Dry Steam Research Articles

Thermodynamic analysis of high temperature cascade heat pump with R718 (high stage) and six different low-GWP refrigerants (low stage)

Decarbonizing industrial heating globally is a significant challenge, driving the integration of high-temperature heat pumps for heat recovery and electrification in the industrial sector. However, current high-temperature heat pumps with low global warming potential refrigerants face limitations in delivering high-temperature heat due to their restricted compressor discharge temperature or require several compressors/intercoolers. To address these issues, a novel high-temperature cascade heat pump system is proposed, utilizing water (R718) in the high stage, while selecting one among six low GWP refrigerants (R1234ze(Z), R1233zd(E), R1336mzz(Z), R600, R600a, R601) in the low stage, with single compressor at each stage. To manage high discharge temperatures of high stage, liquid water injection is applied during high stage compression, modeled for both wet and dry steam. The model is validated against available experimental data with maximum error less than 5 %. Further, the effectiveness of the internal heat exchanger in low stage cycle is assessed for all investigated low stage refrigerants. Results reveal that R718 + R600 offers the optimal refrigerant working pair, achieving a maximum COP × VHC of 2895.1 kJ m−3 for delivering high temperature heat at water condensation temperature of 190 °C and recovering heat from low temperature waste energy of 50 °C.

An investigation comparing various numerical approaches for simulating the behaviour of condensing flows in steam nozzles and turbine cascades

The process of condensation takes place within the low-pressure stages of the steam turbine when undergoing rapid expansion. The dry supercooled steam turns into very tiny liquid droplets, and the resulting wet steam mixture causes additional losses and maintenance problems. Accurate simulation of steam condensing flows helps to obtain accurate information about the thermodynamics of such flows and use this information in the design of highly efficient steam turbine stages. In this study, by using the available numerical models in commercial CFD codes, seven cases are considered for simulating steam condensing flows. The important difference between these cases is the use of different condensation models and different equations of state to calculate the thermodynamic properties of wet steam. The objective of this research is to identify an appropriate model that can be used to simulate the flow of steam condensation effectively. In recent studies, it is still necessary for further improvement of the modelling methods because the numerical results did not fully match the experimental findings, underscoring the persisting uncertainties within this domain. The current study explores various condensation models and equations of state for calculating the thermodynamic properties of wet steam. This diversity of approaches is novel and allows for the comparison of different models to determine the most suitable one for effective flow simulation. The geometries of the IWSEP nozzle (International Wet Steam Experimental Project) and linear cascade of the last-stage rotor blades were considered. To identify the most appropriate model for the simulation of steam condensing flows, the numerical results are validated against in-house experiments. The results indicate that combining the Young droplet growth model with the Vukalovich and Young equations in cases 1 and 2 is not a suitable method for modelling steam condensing flows. However, cases 3 & 4, which are the combination of Gyarmathy and Fuchs-Sutugin droplet growth models with NIST real gas models, are the most appropriate ones. The findings of this research confirm the high sensitivity of the modelling of such flows, and emphasize that the necessary care should be taken in choosing the appropriate numerical model.

Environmental performance of nonthermal plasma dry and conventional steam reforming of methane for hydrogen production: Application of life cycle assessment methodology

