INFLUENCES OF LOCAL RESISTANCES OF TECHNOLOGICAL CHANNELS OF PULP AND PAPER PRODUCTION ON THE OPERATION OF VORTEX FLOW METERS OF WATER AND WATER SUSPENSIONS OF LOW CONCEN-TRATIONS
The question of the features of operation of submersible vortex flowmeters of water and water suspensions of low concentrations in pulp and paper production, which are installed in process pipelines with local hydraulic resistance, is considered. It is shown that with an insufficient straight section after local resistance, an additional error appears, which appears due to the influence of local resistance (transition or retraction) on the symmetry of the velocity diagram in front of the device. This error arises due to a change in the Strouhal number (Sh) and is related to the measurement method. The Strouhal number begins to depend on both the distance to the local resistance and the fluid flow rate. Identify this relationship and is dedicated to this work. Recommendations on the length of straight pipeline sections in front of the flow meter have been developed, which can be significantly reduced by limiting the range of operating flow rates. The studies were carried out by the method of numerical simulation of hydrodynamic processes with subsequent processing of the results by the method of experiment planning. The dependence of the number Sh on the length of the relative diameter of the pipeline L/ for hydrodynamic resistance in the form of a transition is presented. This error shows that the measurement error is within 2% already with a straight section in front of the flowmeter equal to 5-7 diameters. The response surface for pipe bends (rotations) is considered at 90º from which it follows that while maintaining the length of the straight section within 5-7 pipe diameters, it is necessary to narrow the measurement range of the instruments 2.5 times.