Individual and synergistic effects of modifications of the carrier medium of carbon-containing slurries on the viscosity and sedimentation stability

The study is devoted to revealing the individual and synergistic effects of modifications of the carrier medium of the coal-water slurries (CWS) based on coking coal and carbon-containing flotation wastes of this coal on the effective viscosity and sedimentation stability. Synthetic and natural wetting agents as well as liquid solvents (alcohol, oil, conventional liquid fuel, methyl ethers) and solid organic compounds exemplified by sawdust are used for this. The relationships between the effective viscosity, water separation ratio, and zeta potential for the CWS with the separate addition of a wetting agent and a solvent is established. The categories of fuel compositions are identified according to the “stability” criterion. The synergistic effect of the additions of a wetting agent and a solvent on the sedimentation stability and effective viscosity is demonstrated. The physicochemical model of interaction between the solid particles and the additives in CWSs is proposed

Secondary atomization of a biodiesel micro-emulsion fuel droplet colliding with a heated wall

Using high-speed video recording, we establish the following regimes of hydrodynami

Water Droplet With Carbon Particles Moving Through High-Temperature Gases

An experimental investigation was carried out on the influence of solid inclusions (nonmetallic particles with sizes from a few tens to hundreds of micrometers) on water droplet evaporation during motion through high-temperature gases (more than 1000 K). Optical methods for diagnostics of two-phase (gas and vapor-liquid) flows (particle image velocimetry (PIV) and interferometric particle imaging (IPI)) were used. It was established that introducing foreign solid particles into the water droplets intensifies evaporation rate in high-temperature gas severalfold. Dependence of liquid evaporation on sizes and concentration of solid inclusion were obtained

Biodiesel from rapeseed and sunflower oil: Effect of the transesterification conditions and oxidation stability

In this study, we produced biodiesel fuel from two vegetal sources, rapeseed oil and sunflower oil, by transesterification reaction. The study aims to evaluate the impact of type of alcohol, its concentration and the reaction time, while keeping constant the temperature and the catalyst on the yield and quality of the biodiesel. For alcohol, methanol and ethanol were used at a molar ratio with the oil from 3 to 24. Transesterification was performed at various reaction times; 20, 40, 60 and 90 min for each oil and defined alcohol:oil molar ratio. The influence of these parameters on the biodiesel yield and properties were investigated in terms of density, viscosity, heating value, flash point, elemental content, density and oxidative stability of the final product. The benefit of oxidation stabilizers, catechol and 4-allyl-2,6-dimethoxyphenol was investigated. Results demonstrate that for rapeseed oil, the optimum reaction conditions to obtain a higher yield and quality of biodiesel were an alcohol:oil molar ratio of 15:1, with 60-min reaction time at 50 degrees C; while in the case of sunflower oil, the best yield and biodiesel quality were at an 18:1 molar ratio, with a 40-min reaction time and at 50 degrees C. In both cases, methanol provides the highest yields of biodiesel, and the obtained products satisfy the required standards and present a similarity with mineral diesel tested in same conditions.Ministry of Education and Science of the Russian Federation, Minobrnauka: 075-03-2021-287/6, WSWW-2020-0011Ministry of Education and Science of the Russian Federation [075-03-2021-287/6]; Ministry of Science and Higher Education of the Russian Federation: Science [WSWW-2020-0011

Destruction of low-temperature insulation under the condition of periodic duty

The numerical investigation of thermal stresses within low-temperature insulation covering cryogenic pipelines and the numerical probability analysis of low-temperature insulation destruction under the condition of periodic duty were carried out. The minimal longevity values for foamed polyurethane and mineral cotton were established. The results of longevity analysis for foamed polyurethane and mineral cotton under the condition of environment temperature variation were obtained

Destruction of low-temperature insulation under the condition of periodic duty

The numerical investigation of thermal stresses within low-temperature insulation covering cryogenic pipelines and the numerical probability analysis of low-temperature insulation destruction under the condition of periodic duty were carried out. The minimal longevity values for foamed polyurethane and mineral cotton were established. The results of longevity analysis for foamed polyurethane and mineral cotton under the condition of environment temperature variation were obtained

Properties and phase behavior of water-in-diesel microemulsion fuels stabilized by nonionic surfactants in combination with aliphatic alcohol

We investigate the properties and phase behavior of the water−diesel fuel−Neonol AF 9-6/2-ethylhexanol system

Numerical Investigation of the Main Characteristics of Heat and Mass Transfer while Heating the Heterogeneous Water Droplet in the Hot Gases

The processes of heat and evaporation of heterogeneous water droplet with solid (by the example of carbon) inclusion in hot (from 800 K to 1500 K) gases were investigated by the developed models of heat and mass transfer. We defined the limited conditions, characteristics of the droplet and the gas medium which are sufficient for implementing the “explosive” destruction of heterogeneous droplet due to intensive vaporization on an inner interface, and intensive evaporation of liquid from an external (free) droplet surface. The values of the main characteristic of the process (period from start of heating to “explosive” destruction) obtained in response to using various heat and mass transfer models were compared

Numerical Investigation of the Main Characteristics of Heat and Mass Transfer while Heating the Heterogeneous Water Droplet in the Hot Gases

The processes of heat and evaporation of heterogeneous water droplet with solid (by the example of carbon) inclusion in hot (from 800 K to 1500 K) gases were investigated by the developed models of heat and mass transfer. We defined the limited conditions, characteristics of the droplet and the gas medium which are sufficient for implementing the “explosive” destruction of heterogeneous droplet due to intensive vaporization on an inner interface, and intensive evaporation of liquid from an external (free) droplet surface. The values of the main characteristic of the process (period from start of heating to “explosive” destruction) obtained in response to using various heat and mass transfer models were compared

Influence of surface roughness and porosity of inclusion in water droplet on heat transfer enhancement

Using high-speed camera, the experiments were performed to research evaporation of 10 μl water droplets containing 2 mm solid inclusions in the shape of cube, when heated (up to 850 K) in combustion products of technical ethanol. Adding solid inclusions in water droplets allowed considerably decreasing (by 70%) their evaporation times. Also, the artificial irregularities (roughness and porosity) at the surfaces of solid inclusions were manufactured to increase heat transfer area. Such approach enabled to decrease evaporation times of heterogeneous liquid droplets in high-temperature gases by 40% (when comparing inclusions with artificial irregularities and smooth surface)