The environmental performance of nonthermal plasma assisted dry reforming of methane (NTP-DRM) for hydrogen production from methane rich natural gas is investigated and compared with the current state of the art steam reforming technology through a cradle-to-gate life cycle assessment (LCA). The NTP-DRM technologies studied in this analysis include dielectric barrier, microwave, and pulsed plasma discharges. Due to the level of technology the study is considered as the prospective LCA of selected types of NTP-DRMs for hydrogen production. Of these, the NTP-DRM using microwave and pulsed plasma presented better environmental performance. The impact categories include midpoints levels applying TRACI 2.1 and AWARE for the water scarcity, using ecoinvent 3.8 and US NETL databases. The scenario analysis regarding carbon dioxide, electricity, and natural gas sources, revealed the highly dependency of NTP-DRMs technologies environmental performance to the energy efficiency of the processes. In terms of steam reforming of methane (SRM) despite the main contribution of steam use in the technology environmental performance, the uncertainty analysis showed higher sensitivity to natural gas input. Investigation showed that using renewable energy sources can have significant improvement regarding NTP-DRMs environmental performance and specifically global warming potential. Accordingly, at their current reactant conversion and product selectivity reaching the energy use of eV per molecule of reactant equal or less than 2, can be a proper target for the studied best case NTP-DRM to make their environmental behavior competitive with the state-of-the-art SRM technologies.

Suitability of a superheated steam dryer for drying sardines

The suitability of a superheated steam dryer for drying sardines was investigated. Proximate composition (moisture, crude protein, crude fat, ash, and crude fibre; minerals-calcium, zinc, iron) for fresh, oven dried (OD) at 100 °C, oven dried (OD) at 120 °C and superheated steam dried (SSD) sardines at 120 °C was evaluated and the results reported on a dry matter basis. There were significant differences (p<0.05) in moisture, crude fat, and ash content among fresh and dried samples, but not for crude protein or crude fibre. The crude protein % content of fresh, OD at 100 °C, OD at 120 °C, and SSD, was 78.17, 78.40, 75.77, and 76.05 and crude fibre % was 0.59, 0.12, 0.02, and 0.13, respectively. The SSD sardines had the highest fat content (11.8 %) and the fresh sardines had the lowest (8.1 %). There was a significant difference in calcium content (p<0.05) but not for zinc and iron content. Overall, SSD retained the nutrients of sardines well.

Economic feasibility of retrofitting blowdown heat recovery system using steam dryer to lignite-fired power plant for reduced fuel consumption

Blowdown is responsible for heat losses in boiler systems. The main objective of this paper is to propose a system to recover blowdown heat using steam dryer. The system consists of a flash tank, a steam dryer, and an air preheater. The flash tank is used to produce flash steam that is supplied to the steam dryer. Fuel moisture is removed in the steam dryer, resulting in fuel with lower moisture content and exhaust vapor. Exhaust vapor is supplied to the air preheater to increase air temperature before combustion. Due to lower fuel moisture content and higher air temperature, exhaust flue gas temperature can be decreased by adding air heater area. An analysis was performed to determine the payback period for the investment cost of the proposed heat recovery system. It was demonstrated that retrofitting a power plant with this system led to increased energy efficiency of the power plant. A case study of 250-MW existing power plant operating at the boiler pressure of 12.34 MPa was considered. Simulation results indicate that the power plant retrofitted with this blowdown heat recovery system consumes 0.87% less fuel than the power plant without this system. The payback period or the investment in this system is 7 years.

MATHEMATICAL MODELING OF THE PROCESS EVAPORATION OF MULBERRY FRUITS JUICE

When evaporating the juice of mulberry fruits, a differential equation was obtained for changing the amount of liquid over time, expressed as a material balance, converted to the liquid level in the separator of the evaporator, an expression for the density of the liquid, its flow rates at the inlet and outlet of the apparatus, the differential equation for changing the temperature of the liquid over time. Using the reference data of the state of water and steam, equations for the temperature, enthalpy of liquid and dry steam are obtained. A system of equations has been obtained - a mathematical model of the dynamics of the process of liquid evaporation in a single-vessel vacuum evaporator. Using the SIMULINK part of the MATLAB program, a computer model for solving equations was compiled. Some results of studies of the evaporation of mulberry juice on a five-case vacuum evaporator are given, the optimal number of stages of the complex is found.
 Since the calculation of the process of evaporation of water vapor is associated with the thermodynamic parameters of the state of water, it is necessary to obtain equations for the dependence of the boiling point of water, the heat of vaporization of water, the enthalpy of steam, the enthalpy of water on pressure. Experimental data have been obtained for a long time, they are successfully used, however, there are no uniform empirical equations used by all researchers.
 Using the capabilities of the MATLAB program, by statistical processing of tabular data, we obtain empirical equations in the form of polynomials for the state of water and water vapor, describing the real picture with an accuracy of 98% or more.

