The article deals with application of flow patterns and hydrodynamic effects in the course of upgrading distribution header systems (DHS) used in heat exchangers and reactors of nuclear power plants (NPP). Consideration is given to four typical axisymmetric DHSs of flat and cylindrical types, which differ in the ways of fluid supply to the collector and its removal from it. The schematic diagrams of flow patterns are shown for different DHS designs of the cylindrical types with central and lateral fluid inlets of the collector. Besides, the water flow pattern is given for the flow path of various DHS designs of a flat type, also with central and lateral fluid inlets of the collector. Hydrodynamic features of the fluid flow in the DHS have been analyzed. It is shown that in a restricted and free DHS the coolant flow is of a jet nature. The fluid flow in the header is characterized by transformation of some types of jets into others, by the presence of eddy and stagnant zones. The designs of heat exchangers and reactors for nuclear power plants with the considered typical DHS characteristics implemented are presented. The DHS designs upgraded with the use of the indicated patterns and effects are demonstrated. The revealed regularity of liquid distribution at the outlet of the DHS flow paths and the hydrodynamics identity property for axially symmetric DHS with flow reversal are analyzed.

The particularities of the experimental investigation of the hydrodynamics of the fl ow parts of heat-exchange equipment and reactor facilities that are associated with the design of the experimental sections, performing experiments on them, and processing the experimental data are examined. Specifi c practical recommendations for increasing the determination accuracy of the hydrodynamic parameters, cost reduction of the experimental work, and reduction of the expenditures on materials are given. The recommendations can be used to validate the heat-exchange equipment, reactor facilities with a fast neutron spectrum, and VVER.Obtaining experimental data on the hydrodynamic parameters of the fl ow parts of reactor facilities is one of the conditions for reliable and effi cient operation.The aim of the present work is to examine the design particularities of the experimental sections and perform and process the results of experimental investigations of the hydrodynamic parameters of the fl ow parts of reactor facilities and heat-exchange equipment [1][2][3][4][5].In some cases, individual complex fragments of the fl ow part are investigated in the experimental process of design validation of natural reactor facilities. For example, in distributing manifold systems of reactor facilities the core, arranged at the exit from a manifold, is simulated by a pipe bundle of relatively short length with throttling diaphragms placed in the exit part. The coeffi cient of hydraulic resistance ζ of the diaphragms is a complicated function of the Reynolds number. So, for the ratio f = 0.26 of the fl ow section of the diaphragm to the fl ow section of the tube, a distinct minimum of the coeffi cient of hydraulic resistance is characteristic for the transition from laminar to turbulent; it increases by a factor of 1.4 with Reynolds number in the tube increasing from 1·10 4 to 16·10 4 (Fig. 1). The use of a simulator could lead to a larger error in the determination of the fl ow profi le at the exit from the manifold in the presence of a large nonuniformity at its entry. To increase the accuracy with which the indicated profi le is determined in the experiment, it is suggested that throttling diaphragms with Reynolds number in the tubes for which the fl ow regime of the working medium has a relatively weak effect on its value be used.The investigation of the coeffi cient of hydraulic resistance of the complicated fl ow parts of reactor facilities with relative large energy losses to pumping of the incompressible working medium using a compressible working medium in the experiments is always associated an uncertainty in transferring the data to reactor facilities. This is due to the change in the density of the compressible working medium along the fl ow part of the experimental section, which is used to determine the coeffi cient of hydraulic resistance. The larger the head losses during pumping of the compressible working medium along the fl ow part of the experimental section, the larger the changes in the density of the working me...

