Increasing the energy efficiency of thermal power plants operating according to the Rankine cycle is one of the priority tasks of the Russian energy sector. Despite a significant amount of scientific research, the efficiency of installations of this type still remains low. As a technological solution to increase their efficiency, the authors consider a modernized Rankine cycle in which an aqueous solution of lithium bromide is used as a working fluid, the condensation process of exhaust steam after the turbine is replaced by the process of its absorption, and the second working fluid is an absorbent. The features of the functioning of such a cycle are outlined, and the methodology for its calculation is presented. Studies have shown that the use of lithium bromide solution can reduce the steam pressure after the turbine and increase the useful heat drop as well as the degree of cycle filling. In addition, when the heat of the solution returned from the boiler is regenerated, the average temperature of the heat supply to the cycle increases, which also increases its thermal efficiency compared to the traditional circuit. The energy efficiency of the modernized cycle was analyzed and compared with the traditional Rankine cycle on water vapor. Calculations have shown that the use of a modernized cycle allows increasing thermal efficiency by an average of 1–2% compared to the traditional solution. The indicators characteristic of both steam power and absorption cycles were studied, and graphical dependences of efficiency on the main parameters were derived. The economic effect of using the modernized scheme is to reduce fuel consumption and emissions of harmful substances into the atmosphere in proportion to the reduction in fuel consumption.

Heat and mass transfer and gas distribution in a nonequilibrium steam-water volume with a phase separation level containing a noncondensable gas are considered. These processes relate primarily to the steam–gas pressurizer (SGP) of the integral reactor and determine the behavior of the SGP in normal and emergency modes. Similar processes occur in a pressurized water reactor and in a containment volume at the final stage of emergency regimes with loss of coolant. For small-power reactors of the RITM-200 type with a gas pressurizer, it is necessary to take into account the phenomena associated with the behavior of noncondensable gases. A brief description is given of the GARRIC 2.2 computer program for calculating the distribution of noncondensable gases in the primary circuit and the characteristics of the SGP of a pressurized water reactor of an integral layout. The description of the processes of heat and mass transfer and gas distribution is based on the results of experiments carried out on SGP models in a wide range of parameters and gas contents. Calculation of mass transfer, including surface evaporation and steam condensation, and gas transfer on the surface is carried out using the analogy model of heat and mass transfer under conditions of natural convection of the medium. The results of the verification of the GARRIC 2.2 program on the experimental data obtained in the study of vapor condensation on the walls, evaporation on the free surface of water, and gas distribution in the steam–gas volume at full-scale parameters are presented. The GARRIC 2.2 program was certified by Rostekhnadzor in 2014.

The article addresses general matters concerned with the occurrence of low-frequency vibration (LFV) in turbine units. It is pointed out that, despite the level of knowledge that has been achieved in regard to LFV, it still arises from time to time in power plant turbine units. Along with LFV caused by aero- and hydrodynamic excitation, LFV can also bear a subharmonic pattern. It is emphasized that the measures taken to remove LFV depend on the LFV occurrence origin. The article presents LFV occurrence and removal examples, including those relating to the use of honeycomb seals in high-pressure cylinders. With honeycomb seals, decreased sizes of channels and an increased channel component of overshroud forces caused by aerodynamic excitation are typically observed. It is pointed out that, in some cases that involve rotor rubbing against the stator, a multicomponent LFV with subharmonic and self-oscillation components is observed. It is shown that the regulatory documents do not contain criteria for estimating a multicomponent vibration in the low-frequency band. It is pointed out that multicomponent LFV can be a diagnostic indicator pointing to rubbing of the rotor against the babbit or seals. Recommendations on removing LFV of various origins are suggested. A diagnostic table that helps determine factors causing the LFV and that produces recommendations on increasing the turbine units operational reliability is given. It is stated for the first time that the turbine thrust bearing can behave as a source of oil excitation. It is also noted that the conditions under which a self-oscillation type LFV occur and its suppression methods should differ from the methods for suppressing self-excited LFV of a subharmonic nature.

