Showing papers in "Thermal Engineering in 2018"

The Conceptual Process Arrangement of a Steam–Gas Power Plant with Fully Capturing Carbon Dioxide from Combustion Products

Abstract: The article proposes a new concept for designing power plants operating on natural gas and involving means for fully removing carbon dioxide from the cycle in the liquid phase form in order to subsequently bind or bury it for reducing the emissions of greenhouse gases into the atmosphere. In contrast to means used in the conventional power plant process arrangements for capturing CO2 from the combustion products, the proposed concept involves the need to develop fundamentally new power engineering technologies, in which the CO2 utilization system is intrinsically built into the cycle structure already at the initial stage of power plant design and optimization of its parameters. As an example, the process flow diagram of a natural gas fired power plant generating electricity and heat is considered. The integral indicators characterizing the thermal efficiency of such a power plant are given and compared with the similar indicators of the operating or newly designed plants fitted with CO2 capturing systems, the process arrangement of which implies direct emission of carbon dioxide into the atmosphere. The comparison is carried out for the average ratio between the generated electricity and heat that has historically been established in the climatic zone of central Russia. It is shown that the proposed cycle features high thermodynamic efficiency and competitiveness with respect to the same indicators of alternative systems for combined generation of electricity and heat. The article suggests versions of the CO2 capturing system configuration that allows, with the modern technological level of equipment, the carbon dioxide emissions to be reduced down to 0.5–5.0% of the total amount produced in firing natural gas.

CHP Plants in Russia: the Necessity for Technological Renovation

Abstract: The role of combined heat and power (CHP) plants in the electric power industry of Russia is shown. The operational efficiency analysis of public service CHP plants and the fuel, power, and age structure of the existing CHP plants are carried out. Their main problems, such as underuse of generating equipment, excessive production in the condensing mode, high degree of equipment wear, and technological heterogeneity, are identified. The necessity of technological renovation of the CHP plants is shown. The energy efficiency of the combined production of electric and thermal energy by the existing CHP plants is compared to modern technologies for their separate gas and coal production. It is shown that the thermal capacity of the CHP plants in Russia exceeds the required capacity by almost two times. Estimates of the CHP plant thermal capacity necessary to cover the current heat loads are obtained for Russian regions. Main directions of the CHP plants' renewal based on the use of competitive domestic equipment and operation according to the heat load schedule are determined. Systemic impacts achieved by technological renewal are determined for gas-fired CHP plants with allowance for the climatic and load features of the Russian regions. It is shown that the technological renewal of gas-fired CHP plants will allow saving up to 16% of today’s fuel consumption, reducing the total CHP thermal capacity by 47.5% with the same volume and heat supply mode. The operation of a CHP plant according to the heat load schedule leads to a reduction in the electric capacity of the CHP plant by 20% with an increase in electricity generation by 11%. As a result, the consumption of the installed electric and thermal capacity of the CHP plant increases dramatically as does the fuel efficiency and the annual loading balance of external gas-fired condensing power plants. The needs for GTPs and CCGTs required for the technological renovation of the CHP plants is assessed. The necessity for developing competitive domestic medium and high power GTPs is considered.

A Review of Technologies for Multistage Wood Biomass Gasification

Abstract: Currently, small-scale distributed power generation is being intensively developed in Russia and abroad. Given the rise in the rates for the electric and thermal energy, the development of new territories, and the technical infeasible connection to the power supply system, one of the most promising variants of supplying isolated consumers with power is the application of wood biomass gasification technologies. Analysis of the studies in this sphere shows that considerable attention is paid to enhancing the gasification efficiency and ensuring the purity of the gas. These problems are solved using multistage gasification technology. This technology involves the pyrolysis and gasification in separated zones of the gasifier or individual interconnected reactors, which enables achieving the optimal conditions for the conversion of biomass at every separate stage. The major advantage of multistage gasifiers is the production of synthesis gas with a low content of tar. The article represents a review of technologies for multistage wood biomass gasification and comparison of the relevant gasifiers of various types; the basic single-stage and multistage wood biomass gasification technologies are examined and their technical characteristics and examples of their commercial implementation are provided. Analysis of the current situation shows that predominantly foreign multistage wood biomass gasification technologies/plants have found practical application. These technologies allow the produced syngas to be directly used in internal combustion engines and gas turbines without employing expensive auxiliary detarring plants.

A Study of the Absorption of Nitrogen Oxides from the Boiler Flue Gases

Abstract: In the past decade, the number of unsolved ecological problems has been steadily increasing. Among the numerous causes of this situation, the exposure of the environment to industrial waste should be mentioned. For example, enterprises of the fuel and energy industry emit a significant amount of hazardous substances into the atmosphere. Flue gases formed in boiler-houses and at thermal power stations get through flue gas stacks into the upper atmosphere and pollute it. In this work, a method is proposed for adsorption treatment of the flue gases from boilers fired with associated petroleum gas. The chemical composition of the associated petroleum gas of Romashkino oil field, the Republic of Tatarstan, is presented and the practicality of its use is demonstrated. Nitrogen oxides contained in the boiler flue gases result from oxidation of molecular air nitrogen during combustion of the fuel. In order to reduce the adverse effect of hazardous substances on the environment, the flue gases are to be compulsorily cleansed of nitrogen oxides. The use of the sludge resulting from coagulation and liming of natural water during the chemical water treatment at Kazan CHPP-1 as a sorption material is proposed. The chemical composition and technical characteristics of the sludge are presented. The properties of the sludge were studied using a laboratory fixed-sorbent-bed setup. The sorption capacity and water-absorption of the sludge were determined and curves of the kinetic and isothermal dependences of the nitrogen oxide adsorption by the sludge were constructed. The change in the nitrogen- oxide sorption capacity of the sludge depending on the sludge particle size was established. The optimal characteristics of a batch-type fixed-bed absorber were calculated. The results of calculating the economic and ecological effects of introducing the adsorption treatment of flue gases to remove nitrogen oxides for the boiler-house of AO Karpov Chemical Plant are provided.

