[en] A technique is described for numerical calculation of two-dinonsional ditributions of mutually-consistent flow characteristics and temperatures in coolant and structural elements of heat exchangers, flow parts of reactors etc. (associated problem), without reference to configuration of the flow part and element relative position. The calculation is performed with account of inertial forces, friction against distributed hydraulic obstacles and adjacent fluid layers, thermal convection forces, with regard to the effect of distributed in flow part consumption sources and sinks and different types of boundary conditions. The temperature distribution calculation is distinguished by similar universal character

[en] Development of numerical methods for calculation of equipment operation modes, in particular for NPPs, leads to thorough analysis of local characteristics in space of the objects considered obtaind on the basis of two- and three-dimensional approximations. Except the possibility of more qualified estimation of equipment serviceability, the numerical methods, representing the information as a set of concrete values depending on the initial data, don't give the evident representation about the degree of some factor influence on the remelts obtained that decreases essentially the usefulness of the numerical methods for estimation of the perspective of equipment structure modifications, for analysis of permissible operation modes, for optimization of the construction and operation modes. Thus, the problem on description of equipment characteristics obtained by the numerical methods (or as a result of natural experiment) as analytical functions (or table functions) of the initial data (factors) arises. A way of data table processing is described. Data present a form of latin square-type allowing to construct a linear analytical model. As an example, the table of values of thermal efficiency of a heat exchanger is considered. The values are obtained by numerical calculation (two-dimensional approximation for fields of flow and heat exchange characteristics) for series of fixed values of three parameters (the flow rate of heating and heated media and power). The function approximating the data obtained and determined by the methods described is also given

[en] The problem of adequate coolant mixing and flow pattern optimisation becomes more significant while considering pool type fast reactors. Within a vessel of this reactor type there are considerable bulks of coolant at different temperatures. Because of the complex design requirements certain difficulties exist in the problem of ensuring sufficient mixing of the coolant at the outlet of the core, radial blanket, in-pile fuel storage and in-pile neutron shielding. n the framework of the R and D activities carried out to justify fast reactor design solutions a proper attention is given to investigations of the coolant flow pattern within plena and in those sections of pool type reactor, where the coolant now takes place. In this connection It should be noted that, up to now, we did not obtain any clear evidence of the presence of a pronounced thermal stratification of sodium within reactor mixing chambers under normal operating conditions. The conclusion may be drawn on the basis of our experiments and design experience that there are certain gradients of temperature and Inefficient mixing of coolant flows with different temperatures within the chambers (both 'hot' and 'cold' ones). All these factors to a certain degree complicate a reactor operation. However, from our point of view, the main point in the problem of arranging an 'optimum' coolant flow pattern within the chambers is to insure the stability of coolant motion in the chambers (Including flows with different temperatures) by means ol special design solutions based on results of experimental and calculation studies. It is considered that the instability of coolant flow could be the most important factor influencing temperature distribution within structures and components. That is why coolant flow in all reactor chambers and cavities should be stable, including natural convection flows

[en] An algorithm for calculating the process of heat transfer in NPP multicircuit branched cooling systems with forced circulation is described. Thermal circuits including pipeline, collectors, pumps, heat exchangers, steam generators, fuel assemblies and other elements are described. In the mathematical model used such thermal circuit is described as a consequence of universal elements connected with each other by coolant inlet and outlet in closed and open circuits. Changes in the plant power, coolant flow rate and the circuit configuration connected with the plant operational regime are taken into account as parameters determining heat transfer processes. Each calculational step includes determination of coolant flow rate in each element of the circuit and iterative process of calculating enthalpies at all element inlets. The considered algorithm is realized in the form of the FORTRAN program for the BESM-6 computer. The conclusion is drawn on the applicability of the described algorithm for calculating heat transfer processes in arbitrary complicated circuits with different coolants in real time scale

[en] An effective method for numerical calculation of temperature field in a coolant flowing for example, through a heat exchanger intertube space or in a fuel element cluster is described. The number of arithmetic operations involved has the order of a number of calculating point in a grid area. As an example the results of coolant temperature calculation for an axially symmetrical straighttube steam generator with external radial coolant supply in the upper part of a cluster, practically axial flow in the middle by height section of the cluster and volume heat run-off in the calculational area are presented. The temperature field presented is characterized by considerable temperature gradients. In spite of this the solution requires only 10 interations which testifies to high efficiency of the method

[en] In the theoretical study of the characteristics of liquid flow in geometrically complex regions (such as the intratank space of fast reactors with an integral layout) in a multidimensional representation, it is usual to construct a theoretical model of the object being studied. Since the space of this model is discrete in character and there is a tendency to reduction in complexity of the problem by reducing the number of points of the discrete region, the theoretical model differs from the object in terms of the form of the boundary surfaces and other relatively small details. There arises the question of the degree of influence of these differences on the solutions obtained and the possibility of introducing corrections to the boundary conditions, which, in the distorted geometry of the model, would allow solutions close to those existing at the object to be obtained. It is important to know precisely which sections of the flow-region boundary have the greatest influence on the spatial distribution of the characteristics, i.e., which sections must be described with the greatest accuracy and, conversely, the sections whose description may be simplified

[en] Boundary conditions for solution of the problem of liquid flow in variables of current function and vorticity are considered. Nonequivalence of different sections, limiting the flow of surfaces from the viewpoint of their contribution to flow structure formation is shown. Character of changes in solution, caused by the errors in describing form and boundary conditions in one of boundary sections, determining the flow, is illustrated by calculations of flow in the BN-600 reactor tank

[en] A generalized program for calculating three-dimensional nonstationary temperature fields for investigation of the nuclear reactor construction units is described. The calculation method of the temperature fields of the studied arbitrary three-dimensional body is based on solving thermal balance difference equations. The solution algorithm of these equations is presented, as well as construction of curvilinear orthogonal coordinates is considered. The program text is itten in FORTRAN and it is intended for operating at the ES-1030 computer. To illustrate utilization of the given program the calculation results of the temperature fields in the upper part of the reactor pressure vessel are presented. The ES-1030 computation time of the nonstationary process in the two-dimensional range for the case of sharp drop of the coolant temperature inside the vessel from 290 deg C to 220 deg C is 30 min

[en] The temperature regime and stressed state of the drum-separator vessel in the transient regime with alternating pressure and water level are investigated using calculations. The temperature fields are calculated by the alternating directions method. Stresses and deformations are calculated by the method of finite elements. The stressed state of the vessel is determined for a series of fixed time moments tausub(i), when the T(tausub(i), r, phi) temperature distribution and P(tausub(i)) internal pressure are known. The methods described are used while developing the calculation program for the temperatures and stressed state (FORTRAN, EC-1050). Given are the calculation results obtained using these programs for the processes following the safety system response at the first block of the Bilibinsk NPP and the processes of power regulation in the ''Sever-2'' facility. The comparison of the obtained calculated curves with the experimental data confirms fitness of the proposed calculated scheme for description of the real processes taking place in the drum-separator vessels in the transient regimes. It is emphasized that the given scheme of solution of the equations describing a thermostressed state of the drum-separator vessels can be used while estimating their operation capacity

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