickness and increasing water bridge thickness tend to reduce gas transport ability. A better understanding of the structure and transport of water and gas molecules is conducive to figure out the specific gas–water flow behavior and predict shale gas production.

Micro–Nano Water Film Enabled High‑Performance Interfacial Solar Evaporation

Interfacial solar evaporation holds great promise to address the freshwater shortage.However,most interfacial solar evaporators are always filled with water throughout the evaporation process,thus bringing unavoidable heat loss.Herein,we propose a novel interfacial evaporation structure based on the micro–nano water film,which demonstrates significantly improved evaporation performance,as experimentally verified by polypyrrole-and polydopamine-coated polydimethylsiloxane sponge.The 2D evaporator based on the as-prepared sponge realizes an enhanced evaporation rate of 2.18 kg m^(−2)h^(−1)under 1 sun by fine-tuning the interfacial micro–nano water film.Then,a homemade device with an enhanced condensation function is engineered for outdoor clean water production.Throughout a continuous test for 40 days,this device demonstrates a high water production rate(WPR)of 15.9–19.4 kg kW^(−1)h^(−1)m^(−2).Based on the outdoor outcomes,we further establish a multi-objective model to assess the global WPR.It is predicted that a 1 m^(2)device can produce at most 7.8 kg of clean water per day,which could meet the daily drinking water needs of 3 people.Finally,this technology could greatly alleviate the current water and energy crisis through further large-scale applications.

Permeability evolution and gas flow in wet coal under non-equilibrium state:Considering both water swelling and process-based gas swelling

Accurate knowledge of gas flow within the reservoir and related controlling factors will be important for enhancing the production of coal bed methane.At present,most studies focused on the permeability evolution of dry coal under gas adsorption equilibrium,gas flow and gas diffusion within wet coal under the generally non-equilibrium state are often ignored in the process of gas recovery.In this study,an improved apparent permeability model is proposed which accommodates the water and gas adsorption,stress dependence,water film thickness and gas flow regimes.In the process of modeling,the water adsorption is only affected by water content while the gas adsorption is time and water content dependent;based on poroelastic mechanics,the effective fracture aperture and effective pore radius are derived;and then the variation in water film thickness for different pore types under the effect of water content,stress and adsorption swelling are modeled;the flow regimes are considered based on Beskok’s model.Further,after validation with experimental data,the proposed model was applied to numerical simulations to investigate the evolution of permeability-related factors under the effect of different water contents.The gas flow in wet coal under the non-equilibrium state is explicitly revealed.

An analytical model for water-oil two-phase flow in inorganic nanopores in shale oil reservoirs

The existence of water phase occupies oil flow area and impacts the confined oil flow behavior at the solid substrate in inorganic nanopores of shale oil reservoirs,resulting in a completely different flow pattern when compared with the single oil phase flow.This study proposes an analytical model to describe the water-oil two-phase flow.In this model,water slippage at the solid substrate is considered while oil slip is introduced to calculate the oil movement at the solid-oil boundary in dry conditions.It is proven that the oil flow profiles of both the two-phase model and single-phase model show parabolic shapes,but the oil flow capacity drops when water takes up the flow space and the impact of water is more significant when the pore dimension is smaller than 30 nm.Also,the oil flow velocity at a pore center is found to drop linearly given a larger water saturation in wet conditions.The effects of surface wettability and oil properties on water-oil flow are also discussed.Compared with the existing singlephase models,this model describes oil flow pattern in the wet condition with the incorporation of the influence of nanopore properties,which better predicts the oil transport in actual reservoir conditions.Water-oil relative permeability curves are also obtained to improve oil yield.

Removal of NO and SO2 in Corona Discharge Plasma Reactor with Water Film

In this paper, a novel type of a corona discharge plasma reactor was designed, which consists of needle-plate-combined electrodes, in which a series of needle electrodes are placed in a glass container filled with flue gas, and a plate electrode is immersed in the water. Based on this model, the removal of NO and SO2 was tested experimentally. In addition, the effect of streamer polarity on the reduction of SO2 and NO was investigated in detail. The experimental results show that the corona wind formed between the high-voltage needle electrode and the water by corona discharge enhances the cleaning efficiency of the flue gas because of the presence of water, and the cleaning efficiency will increase with the increase of applied dc voltage within a definite range. The removal efficiency of SO2 up to 98%, and about 85% of NOx removal under suitable conditions is obtained in our experiments.