Fuel Cell Based Power-Generating Installations: State of the Art and Future Prospects

Abstract: Specific features of power-generating installations constructed using different types of fuel cells are considered. Problems and trends of their development in Russia and abroad are analyzed. Fuel cell commercialization lines, their application niches, and the most well-known projects of constructing and exploiting fuel cell-based power-generating installations are described. Special attention is paid to analyzing the specific features pertinent to the domestic market of fuel cells and prospects of different lines of their application taking into account competition from other energy sources. Conclusions about the most topical development lines of the considered technologies under the conditions of Russia are drawn with due regard to the available groundwork as well as technical and economic aspects. It is pointed out that the main application field of fuel cells in Russia may be distributed generation of electricity, including off-grid supply of power to consumers on the basis of network and liquefied natural gas, liquefied hydrocarbon gases, and also renewable energy sources. In this regard, installations involving combined generation of electricity and heat, including small ones with a capacity of a few tens or hundreds of kilowatts, are of special interest. Prospective market niches for using fuel cells may include pipeline cathodic protection stations, utilization of biogas obtained, e.g., in reprocessing domestic waste, emergency and uninterruptible power supply systems, propulsion power installations of air drones, auxiliary power installations with a capacity of 1–3 kW, and utilization of hydrogen rejected from chemical production facilities. In view of existing groundwork and cooperation, concentration of efforts aimed at developing solid oxide, solid polymeric, and alkaline fuel cells in Russia seems to be the most topical issue. The use of molten carbonate fuel cells may be of considerable practical interest for reclaiming landfill gas at solid domestic waste landfills and at aeration fields, a problem that is an issue for many cities in the country; such cells can also be used for concentrating and extracting CO2 from fuel gases.

Development of an Environmentally Safe Process for Medical Waste Disposal Based on Pyrolysis

Abstract: Upon analyzing the methods for processing epidemiologically hazardous medical waste (MW), it has been shown that the problem of safe disposal of MW with respect to the formation of polychlorinated dibenzo-para-dioxins and dibenzofurans (dioxins and furans) is acute and requires scientifically sound solutions. The typical morphological and elemental composition of the MW classes B and C and their thermal properties were determined, and the modern literature on the processes of thermal detoxification of dangerous MW was analyzed. It has been found that the process of pyrolysis is the most adaptive to various types of solid waste. Currently, pyrolysis attracts special attention due to its flexibility in treating various combinations of wastes only by changing the operating parameters of the process, such as temperature and heating rate. Pyrolysis is particularly important in connection with the growing amount of polymers in the waste of medical institutions, including those containing chlorine. In this case, the pyrolysis method presents the possibility of using a number of circuit solutions to prevent the formation of dioxins and furans. It has been shown that the use of the pyrolysis method ensures, along with full satisfaction of the requirements of sanitary and hygienic standards, the environmental safety of the MW detoxification process as compared to other high temperature methods (combustion and gasification). Next, possible directions of utilization of secondary resources received in the process under consideration were analyzed. In the proposed scheme of the installation for safe disposal of medical waste on the basis of the pyrolysis process, its products (excess gas, heat of the products of combustion, etc.) are expected to be used to generate electrical and thermal energy; semicoke as a solid residue of the process will be converted to activated carbon.

The EUCLID/V1 Integrated Code for Safety Assessment of Liquid Metal Cooled Fast Reactors. Part 1: Basic Models

Abstract: The article describes the basic models included in the EUCLID/V1 integrated code intended for safety analysis of liquid metal (sodium, lead, and lead-bismuth) cooled fast reactors using fuel rods with a gas gap and pellet dioxide, mixed oxide or nitride uranium–plutonium fuel under normal operation, under anticipated operational occurrences and accident conditions by carrying out interconnected thermal–hydraulic, neutronics, and thermal–mechanical calculations. Information about the Russian and foreign analogs of the EUCLID/V1 integrated code is given. Modeled objects, equation systems in differential form solved in each module of the EUCLID/V1 integrated code (the thermal–hydraulic, neutronics, fuel rod analysis module, and the burnup and decay heat calculation modules), the main calculated quantities, and also the limitations on application of the code are presented. The article also gives data on the scope of functions performed by the integrated code’s thermal–hydraulic module, using which it is possible to describe both one- and twophase processes occurring in the coolant. It is shown that, owing to the availability of the fuel rod analysis module in the integrated code, it becomes possible to estimate the performance of fuel rods in different regimes of the reactor operation. It is also shown that the models implemented in the code for calculating neutron-physical processes make it possible to take into account the neutron field distribution over the fuel assembly cross section as well as other features important for the safety assessment of fast reactors.

Flow-Accelerated Corrosion Wear of Power-Generating Equipment: Investigations, Prediction, and Prevention: 1. Flow-Accelerated Corrosion Processes and Regularities