For numerically simulating the melt behavior in the core catcher of a sodium-cooled reactor, the HEFEST-FR module—a software tool based on the SAFR computer code elaborated at the Nuclear Safety Institute, Russian Academy of Sciences, for simulating the meltdown and destruction of liquid metal-cooled fast reactor core components—has been developed and incorporated into the EUCLID/V2 integrated computer code. This module is intended for numerically simulating the melt retention and cooling-down processes in the reactor vessel with taking into account the heat transfer from the vessel’s internal structures to the coolant. For this purpose, a 2D-problem (implying that there is no dependence of temperature on the azimuthal angle) of unsteady heat conduction for materials located in the reactor’s core catcher tray is solved in a cylindrical coordinate system. The heat-conduction equation coefficients depend on time, coordinates, and temperature, the latter being the solution of equation. Boundary conditions of the first, second, and third kind are used, and heat loss by radiation at the boundary is specified. The total or volumetric decay heat power is given inside of the melt. For numerically solving the 2D heat-conductivity problem, an enthalpy approach based method is applied. The formulations used in the method make it possible to overcome, in a natural manner, the problem relating to discontinuity of material specific melting point enthalpy in solving the heat-conduction problem with taking phase transitions into account. The solution yields the temperature field in melting/freezing of materials (steels of various grades and fuel) in the fast reactor’s core catcher tray. The results of verifying the HEFEST-FR module against the solution of an analytical problem have been demonstrated. Using the module, methodical computations of the fuel and fuel pin cladding melt behavior in the sodium-cooled reactor’s core catcher have been carried out.

A complex for studying the structure of the wet-steam flow for a stand with a model turbine of the NPO TsKTI is presented. On the stand, the flow parts of steam turbines have been tested for more than 20 years. The experimental turbine is a model of the flow part of a low-pressure cylinder at a scale of 1 : 3. It is equipped with an extensive measuring system for the study of the vibration reliability of the elements of the flow part and the structural and kinematic characteristics of the flow. One of the most important parts of the measuring system is a complex for studying the dispersed structure of the wet-steam flow, which allows measurements to be carried out simultaneously in three control sections of the flow part and in two sampling pipes. It includes optical probes, secondary hardware units, a traversion system, and software. Measurements made using the optical spectral transparency method allow one to set the size and volume concentration of droplets in the wet-steam stream. A new method for determining droplet size distribution based on optical measurements is described. The droplet size distributions obtained by this method in two control sections are presented. It is shown that the calculation of the degree of humidity according to optical measurements is possible with the involvement of the results of independent measurements of both the vapor pressure and its temperature recorded by the optical probe. A comparison of the calculations of the degree of humidity based on pressure and temperature measurements for model and full-scale turbines was made. The result of the complex is the distribution of the degree of humidity, the size of the droplets, and the temperature of the flow along the height of the blade. The distribution of moisture parameters by the height of the blade in three control sections is given.

Data centers, being one of the main consumers of energy, deserve attention as objects in which there is a significant loss of energy in the form of heat, discharged from its equipment and discharged into the environment. Currently in Russia, the potential for energy saving through the efficient use of waste heat of data centers is estimated at 2 × 106 MW h/year and it can reach 6.3 × 106 MW h/year by 2030. With regard to the waste heat of the data center, questions arise: how large are these losses and how to use them, if we consider waste heat as a secondary energy resource, and how energy efficient are the utilization and application of this heat? The paper discusses the possibilities of estimating the amount of waste heat of the data center, which can be directed to its own needs and external applications. Estimates are made for data centers that use ventilation air for cooling equipment, taking into account the climatic conditions of the location of the data center, the range of optimal operating temperatures of the cooled equipment, and the characteristics of the utilization equipment, which includes a heat exchanger and a heat pump that increases the potential of the heat used. The factors affecting the quantitative estimates of the utilized and used heat of the data center are analyzed. The calculated ventilation model of the data center premises is based on the balance equations of energy and mass preservation recorded for the serviced room and individual elements of the utilization plant. The energy efficiency of utilization and application of waste heat is represented as a share of the amount of heat used relative to the basic value of the savings of the conventional fuel at the heat source taking into account the costs of electrical energy for the operation of the heat pump. The dependence of specific fuel economy at the source of thermal energy on climatic conditions, the ratio of specific fuel costs for the production of thermal and electrical energy $${{{{b}_{P}}} \mathord{\left/ {\vphantom {{{{b}_{P}}} {{{b}_{Q}}}}} \right. \kern-0em} {{{b}_{Q}}}}$$ , the degree of approximation of the thermodynamic vapor-compression cycle of the heat pump to the ideal cycle, heat efficiency of heat exchanger-recovery, and temperature of intermediate heat carrier are analyzed.

