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According to the actual Polish standard PN-M-34034:1976 determination of local pressure loss value is based on tabularized local pressure loss coefficients, generally dependant only to geometrical characteristics of pressure drop location and value of dynamic pressure. However, numerous scientific reports showed that calculated, according to actual procedures, values of local pressure loss are not in agreement than the observed ones. Thus, actually used method of local pressure loss determination should be improved for new materials and types of fitting, such as anti-pollution non-return valve, unavailable during PN-M-34034:1976 publishing. In most cases producers of available non-returnvalves publish the constant values of local pressure drop coefficients and graphs of pressure loss in function of volumetric flow rate. From the other hand, construction of this valve, with variable area of flow allows to predict the changeable, subjected to Reynolds number, value of pressure loss coefficient. This paper presents the results of laboratory and modeling studies of pressure drop and coefficient of pressure loss for anti-pollution non-return valve EA 291 NF DN 15 conducted for variable range of Reynolds number. Numerical researches of water flow velocity distribution and flow turbulence intensity inside the tested value were conducted by commercial FLEUENT, Ansys Inc. software. Our studies allowed to determine the relation of pressure drop coefficient to Reynolds number and to identify the changes in water flow characteristics resulting in pressure loss. Results of the presented modeling calculations may be also applied in numerical analyses of pollutants migration from valve body and sealing materials.
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