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No 6 (2024)
Articles
Model for integral codes for calculating containment thermohydraulics in severe accidents at nuclear power plants with a water coolant
Abstract
The article describes a model for calculating the containment thermal in severe accidents at nuclear power plants with a water coolant. The model is implemented in the SOCRAT integral code in the form of a CONT_TH module, which allows performing self-consistent calculation of parameters in a VVER reactor plant and a containment during a severe accident. In conjunction with other modules of the SOCRAT code, a realistic calculation of the transfer of radioactive substances to the containment is provided, which is necessary to calculate source term into the environment when justifying the safety of nuclear power plants, including probability safety assessment level 2. With a slight adaptation, the model can be used to calculate the parameters of containment in a water-cooled NPP as part of other integral codes.
3-31
Scientific approaches to solving the problem of joint processes of bubble boiling of freon and its movement in a coil
Abstract
The combined processes of nucleate boiling and refrigerant movement in the tubes of a heat pump are considered. A coil located on the back side of the photovoltaic panel (PV) is used as an additional heating surface. A mathematical model has been created to theoretically determine the temperature on the front surface of a solar cell cooled by freon in a coil from the rear side. A peculiarity of the numerical modeling of nucleate boiling of freon in a coil was the insufficiently detailed study of the process and the lack of references to the results obtained in earlier works. The boundary conditions and assumptions in the numerical modeling of the process of nucleate boiling of freon R407C are clarified, the results are compared with the theoretically found values, which are subsequently used in the design of an energy technology complex consisting of a heat pump and a photovoltaic panel. A mathematical model for theoretical calculation of PV temperature and a methodology for constructing a numerical model of nucleate boiling of freon as part of the methodology for designing energy technology complexes based on renewable energy sources are presented for the first time.
32-48
Emissivity of group V elements periodic table in a wide temperature range
Abstract
The results of a study of the normal integral emissivity of the elements of group V of the Periodic system in the solid–liquid temperature range are presented. The choice of research objects – metallic vanadium, antimony and bismuth, is justified by the absence of data on the emissivity of these elements in the open press. The measurement method is absolute radiation. The experimental data obtained on the normal integral emissivity within each of the phases of the state of the elements monotonically increase. The emissivity jumps are positive or negative and depend on the individual physico-chemical parameters of the studied elements. A theoretical calculation of the emissivity of the studied elements according to the Foot approximation was carried out and analyzed.
49-61
Melting conditions for porous heat-generating device with active cooling: approximate analytical solution
Abstract
In thermal engineering applications (for example, when studying the operating conditions of thermal storage and electrochemical devices), problems often arise related to the phase transition front propagation in thermally stressed elements. This paper considers the solution of a simplified problem of heating element flow cooling. To this end, analytical estimates were obtained for the critical values of heat release intensity corresponding to the onset of melting and complete melting of the porous sample. The results are compared with numerical calculations.
62-70
Criterion of damaging effect caused by secondary arc discharge impact onto high-voltage solar batteries of the spacecraft
Abstract
One problem of space solar power engineering is how to increase the solar batteries (SB) operating voltage up to 100 V and higher. It makes possible to decrease greatly the cabling mass and the mass of voltage transducers, but it can cause secondary arc discharges (SAD) able to destroy SB structure and to decrease SB output power. In the present paper we analyse how to choose criteria of damaging effect caused by secondary arc discharge impact onto SB, which make possible to determine the prevalent impact mechanism, and to estimate permissible number of discharges in each point of the solar battery. In brief, we examine methods for determining experimentally criteria of damaging effect caused by SAD impact to SB.
71-87
Calculated determination of spark discharge parameters in capacitive ignition systems of gas turbine engines based on diagnosing voltages on storage capacitors
Abstract
The calculation results of the spark discharges probabilistic parameters in semiconductor spark plugs of capacitive ignition systems are presented: the energy and duration of discharges, discharge current and the criterion for the ignition ability of ignition systems based on measurements of two diagnostic quantities when it is impossible to directly measure these parameters under the conditions of gas turbine engines and full-scale test benches. Two voltages on the storage capacitor of ignition systems, measured by easily accessible means, are taken as diagnostic parameters – the voltage during the transition of the preparatory stage of the discharges to the spark stage and the voltage on the capacitor after the discharge in the semiconductor spark plug goes out. The laws of distribution of diagnostic quantities were experimentally determined, using methods of probability theory, expressions were obtained for the numerical characteristics of discharge parameters as a function of diagnostic quantities and characteristics of the elements of discharge circuits of ignition systems.
88-97