The recovery of blowdown heat using steam dryer in biomass power plant

The main objective of this paper is to propose the blowdown heat recovery system using a steam dryer. A flash tank is used to reduce blowdown water pressure and generate flash steam. Flash steam is supplied to the steam dryer to decrease fuel moisture content. Exhaust vapor vented from the steam dryer is also used to increase air temperature in an air heater. Furthermore, due to decreased fuel moisture content and increased air temperature, the exhaust flue gas temperature may be decreased by increasing the air heater surface area in the boiler. This method of blowdown heat recovery has never been proposed before. Therefore, it may be considered as knowledge gap that is worth an investigation. The use of blowdown heat for steam drying is compared with the use of blowdown heat for feed water heating. Simulation results show that using blowdown heat for steam drying results in a significantly larger net power output. Furthermore, the integration of this heat recovery system is economically feasible.

Sustainable Superheated Steam Drying of Unripe Banana (Musa acuminata cv. Hom Thong): Effects on Resistant Starch and Physicochemical–Functional Properties

AbstractUtilizing unripe banana flour (UBF) has gained considerable interest recently due to its functional components, particularly its resistant starch (RS), which could control obesity and diabetes. This study explores the novel approach of superheated steam drying (SSD) to produce UBF. Banana slices with 1, 2, or 3 mm thicknesses are dried using SSD at 75, 85, 95, or 105 °C. The resulting UBFs are analyzed for starch content and physicochemical–functional properties and compared with conventional hot‐air drying (HAD) at 55 or 75 °C. Replacing HAD with SSD saves 75% of the drying time and increases the whiteness index. SSD‐produced UBF has a high RS content, excellent resistance to enzyme digestion, and potential beneficial health effects. At the same time, scanning electron microscopy shows that the SSD‐ and HAD‐dried samples have similar morphological characteristics. The swelling power, water solubility index, and water holding capacity of the UBF increases rapidly above 70 °C. The peak viscosity, breakdown, and setback of SSD‐dried UBF are greater than those of HAD at the same temperature. Technological properties (high hydration value and peak viscosity) and reduced processing time make SSD‐dried UBF a potential natural thickening ingredient for the food industry.

Reduction in Fuel Consumption in Biomass-Fired Power Plant Using Hybrid Drying System

Fuels used in biomass power plants usually have high moisture contents. Two methods of fuel drying that have been proposed are steam drying and flue gas drying. Steam drying requires extracted steam as its energy source, whereas flue gas drying requires flue gas leaving the boiler as its energy source. Previous works have mostly been concerned with the integration of either dryer in a power plant. There have been a few investigations on the integration of both dryers. This paper proposes a novel hybrid drying system that uses a steam dryer to dry a portion of the fuel. Exhaust vapor from the steam dryer is then used for the heating of combustion air, which increases the flue gas temperature. The higher flue gas temperature increases the potential of the flue gas dryer, which is used to dry another portion of the fuel. It is shown that the hybrid drying system is capable of reducing fuel consumption to 7.76% in a 50 MW power plant. Furthermore, the integration of hybrid drying is shown to be economically justified because the simple payback period is 4.28 years.