Study on water treatment effect of dispersion discharge plasma based on flowing water film electrode

To improve the utilization rate of plasma active species,in this study,a closed non-uniform air gap is formed by a flowing water film electrode and a sawtooth insulating dielectric layer to realize the diffuse glow discharge in the atmosphere.Firstly,the electric field distribution characteristics of non-uniform air gap in the sawtooth dielectric layer are studied,and the influence of aspect ratio on the characteristics of diffuse discharge plasma is discussed.Subsequently,the effects of wire mesh,the inclination angle of the dielectric plate,and liquid inlet velocity on the flow characteristics of the water film electrode are analyzed.The results show that the non-uniform electric field distribution formed in the sawtooth groove can effectively inhibit the filamentous discharge,and the 1 mm flowing water film is directly used as the electrode,and high-active plasma is formed directly on the lower surface of the water film.In addition,a plasma flowing water treatment device is built to treat the methyl orange solution and observe its decolorization effect.The experimental results show that after 50 min of treatment,the decolorization rate of the methyl orange solution reaches 96%,which provides a new idea for industrial applications of wastewater treatment.

Water film area and dust removal efficiency of string grilles:a theoretical analysis

Based onmultiphase flowtheory and capillary mechanics,the dimensionless bond number expression of the influence of string grille wire spacing on droplet spreading is derived.Taking a liquid film formed by spreading droplets based on Kelvin correlation,the Young-Laplace equation,and the Hagen-Poiseuille law,an equation for calculating the thickness and height of the liquid film is established with temperature,relative humidity and molar volume of liquid phase as independent variables.According to the theory of string grille filtration and dust removal,a dust removal efficiency calculation model covering the wet string grille wire group is constructed based on the liquid film thickness,height,wire diameter,water film area,and vortex shedding frequency.Finally,a theoretical analysis of the influence of water film area on the efficiency of wet string grille dust removal is carried out based on the spray pressure and the ratio of string grille wire distance to wire diameter.It is found that the effect of spray pressure on water film area and dust removal efficiency is more significant than the string grille wire distance diameter ratio.Moreover,the optimized combination of wet string grille wire distance diameter ratio 0.84,wind speed 3m/s and spray pressure 0.8 MPa is found,which could provide an important reference for engineering applications.

Stable Isotopes and Chloride Applied as Soil Water Tracers for Phreatic Evaporation Experiment

A phreatic water evaporation experiment,without rainfall influence,was designed to study the mechanisms of soil water movement through groundwater recharge to the unsaturated zone. Soil moisture content,chloride concentration,and δD and δ~18 O values of soil water were measured. Results showthat with decreasing soil moisture content,the chloride concentration of leachate( ρ_f(Cl)) in the capillary water layer decreases,whereas the ρ_f(Cl) value of the hanging and film water layers above the capillary water layer increases. With the combined δD and δ~18 O values,the soil water in the hanging and film water layers is influenced by evaporation,although a dry sand layer of 39 cm exists above the wet sand layer. The highest evaporation rate and the largest salt accumulation occur at a depth of about 39 cm in columns d,e,and f(Six polyvinyl chloride columns were assigned as column a,b,c,d,e,and f). We deduce that soil water migrates in the form of liquid water above the capillary water layer. In the experiment,a part of phreatic water consumed is used for the movement of soil water,whereas the other part is lost to evaporation. Soil water could continue migrating upward with prolonged experiment duration.

Numerical Simulation of an Airfoil Electrothermal-Deicing-System in the Framework of a Coupled Moving-Boundary Method

A numerical method for the analysis of the electrothermal deicing system for an airfoil is developed taking into account mass and heat exchange at the moving boundary that separates the water film created due to droplet impingement and the ice accretion region.The method relies on a Eulerian approach(used to capture droplet dynamics)and an unsteady heat transfer model(specifically conceived for a multilayer electrothermal problem on the basis of the enthalpy theory and a phase-change correction approach).Through application of the continuous boundary condition for temperature and heat flux at the coupled movingboundary,several simulations of ice accretion,melting and shedding,runback water flow and refreezing phenomena during the electrothermal deicing process are conducted.Finally,the results are verified via comparison with experimental data.A rich set of data concerning the dynamic evolution of the distribution of surface temperature,water film height and ice shape is presented and critically discussed.

Pyrolysis preparation of WO_3 thin films using ammonium metatungstate DMF/water solution for efficient compact layers in planar perovskite solar cells

The tungsten trioxide（WO3） thin films were firstly prepared by spin-coating-pyrolysis methods using the ammonium metatungstate（（NH4）6H2W12O40）DMF/water solution, and successfully applied as the efficient compact layers for the planar perovskite solar cells. The influence of the WO3 film thickness and the rinsing treatment of CH_3NH_3 PbI_3 thin film with isopropanol on the photovoltaic performance of the corresponding perovskite solar cells was systematically investigated. The results revealed that the perovskite solar cell with a 62 nm thick WO3 compact layer achieved a photoelectric conversion efficiency of 5.72%, with a short circuit photocurrent density of 17.39 mA/cm^2, an open circuit voltage of 0.58 V and a fill factor of 0.57. The photoelectric conversion efficiency was improved from 5.72% to 7.04% by the isopropanol rinsing treatment.