Abstract: The first part of this review considers the prerequisites and scales of damage inflicted to the equipment and pipelines of power plant units as a consequence of flow-accelerated corrosion, and examples of accidents involving lethal outcomes that occurred at nuclear power plants as a result of pipeline ruptures caused by flow-accelerated corrosion are given It is shown that the scope of items susceptible to flow-accelerated corrosion includes components of condensate–feedwater and wet steam path equipment and pipelines made of carbon and low-alloy steels The main negative consequences caused by flow-accelerated corrosion are local metal thinning spots that can lead to abrupt failures and depressurization of the process circuit and contamination of working fluid with iron containing products of flow-accelerated corrosion Sedimentation of these products in a steam generator is one of factors causing damage to and failure of its heat transfer tubes It is proposed to draw a distinction between general and local flow-accelerated corrosion General flow-accelerated corrosion causes ingress of iron-containing compounds into the working fluid and is characterized by a moderate metal thinning rate that does not lead to destructions or occurrence of wormholes involving loss of process circuit leak tightness The effects of local flow-accelerated corrosion manifest themselves in small parts of intricately shaped channels and are characterized by a significant metal thinning rate with possible occurrence of wormholes or abrupt destruction of the pipeline and power-generating equipment components Typical cases of and statistical data on damages inflicted to nuclear power plant components due to flow-accelerated corrosion are presented The physicochemical fundamentals and regularities relating to flow-accelerated corrosion of metal occurring in one- and two-phase flows are considered It is pointed out that the hydrodynamic factor plays the determining role in the occurrence of zones and rate of local thinning caused by flow-accelerated corrosion The key hydrodynamic characteristics influencing the local flow-accelerated corrosion rate are determined Fundamental differences between the mechanisms governing flow-accelerated corrosion in two-phase medium and single-phase water flow are shown These differences stem from the specific features of hydrodynamics pertinent to the motion of liquid film and interphase redistribution of admixtures and gases that gives rise to a change in the pH value of liquid The results from experiments aimed at studying the effect of temperature on the flow-accelerated corrosion rate of different metals in a two-phase wet steam flow and the effect of steam wetness degree on the liquid film flow mode are presented

Studying the Aerodynamics of the TPP-210A Boiler Furnace When It Is Shifted to Operate with Dry-Ash Removal and Vortex Fuel Combustion

Abstract: To reduce the amount of nitrogen oxide emissions and achieve more reliable operation of the TPP-210A boiler, a process arrangement for firing Grade TR Kuznetsk coal that involves using straight-flow burners and shifting the boiler from slag-tap to dry-ash removal is developed. Owing to a large burner downward slope angle and special arrangement of burners and nozzles, four large vertical vortices rotating in opposite directions are produced in the furnace lower part, as a result of which the combustion products dwell for a longer period of time in the burning zone and more complete fuel combustion is achieved. For verifying the operability and efficiency of the proposed combustion arrangement, investigations on a boiler furnace physical model were carried out using a technique for visualizing fuel jets and secondary and tertiary overfire air jets. The fuel jet temperature boundaries in the course of jet propagation in the furnace model are also determined. The study results have shown that staged fuel combustion will be set up with using the proposed arrangement of burners and nozzles. In addition, large vertical vortices produced in the furnace lower part will help to achieve more efficient use of the dry bottom hopper heating surfaces, due to which lower coal combustion product temperature in the furnace upper part and smaller content of combustible products in fly ash will be obtained. Owing to low values of air excess factor at the pulverized coal burner outlet and gradual admission of air into the vortex zone through a few nozzles with intense inner recirculation of combustion products to the jet initial section, staged combustion of pulverized coal and low nitrogen oxide emissions will be secured. Owing to expansion of fuel jets, a rapid growth of mass in the fuel jet is achieved, which is obtained both due to ejection of the jet itself and due to forced admission of hot fuel gases from other jets. Investigations carried out on the physical model have confirmed that the proposed combustion arrangement features high efficiency and that a low content of nitrogen oxides in flue gases is obtained.

The EUCLID/V1 Integrated Code for Safety Assessment of Liquid Metal Cooled Fast Reactors. Part 2: Validation and Verification

Abstract: The article presents information on the validation and verification (V&V) of the first version (V1) of the EUCLID integrated code intended for safety analysis of operating or designed liquid metal (sodium, lead, or lead–bismuth) cooled reactors under normal operation and under anticipated operational occurrences by carrying out interconnected neutronics, thermal–mechanical, and thermal–hydraulic calculations. The list of processes and phenomena that have to be modeled in the integral code for correctly describing the above-mentioned operating conditions is given. Based on this list, the most high-quality experimental data are selected for carrying out the validation. It is shown that, for sodium cooled reactors, a significant number of experiments was carried out around the world on studying individual thermal–hydraulic processes and phenomena, which made it possible to perform validation of the thermal–hydraulic module. The validation of the code—as applied to description of processes that take place in fuel rods with oxide or nitride fuel and gas gap—is carried out against the results of post-pile investigations of fuel rods irradiated in fast sodium cooled research and power-generating reactors. The obtained results opened up the possibility to determine the errors of calculating such fuel rod parameters as release of gaseous fission products from the fuel and sizes of pellet and cladding in a limited range of burnup values. To perform validation of the neutronics module as applied to calculation of such parameters as power density distribution over the core and decay heat release, a sufficient number of experiments and benchmarks were selected. The results obtained from experimental operating conditions of a BN-600 reactor and startup conditions of a BN-800 reactor made it possible to estimate how correctly the integral code performs calculations of interconnected thermal–hydraulic and neutronic processes. Only a limited set of experimental investigations is available for heavy liquid metal cooled reactors. In view of this circumstance, programs for obtaining the lacking data are developed. To estimate the quality with which the experiments are modeled by means of the EUCLID/V1 integrated code, a procedure for evaluating the errors of calculation results is developed. In accordance with this procedure, the error of calculating the parameters playing the main role in the reactor safety assessment is evaluated.

Developing a Procedure for Segmenting Meshed Heat Networks of Heat Supply Systems without Outflows

Abstract: The heat supply systems of cities have, as a rule, a ring structure with the possibility of redistributing the flows. Despite the fact that a ring structure is more reliable than a radial one, the operators of heat networks prefer to use them in normal modes according to the scheme without overflows of the heat carrier between the heat mains. With such a scheme, it is easier to adjust the networks and to detect and locate faults in them. The article proposes a formulation of the heat network segmenting problem. The problem is set in terms of optimization with the heat supply system’s excessive hydraulic power used as the optimization criterion. The heat supply system computer model has a hierarchically interconnected multilevel structure. Since iterative calculations are only carried out for the level of trunk heat networks, decomposing the entire system into levels allows the dimensionality of the solved subproblems to be reduced by an order of magnitude. An attempt to solve the problem by fully enumerating possible segmentation versions does not seem to be feasible for systems of really existing sizes. The article suggests a procedure for searching rational segmentation of heat supply networks with limiting the search to versions of dividing the system into segments near the flow convergence nodes with subsequent refining of the solution. The refinement is performed in two stages according to the total excess hydraulic power criterion. At the first stage, the loads are redistributed among the sources. After that, the heat networks are divided into independent fragments, and the possibility of increasing the excess hydraulic power in the obtained fragments is checked by shifting the division places inside a fragment. The proposed procedure has been approbated taking as an example a municipal heat supply system involving six heat mains fed from a common source, 24 loops within the feeding mains plane, and more than 5000 consumers. Application of the proposed segmentation procedure made it possible to find a version with required hydraulic power in the heat supply system on 3% less than the one found using the simultaneous segmentation method.