CYCLE DIAGRAM OF GEOTHERMAL ENERGY

Link for citation: Yankovsky S.A., Lavrinenko S.V., Tsibulskiy S.A., Yankovskaya N.S., Gamov D.L. Cycle diagram of geothermal energy. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 122-136. In Rus. The relevance of the research is caused by the need to develop alternative and environmentally friendly energy sources in conditions of global warming. The development of geothermal energy will make it possible to produce thermal and electric energy without emissions of CO2 into the environment and reduce the dependence of the energy sector on hydrocarbon raw materials. The main aim of this study is a comprehensive analysis of the features of geothermal power plants, including the existing technologies for converting geothermal energy to provide consumers of electric and thermal energy. Objects: diagrams of geothermal power plants operating in different geographical and climatic conditions, as well as their working fluids. Methods: analytical review of thematic publications using the materials of the databases of the RSCI, Scopus and Web of Science, a comparative analysis of the effectiveness of geothermal power plants for various indicators. Results. Currently, there are about 400 geothermal power plants in the world. The active development of geothermal energy is caused by environmental friendliness, low cost of energy produced, minimal operating costs, lack of dependence on atmospheric influences, and the absence of the need to burn fuel, etc. At the same time, most of the world's geothermal power plants use the energy of a geothermal source with a water temperature of 100–200 °C. Among the main thermodynamic cycles and thermal schemes implemented, it is possible to single out direct cycle geothermal power plants with one-stage and two-stage separation of a geothermal source, with direct supply of dry steam to the turbine, binary and combined versions. The analysis shows that direct cycle geothermal power plants have the lowest cost of installed electrical power due to the relative simplicity and high thermal efficiency, but require high parameters of a geothermal source. On the other hand, binary geothermal power plants have the highest unit cost, but can be implemented on geothermal sources with relatively low water parameters, which was the main reason for their greatest spread in the world. At the same time, the implementation of a binary geothermal power plant with a Organic Rankine сycle has a number of advantages compared to the thermodynamic cycles of Kalina, Stirling and Brighton, among which the main ones are relative ease of adaptation and application, as well as low maintenance costs.

Performance degradation analysis of a medium pressure superheater due to tube deactivation

Steam is essential in petrochemical industries for the transportation of thermal energy and usage in some reforming process. Superheaters are heat exchangers that convert saturated steam to dry steam by utilizing waste heat from the flue gas stream. Medium pressure steam superheaters are prone to tube deterioration due to service at elevated temperatures and erosion from the presence of liquid phase in the steam, leading to tube plugging after tube failure. This reduces the overall surface heating area of the superheater. Relations between the tube plugging practice and the energy dynamics of the superheaters are important for engineers to identify the responses of the superheater for operation planning, and this issue has not been extensively explored academically. This article analyses the deterioration of superheater performance due to reduction of surface heating area based on operational data of a petrochemical steam generation line. The objective is to find relations between the effect of tube plugging on the states of both steam and flue gas streams, as well as its impact on the overall energy exchange. The operating conditions of a superheater at two separate service years, before (year 2014) and after (year 2017) tube plugging, were compared through the first law energy analysis. The average steam inlet temperatures were between 248 °C and 250 °C, at flow rates between 70 and 90 ton/hour. The analysis indicated that 0.3 to 0.8 % increase in inlet energy is required for every plugged tube to compensate for the reduction of heating surface. At 3 % reduction of heating surface area, the heat exchanger effectiveness decreases by an average of 11 % that also leads to a lower steam temperature output by approximately 6% from the design operating temperature. These results would assist steam engineers to analyse changes to the energy economics of the whole plant and decide the feasibility of replacing existing superheaters with new ones. Also, another significant finding to be considered by steam engineers is that the current practice of increasing the steam flow rate does not offset the loss of energy effectiveness due to tube plugging.