Asphalt pavement water film thickness detection and prediction model:A review

Over the course of storm or rainfall event,water thickness builds up on road surface resulting in a loss of contact between vehicle tires and road surface and puts drivers into immediate danger especially at high speeds.Therefore this is a considerably dangerous condition of the road and the realistic measurements and prediction model of water film thickness(WFT)on pavement surface is crucial for determining the road friction coefficient and evaluating the impact of rainfall on traffic safety.A review of the principle as well as critical evaluation of current detection methods of pavement WFT were compared for consistency and accuracy in this paper.The method selection guidelines are given for different road surface water film thickness detection requirements.This paper also introduces the latest development of WFT detection and prediction models for asphalt pavement,and gives the calculation elements and conditions of different WFT prediction models from different modeling ideas,which provides a basis for the selection and optimization of WFT models for future researchers.This article also suggests a few insights as further research directions on this topic.(1)The research can consider the influencing factors of WFT to conduct research on the delineation standard of pavement WFT.(2)In order to meet the future traffic safety dynamic early warning needs,road factors of different material types,disease conditions and linear conditions should be studied,as well as a comprehensive and accurate real-time water film thickness detection and evaluation method considering meteorological factors of rainfall timing,scale and intensity.(3)The prediction model of WFT should be further studied by the analytical method to clarify the influence of the pavement WFT on the driving safety.

Investigation of surface textures deterioration on pavement skid-resistance using hysteresis friction models and numerical simulation method

Many rubber friction theories or some method combined theories and field-experiments are employed to evaluate the pavement skid-resistance deterioration due to the evolution of surface textures.However,these methods are difficult to be implemented in the analysis of situations with multi-factor coupling and some extreme conditions.This study developed a framework to evaluate the skid-resistance deterioration of asphalt pavements.In this framework,the portable laser scanning was used to create the digital worn pavement model,and a hydroplaning finite element(FE)model for these digital worn pavements was constructed to evaluate coupling effects of the texture evolution and factors of slip ratio,slip angle,velocity and water film on braking-cornering characteristics of tire.In this study,the deterioration of skid-resistance of five typical asphalt pavements due the surface texture wear was systematically investigated by this framework.Compared with previous works,this study established the rubber friction models for each digital worn pavement considering the energy hysteresis of rubber and the power spectrum density of surface texture.And the rubber friction model was used to define the interaction behaviors between the tire and corresponding wore pavements in the FE hydroplaning model,rather than using an empirical friction model or a fixed friction coefficient.

Surface removal of a copper thin film in an ultrathin water environment by a molecular dynamics study

The surface planarity and asperity removal behavior on atomic scale in an ultrathin water environment were studied for a nanoscale process by molecular dynamics simulation.Monolayer atomic removal is achieved under both noncontact and monoatomic layer contact conditions with different water film thicknesses.The newly formed surface is relatively smooth without deformed layers,and no plastic defects are present in the subsurface.The nanoscale processing is governed by the interatomic adhering action during which the water film transmits the loading forces to the Cu surface and thereby results in the migration and removal of the surface atoms.When the scratching depth≥0.5 nm,the abrasive particle squeezes out the water film from the scratching region and scratches the Cu surface directly.This leads to the formation of trenches and ridges,accumulation of chips ahead of the particles,and generation of dislocations within the Cu substrate.This process is mainly governed by the plowing action,leading to the deterioration of the surface quality.This study makes the"0 nm planarity,0 residual defects,and 0 polishing pressure"in a nanoscale process more achievable and is helpful in understanding the nanoscale removal of materials for developing an ultra-precision manufacture technology.

Degradation of sulfadiazine antibiotics by water falling film dielectric barrier discharge

A new water falling film dielectric barrier discharge was applied to the degradation of sulfadiazine in the aqueous solution. The various parameters that affect the degradation of sulfadiazine and the proposed evolutionary process were investigated. The results indicated that the inner concentrations of 10 mg/L sulfadiazine can be all removed within 30 min. The optimum pH value was 9.10 and both strong acidic and alkaline solution conditions were not suitable for the degradation. The degradation of sulfadiazine can be enhanced by the addition of hydrogen radical scavengers, but be inhibited by adding hydroxyl radical scavengers. The water falling film dielectric barrier discharge was rather ineffective in mineralization, because of the intermediates were recalcitrant to be degraded. The existence of Fe2＋ and CCI4 in the liquid phase can promote the degradation and mineralization of sulfadiazine. It was found that the degradation of SDZ was enhanced by CC14 was mainly because of the increase of＇OH due to the reaction of CC14 with ＊H that reduce the chances of their recombination with ＂OH. Based on the 8 intermediate products identified by LC-MS, the proposed evolution of the degradation process was investigated.

