As the global demand for energy grows, numerous studies in the field of energy efficiency are stimulated, and one of them is certainly the use of pumps in turbine operating mode. In order to reduce time necessary to determine pump characteristic in turbine operating mode problem was studied by computational fluid dynamics approach. The paper describes various problems faced during modeling (pump and turbine mode) and the approaches used to resolve the problems. Since in the majority of applications, the turbine is a pump running in reverse, many attempts have been made to predict the turbine performance from the known pump performance, but only for best efficiency point. This approach does not provide reliable data for the design of the system with maximum energy efficiency and does not allow the determination of the head for a wide range of flow rates. This paper presents an example of centrifugal norm pump operating in both (pump and turbine) regime and comparison of experimentally obtained results and computational fluid dynamics simulations. Key words: pump used as a turbine, computational fluid dynamics analysis, BUTU method, energy efficiency Bogdanovi}-Jovanovi}, J. B., et al.: Pumps Used as Turbines -Power Recovery, .

Original scientific paper https://doi.org/10.2298/TSCI180308167B This paper analyzes the impact of Trombe wall construction on heating and cooling demands of building with form (rectangular single-store building of about one hundred square meters area) which is common for individual residential buildings in the Republic of Serbia. Trombe wall, as a representative of a passive solar design, was installed on the south wall of the building. Model of the building was made in the Google SketchUp software, while the results of energy performance were obtained using EnergyPlus and jEplus. Parameters of thermal comfort and climatic data for the area of city of Belgrade, Republic of Serbia, were taken into account. Coverage of the south façade was varied, as well as the thickness of the thermal mass and orientation. Energy consumption of the object is discussed, based on obtained results of the analysis. According to comparative analysis of the above mentioned models it can be concluded that the application of the Trombe wall structure on south side may lead to savings of 33% on heating, but also the higher energy consumption for cooling. Total energy consumption on an annual basis is reduced by using this system.

Buildings are one of the biggest energy consumers in urban environments, so its efficient use represents a constant challenge. In public objects and households, a large part of the energy is used for heating and cooling. The orientation of the object, as well as the overall heat transfer coefficient (U-value) of transparent and non-transparent parts of the envelope, can have a significant impact on building energy needs. In this paper, analysis of the influence of different orientations, U-values of envelope elements, and size of windows on annual heating and cooling energy for an office building in city of Nis, Serbia, is presented. Model of the building was made in the Google SketchUp software, while the results of energy performance were obtained using EnergyPlus and jEplus, taking into account the parameters of thermal comfort and climatic data for the area of city of Nis. Obtained results showed that, for varied parameters, the maximum difference in annual heating energy is 15129.4 kWh, i. e per m 2 27.75 kWh/m 2 , while the maximum difference in annual cooling energy is 14356.1 kWh, i. e per m 2 26.33 kWh/m 2. Considering that differences in energy consumption are significant, analysis of these parameters in the early stage of design process can affect on increase of building energy efficiency.

With increasing needs for energy, renewable energy sources have been nowadays the one of the main subject of interest all around the world. Therefore, we made an effort to develop a gamma of axial micro turbines, for a purpose of generation of electrical energy on small water derivation, as well as a part of an irrigation turbine-pump aggregate. In this paper are presented constructive solution of a turbine-pump aggregate with micro turbine and standard norm centrifugal pump. Based on project calculation, expected operating parameters are obtained. After defining conceptual solution of the aggregate detailed development of model on computer and numerical simulation of fluid flow in axial turbine are conducted. .