Volume 66, Nº 11 (2019)

The aims of this work are to analyze the changes in the world power industry during the time after the adoption of the United Nations Framework Convention on Climate Change of 1992 and to assess the extent to which the commitments of the Kyoto Protocol of 1997 have been met and evaluate the prospects of implementing the tasks of the Paris Agreement of 2015. Based on data on the production and consumption of various kinds of energy and the emissions of greenhouse gases, primarily carbon dioxide, in 1990–2017, changes in the structure of the global energy consumption, trends in electric power generation, and the influence of different factors on the carbon dioxide emissions in power-generating enterprises are investigated. It is shown that the power industry, which is the main source of anthropogenic greenhouse gases (GHGs), is the most inertial branch of the economy in terms of its contribution to the reduction in GHG emissions. Thus, in the first 2008–2012 commitment period of the Kyoto Protocol, GHG emissions in the state parties to the protocol decreased by 7.6% compared the base year, while other GHG sources reduced the emission by 18%. The corresponding figures for the following 2013–2017 commitment period were 10.6 and 17.1%, respectively. The maximum reduction in the carbon dioxide emissions in the power industry resulted from an increase in the global average efficiency of the thermal power stations from 32% in 1990 to 36% in 2017; as a consequence, the cumulative decrease in the CO₂ emissions in the world during the 1990–2017 period was approximately 22 billion t. The increase in the electric power generation at HPPs and NPPs resulted in a reduction in GHG emissions by 16.7 and 10.7 billion t, respectively. The substitution of coal and fuel oil by gas at thermal power stations facilitated reducing the emissions by 5.2 billion t, while the use of renewable energy sources for generation of electric energy resulted in a reduction of 1.1 billion t. The contribution of the carbon capture and storage technologies amounting to only 0.2 billion t is not noticeable so far.

The article is a review devoted to boiling heat transfer problems based on the reports discussed at the two largest conferences held in 2018. Boiling and evaporation issues were addressed in approximately 150 reports, and approximately half of them are considered in this review. The review contains four sections: vapor phase incipience and vapor bubble dynamics, pool boiling heat transfer and burnout, boiling in channels, and unsteady film boiling. This division is conditional in nature because some reports can be related to two sections according to their content. Although the author of the review tried to reflect the content of reports in a maximally unbiased manner, the review text also reflects his own assessments. The author’s 50 years of experience in the scientific research fields that are the subject of analysis enables him to do so.

A model of steam film condensation from a flowing steam-air mixture on a bundle made of horizontal tubes was described in previous publications. In the model, the bulk flow is simulated using single-phase flow equations, and the condensation is simulated by means of the boundary conditions on the tube surface considering the laminar flow of the condensate film. This model was supplemented with a simplified model to describe irrigation of the lower tubes in the bundle with condensate formed on the upper tubes. The results are presented of the model verification against the published experimental data on condensation on horizontal smooth tubes in a staggered tube bundle at a steam-air mixture pressure of 30 kPa, a forced horizontal flow velocity upstream of the tube bundle between 1.3 and 4 m/s, and an air volume fraction from 0 to 12%. Disagreement between the predicted and the experimental heat-transfer coefficients does not exceed 20% for all considered regimes. The calculations were performed using the ANES CFD-code being developed by the authors.

An imbalance of thermal operating conditions in a subway has a negative effect on the microclimate in tunnels and stations and eventually leads to accumulation of “thermal pollution” of the soil strata surrounding the subway tunnels and facilities. In turn, such “thermal pollution” results in less intense heat removal to the soil and in air overheating in stations. One of the efficient methods for achieving better energy efficiency of the climate systems and for improving the microclimate in the Moscow Subway’s underground facilities is to use heat pump systems with recovery of the tunnel air heat for supplying heat and cold for station complexes. The article presents the main results obtained from experimental investigations of the thermal operating conditions at some stations of the Moscow Subway. In particular, air temperature in the subway tunnel spaces was measured in the summer and winter seasons. As a result, the main factors influencing the temperature operating conditions in the subway tunnels have been revealed. Based on the results of the experiments, it can be recommended to put heat pumps into operation in the tunnels for setting up a comfortable microclimate in the subway. As an example, the results from testing this process solution are presented through analyzing the efficiency of the heat pump-based heat supply system of the Salar’evo experimental station’s complex. The analysis of the Salar’evo station’s heat pump-based heat supply system has demonstrated its successful operation in the subway along with good compatibility between the subway systems and heat pump unit at the design and operation stages. Application of heat pump equipment in the heat and cold supply systems of subway facilities is not only significantly cheaper than the conventional technology in terms of one-time capital investments but also makes it possible to save more than 80% of energy in the course of operation.