Influences of fiber length and water film thickness on fresh properties of basalt fiber-reinforced mortar

In plain mortar,the water film thickness(WFT)has been found to play a key role in the fresh properties.However,in fiber-reinforced mortar,the role of WFT has not been investigated yet.In this research,basalt fibers of different lengths were added to the mortar,and the dynamic and static flowability,cohesiveness,adhesiveness,and packing density were tested to study the effects of fiber length on the packing density and WFT,and the combined effects of fiber length and WFT on the fresh properties.The results showed that in fiber-reinforced mortar,the WFT also plays a key role,whereas the fiber length exerts its influences through the indirect effects on the packing density and WFT and the direct effect on fiber-mortar interaction.Basically,an increase in fiber length decreases the packing density and WFT,decreases the dynamic and static flowability needed for placing,increases the cohesiveness needed for avoiding segregation,and,quite unexpectedly,decreases the adhesiveness needed for rendering and spraying applications.Regression analysis yielded good correlation of the fresh properties to fiber length and WFT,and best-fit formulas for the mix design for basalt fiber-reinforced mortar were obtained.

Corrosion Behavior of Ni–20Cr–18W–1Mo Superalloy in Supercritical Water

The corrosion behavior of Ni–20Cr–18 W–1Mo superalloy in supercritical water 500 °C/25 MPa for 200 h is investigated using gravimetry, SEM/EDS, XPS, and TEM. The oxide films show a layered structure with Ni rich in the outer layer, and Cr rich in the inner layer, consisting of an outer Ni（OH）2and NiO layer, including some Cr（OH）3, and an inner Cr2O3, Ni Cr2O4, and WO3 layer. Mo elements are not oxidized. The oxide films grow via a mixed mechanism,namely metal dissolution/oxide precipitation mechanism and solid-state growth mechanism. The effects of secondary and primary carbides on the weight-gain trend and oxide formation are discussed.

Evaporation-driven water flow induced electricity from porous carbon film

Subject code:E02 With the support by the National Natural Science Foundation of China,a collaborative study by the research group led by Prof.Zhou Jun(周军)from Wuhan National Laboratory for Optoelectronics,Huazhong University of Science and Technology,Prof.Guo Wanlin(郭万林)from Nanjing University

Characteristics of Oxidation and Oxygen Penetration of Alloy 690 in 600°C Aerated Supercritical Water

The oxide films formed on Alloy 690 exposed to 600 ℃ supercritical water were characterized using mass measurement, X-ray diffraction. Raman spectroscopy, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. It was found that the mass gain of the alloy in supercritical water decreased with increasing exposure time. The oxide films have a double-layer structure, with an inner layer rich in Cr and outer layer rich in Ni and Fe after short time and long time exposure. The penetration of the oxide along the grain boundaries was observed, and the penetration depth increased with increasing exposure time. The grain boundaries and voids are the short-path of oxygen diffusion into the metal.

Bionic Design to Reduce Jacking Force for Trenchless Installations in Clay Soil

The application of trenchless technology is the trend of underground public facilities'installation,replacement and repairing.As the soil-engaging component during penetrating bore,the working resistance of penetration head has remarkable effect on energy consumption of the whole working process.Some typical soil-digging animals,like pangolin and earthworm,they own special micro structures on their surface.It has been widely proved that some micro geometrical structures can effectively reduce adhesion resistance.Four kinds of bionic penetration heads were designed by imitating micro geometrical structures inspired by the soil animals.In this work,the real time jacking forces of the bionic penetration heads were measured and compared with a smooth penetration head(control group)without micro geometrical structures.The result indicated that the jacking forces of the bionic penetration heads were smaller than that of the smooth penetration head.This proved that the bionic penetration heads have the ability of reducing adhesion resistance.The vertical concave penetration head got the smallest jacking force,of which the average jacking force was 18.7%lower than that of the smooth penetration head.The interaction between soil and bionic surface of penetration head was discussed on the condition of wet friction.The bionic surface reduced the adhesion resistance by disturbing the soil and braking the continuous water film between soil and the surface of the penetration head.