The results of experimental studies into the hydrodynamics of the coolant at the outlet section of the cassette fuel assembly (FA) of the RITM-type reactor of a low-power ground-based nuclear power plant are presented. The purpose of the work is to analyze the distribution of the axial velocity and flow rate of the coolant at the exit from the fuel bundle, in the modernized head of the fuel assembly, near the coolant extraction pipe and the openings of the upper base plate as well as to determine those areas of the fuel bundle from which the coolant flow is most likely to enter the pipe selection to the resistance thermometer. To achieve this goal, experiments were carried out on a research stand with an air working medium on a model of the outlet section of a fuel cassette, which includes an outlet fragment of a fuel bundle with spacer grids, models of an upgraded fuel cassette head, an upper support plate, and a coolant extraction pipe. When studying the flow of the coolant flow in the outlet part of the fuel cassette, the pneumometric method and the method of injection of a contrasting impurity were used. An area covering the entire cross section of the model was chosen as the area under study. The picture of the coolant flow is represented by cartograms of the distribution of its axial velocity and flow rate as well as cartograms of the distribution of the contrasting impurity in the cross section of the experimental model. The results of the experiments can serve as a basis for making engineering decisions when designing new cores of RITM type reactors. The obtained database of experimental data can be used for validation of modern CFD programs and one-dimensional thermal-hydraulic codes used to justify the thermal reliability of cores.

Integrated gasification combined-cycle (IGCC) units, which use solid fuels (coal, petroleum coke, etc.) for combined-cycle power generation, have been under development for approximately half a century. At present, the countries of the Asian region show the greatest interest in this type of power plants. Two large IGCC power units entered into commercial operation at Nakoso and Hirono thermal power plants (TPPs) in Japan; in addition, the Osaki CoolGen project is advancing greatly. The People’s Republic of China and the Republic of Korea are also improving their IGCC projects. Development of more efficient technologies for generator gas cleaning and application of the next generation of gas-turbine units (GTUs) at new IGCC units have cut down harmful emissions and increased the efficiency up to 48%. The 21st century has brought increased interest in IGCC units due to the ability of their equipment to capture CO2. Besides the above-mentioned advantages, IGCC units also have disadvantages, the biggest of which is their high cost. That is why, despite many IGCC projects to be deployed in the 2000s, most of these projects were subsequently canceled, and the plants built in the 1990s are being gradually decommissioned. The promising direction for future application of IGCC units is the production of hydrogen for fuel cells with simultaneous CO2 capture. The polygeneration technology already used at some facilities, which enable the generation and delivery to the consumer of not only electricity but also gasification by-products, will also render support to the solution of the economic problems of IGCC units.

The processes of film condensation of stagnant and moving vapor on a single tube and various tube bundles were examined in many studies. Nevertheless, the local characteristics of heat transfer and the details of the interaction of the flowing down condensate with a moving vapor flow, which can have a significant effect on the characteristics of the condensation process in tube bundles, are not well understood. The paper presents the results of simulation of the condensation of practically stagnant and of moving saturated vapor on a horizontal cylinder. The mathematical model of a two-phase flow is based on the Volume of Fluid (VOF) method, which is implemented in the in-house CFD-code ANES. The main advantage of the proposed simulation method is that it can capture the interface without any assumptions. The modified Lee model was used to model interfacial mass transfer. An algorithm is proposed for the automatic selection of a constant in this model on the basis of the specified properties of the coolant and parameters of the computational grid. The model was validated against the classical Nusselt solutions for a vertical plate and a horizontal cylinder, known calculating correlations, and predictions obtained using a simplified condensation model proposed by the authors of this paper in previous studies. Information is presented on the drip-off diameters of droplets, the dynamics of heating of subcooled condensate droplets after their drip-off from the tube surface, and the effect of external tube spraying on the condensation rate. The obtained data are compared with the available experimental results.