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, .

Flow over a sphere is a typical bluff-body flow with many engineering applications. However, it has not been studied in depth, as compared to flow over a circular cylinder, because of the difficulties in the experimental set-up as well as in the computational approach for studying flow over a sphere. The main challenges are to understand the flow hydrodynamics and to clarify the flow pattern around a dimpled sphere because the flow pattern complying with the dimple structure on its surface is very complicated. In this paper experimental and numerical investigations of the fluid flow around a sphere with dimples, are represented. The sphere with dimples is placed in a quadratic cross section duct (measuring section) and numerical simulation results are obtained by solving RANS equations. Furthermore, experimental measurements are carried out using a Laser-Doppler Anemometer (LDA). Experimental and numerical results of flow velocity fields were compared for three different flow regimes (Re=8×103, 2×104 and 4×104). Numerical investigation was performed for wide range of Reynolds numbers (Re=270%106). The final purpose of this paper is experimental and numerical determination of velocity field, separation point, pressure and drag coefficient, the length of reverse flow region in the wake and RANS turbulent model which gives the best results for engineering practice

In the increasing need for energy saving worldwide, the designing process of turbomachinery, as an essential part of thermal and hydroenergy systems, goes in the direction of enlarging efficiency. Therefore, the optimization of turbomachinery designing strongly affects the energy efficiency of the entire system. In the designing process of turbomachinery blade profiling, the model of axisymmetric fluid flows is commonly used in technical practice, even though this model suits only the profile cascades with infinite number of infinitely thin blades. The actual flow in turbomachinery profile cascades is not axisymmetric, and it can be fictively derived into the axisymmetric flow by averaging flow parameters in the blade passages according to the circular coordinate. Using numerical simulations of flow in turbomachinery runners, its operating parameters can be preliminarily determined. Furthermore, using the numerically obtained flow parameters in the blade passages, averaged axisymmetric flow surfaces in blade profile cascades can also be determined. The method of determination of averaged flow parameters and averaged meridian streamlines is presented in this paper, using the integral continuity equation for averaged flow parameters. With thus obtained results, every designer can be able to compare the obtained averaged flow surfaces with axisymmetric flow surfaces, as well as the specific work of elementary stages, which are used in the procedure of blade designing. Numerical simulations of flow in an exemplary axial flow pump, used as a part of the thermal power plant cooling system, were performed using Ansys CFX. [Projekat Ministarstva nauke Republike Srbije, br. TR33040: Revitalization of existing and designing new micro and mini hydropower plants (from 100 kW to 1000 kW) in the territory of South and Southeast Serbia

Low-pressure axial fan impellers designed according to the principle of equal specific work of all elementary stages have blades whose profile near the fan hub is under a significantly larger inclination angle than at the impeller periphery. In order to minimize the spatial curvature of the fan blades and the fan hub length, impeller blades of low-pressure axial fans can be designed with different specific work of elementary stages, so that the specific work of elementary stages is smaller at the hub than at the periphery. This paper presents the operating characteristics of a low-pressure reversible axial fan with straight blade profiles, designed with different specific work of elementary stages. The fan was tested on a standard test rig, with air intake loading on the suction side of the fan

In this paper, the steady flow and heat transfer of an incompressible electrically conducting micropolar fluid through a parallel plate channel is investigated. The upper and lower plates have been kept at the two constant different temperatures and the plates are electrically insulated. Applied magnetic field is perpendicular to the flow, while the Reynolds number is significantly lower than one i. e. considered problem is in induction-less approximation. The general equations that describe the discussed problem under the adopted assumptions are reduced to ordinary differential equations and three closed-form solutions are obtained. The velocity, micro-rotation and temperature fields in function of Hartmann number, the coupling parameter and the spin-gradient viscosity parameter are graphically shown and discussed.