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, .
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
Paragangliomas are tumors arising from the extra-adrenal paragangliar neural crest cells. The sympathoadrenal neuroendocrine system consists of extra-adrenal paragangliar cellular layer along the paravertebral and para-aortic axis, and the adrenal medullae. Paraganglioma should be included in the differential diagnosis of secondary erythrocytosis due to its possible ectopic erythropoietin (EPO) secretion. Thus, in this report we present a 24-year-old female patient with onset of unregulated ectopic EPO secretion, and consecutive erythrocytosis followed by hypertension, secondary to paraganglioma of multifocal retroperitoneal localization. Clinical, laboratory, and radiological investigations confirmed both an elevated EPO level and the presence of multiple paraganglioma. This paraneoplastic-mediated medical condition with high risk of cellular hyperviscosity syndrome (CHVS) requires prompt diagnosis and rapid therapeutic interventions. Initially, simple phlebotomy procedures were used; following that, tumors were surgically removed. In the course of the disease, this tumor relapsed, and urgent apheresis, as a treatment of life-threatening state, was used. The therapy performed resulted in a rapid blood viscosity depletion and a significant (P < 0.01) serum EPO reduction, as well as the general clinical benefit. Therefore, we conclude that the use of our own "multi-manner" apheresis (erythrocythapheresis plus plasma exchange), for long-time interval (until further causative therapy), effectively cross-bridged the possible hazards of EPO-dependent CHVS.
This paper is devoted to the analysis of unsteady plane laminar magnetohydrodynamic boundary layer flow of incompressible and variable electrical conductivity fluid. The present magnetic field is homogeneous and perpendicular to the body surface. Outer electric filed is neglected and magnetic Reynolds number is significantly lower then one i. e. considered problem is in inductionless approximation. Free stream velocity is an arbitrary differentiable function. Fluid electrical conductivity is decreasing function of velocity ratio. In order to solve the described problem multi-parametric (generalized similarity) method is used and so-called universal equations are obtained. Obtained universal equations are solved numerically in appropriate approximation and a part of obtained results is given in the form of figures and corresponding conclusions.past an arbitrary shape surface has attracted the interest of many researchers in view of its important applications in many engineering problems.Recently the problem of magneto-hydrodynamic (MHD) flow over surfaces has become more important due to the possibility of applications in areas like nuclear fusion, chemical engineering, medicine, and high-speed, noiseless printing. Problem of MHD flow in the vicinity of plate has been studied intensively by a number of investigators [3][4][5][6][7]. Most of previous investigations were concerned with studies of the steady flow of fluid whose electrical conductivity is constant.The subject of the present research is to give an analytic investigation to the problem of unsteady laminar MHD boundary layer flow of a viscous incompressible fluid. The external magnetic field is homogeneous and perpendicular to the body. The fluid which forms the boundary layer is incompressible and its electrical conductivity is variable and can be assumed in the following form:
Performance characteristics of fans are generally provided for the normal temperature and pressure conditions (t I = 20 °C, p I = 101.325 kPa, ρ I = 1.2 kg/m 3). Very often, fans operate in different air conditions, occasionally at different air temperatures. In these cases, equations obtained by the law of similarity are usually used for recalculation of the fan operating parameters. Increasing the inlet air temperature causes a decrease in the characteristic of Reynolds number, and may lead to efficiency lowering of the fan. There are also some empirical formulas for recalculation of fan efficiency, when operating at different air temperatures. In this paper, the common way for obtaining fan performance for different operating conditions (air temperature changing) is presented. The results, obtained by recalculation of fan parameters using a law of similarity, are compared to numerical simulation results of the axial-flow fan operating with different air temperatures. These results are compared with results obtained by some recommended empirical formulas, as well. This paperwork is limited to low-pressure and mid-pressure fans, which represents the majority of all fans used in practice, for different purposes.
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