The anti-freezing operation parameters of indirect air-cooled finned bundle are insufficient at present. To solve this problem, this research firstly concludes the anti-freezing model of finned tube bundle, including the thermal equilibration equations, water side and air side transport equations, as well as anti-freezing constrains. Secondly, based on the co-current and counter-current air-cooled finned tube bundles, the critical anti-freezing characteristics and margin are analyzed. Then, the critical values are discovered for finned tube bundles with middle inlet, left inlet and side inlet patterns. The research shows that, as the ambient temperature or inlet water temperature reduces, as well as the ambient wind increases, the critical anti-freezing water flow rate ascends. Besides, when the inlet water temperature decreases, the wind effects get intensified. The anti-freezing performance of counter-current finned tube bundle is inferior to that of the co-current type, meanwhile the difference becomes expanded if the wind increases or water inlet temperature decreases. The effects of inlet water temperature elevation on anti-freezing margin can be classified into three levels, which are termed as obvious range (0 ℃, 10 ℃], slow range (10 ℃, 20 ℃], and stable range (20 ℃, 40 ℃]. Therefore, power plants should not always increase the water flow rate for anti-freezing operation. The air-cooled finned tube bundle with middle inlet pattern has better anti-freezing performance than others, so it’s suggested preferentially for coal-fired or nuclear power plants. This research may provide guidelines of anti-freezing operation for dry-cooling power stations in China.

Flue gas flow is one of the key factors affecting the accuracy of carbon monitoring, and the complex flow field environment with uneven velocity distribution and changing with unit load is the main factor impeding the accurate measurement of flue gas flow. By taking a chimney inlet flue of a 660 MW unit in a power plant as the research object, the influence of the number of points and the layout of the process on measurement accuracy of the flowmeter with four different measurement principles was compared and analyzed based on numerical simulation results of the flue gas flow field. The results show that, the multipoint Pitot tube flowmeter has better adaptability to the complex flow field environment compared with the matrix flowmeter. When the number of measuring points is 28, the deviation of the matrix flowmeter is 1.54 times that of the multipoint Pitot tube flowmeter. The measurement accuracy of the light scintillation flowmeter is greatly affected by the elevation of the installation position, with the maximum deviation being 23.3 times the minimum deviation. This indicates that the light scintillation flowmeter has poor adaptability to complex flow field environments. The ultrasonic flowmeter can be installed obliquely and in multiple channels, with a more flexible and varied process layout, significantly improving its adaptability to complex flow fields. The dual-channel arrangement can control the deviation within ± 1.5%. The research results provide important theoretical basis and data support for the selection of flow meter equipment and process design, and have important theoretical research and engineering application value.

The existing thermal power flexibility renovation plan is difficult to eliminate the thermal system life loss and unit safety operation risks caused by frequent and rapid load changes. In order to effectively ensure the safety, economy, and health of thermal power units participating in grid peak shaving, a full capacity and long life peak shaving technology scheme for thermal power units based on the coupling of solid oxide electrolysis cell hydrogen production technology (SOEC) and burner local oxygen enriched combustion technology (OEC) is proposed and constructed. Taking an ultra supercritical 1 000 MW secondary reheat unit as an example, energy efficiency calculation is conducted on the SOEC-OEC system participating in power grid peak shaving at a depth of 70%~100%, and the results are compared with that of the conventional alkaline water electrolysis hydrogen production (ALK) system. The results show that, the energy efficiency of the extraction electrolysis hydrogen production system in SOEC-OEC is as high as 49.86%, which is about 26.40% higher than that of the ALK system. The oxygen enriched combustion system can reduce the boiler exhaust gas by up to 23.7%, reduce the unit coal consumption by 2.83 g/(kW·h), and reduce the carbon emissions by about 2.82 t/h. In addition, the SOEC-OEC system can also bring excess peak shaving subsidy benefits, hydrogen sales revenue, oxygen enrichment and coal saving and carbon reduction revenue, as well as equipment life extension benefits to the unit, fully ensuring the economic efficiency, safety, and environmental protection of the thermal power peak shaving process.

