• Energy Research

This paper presents the experimental investigation of turbulent structures of flow around a sphere. The mean velocity field and the turbulence quantities are obtained in a small low speed wind tunnel using, laser-Doppler anemometry, for the flow around a sphere at subcritical Reynolds number of 50,000. The results of laser-Doppler measurements are compared with results obtained by large eddy simulation. In this paper also flow visualization around sphere in the bigger wind tunnel and water channel for Reynolds numbers between 22,000 and 400,000 have been done.

This paper presents the experimental investigation of turbulent structures of flow around a sphere. The mean velocity field and the turbulence quantities are obtained in a small low speed wind tunnel using, laser-Doppler anemometry, for the flow around a sphere at subcritical Reynolds number of 50,000. The results of laser-Doppler measurements are compared with results obtained by large eddy simulation. In this paper also flow visualization around sphere in the bigger wind tunnel and water channel for Reynolds numbers between 22,000 and 400,000 have been done.

The model of development of a vapor phase in porous structures of heat exchangers for cooling of melting units on the basis of cinema observations which ex-plains the mechanism of nucleation, development, and death of steam bubbles is created. In case of crisis of heat exchange, there are the limiting conditions of a surface of a porous coating and metal substrate. The process of destroying can come from melting, or from heat stresses of compression and stretching. The reliability of a cooling system of melting units is defined by the combined action of capillary and mass forces.

The model of development of a vapor phase in porous structures of heat exchangers for cooling of melting units on the basis of cinema observations which ex-plains the mechanism of nucleation, development, and death of steam bubbles is created. In case of crisis of heat exchange, there are the limiting conditions of a surface of a porous coating and metal substrate. The process of destroying can come from melting, or from heat stresses of compression and stretching. The reliability of a cooling system of melting units is defined by the combined action of capillary and mass forces.

Although the countries of the Western Balkans are mostly electrified, there are still regions which do not have access to the electricity network or where the network capacity is insufficient. For the most part such areas are under special care of the state (i. e. underdeveloped, devastated by war, depopulated), on islands or in mountainous regions. Since the decentralized energy generation covers a broad range of technologies, including many renewable energy technologies that provide small-scale power at sites close to the users, such concept could be of interest for these locations. This paper identifies the areas in Western Balkans where such systems could be applied. Consideration is given to geographical locations as well as possible applications. Wind, hydro, solar photovoltaic, and biomass conversion systems were taken into consideration. Since the renewable energy sources data for Western Balkans region are rather scarce, the intention was to give a survey of the present situation and an estimate of future potential for decentralized energy generation based on renewable energy sources. The decentralized energy generation based on renewable energy sources in Western Balkans will find its niche easier for the users that will produce electricity for their own needs and for the users located in remote rural areas (off-grid applications).

Although the countries of the Western Balkans are mostly electrified, there are still regions which do not have access to the electricity network or where the network capacity is insufficient. For the most part such areas are under special care of the state (i. e. underdeveloped, devastated by war, depopulated), on islands or in mountainous regions. Since the decentralized energy generation covers a broad range of technologies, including many renewable energy technologies that provide small-scale power at sites close to the users, such concept could be of interest for these locations. This paper identifies the areas in Western Balkans where such systems could be applied. Consideration is given to geographical locations as well as possible applications. Wind, hydro, solar photovoltaic, and biomass conversion systems were taken into consideration. Since the renewable energy sources data for Western Balkans region are rather scarce, the intention was to give a survey of the present situation and an estimate of future potential for decentralized energy generation based on renewable energy sources. The decentralized energy generation based on renewable energy sources in Western Balkans will find its niche easier for the users that will produce electricity for their own needs and for the users located in remote rural areas (off-grid applications).

Biomass has remarkable potential to reduce harmful emissions and ensure stable and sustainable energy production. In this paper, various parameters such as operating temperature, type of gasifying agent, air–fuel ratio and steam-fuel ratio are investigated on the qualitative characteristics of the syngas obtained from biomass gasification. The qualitative indicators considered were the percentage of combustible components under the energy aspect and the percentage of undesirable components under the environmental aspect. The composition of the syngas was determined for a temperature range of 500–1000 °C as an equilibrium composition using the Gibbs free energy minimisation method. The results showed that increasing the gasification temperature above 900 °C had a positive effect on the energy and environmental properties of the syngas. Air and water vapour were selected as possible gasifying agents. The results showed that water vapour was significantly more favourable than air as a gasifying agent in terms of syngas quality. In the best case, the H2 yield for gasification with air is 35 %vol, while this value reaches 65 %vol for gasification with steam. In addition to the type, the ratio of the gasifying agent to the amount of fuel was also analysed. The analysis showed that it was more favourable to carry out the gasification process at lower air-to-fuel and steam-to-fuel ratios, which is consistent with the work of other authors.

Biomass has remarkable potential to reduce harmful emissions and ensure stable and sustainable energy production. In this paper, various parameters such as operating temperature, type of gasifying agent, air–fuel ratio and steam-fuel ratio are investigated on the qualitative characteristics of the syngas obtained from biomass gasification. The qualitative indicators considered were the percentage of combustible components under the energy aspect and the percentage of undesirable components under the environmental aspect. The composition of the syngas was determined for a temperature range of 500–1000 °C as an equilibrium composition using the Gibbs free energy minimisation method. The results showed that increasing the gasification temperature above 900 °C had a positive effect on the energy and environmental properties of the syngas. Air and water vapour were selected as possible gasifying agents. The results showed that water vapour was significantly more favourable than air as a gasifying agent in terms of syngas quality. In the best case, the H2 yield for gasification with air is 35 %vol, while this value reaches 65 %vol for gasification with steam. In addition to the type, the ratio of the gasifying agent to the amount of fuel was also analysed. The analysis showed that it was more favourable to carry out the gasification process at lower air-to-fuel and steam-to-fuel ratios, which is consistent with the work of other authors.