A model for the process of coarse liquid particle formation in the flow-through parts of steam turbines is considered. A numerical approach is proposed to describe the formation and development of a water film on the surface of the interblade channels, and the main factors affecting the distribution of the film parameters along the curvilinear walls of the blades are presented. It is assumed that the only source of the water film is represented by liquid-phase particles deposited on the blade surfaces. The process of film detachment from the exit edge of the blade together with its subsequent destruction and the formation of large erosion-hazardous droplets is considered. The developed model has been integrated into the earlier proposed numerical approach to the description of the motion of liquid-phase particles and their interaction with solid surfaces. At the same time, an amendment has been introduced therein taking into account the presence of a water film when a liquid phase particle collides with a solid wall. The developed numerical method makes it possible to describe all the main gas-dynamic processes occurring in the course of motion for erosion-hazardous droplets in the interblade channels. This method has been tested using experimental studies on streaming wet-steam flow in a flat nozzle grating at different initial humidity of the working medium. Using the laser flux diagnostics system, velocities and sizes inherent in droplets beyond the grating along its spacing have been determined. The developed model provides a good agreement of these parameters with the experimental data in the places of the maximum concentration of coarse droplets. However, there is a significant discrepancy for some areas of the flow in the obtained results concerning the velocity distribution. The effect that the initial steam moisture exert on the characteristics of the water film on the blade surface is considered. It is established that the film thickness significantly affects the interaction between the droplets and the blade surface in the areas wherein the collision energy is small. These areas are characterized by a large angle between the velocity vector of the projectile droplet and that normal to the surface at the collision site.

The KORSAR/CFD code results from the development of the KORSAR/GP system code certified in 2009 by the Rostekhnadzor (Federal Service for Ecological, Technological, and Nuclear Supervision) as applied to the calculated justification of the safety for VVER reactors. One of the important aspects of development consists in the introduction of the CFD-module code into functional content for the simulation of spatial turbulent flows in the mixing chambers of reactors using a nested boundary method in the RANS-approximation. The CFD module is combined with a one-dimensional model according to a semi-implicit scheme as a standard code element. Calculation results using the KORSAR/CFD code are presented for the following three modes with the asymmetrical operation of a VVER-1000 reactor’s flow-circuit loops. They consist in breaking the steam pipeline in the steam generator, in connecting the main circulation pump while initially operating three pumps at the reactor power of 71% with respect to the nominal one, and in connecting a pump while initially operating two opposite pumps at the reactor power of 52% with respect to the nominal one. The calculations have been carried out based on the input data file for the NPP power unit with a VVER-1000 developed by the specialists in VVER design at OKB Gidropress, the Chief Designer in the field of VVER reactor units. A three-dimensional simulation of coupled neutron-physical and thermohydraulic processes in the reactor core has been performed. A thermohydraulic model of the reactor core has been used in a channel-by-channel approximation and a program block for the calculation of three-dimensional neutron kinetics. In the problems under consideration, the three-dimensional simulation domain for the CFD module includes four inlet manifolds and a part of the reactor pressure chamber before entering the holes in the elliptical bottom of the shaft. The holes in the elliptical bottom and the area beyond the shaft up to the outlet manifolds have been represented by the elements of a one-dimensional model. Based on the results of the calculations, the heat-carrier flow pattern in the reactor pressure chamber has been analyzed. A flow pattern effect exerted on the dynamics of the liquid temperature distribution at the entry into the fuel assemblies of the core and on the energy release power of the fuel assemblies in the simulated modes has been demonstrated.

Nowadays, most heat sources of centralized heat-supply systems are unable to maintain the designed high-temperature schedules of the centralized regulation. Therefore, the area of qualitative regulation of the heat load has considerably reduced. The low-temperature heat-supply system is treated as the most plausible alternative to the high-temperature heat-supply system; however, no detailed calculations of the thermal and hydraulic modes for low-temperature schedules of qualitative regulation were carried out. This paper is devoted to the problems of providing the qualitative regulation of heat-supply systems and the possibility of switching to schedules with a lower design temperature without upper cutoff. The analysis of thermal schemes for some cities of the Russian Federation showed that the implementation of schedules with low design temperature of water in the supply line without upper cutoff does not increase the range of qualitative regulation and even reduces it in some cases. In a schedule without cutoff, the area of regulation is shifted to the region of lower outdoor temperatures, which allows for providing the optimum internal temperature. However, at low temperatures, the load of the second stage of the hot water heat exchanger is small, which makes it possible to provide the acceptable internal temperature even in a schedule with cutoff and with lower consumption of the water of heat-supply network. The most unfavorable internal temperature regime is observed near the breakpoint of the temperature graph when the load in the second stage of the hot water supply system’s heater is at its maximum. At the same time, the breakpoint in the temperature graph without cutoff is located in the region of lower outdoor temperatures, when the heat losses are still high and even the acceptable values of the internal temperature are unavailable.