Effect of TiAlNbCrSi Alloy Microstructure Produced by Mould Casting (MC) or Electron Beam Powder Bed Fusion (EB-PBF) on Scale Grown Under Dry Air and Steam

TiAl parts fabricated with additive manufacturing have begun to find applications in car and aviation industry. Optimization of their properties concentrates on introduction of new alloying additions improving the TiAl ductility and oxidation resistance. Their effect on the mechanical properties was worked out quite well, but the knowledge how they affect the oxidation processes is still limited. Therefore the present experiment was aimed at investigation of scale grown over mould cast (MC) and electron beam powder bed fusion (EB-PBF) Ti–48Al–2Nb–0.7Cr–0.3Si (at. pct) alloys. It was conducted at 650 °C for 1000 hours both in dry air and steam covering early stages of this process. The scale microstructure, chemical and phase composition was examined with the transmission electron microscopy (TEM). Applied treatment caused development of three-layer scale, i.e. with major portions of R-TiO2 + α-Al2O3/R-TiO2/α-Al2O3. The one formed during dry-air oxidation of the EB-PBF alloy was most compact. Steam oxidizing changed morphology of rutile present at its surface from rod/plate-like into whiskers. The Si turned out to be especially active during scale growth diffusing up to its surface. The presence of steam further increased mobility of both Si and Cr rising their presence in the upper part of the scale. The Nb was found to accumulate within the substrate area adjoining to the scale. Refinement of EB-PBF microstructure as compared with the MC alloy resulted in promoting reaction at the scale/substrate front contributing significantly to development of thicker oxide coating and nitrides bearing oxidation affected zone.

Research on dehumidification optimization of steam turbine wet steam stage hollow stator cascade heating

The secondary water droplets in the steam turbine wet steam stage are easy to cause water erosion damage to the rotor cascade, and there is a large speed slip between the main steam flow and the secondary water droplets, which will seriously affect the safe and stable operation and reduce the efficiency of the steam turbine. Secondary water droplets are formed when the water film deposited on the stator blade surface falls off at the trailing edge. Therefore, controlling the formation of a water film on the stator blade surface plays an important role in improving the efficiency and safety of the steam turbine wet steam stage. Based on the current research situation at home and abroad, taking the Dykas cascade as the research object, it is found that the covering area of dry steam film on blade surface expands with the increase of temperature and flow of hot steam inlet. With the increase of hot steam back-pressure, the wetness of blade surface increases. When the average heat flux on the blade surface reaches 5000W/m2, there will be no water film falling off the blade surface. By orthogonal test, the expression between the average heat flux on the blade surface, the inlet temperature, the flow rate and the back-pressure was obtained. The research results can provide reference for the parameter design of steam turbine hollow stator heating dehumidification.

Stress Corrosion Cracking in Metal Alloys Exposed to Geothermal Fluids with High Non-Condensable Gas Content

Geothermal energy production equipment operates under a host of corrosion conditions. Field corrosion testing of metals and alloys is a key part of plant design in most geothermal systems. This work focuses on field testing selected metal alloys in geothermal fluid containing a very high concentration of non-condensable gases (NCG) to evaluate the predisposition to stress corrosion cracking (SCC). SCC is caused by the simultaneous existence of stress and susceptible material in a corrosive environment, such as intermittent shut-down and discharge activities.U-bend coupons made from one standard API carbon steel and five different corrosion-resistant alloys were exposed for 95 days to almost dry steam with an enthalpy of 2745 kJ/kg at 307 °C and NCG content of 13.8% by weight.The analysis of the different coupons shows that L80 Type 1 carbon steel is the most susceptible to this corrosion damage. However, the risk of this occurring in tested well is likely low due to high temperatures and the scarcity of aqueous phase and chloride in the geothermal fluids.