Mechanisms Governing Fine Fragmentation of Hot Melt Immersed in Cold Water

Abstract: Hypotheses about the mechanisms governing fragmentation of superheated liquid metal droplets falling into cold water are analyzed. It is shown that a physical model based on the cavitation–acoustic mechanism governing fine fragmentation of melt under steam explosion conditions is likely the most suitable one for consistently describing the fragmentation of both low-melting and refractory metals. For checking this conjecture, special experiments for studying the processes triggered when cold (20°С) water comes into contact with a heated surface and for measuring the pressure impulses (arising both in coolant and in the hot body) accompanying the coolant flashing were carried out using liquid metal (tin and steel) droplets and superheated solid steel bodies. The working substance temperatures were varied in the range from 200 to 1600°С. The results obtained from the performed experiments are not in contradiction with the melt fine fragmentation process represented by the cavitation–acoustic model. It is shown that the acoustic waves generated during explosive growth of bubbles on a hot surface propagate in the solid body and are alternating in nature. Their intensity (including that at negative pressure values) differs only slightly in the modulus from the pressure impulses measured in the coolant and is sufficient for finely fragmenting the droplets. It is experimentally found—with the use of a conductance measuring technique—that the transition from the coolant film to bubble boiling mode is preceded by a short-term (lasting a few milliseconds) process involving intense interaction of waves at the steam–liquid boundary with the heated surface. The signal from the conductance measuring transducer was subjected to a wavelet analysis for different values of the heated surface temperature. The study results testify that high-frequency (several tens of kilohertz) pulsations of electric current are generated in the preburnout region with their characteristics varying (toward increasing the amplitude and intensity) with time as the heating and heated media come closer into contact with each other. A probabilistic process development scenario is suggested.

A Thermodynamic Analysis of a New Cycle for Adsorption Heat Pump "Heat from Cold": Effect of the Working Pair on Cycle Efficiency

Abstract: A thermodynamic analysis was carried out for a new “Heat from Cold” (HeCol) adsorption cycle for transformation of the ambient heat using the following working pairs: activated carbon ASM-35.4–methanol or composite sorbent LiCl/silica gel–methanol. Unlike the conventional cycle of an adsorption thermal engine where the adsorbent is regenerated at a constant pressure by its heating up to 80–150°C, the adsorbent in the HeCol cycle is regenerated by depressurization, which is performed due to a low ambient temperature. The balances of energy and entropy are calculated at each cycle stage and each element of the transformer under conditions of ideal heat transfer. The performance of the cycle for both pairs is compared. The threshold ambient temperature above which useful heat is not produced has been determined. The threshold values depend only on the absorption potential of methanol. It is demonstrated that useful heat with a high temperature potential of approximately 40°C can be obtained from a natural source of low-potential heat (such as a river, lake, or sea) only at a sufficiently low ambient temperature. The cycle with the composite sorbent LiCl/silica gel–methanol yielded much more useful heat than the cycle with the activated carbon ASM-35.4–methanol due to the features of the characteristic curve for methanol vapor adsorption on the composite sorbent. The amount of useful heat increases with decreasing ambient temperature and increasing temperature of the natural low-temperature heat source. The examined cycle can be used for upgrading the ambient heat temperature potential in countries with a cold climate.

Analysis of the World Experience of Smart Grid Deployment: Economic Effectiveness Issues

Abstract: Despite the positive dynamics in the growth of RES-based power production in electric power systems of many countries, the further development of commercially mature technologies of wind and solar generation is often constrained by the existing grid infrastructure and conventional energy supply practices. The integration of large wind and solar power plants into a single power grid and the development of microgeneration require the widespread introduction of a new smart grid technology cluster (smart power grids), whose technical advantages over the conventional ones have been fairly well studied, while issues of their economic effectiveness remain open. Estimation and forecasting potential economic effects from the introduction of innovative technologies in the power sector during the stage preceding commercial development is a methodologically difficult task that requires the use of knowledge from different sciences. This paper contains the analysis of smart grid project implementation in Europe and the United States. Interval estimates are obtained for their basic economic parameters. It was revealed that the majority of smart grid implemented projects are not yet commercially effective, since their positive externalities are usually not recognized on the revenue side due to the lack of universal methods for public benefits monetization. The results of the research can be used in modernization and development planning for the existing grid infrastructure both at the federal level and at the level of certain regions and territories.

Impact of Climate Change on Energy Production, Distribution, and Consumption in Russia

Abstract: An assessment of the overall impact of the observed and expected climatic changes on energy production, distribution, and consumption in Russia is presented. Climate model results of various complexity and evaluation data on the vulnerability of various energy production sectors to climate change are presented. It is shown that, due to the increase of air temperature, the efficiency of electricity production at thermal and nuclear power plants declines. According to the climate model results, the production of electricity at TPPs and NPPs by 2050 could be reduced by 6 billion kW h due to the temperature increase. At the same time, as a result of simulation, the expected increase in the rainfall amount and river runoff in Russia by 2050 could lead to an increase in the output of HPP by 4–6% as compared with the current level, i.e., by 8 billion kW h. For energy transmission and distribution, the climate warming will mean an increase in transmission losses, which, according to estimates, may amount to approximately 1 billion kW h by 2050. The increase of air temperature in summer will require higher energy consumption for air conditioning, which will increase by approximately 6 billion kW h by 2050. However, in total, the optimal energy consumption in Russia, corresponding to the postindustrial level, will decrease by 2050 by approximately 150 billion kW h as a result of climate- induced changes. The maximum global warming impact is focused on the heat demand sector. As a result of a decrease in the heating degree-days by 2050, the need for space heating is expected to fall by 10–15%, which will cause a fuel conservation sufficient for generating approximately 140 billion kW h of electricity. Hence, a conclusion about the positive direct impact of climate change on the Russia’s energy sector follows, which is constituted in the additional available energy resource of approximately 300 billion kW h per year.