In order to study the microstructure properties of different regions of welding heat affected zone (HAZ) of 1 000 MPa grade ultra-high strength steel, the samples of test steel at different peak temperatures of thermal cycle were prepared by welding thermal simulation technique, and the impact toughness of different regions of HAZ was studied through Charpy impact tests. The results showed that, in the subcritical region of HAZ (SCHAZ), the intercritical region of HAZ (ICHAZ) and the fine-grained region of HAZ (FGHAZ), the samples had relatively high impact absorption energy, crack propagation energy and dynamic impact toughness, and a large area of fiber region and shear lip formed on the fracture surface. Toughness dimples of different sizes can be seen at the microscopic level. The samples had good impact toughness. In the coarse-grained region of HAZ (CGHAZ), all impact data of the samples sharply decreased, and the fracture showed a macroscopic brittle fracture, almost all of which are radiological regions. At the microscopic level, it showed quasi cleavage fracture characteristics, indicating that the resistance to crack propagation decreased, and the time for stable propagation decreased after crack initiation, and the instability propagation was fast. The impact toughness of the samples deteriorated, and the CGHAZ region was a ductile valley region in HAZ. The results showed that the coarse grains and the coarse M-A island were the main causes of embrittlement in the CGHAZ region. The conclusion lays a theoretical foundation for the selection, development and engineering application of 1 000 MPa grade ultra-high strength steel in hydropower projects.

The gas cooler, as an essential heat exchange device in Brayton cycle system, has a significant influence on structural compactness and operational efficiency of the cycle system. The performance and influencing factors of a cross flow printed circuit heat exchanger (PCHE)-plate-fin gas cooler are analyzed. A calculation model is established for this type of heat exchanger, and a MATLAB program is written to verify its reliability. Based on this, the coolers are designed, and the power density is above 1 MW/m³, indicating the cooler is compact heat exchanger. Moreover, the design and performance analysis of the heat exchanger are carried out under varying working conditions, and the change law of the pressure drop and heat transfer performance of the gas cooler with the inlet state of the circulating working medium and cooling air is given. The pressure drop and heat transfer performance are compared when the working medium of the Brayton cycle is supercritical carbon dioxide, nitrogen and air. The results show that, the change of cold and hot fluid mass flow has the most obvious influence on the heat transfer performance. The research has reference significance for the design and operation of Brayton circulating air cooling heat exchangers.

To address the mismatch between electricity supply and demand caused by the intermittency and fluctuation of renewable energy sources, a combined cycle energy storage and power generation system incorporating a closed supercritical carbon dioxide (S-CO₂) cycle and a high-temperature heat pump is proposed, which is an innovative exploration of the Carnot battery form. Through energy exchange via molten salt heat storage and water cold storage devices, this system efficiently integrates the heating process of the heat pump cycle with power generation process of the S-CO₂ cycle, which achieves a favorable round-trip efficiency for the energy storage power generation system. Simulations are performed to calculate the typical operational parameters and thermodynamic performance of the combined cycle, and to analyze the influence of main parameters of the S-CO₂ cycle on the overall efficiency of the system. The results indicate that, increasing the inlet temperature of the expander aids in enhancing the overall cycle efficiency, achieving an optimal electrical-to-electrical efficiency of 62.8%, while reducing the demand for heat storage molten salt. Elevating the inlet gas parameters of the main compressor will lead the system efficiency to reach a peak value, beyond which the overall cycle efficiency no longer increases. The optimal bypass ratio for the main recompressor is 0.35, which allows the system to achieve optimal efficiency. The optimal operating conditions of the S-CO₂ cycle system are identified, offering an electrical-to-electrical efficiency that is 7.98% higher than a reversible Brayton system under the same conditions.

A new kilowatt-class methane reforming hydrogen production reactor is designed, using solid oxide fuel cell exhaust gas for heat supply. The system can make full use of the waste heat and combustible components in the exhaust gas to form a compact and efficient natural gas power generation system. Computational fluid dynamics was used to numerically simulate the combustion and reforming reactions in the reactor. The results show that the solid oxide fuel cell anode and cathode exhaust gases can be stably burned in the reactor to form a high-temperature flame of 1 486 ℃ to provide heat for the methane steam reforming reaction. In the reaction tube, the concentrations of H₂O and CH₄ continue to decrease along the way. Due to excess water vapor, the H₂O volume concentration at the outlet is 35%, the hydrogen concentration volume fraction is 45%, and the methane conversion rate reaches 90%. Nickel catalyst has a high thermal conductivity, so the temperature difference between the inside and outside of the reaction tube is less than 15 ℃. At the same time, experimental research was used to obtain data such as temperature, methane concentration and methane conversion rate in the reactor. The simulation results were compared to verify the accuracy of the numerical simulation.

