Growth rate of CO_(2) hydrate film on water-oil and water-gaseous CO_(2) interface

It is known that injection of carbon dioxide into the petroleum reservoir(CO_(2) flooding) is one of the effective methods for enhanced oil recovery. CO_(2) flooding may be complicated by formation of CO_(2) hydrate plugs. It makes topical investigation of CO_(2) hydrate formation in the system gaseous CO_(2)-oil-water. In this work, the growth rates of carbon dioxide hydrate films at the water-oil as well as the water-gas interface are studied in the pressure range of 2.30-3.04 MPa and at temperatures between -5.4 and 5.0℃. It is found that the growth rate for the water-oil interface is 3.5 times lower than that for the water-gas interface with carbon dioxide. It is hypothesised that the observed decrease in the growth rate is related to the mechanical resistance of the oil components adsorbed on the interface to the growth of the hydrate film. The growth rate of the film has been shown to depend on the experimental procedure,most likely due to the different initial concentrations of carbon dioxide in the aqueous solutions.

Plasma-Chemical Synthesis of Oxide Powders Using Transformer-Coupled Discharge

An experimental investigation of transformer-coupled discharge in an Ar-O2 mixture with the addition of SICl4, TiCl4 and ZrCl4 has been carried out under the atmospheric pressure of plasma-forming gases. Discharge power and discharge heat losses have been determined, and the dispersion and phase composition of reaction products （oxide powders） has been analyzed with SEM and X-ray diffraction analysis. Investigations reveal the formation of ultrafine oxide powders in the case of vaporized chloride （SiCl4 and TiCl4） injecting into the transformer coupled discharge. In the case of fine powder （ZrCl4） injection, full oxidation was not observed and reaction products consisted of a mixture of ZrO2 and ZrOCl2. A conclusion has been made regarding the perspectives of using transformer-coupled discharge to produce ultrafine oxide powders.

Numerical Modelling of Coal Combustion Processes in the Vortex Furnace with Dual-Port Loading

The work is devoted to numerical simulation of pulverized-coal combustion processes in the vortex furnace which is a prospective design of a boiler unit for thermal power plants. New modification of this design characterized by additional tangential-injection nozzle located at the bottom of combustion chamber has been studied. Numerical results for the case of Siberian brown coal combustion in this vortex furnace with dual-port loading are presented, including 3-D aerodynamic structure, the fields of temperatures, radiated heat fluxes, species and dispersed phase concentrations, and NOx emissions.

3D pore-scale modeling of nanofluids-enhanced oil recovery

The numerical modeling of oil displacement by nanofluid based on three-dimensional micromodel of cores with different permeability was carried out by the volume of fluid(VOF)method with experimentally measured values of interfacial tension,contact angle and viscosity.Water-based suspensions of SiO_(2) nanoparticles with a concentration of 0–1%and different particle sizes were considered to study the effect of concentration and size of nanoparticles,displacement fluid flow rate,oil viscosity and core permeability on the efficiency of oil displacement by nanofluid.The oil recovery factor(ORF)increases with the increase of mass fraction of nanoparticles.An increase in nanoparticles’concentration to 0.5% allows an increase in ORF by about 19% compared to water flooding.The ORF increases with the decrease of nanoparticle size,and declines with the increase of displacing rate.It has been shown that the use of nanosuspensions for enhanced oil recovery is most effective for low-permeable reservoirs with highly viscous oil in injection modes with capillary number close to the immobilization threshold,and the magnitude of oil recovery enhancement decreases with the increase of displacement speed.The higher the oil viscosity,the lower the reservoir rock permeability,the higher the ORF improved by nanofluids will be.

Synthesis of Hollow Nanoparticles <i>γ</i>-Al₂O₃

The formation of hollow nanoparticles of alumina was detected when nanostructured carbon–aluminum material, synthesized by composite electrode sputtering in an electric arc, was annealed in oxygen. The synthesized material was characterized by the methods of transmission electron microscopy, thermogravimetry, and roentgen-phase analysis. It is shown that the alumina is the γ-phase;the typical size of particles is 6 - 12 nm and they have a wall thickness of 2 - 3 nm. The mechanism of formation of the hollow nanoparticles of alumina is suggested.