Thermodynamic Simulation of Equilibrium Composition of Reaction Products at Dehydration of a Technological Channel in a Uranium-Graphite Reactor

Abstract: The problems of accumulation of nuclear fuel spills in the graphite stack in the course of operation of uranium-graphite nuclear reactors are considered The results of thermodynamic analysis of the processes in the graphite stack at dehydration of a technological channel, fuel element shell unsealing and migration of fission products, and activation of stable nuclides in structural elements of the reactor and actinides inside the graphite moderator are given The main chemical reactions and compounds that are produced in these modes in the reactor channel during its operation and that may be hazardous after its shutdown and decommissioning are presented Thermodynamic simulation of the equilibrium composition is performed using the specialized code TERRA The results of thermodynamic simulation of the equilibrium composition in different cases of technological channel dehydration in the course of the reactor operation show that, if the temperature inside the active core of the nuclear reactor increases to the melting temperature of the fuel element, oxides and carbides of nuclear fuel are produced The mathematical model of the nonstationary heat transfer in a graphite stack of a uranium-graphite reactor in the case of the technological channel dehydration is presented The results of calculated temperature evolution at the center of the fuel element, the replaceable graphite element, the air gap, and in the surface layer of the block graphite are given The numerical results show that, in the case of dehydration of the technological channel in the uranium-graphite reactor with metallic uranium, the main reaction product is uranium dioxide UO2 in the condensed phase Low probability of production of pyrophoric uranium compounds (UH3) in the graphite stack is proven, which allows one to disassemble the graphite stack without the risk of spontaneous graphite ignition in the course of decommissioning of the uranium-graphite nuclear reactor

Investigation into Behavior of a Steam-Water Mixture Flow Through Holes in a Submerged Perforated Sheet at High Void Fractions

Abstract: Processing of experimental data on the pressure difference across a submerged perforated sheet (SPS) revealed that, at sufficiently high void fractions under SPS, the pressure difference across it became less than the pressure difference for the pure steam stream with the same flowrate. To find the cause of this, the effect of a liquid film, which can be formed on the SPS upstream surface as a result of water droplets’ impact and can smooth over sharp edges of holes in SDS, was examined. This can decrease the pressure drop across the sharp edges of holes. This assumption was checked through numerical solution to several model problems in the axisymmetric formulation for a steam flow in a round pipe with an orifice. The flow of steam and water was modeled using the viscous incompressible liquid approximation, while the turbulence was described by the k–e model. The evolution of the interfacial area was modeled using the VOF model. The following model problems of steam flow through an orifice were studied: a single-phase flow, a flow through the orifice with a liquid film on its upstream surface, a flow through a chamfered hole, and a flow through the orifice with a liquid film on its upstream surface without liquid supply to the film. The predictions demonstrate that even the approximate account of the liquid film effect on the steam flow yields a considerable decrease in the pressure drop across the hole (from 8 to 24%) due to smoothing its sharp outlet edges over. This makes it possible to make a conclusion that the cause of a decrease in the pressure drop across SPS observed in the experiments at high void fractions is the formation of a liquid film, which smooths the sharp edges of the hole.

Radio-Frequency Ion Thruster with Additional Magnetic Field: Experimental Investigation

Abstract: Performances of a radio-frequency ion thruster with an additional external magnetic field in the area of the high-frequency discharge are experimentally investigated and the results of the investigation are presented. The calculated distribution of a magnetic field generated by an additional magnetic system for the current in the winding 1 A is given. How an additional external magnetic field influences on the ion current is examined. Performances of a laboratory model of a radio-frequency ion thruster with and without a constant external magnetic field are compared. Modes of thruster operation and current values in a magnetic system’s windings under which the increment of ion current is minimal are determined.

An Efficient Unified Approach for Performance Analysis of Functionally Graded Annular Fin with Multiple Variable Parameters

Abstract: The present work investigates the performance of an annular fin of constant thickness, made up of a functionally graded material (FGM). The fin surfaces are exposed in an environment where the heat loss occurs through convection and radiation. The various parameters, describing the fin performances, are considered to be varying with the local temperature and fin radius. An efficient and unified approach, homotopy perturbation method (HPM), is applied for obtaining the closed form solution from the non-linear heat transfer equation of equilibrium. The effects of key thermal parameters, i.e. thermo-geometric, conduction— radiation, thermal conductivity variation, heat generation, exponent of heat transfer co-efficient and the parameter of surface emissivity are explored on the temperature field leading to an overall investigation of thermal performance. And, the effects of such parameters on heat transfer rate, efficiency, effectiveness and temperature distributions are found to be significant. The accuracy of the present closed form solution is measured when its results are verified with the results of FEM and FDM solutions. The present results agree very well with those of FDM results and FEM results which is obtained using COMSOL software.