Effects of Vacuum Packaging and Chilling Storage on the Microbiological Changes of the Superheated Steam Dried Sardines

Fish are important sources of protein and micronutrients for combating malnutrition. Since fish are highly perishable, methods for processing and preserving them should be the main focus to increase their shelf life and maintain their quality. The present study assessed the effectiveness of the superheated steam dryer (SSD) in processing sardines, and examined the effects of packaging and storage conditions on their microbiological quality. Sardines collected from the Mafia Island were dried in SSD, air-packed and stored at room temperature (AR), air-packed and stored at chilling temperature (AC), vacuum-packed and stored at room temperature (VR), and vacuum-packed and stored at chilling temperature (VC) for 49 days. Following drying, the total viable bacterial counts (TVBC) and total yeast and mould counts (TYMC) both decreased from the initial values of 9.14 (TVBC) and 2 (TYMC) log CFU/g in the fresh samples to 0.00 log CFU/g. The AR samples had the highest microbial growths during storage (7.48 (TVBC) and 2.82 (TYMC) log CFU/g), whereas the VC samples had the lowest (1.79 (TVBC) and 1.42 (TYMC) log CFU/g). The AR treatment was rejected within 21 days, whereas the AC, VR, and VC treatments prolonged the sardines’ shelf life throughout the storage time.
 Keywords: Superheated steam dryer, sardine, microbial analysis, vacuum packaging, chilling storage

Assessing economic feasibility of retrofitting steam dryer and steam-air preheater to existing biomass power plant

Conventionally, the thermal design a biomass power plant is aimed at maximizing the energy efficiency by using extracted steam to increase feed water temperature in feed water heaters and installing heating surface areas of heat exchangers in boiler to recover flue gas energy. The temperature of flue gas at the boiler outlet must not be so low that a risk of acid corrosion is unacceptable. The energy efficiency can also be improved by reducing fuel moisture content in steam dryer and increasing air temperature in steam-air preheater. However, both devices require extracted steam, which is already used for raising feed water temperature in an existing power plant. In this paper, it is hypothesized that retrofitting steam dryer and steam-air preheater to an existing power plant can improve the energy efficiency. Performances of the existing power plant and the retrofitted power plant integrated with steam dryer and steam-air preheater are compared. Simulation results indicate that, despite lower final feed water temperature in the retrofitted power plant, the retrofitted power plant is more energy efficient than the existing power plant. Economic assessment is carried under the condition that both power plants generate the same power output, which means that the retrofitted power plant consumes less fuel than the existing power plant. The payback period for the retrofitting investment is approximately 7 years.

DESIGN CHARACTERISTICS OF THE HORIZONTAL STEAM GENERATOR PGV-1000

The materials of the article consider the design characteristics of horizontal steam generators PGV-1000 for WWER NPPs. The NPP steam generator, in particular the PGV-1000 steam generator, is a specific heat exchange unit. This unit, together with a nuclear reactor and a steam turbine, is one of the main equipment of multi-circuit (double-circuit) steam turbine NPPs. The steam generator produces working steam using heat dissipated from the reactor core by the cooling medium and sent to the heat exchange surface of the steam generator. NPP steam generators, connecting the contours of the coolant and the working substance, equally belong to each of them. The heat-absorbing medium in the steam generator is the working substance (water, steam). PGV-1000 type NPP steam generators with pressurized water reactors produce dry saturated steam. The requirement to maintain high purity of the coolant is due to the heat transfer surfaces of such steam generators made of austenitic stainless steel with electropolished surfaces. WWER reactors do not allow the coolant to boil in the core, so the temperature of the coolant at the outlet of the reactor (at the inlet to the steam generator) is always lower than the saturation temperature corresponding to the water pressure in the coolant circuit. Underheating of the coolant to the saturation temperature (approximately 25 ÷ 30 °С) guarantees the exclusion of vaporization even in the most loaded reactor channels. The design characteristics of modern horizontal steam generators such as PGV-1000 of various modifications provide high technical and economic performance of NPP units with WWER-1000 and high maintainability, which allows to extend the service life of domestic NPPs.