Calculation of the Efficiency of Regenerative Air Heat Exchanger with Intermediate Heat Carrier

The study deals with a new regenerative air heat exchanger with an inter­mediate heat carrier used in the systems of room ventilation.A physical and mathematical model of the heat transfer process is proposed.The in­fluence of design and operating parameters on the temperature efficiency of the heat exchanger is analyzed.The possibility of a significant increase in its efficiency with a decrease in the packing diameter is shown.As a re­sult of calculations,it was found that with a decrease in the filling height,the maximum temperature efficiency shifted towards a decrease in the air flow rate from its value determined from the equality of water equivalents of liquid and air.

On the Potential Application of the Wrinkled SiGe/SiGe Nanofilms

Terahertz radiation (THzR) consists of electromagnetic waves within the band of frequencies from 0.3 to 3 terahertz with the wavelengths of radiation in the range from 0.1 mm to 1 mm, respectively. The technology for generating and manipulating THzR is still in its initial stage. Herein, we demonstrate that the wrinkled Si1–xGex/Si1–yGey films can be used as radiation sources, which emit electromagnetic waves (EMW) in a very wide range of the frequencies including the terahertz band from 0.3 to 3 THz and far IR from 3 THz to 20 THz. These findings provide the theoretical foundation for the wrinkled nanofilm radiation emission and may allow, to some extent, to fill the terahertz gap.

Systematic experimental study of the temperature dependence of viscosity and rheological behavior of water-based drilling fluids with nano-additives

The paper presents the results of a systematic study of the influence of nano-additives of various concentrations,average sizes and composition on the temperature dependence of the viscosity and rheological behavior of water-based drilling fluids.Typical compositions of drilling fluids,such as water suspensions of various clay solutions and gammaxan-based polymer solutions,were considered.Hydrophilic nanoparticles of silicon and aluminum oxides were used as nano-additives at concentrations ranging from 0.25 to 3 wt%.The average nanoparticle size varied from 10 to 151 nm.The temperature of drilling fluids varied from 25℃ to 80℃.It is shown that the addition of nanoparticles to drilling fluids leads to a significant change in their rheological properties depending on the temperature.It was found that with increasing temperature,the yield stress and consistency index of drilling fluids with nanoparticles increase,while the behavior index,on the contrary,decreases.This behavior depends on the size of the nanoparticles.As the particle size increases,their influence on the temperature dependence of the drilling fluids’viscosity increases.In general,it is shown that the addition of nanoparticles makes the viscosity of drilling fluid more stable with regard to the temperature.This is an essential fact for practical application.

Co-milling as a synergy factor for co-firing.A case study of wood/coal blends

It is known that simple adding of wood allows one to accelerate the ignition of powder mixtures compared to the situation when pure coal is used.This study focuses on testing the hypothesis about the effect of co-milling coal and wood on their co-firing:is the case of composite powdered fuels should ensure the maximum possible efficiency of heat and mass transfer?Firstly,we will show that co-milling of coal and wood leads not independent size reduction of two materials but gives composite powder-coal-covered wood.For the composite fuel further reduction of the ignition delay time of air suspension and reduction of the limit volume concentration required for flame propagation have demonstrated.Obtained synergy also manifests in thermogravimetry.Here we propose a simple method for analyzing the mass loss curves.For any coal-to-wood sawdust ratio,combustion of the composites and mixtures both can be viewed as a weighted sum of the curves of individual components.But only in the case of composites calculated sawdust content is higher than the actual one:the mass loss is redistributed towards the stage occurring at lower temperatures due to geometry of wood/coal contact.

Recent advances in nanoparticle generation in liquids by lasers:Revealing formation mechanisms and tailoring properties

When Fojtik and Henglein [1] submitted in 1992 the first scientific paper on generation of nanoparticles(NPs) by laser ablation in liquids, the authors probably could not realize how it will revolutionize the nanoparticle science and technology. In 2017, marking a quarter century of this pioneering study, Amendola and Barcikowski [2] pointed out that the simple and bright idea of Henglein and Fojtik was an inspiration to hundreds of scientists worldwide over 25 years and opened a way to use lasers in synthesis of colloids.