A Model of the Motion of Erosion-Hazardous Droplets in Steam Turbines' Interblade Channels

Abstract: A model is discussed describing the interaction of liquid droplets with interblade channel walls in condensing steam turbines. It is based on the experimental data on the impact of individual droplets on a surface that are presented in the form of statistical models with free empirical parameters. The motion of liquid particles is simulated using individual streams of droplets under the action of aerodynamic drag force from the steam. Their interaction with the interblade channel surface is determined by the kinetic energy of impingement affecting the subsequent process. The proposed numerical approach deals with two droplet impact cases, i.e., a droplet deposits on the profile of the blade airfoil or becomes a source of secondary moisture leaving the surface. Liquid droplets formed in the latter case are also simulated using streams. The empirical coefficients of the model were selected based on the results of experimental investigation of the motion of liquid particles in a flat vane cascade. Parameters of wet steam flow in an interblade channel were determined using a laser flow diagnostic system and the particle tracking velocimetry (PTV) method implemented on its basis. The investigations were performed in a two-dimensional flow. The measured patterns of liquid particles’ motion were compared with predicted ones. The velocity distributions of primary and secondary droplets were examined in six characteristic regions of the flat cascade. Causes responsible for disagreement between the experiment and the predictions were outlined. It has been found that the angle at which droplets impinge on the interblade channel wall has a considerable effect on characteristics of the formed secondary droplets. Verification of the model demonstrated a satisfactory agreement of the experiment with the predictions.

Investigation of Active Identification Methods for Thermohydraulic Testing of Heat Networks

Abstract: Considerable uncertainty of the information about actual characteristics and parameters is the key factor restricting the effective use of mathematical modeling and computer simulation methods in solving problems of optimal retrofitting, commissioning, development of operating regimes, and dispatch control of heat networks. Application of the existing industrial procedures in testing a heat network for hydraulic and heat losses does not make the issue less urgent, because of the fact that the test conditions have not been properly standardized as yet and no guarantee is provided for the completeness and accuracy of the obtained results. The employment of the available methods of parametric identification during passive monitoring of heat networks during their normal operation does not ensure that the required solution will be obtained due to insufficient number of measurement points and a narrow range where the operating conditions can be varied. The paper presents a unique formalization of the problems of testing heat networks for hydraulic and heat losses as problems of active identification assuming optimal planning and processing of the test results with the use of a mathematical model of steady-state thermohydraulic regimes. A description of the model, a substantiation of selection of test optimality criteria, mathematical formulations of problems for optimal planning of test conditions and optimal location of instruments, and test result processing procedures are presented. The proposed procedure is in a step-wise test strategy giving maximum information with a minimal risk that too many tests will be performed. It is applicable for testing various types of heat networks having any structure or configuration. The potential efficiency of simultaneous performance of thermal and hydraulic testing of a heat network is demonstrated for the first time theoretically and by an example. It manifests itself in minimizing the total number of experiments required for reaching the prespecified accuracy in determining the actual characteristics of heat networks and of the model predictions.

Hybrid Electric Energy Storages: Their Specific Features and Application (Review)

Abstract: The article presents a review of various aspects related to development and practical use of hybrid electric energy storages (i.e., those uniting different energy storage technologies and devices in an integrated system) in transport and conventional and renewable power engineering applications. Such devices, which were initially developed for transport power installations, are increasingly being used by other consumers characterized by pronounced nonuniformities of their load schedule. A range of tasks solved using such energy storages is considered. It is shown that, owing to the advent of new types of energy storages and the extended spectrum of their performance characteristics, new possibilities for combining different types of energy storages and for developing hybrid systems have become available. This, in turn, opens up the possibility of making energy storages with better mass and dimension characteristics and achieving essentially lower operational costs. The possibility to secure more comfortable (base) operating modes of primary sources of energy (heat engines and renewable energy source based power installations) and to achieve a higher capacity utilization factor are unquestionable merits of hybrid energy storages. Development of optimal process circuit solutions, as well as energy conversion and control devices facilitating the fullest utilization of the properties of each individual energy storage included in the hybrid system, is among the important lines of research carried out in this field in Russia and abroad. Our review of existing developments has shown that there are no universal technical solutions in this field (the specific features of a consumer have an essential effect on the process circuit solutions and on the composition of a hybrid energy storage), a circumstance that dictates the need to extend the scope of investigations in this promising field.

Computational-Experimental Verification of Technologies of Utilization of the Concentrate Formed in the Reverse-Osmosis Water Demineralization Cycle

Abstract: Technologies for utilizing the wastewater of the reverse-osmosis plants (ROPs) to prepare the make-up water for power-generating plants of combined heat and power plants and nuclear power plants are proposed and substantiated using mathematical models and full-scale experiments. The ROPs use natural feedwater with a wide range of quality characteristics. For the first time, variants of the treatment of the concentrate formed in the ROP cycle have been proposed for the reuse of the latter by acidifying it in H-type cation- exchange filters charged with a weakly acidic cation-exchange resin. By admixing part of the filtrate processed in the H-type cation-exchange filters to the feedwater, the latter is acidified thus reducing the probability of formation of carbonaceous sediments and water consumption. The rest of the filtrate subjected to a conversion process is used as a constituent of the make-up feedwater of the heating system or potable water, which eliminates the discharge of the reverse-osmosis plant wastewater into the environment. Another feature of the proposed technology is that the H-type cation-exchange filters are integrated into a regenerant solution reuse circuit (RSRC). As a result, the consumption rate of sulfuric acid for regeneration equals the stoichiometric rate and the regeneration yields gypsum used to produce a binding agent for construction. The kinetics of separation of gypsum from the spent regenerant solutions with different chemical compositions was studied experimentally as applied to the RSRC conditions. The procedure of operating filters charged with the Lewatit CNP-LF cation-exchange resin was trialed under production conditions. It was established that the height of the filtering cation-exchange resin layer should be 1.0–1.5 m and the concentration of the regenerant solution should not exceed 0.8% at a rate of 10–15 m/h. The basic components of the technological scheme were trialed under production conditions on a water treatment plant in service.