In recent years, numerous incidents of harmonic resonance accidents involving new energy power stations have occurred both domestically and internationally. The frequency scanning method, characterized by its simplicity of operation and clear physical significance, has been widely employed in engineering for the assessment of system resonance. When establishing electromagnetic transient simulation models for large-scale new energy power stations and conducting frequency scans, it is common to substitute a single or multiple generators for the actual power station to reduce modeling complexity. However, the applicability of this approach in addressing high-frequency harmonic resonance issues has not been effectively revealed. To address this gap, this study takes a large-scale photovoltaic power station as an example and employs a bottom-up modeling approach to establish a detailed impedance model for the photovoltaic power station. Building upon this, a dynamic equivalent model is developed using the principle of equal power loss. The two models are then thoroughly compared and analyzed based on actual field station parameters. The research findings indicate that the series impedance of the collector lines has a minimal effect on the harmonic model. As a result, the study proposes a simplified dynamic equivalent model replacing the π-type circuit with a ground capacitor. The results demonstrate that the equivalent model established through the equal power loss method accurately reflects the harmonic resonance characteristics of the photovoltaic power station. Additionally, the model neglecting the inductance of the collector lines proves applicable for analyzing the mid-to-low frequency harmonic resonance in photovoltaic power stations.

In order to ensure safe operation of secondary cycle and reliability of steam generator, it is of great significance to reduce corrosion of equipment & piping of the cycle in nuclear power plant. With the deepening research on organic amines and the continuous accumulation of operation experience, the industry realized that the metal corrosion in the cycle during plant operation depends mainly on the pH at the operating temperature of locations of the cycle, i.e. pHt. To improve pHt at the locations of the cycle, performance characteristics of the main organic amines and their combinations are analyzed in this paper. Combined with the application experience and actual effects of organic amines at home and abroad, the application strategy of the main organic amines and their combinations are discussed and proposed, and the improvement suggestions are put forward with regard to current amine application status of the secondary cycle in China. Selections of amine or its combination should calculate the pHt at various locations to meet anti-corrosion requirements and evaluate effects on service life of resin beds in the system. Ethanolamine with stronger basicity and low volatility is suitably used in plant in which corrosion product is mainly from drain systems and condensate polishers are in continuous operation. 3-methoxyypropyl with strong basicity and moderate volatility can be used in most plants. Morpholine with weaker basicity and moderate volatility is suitably used in plants in which polishers are not in continuous operations. Dimethylamine and ammonia are suitably used with other amines because of their high volatility. Amine mixture application appears advantages on aspects of the anti-corrosion and service life of the resin beds.

The working environment of the ring main unit (RMU) in large solar photovoltaic power plants is complex and variable, faced with harsh environments such as temperature differences and humidity, it is extremely easy to cause operational failures of the ring grid cabinet, which seriously affects the safe and stable connection of solar photovoltaic to transmission lines. Based on the measured temperature and humidity data inside the RMU, utilizing the advantages of ARIMA and RBF model in linear and nonlinear data processing, a temperature and humidity prediction model with ARIMA-RBF weight combination is constructed to dynamically predict the temperature and humidity inside the RMU. The dynamic prediction of temperature and humidity in the actual loop cabinet of a photovoltaic power station is carried out. The prediction results show that, compared with the single model, the ARMI-RBF weight combination model has higher prediction accuracy and better stability. The combined model gives full play to the processing ability of a single model for different characteristics of data through appropriate weighting strategies, and can better evaluate the temperature and humidity state inside the RMU. It can provide a reference for the establishment of a more universal prediction model, and help to reduce the failure caused by long-term operation of the ring cabinet under ultra-mild and humid environment.