Instant controlled pressure-drop assisted pressing for defatting and dewatering of yellow mealworm larvae: process study and optimisation

Insects are gaining interest as a sustainable and highly nutritious source of proteins and lipids for food and feed production sectors. Insect bio-refinery includes lipid extraction by pressing, dewatering, microbiological decontamination, and protein fractionation. The present study is experimenting the use of instant controlled pressure-drop (DIC), an emerging technology, for treating yellow mealworms and evaluating its combined effects on insect bio-refinery steps. A preliminary study allowed identifying the optimal hydraulic pressing conditions forTenebrio molitor larvae. Then, establishing an experimental design with DIC operative parameters of the saturated dry steam absolute pressure and treatment time ranging between (0.15 and 0.45 MPa) and (15 and 35 s), respectively, allowed identifying the DIC impact as a pretreatment on different larvae properties. It was possible to identify the optimal pressing parameters at 6 MPa, 60 °C, 2 cm of thickness, and 0.15 mm/s as initial piston speed. Moreover, DIC performed at 0.15 MPa for 25 seconds stood as an efficient killing method. Thanks to the changes in the membrane’s structure it provokes, DIC treatment modified larvae properties, ensured a partial expulsion of the matter (up to 0.47 g/g dry basis (db)), and resulted in larval expansion (up to 67%) which resulted in a decrease in the apparent density. As for the chemical properties, the larvae and larvae juice colours were found to become lighter as we increased the treatment conditions, which might be caused by the inactivation of oxidative enzymes. Moreover, severe DIC operative parameters decreased the pressing yields from 68 to 55%, possibly caused by protein aggregation and denaturation phenomena that prevent molecules from coming out by pressing. However, the water activity and moisture, lipid, and protein contents remained unaffected.

A comprehensive analysis of binary mixtures as working fluid in high temperature heat pumps

High-temperature heat pumps represent an emerging technology with a great potential in supplying clean heat to energy intensive industries. Suitable refrigerants for high-temperature heat pumps (up to 200 °C) have not been identified yet. This work aims to analyze the performance of binary mixtures as working fluid in high-temperature heat pumps delivering heat up to 200 °C with a special focus on zeotropic mixtures. Three relevant processes with different heat sources and sinks were selected to integrate the heat pump: latent/latent (e.g. distillation processes), latent/sensible (e.g. superheated steam drying), sensible/sensible (e.g. pressurized water production). To determine the best working fluid and cycle configuration for each process, an optimization framework was developed with the maximization of the coefficient of performance as objective function. For the first case with a latent heat sink and heat source, the best performing binary mixtures were near-azeotropic with slightly higher coefficient of performance compared to pure fluids. Moreover, binary mixtures provided several advantages such as the reduction of the compression ratio and compressor outlet temperature compared to pure fluids. A similar behavior was observed for the second case with a latent heat source and a sensible heat sink. For the third case with a sensible heat sink and heat source, binary mixtures resulted in a higher coefficient of performance (10 %) compared to pure fluids. Most of the best performing mixtures were hydrocarbons with high risk of flammability. Water/ammonia was the only mildly-flammable mixture among the top mixtures.

Mathematical model of the horizontal steam generator PGV-1000

The materials of the article consider the design characteristics of horizontal steam generators PGV-1000 for WWER NPPs. The NPP steam generator, in particular the PGV-1000 steam generator, is a specific heat exchange unit. This unit, together with a nuclear reactor and a steam turbine, is one of the main equipment of multi-circuit (double-circuit) steam turbine NPPs. The steam generator produces working steam using heat dissipated from the reactor core by the cooling medium and sent to the heat exchange surface of the steam generator. NPP steam generators, connecting the contours of the coolant and the working substance, equally belong to each of them. The heat-absorbing medium in the steam generator is the working substance (water, steam). PGV-1000 type NPP steam generators with pressurized water reactors produce dry saturated steam. The requirement to maintain high purity of the coolant is due to the heat transfer surfaces of such steam generators made of austenitic stainless steel with electropolished surfaces. The design characteristics of modern horizontal steam generators such as PGV-1000 of various modifications provide high technical and economic performance of NPP units with WWER-1000 and high maintainability, which allows to extend the service life of domestic NPPs.