Computational Study on the Effect of Shroud Shape on the Efficiency of the Gas Turbine Stage

Abstract: The last stages of powerful power gas turbines play an important role in the development of power and efficiency of the whole unit as well as in the distribution of the flow parameters behind the last stage, which determines the efficient operation of the exhaust diffusers. Therefore, much attention is paid to improving the efficiency of the last stages of gas turbines as well as the distribution of flow parameters. Since the long blades of the last stages of multistage high-power gas turbines could fall into the resonance frequency range in the course of operation, which results in the destruction of the blades, damping wires or damping bolts are used for turning out of resonance frequencies. However, these damping elements cause additional energy losses leading to a reduction in the efficiency of the stage. To minimize these losses, dampening shrouds are used instead of wires and bolts at the periphery of the working blades. However, because of the strength problems, designers have to use, instead of the most efficient full shrouds, partial shrouds that do not provide for significantly reducing the losses in the tip clearance between the blade and the turbine housing. In this paper, a computational study is performed concerning an effect that the design of the shroud of the turbine-working blade exerted on the flow structure in the vicinity of the shroud and on the efficiency of the stage as a whole. The analysis of the flow structure has shown that a significant part of the losses under using the shrouds is associated with the formation of vortex zones in the cavities on the turbine housing before the shrouds, between the ribs of the shrouds, and in the cavities at the outlet behind the shrouds. All the investigated variants of a partial shrouding are inferior in efficiency to the stages with shrouds that completely cover the tip section of the working blade. The stage with a unshrouded working blade was most efficient at the values of the relative tip clearance less than 0.9%.

Experimental Simulation of Hydrodynamics and Heat Transfer in Bubble and Slug Flow Regimes in a Heavy Liquid Metal

Abstract: For the confirmation of the claimed design properties of a reactor plant with a heavy liquid-metal coolant, computational and theoretical studies should be performed in order to justify its safety. As one of the basic scenarios of an accident, the leakage of water into the liquid metal is considered in the case of steam generator tube decompression. The most important in the analysis of such a kind of accidents are questions concerning the motion and heat exchange of steam bubbles in the steam generator and the probability of blocking the flow area owing to freezing coolant, since the temperature of boiling feedwater in the steam generator can become lower than the melting point of lead. In this paper, we present main approaches and relationships used for the simulation of the motion of gas bubbles and heat transfer between bubbles and liquid metal flow. A brief description of the HYDRA-IBRAE/LM computational code that can be used to analyze emergency situations in a liquid metal-cooled reactor facility is also presented. It should be noted that the existing experimental data on the motion and heat transfer of gas bubbles in a heavy liquid metal are insufficient. For this reason, in order to verify the HYDRA-IBRAE/LM code models, experiments have been performed on the cooling of liquid lead by argon and on the motion of gas bubbles in the Rose’s alloy. In particular, a change in the temperature of the coolant over time has been studied, and the void fraction of gas at different flow rates of gas has been measured. A detailed description of the experiments and a comparison of the results of the calculations with the experimental data are presented. The analysis of uncertainties made it possible to reveal the main factors that exert the greatest effect on the results of calculations. The numerical analysis has shown that the models incorporated into the HYDRA-IBRAE/LM code allow one to describe to a sufficient degree of confidence the process of cooling liquid lead melt when argon bubbles pass through it, simulating the flow of water into the liquid metal in the course of steam generator tube rupture.

Effect of Channel Geometry and Properties of a Vapor–Gas Mixture on Volume Condensation in a Flow through a Nozzle

Abstract: A method of direct numerical solution of the kinetic equation for the droplet size distribution function was used for the numerical investigation of volume condensation in a supersonic vapor–gas flow Distributions of temperature for the gas phase and droplets, degree of supersaturation, pressure, fraction of droplets by weight, the number of droplets per unit mass, and of the nucleation rate along the channel were determined The influence of nozzle geometry, mixture composition, and temperature dependence of the mixture properties on the investigated process was evaluated It has been found that the nozzle divergence angle determines the vapor–gas mixture expansion rate: an increase in the divergence angle enhances the temperature decrease rate and the supersaturation degree raise rate With an increase or decrease in the partial pressure of incondensable gas, the droplet temperature approaches the gas phase temperature or the saturation temperature at the partial gas pressure, respectively A considerable effect of the temperature dependence of the liquid surface tension and properties on gas phase parameters and the integral characteristics of condensation aerosol was revealed However, the difference in results obtained with or without considering the temperature dependence of evaporation heat is negligible The predictions are compared with experimental data of other investigations for two mixtures: a mixture of heavy water vapor with nitrogen (incondensable gas) or n-nonane vapor with nitrogen The predictions agree quite well qualitatively and quantitatively with the experiment The comparison of the predictions with numerical results from other publications obtained using the method of moments demonstrates the usefulness of the direct numerical solution method and the method of moments in a wide range of input data

Solar Heat Supply: World Statistics and Peculiarities of the Russian Experience

Abstract: Summarized data on the number and types of solar collectors and solar plants in use in various countries of the world, as well as on the market development dynamics and specific thermal capacity of operating solar plants per 1000 people, are given. State demand stimulation activities for solar plants are presented for some countries. It is noted that the modern trend in the improvement of solar collectors is the price reduction for materials with the substitution of copper for aluminum in the absorber manufacturing and the reduction of the energy-output ratio using soldering, crimping, and adhesive joints instead of welding. The minimal cost of the generated heat energy is provided by centralized solar heat supply systems. The values of the area of solar plants in Russia (2017), their structure, the features of solar collectors, including Russian-made, are presented. It is indicated that constructions of solar collectors with the optimal cost-effectiveness ratio are in demand on the Russian market. The information on the state of development and use of solar heat plants in Russia is summarized. The main design decisions and operating features of large solar plants in Narimanov, Astrakhan oblast (4400 m2), and in Ust-Labinsk, Krasnodar krai (600 m2), have been considered. It is established that the prospects of the Russian market are determined by the solar radiation in regions as well as the costs of solar collectors and replaceable conventional energy carriers. With allowance for the existing trends and peculiarities of regional development, the prospective Russian solar power market is estimated at 1400000–1500000 m2 (1100–1200 MW).

