The hydrodynamic features in the header systems of tank reactors and heat exchangers

Full text: The basic element of the flowing parts of tank reactors and heat exchangers is the distributing header systems. To construct economic reliable and safe reactors and heat exchangers, the optimum hydrodynamics of the flowing part of the header systems, namely, the given coolant flow rate (velocity) profile at the header exit, the minimum hydraulic losses for its pumping and maximum flow mixing in the header system, should be provided. In tank reactors, the distributing header systems with lateral flow supply and its central removal are widely used, and in heat exchangers - the distributing header systems with the central flow supply and its lateral removal. In SSC RF IPPE, a wide complex of experimental researches has been performed to study the hydrodynamics of the flowing parts of the header systems. As a result of the experiments conducted on the aerodynamic test facility using cylindrical models, the effect of the ratio of the header dimensions, its design, the coolant flow pattern in the flowing part of the system, the hydraulic resistance of the exit section of the system on the coolant flow rate (velocity) profile at the header exit and the hydraulic resistance coefficients for its flowing part were established. Besides, tracer concentration profiles at the header exit were obtained for the header systems of tank reactors as a result of investigation of coolant mixing. In tests on hydroflume using plane models of the both types of the systems representing the longitudinal axial cross-section of the corresponding cylindrical systems, the extent to which the variation of the ratio of the header dimensions and its design may exert effect on the distribution of the water velocity at the header exit and the sizes of eddy and stagnant zones in the header and on the water flow pattern in the header system was established. Analysis of the results obtained made it possible to determine the typical coolant flow pattern in the flowing part of the systems. The obtained experimental data and due account of the coolant patterns made it possible to develop a universal semi-empirical procedure for evaluation of the distribution of the coolant flow rate (velocity) at the exit of axisymmetric header systems of different types. The relative coolant velocity (flow rate) distributions on the radius and over the header exit width, obtained using cylindrical plane header system models, coincided only qualitatively. 203 The results of investigation of the hydrodynamics of the flowing parts in the header systems can be used in developing and verifying computer codes as well as in designing NPP and heat exchangers. The above investigations have been performed in co-operation with different design organizations available in MINATOM of Russia. (author)