Different ratios of the flow rate and temperature of the coolant flowing into the bottom (discharge) chamber from the circulation pumps of different loops, are possible during the operation of multiloop nuclear reactors. To estimate the operating temperature of the core, it is necessary to know the characteristics of the flow and mixing of the coolant from different loops in the distribution collector systems.Analysis of the results of experimental and computational investigations of the hydrodynamics and mixing processes of the coolant in the distribution collector systems with lateral feeding and central discharge of the flow [1][2][3][4] showed that the character of the flow rate of the coolant and the intensity of the mixing process in these systems depends on the construction of the flow through sections of the distribution collector system.An experimental investigation of the process of mixing of the coolant in the entrance collector of the core was performed for BN-800 ( Fig. 1) and BBER [5] reactors on an aerodynamic stand using the halide-tracer method. In this method an impurity is injected into the air flow and the impurity concentration is measured downstream with a calibrated halide leak detector.An experimental 1:5 scale model of the discharge chamber of a BN-800 reactor was built and met the conditions of geometric similarity with respect to one variant of the reactor design (Fig. 2). The model had two intake pipes for each of the three loops. A uniformly perforated shell was installed concentrically inside the cylindrical vessel of the model in the region of the intake pipes. The shell contained 115 simulators of the liners of the collectors in the core and the screen. A simulator of the liners of the screen and storage collectors were placed in the annular gap between the wails of the vessel and the shell. Openings were made at the bottom ends of the simulators to allow air to flow through and throttling devices were installed at the top ends.In the experiments, air from the loop of the aerodynamic bench, under a head of not more than 30 hPa, was fed through a flow meter and the distribution collector into the air ducts, which were equipped with flow regulators, flow meters, and devices for continuous injection of a tracer gas into the main flow. From the air ducts, the flow, separated in a T-joint into two parts, entered the bottom chamber through the intake pipes. Part of the flow moved in the gap between the vessel and the shell, while the other part entered the central part of the chamber through an opening in the shell. In both cases, the flow through the opening passed into the inner cavity of the liner and into the discharge chamber through the throttling inserts and removed from the model.To simulate the flow of the coolant at the higher temperature into the bottom chamber of the reactor through one of the intake pipes, a mixture of the tracer in the air flow was produced in one of the three air ducts.The liners, the outer wall, and the bottom of the model were equipped with devices for e...

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Distribution collector systems in the form of reverse axisymmetric 180 ~ turns are widely used in intermediate heat exchangers of fast-neutron reactors. In these exchangers the heat carrier flows from the neutral downpipe into a distribution collector, turns in this collector, and flows into a bundle of heat-transfer pipes which is installed in a pipe panel. A great deal of experimental data is now available on the distribution of the flow rate and the velocity of the heat carrier at the exit from distribution collector systems of this type [1-6], but there is no computational method for calculating the hydraulic nonuniformities at the exit from the system.Our objective in the present work is to develop a method for calculating the distribution of the mass flow rate of the heat carrier at the exit from the distribution collector systems with different ratios of the dimensions and hydraulic resistance in the exit part, such that the flow area of the gap between the bottom and the downpipe is not more than 10 times greater than the transverse cross-sectional area of the downpipe and the pipe panel is displaced from the end of the downpipe if the flow area of the gap is less than the transverse cross-sectional area of the downpipe or it is placed in an arbitrary position for other ratios of the indicated areas.A method for calculating the hydraulic nonuniformities at the exit from the axisyrnmetric distribution collector system without any additional constructional elements on the bottom was developed on the basis of the law of conservation of mass under the assumption that the thermophysical properties of the heat carrier remain constant and the flow of the heat carrier is a jet flow.To confirm experimentally the correctness of the computational relations, a cylindrical axisymmetric model of a distribution collector system of an intermediate heat exchanger for fast-neutron reactors with inflow at the center and outflow at the sides (Fig. 1) was investigated on an aerodynamic stand. The flowthrough part of the stand simulated the entrance part of the central downpipe, the distribution collector, and the pipe panel with a bundle of heat-transfer pipes. The collector height H, the height h of the entrance into the collector, the projection a of the central downpipe from the pipe panel, the gap between the step on the casing and the pipe panel, and the inner diameter d o of the diaphragms in the exit part of the heat-transport pipes were varied in the model.The heat carrier flow scheme adopted in this method is depicted in Fig. 2. The following basic assumptions and conditions were used for deriving the working relations.1. In the distribution collector systems in which the flow area of the gap between the bottom and the central downpipe is less than the transverse cross-sectional area of the downpipe, the flow is compressed and in other cases the flow expands according to a law characteristic for the flow of a free submerged jet. In the first case the velocity of the flow increases and in the second case it decreases....