Results from Investigations of Torsional Vibration in Turbine Set Shaft Systems

Abstract: The article generalizes the results obtained from investigations of torsional vibration in the shaft system of the T-175/210-128 turbine set installed at the Omsk CHPP-5 combined heat and power plant Three different experimental methods were used to determine the lowest natural frequencies of torsional vibration excited in the shaft system when the barring gear is switched into operation, when the generator is synchronized with the grid, and in response to unsteady disturbances caused by the grid and by the turbine control and steam admission system It is pointed out that the experimental values of the lowest natural frequencies (to the fourth one inclusively) determined using three different methods were found to be almost completely identical with one another, even though the shaft system was stopped in the experiments carried out according to one method and the shaft system rotated at the nominal speed in those carried out according to two other methods The need to further develop the experimental methods for determining the highest natural frequencies is substantiated The values of decrements for the first, third, and fourth natural torsional vibration modes are obtained A conclusion is drawn from a comparison between the calculated and experimental data on the shaft system’s static twisting about the need to improve the mathematical models for calculating torsional vibration The measurement procedure is described, and the specific features pertinent to the way in which torsional vibration manifests itself as a function of time and turbine set operating mode under the conditions of its long-term operation are considered The fundamental measurement errors are analyzed, and their influence on the validity of measured parameters is evaluated With an insignificant level of free and forced torsional vibrations set up under the normal conditions of turbine set and grid operation, it becomes possible to exclude this phenomenon from the list of main factors influencing the crack formation processes in low-pressure rotors The importance of experimentally confirming the fact that the shaft system has been detuned from resonances at the 50 and 100 Hz excitation frequencies is pointed out

Steam Condensation from a Moving Steam-Gas Mixture

Abstract: To date, heat exchange has been studied to the greatest extent for the case of the condensation of pure still and moving steam as well as for the case of condensation from a still steam-gas mixture. There are hardly any papers available wherein a moving steam-gas mixture with a substantial content of noncondensable gases is considered. To investigate this process, an experimental workbench of the working section has been developed, which makes it possible to determine the local values of the heat transfer coefficient from the steam-gas mixture to the walls of cooled heat-exchange tubes at different parameters and velocities of the gas-steam mixture. In the first four rows of tubes of the working section, there is no cooling, and their function consists in a hydraulic stabilization of the flow. In the fifth and the sixth row of tubes, the wall temperature of the cooled heat-exchange tubes is measured for determining the heat transfer coefficients from the moving steam to the tube walls. The seventh row of tubes is also not under cooling. Measuring tubes with temperature sensors have been manufactured that make it possible to obtain the wall temperature for determining the heat transfer coefficient. The adopted scheme of steam motion and the measurement system make it possible to obtain correct results of the heat and mass transfer investigation in the course of steam condensation from a gas-steam mixture with a significant content of noncondensing gases. The studies on steam condensation from a moving steam-gas mixture have been carried out in the range of parameter ρw2 = 9.5 − 66 Pa and at a volume concentration of air in the steam amounting up to νair = 0.18. Convective heat transfer coefficient α values for the heat transfer from a moving steam-gas mixture to the wall of a cooling tube were obtained. At small values of parameter ρw2 = 9.5 Pa and the volume fraction of the air content νair = 0.06 in the steam, the average heat transfer coefficient exhibits a decrease by a factor of two as compared with that inherent in the condensation of almost pure steam. At the values of parameter ρw2 = 66 Pa and at νair = 0.06, the average heat transfer coefficient decreases by 1.3 times. The studies on almost pure steam are in good agreement with Berman’s dependence.

Geothermal Power Supply Systems around the World and in Russia: State of the Art and Future Prospects

Abstract: Solar and geothermal energy systems are shown to have received the widest use among all kinds of renewable sources of energy for heat supply purposes around the world. The power capacities and amounts of thermal energy generated by solar and geothermal heat supply systems around the world are presented by way of comparison. The thermal power capacity of solar heat supply systems installed around the world as of 2015 totaled 268.1 GW, and the thermal energy generated by them amounted to 225 TW h/year. The thermal power capacity of geothermal heat supply systems installed around the world totaled 70.3 GW, and the thermal energy generated by them amounted to 163 TW h/year. Information on the geothermal heat supply systems in the leading countries around the world based on the data reported at the World Geothermal Congress held in 2015 is presented. It is shown that China, with the installed thermal power capacities of its geothermal heat supply stations totaling 17.87 GW and the amount of thermal energy generated per annum equal to 48.435 TW h/year, is the world’s leader in this respect. The structures of geothermal heat supply systems by the kinds of heat consumption used around the world are presented. The systems equipped with geothermal heat pumps accounted for 70.95% in the total installed capacity and for 55.3% in the total amount of generated heat. For systems that do not use heat pumps, those serving for pools account for the largest share amounting to 44.74% in installed capacity and to 45.43% in generated heat. A total of 2218 geothermal wells with the total length equal to 9534 km (with 38.7% of them for heat supply purposes) were drilled in 42 countries in the period from 2010 to 2014. In Russia, geothermal heat supply systems are in operation mainly in Dagestan, in Krasnodar krai, and in Kamchatka. The majority of these systems have been made without breaking the stream after the well outlet. A cyclic control arrangement is also used. The combined geothermal and solar heat supply system with an installed thermal power capacity of 5 MW that is in operation in the Rozovyi settlement, Krasnodar krai, is described. In the summer time, the solar installation with a capacity of 115 kW is used for supplying hot water to residential houses and for restoring the geothermal well pore pressure. The basic process circuit and characteristics of the geothermal heat supply system with the installed thermal power capacity of 8.7 MW operating in the Khankala settlement, the city of Groznyi, are given. The specific feature of this system is that the spent geothermal heat carrier is reinjected into a specially drilled inclined well. Advanced geothermal heat supply technologies involving reinjection of the spent geothermal heat carrier, combination with binary power units, use of heat pumps for recovering the spent heat carrier, and protection of equipment from corrosion and deposits are proposed.