• Energy Research
• engineering and technology close
• RU close
• BG close

This short report substantiates the advisability of developing a two-stage model for the emergence and development of a boiling crisis. One of the stages is the violation of the stability of the two-phase wall layer, and the other is the appearance and fusion of dry spots on the heating surface. The use of a two-stage (“temporary”) model makes it possible to combine both well-known approaches to crisis analysis—hydrodynamic and thermal—in a single logical system. In the first approach, the characteristics of the boiling crisis are characteristic of high pressures in a boiling liquid, while those in the second are for low pressures.

二重管型輻射加熱バーナの外管内に球形粒子を充填して, 燃焼ガスによりその粒子を流動化させ, 燃焼および粒子流動が継続するバーナを開発した.このバーナ管部の伝熱機構を解析し, 外管への伝熱特性および内管-外管間の伝熱機構を調べた.この結果, 外管内の流動層有無比較から流動層を設けた時は外管温度分布の均一化および外管への伝熱量増加に役立つことを確認した.また, 内管-外管間の流動層有無における熱移動量比較から, 流動層を設けた時の外管温度分布は, 流動層軸方向温度分布が大きく影響し, この流動層温度分布が良いため外管温度分布の均一化が図られるのに対して, 流動層を設けない時の外管温度分布は, 内管温度分布が影響することを確認した.このことから, 二重管型輻射加熱バーナに流動層を設けることによる伝熱上の特長は, 外管軸方向温度分布の均一化および外管への伝熱量促進であることが明らかになった.

The article discusses the problems associated with the tourism industry and the hotel business during the pandemic. A study was carried out and relevant conclusions were presented on how the pandemic affected the hotel business in Europe and Russia. The authors examined and analyzed in detail the indicators of forecasts in the sphere of the Russian hotel business, particularly in the regions. The authors paid special attention to the study of open public spaces and conducted a detailed analysis, which made it possible to identify the opportunities for the development of the hotel business. In the article the main trends of a pandemic and post-pandemic are studied – the need to reinforce sanitary measures. The research focuses on identifying the features of the economic state of the regions during the pandemic. The authors developed and substantiated the areas that are relevant, useful and applicable for the hotel business; revealed the features of the process of restoration of the hotel business. Special attention is paid to the study of state support measures; the features of their further actualization for the development of the tourism industry are presented. The authors have proposed the ways to overcome the crisis, contributing to a slow, but accurate and safe recovery of the hotel business and an increase in demand.

The process of combusting Tuva coals before and after their carbonization was studied using the methods of thermogravimetric analysis and electron microscopy. Coal samples were subjected to thermomechanical and elemental analysis, which revealed a higher content of volatile substances in Kaa-Khem coal (47.5 %) compared to Chadan coal (10 %). Following carbonization, a decrease in volatile substances to 11.5 % and 9.3 %, respectively, was observed. The conducted thermogravimetric analysis showed the ignition temperature of the coke residue of the Kaa-Khem and Chadan coal samples to increase by 76 °C and 90 °C, respectively, after carbonization. The burnup temperature of the coke residue after carbonizing (723 °C) Kaa-Khem coal samples remained effectively the same, while the Chadan coal showed an increase from 704 °C to 727 °C. The carbonization of coals was established to decrease the maximum reaction rate from 19 % per min to 10% per min for Kaa-Khem coal and from 26 % per min to 11 % per min for Chadan coal. The process of combusting the coke residue after coal carbonization was found to shift into the region of higher temperatures: from 448–723°C to 524–724°C for Kaa-Khem coal and from 436–704 °C to 526–727 °C for Chadan coal. A morphological analysis of the surface of coal particles after carbonization showed the appearance of larger-size pores and cracks on the surface of carbonates compared to coal before carbonization. The conclusion is made that the content of volatile substances, rather than the developed pore structure, comprises the main factor in improving the combustion characteristics of Tuva coals under the conditions of non-isothermal heating before and after their carbonization.

Alkali activated concretes have emerged as a prospective alternative to conventional concrete wherein diverse waste materials have been converted as valuable spin-offs. This paper presents a wide experimental study on the sustainability of employing waste sawdust as a fine/coarse aggregate replacement incorporating fly ash (FA) and granulated blast furnace slag (GBFS) to make high-performance cement-free lightweight concretes. Waste sawdust was replaced with aggregate at 0, 25, 50, 75, and 100 vol% incorporating alkali binder, including 70% FA and 30% GBFS. The blend was activated using a low sodium hydroxide concentration (2 M). The acoustic, thermal, and predicted engineering properties of concretes were evaluated, and the life cycle of various mixtures were calculated to investigate the sustainability of concrete. Besides this, by using the available experimental test database, an optimized Artificial Neural Network (ANN) was developed to estimate the mechanical properties of the designed alkali-activated mortar mixes depending on each sawdust volume percentage. Based on the findings, it was found that the sound absorption and reduction in thermal conductivity were enhanced with increasing sawdust contents. The compressive strengths of the specimens were found to be influenced by the sawdust content and the strength dropped from 65 to 48 MPa with the corresponding increase in the sawdust levels from 0% up to 100%. The results also showed that the emissions of carbon dioxide, energy utilization, and outlay tended to drop with an increase in the amount of sawdust and show more the lightweight concrete to be more sustainable for construction applications.

In the framework of the study, the authors consider conceptual approaches to improve the management system of agrarian sphere development of regions in the realities of this industry functioning in the Russian Federation. Agrarian sphere is shown in aspects of socio-economic territorial system with its subsystems. The transition mechanisms of the agrarian sphere to the rails of sustainable development due to the choice of priority development directions within the life cycle are presented. The necessity of applying an integrated approach to the solution of industrial and social problems of the agricultural sector of the country is proved and reasoned.

Abstract The choice of an effective quality management system is a non-trivial task which requires a special approach. We consider the main changes in the new edition of the international standard for quality management systems ISO 9001: 2015, its impact on the workflow and benefits.

Considerable interest is being shown in using biochar production from waste biomass with a variety of disciplines to address the most pressing environmental challenges. Biochar produced by the thermal decomposition of biomass under oxygen-limited conditions is gaining popularity as a low-cost amendment for agro-ecosystems. The efficiency of biochar formation is affected by temperature, heating rate, feedstock type, particle size and reactor conditions. Properties such as pH, surface area and ash content of produced biochar increases with increasing temperatures. Biochar produced at lower heating rates may have high porosity and be beneficial for morphological changes in the soil. Biochar can help to enhance soil health and fertility as well as improve agricultural yield. As a result, biochar can assist in increasing food security by promoting sustainable agricultural systems and preserving an eco-friendly environment. Biochar is also widely being used as a sorbent for organic and inorganic pollutants, owing to its large surface area, allowing it to be immobilized from soil with ease. The functional groups and charges present on the surface of biochar play an important role in pollutants removal. This review focuses on the mechanisms of biochar production using different waste materials as a feed stock, factors that influence biochar quality as well as application of biochar in agricultural soil and their reclamation as well. This article also discusses knowledge gaps and future perspectives in the field of biochar-based toxic-pollution remediation.