ABSTRACT This paper details a hybrid operational and computational study for improving the thermodynamic performance of a Gas-Steam Combined Cycle Power Plant (CCGT) through a novel hybrid optimisation framework Adaptive Annealed NSGA (AANSGA. This framework integrates Non-Dominated Sorting Genetic Algorithm II (NSGA-II) and Simulated Annealing (SA). The study applies second-law (exergy) analysis and optimised heat integration approaches such as the pinch point method and the approach temperature difference method to reduce exergy destruction and improve thermal efficiency. Operational results were obtained from a laboratory-based CCGT study, where the gas turbine inlet temperature was 1400 K, the Heat Recovery Steam Generator (HRSG) outlet steam pressure was 20 bar, and the steam mass flow rate was 25 kg/s. The results show an increase in thermal efficiency from 46.96% to 54.12%, and an increase in the exergy efficiency from 84.95% to 85.55%. Similarly, fuel consumption improved from 2.425 to 2.405 kg/s, and CO2 emissions stabilised at 352 kg/MWh. The HRSG pinch point temperature difference was improved between 9.35°C − 9.47°C. The hybrid AANSGA approach achieved a reduction in total exergy destruction per cycle and improved operational stability. Overall, AANSGA provides a useful decision-support tool for the development of sustainable, high-performance power systems under dynamic conditions.

Abstract The article describes a test rig for the experimental verification of the superheated steam flow through the control and follow-up stage of an experimental steam turbine placed in Doosan Škoda Power laboratory. Due to the innovative solution concept, the turbine is equipped with two mechanically independent rotors and the possibility to measure the performance of the control and follow-up stage separately. In the case of the control stage, it is also possible to simulate the partial admission by covering part of the inlet cross-section and to determine the energy loss by the presence of partial admission. In a wide range of rotational speeds of one or both rotors and steam inlet and outlet pressures and steam inlet temperature, local values of efficiency, stage reactions, Mach and Reynolds numbers and losses in the inter-stage channel can be determined by measurement for both stages separately. It is possible to probe the flow fields along the blade length before and behind second stage. Experiments, including probing, can be carried out at a steam pressure of up to 3.5 bar(a) and a temperature of up to 300 °C. The obtained data are used for tuning and verification of 3D CFD simulations and for corrections of the in-house SW system for the design of flow paths.

An innovative integration of parabolic trough collector with advanced thermochemical heat storage systems

Steam thermal ablation (STA) is an emerging minimally invasive treatment technique that utilizes the energy of high-temperature steam to treat diseased tissues. Compared to traditional techniques such as microwave ablation and radio-frequency ablation, STA has the advantages of lower temperature in the ablation center area and avoiding tissue carbonization. However, the current design of steam ablation needles still faces challenges such as poor controllability of steam flow, uneven heating, and difficult to accurately predict the area of tissue ablation. In response to this issue, this article studies and designs several porous radiation clusters–steam ablation needles (PRC–SAN), and investigates their steam flow characteristics, temperature distribution, and tissue ablation effects. This article designs three PRC–SAN, establishes corresponding fluid dynamics models, analyzes the flow state of steam inside the needle tube, and verifies its ablation effect on tissues through experiments. The research results indicate that different arrangements of porous radiation clusters significantly affect the steam flow rate and outlet temperature distribution, thereby determining the shape and range of the ablation area. The experimental verification used pig liver tissue as the ablation object and recorded the morphology of the ablation area and temperature changes in the tissue. The results indicate that the optimized design of PRC–SAN can provide a more uniform thermal field distribution, improve ablation accuracy, reduce nontarget tissue damage, and avoid carbonization caused by local overheating. In addition, this article also explores the correlation between the steam flow rate at the outlet of the ablation needle and temperature, and finds that the two are positively correlated on a large scale. However, due to the influence of heat loss and pore distribution during steam transmission, there may be small deviations in local areas. The experimental results indicate that optimizing the aperture and spacing of porous radiation clusters can improve ablation efficiency and enhance the controllability of ablation shape. This study provides important theoretical basis and experimental support for the application of STA in precision therapy. In the future, design parameters can be further optimized to meet different clinical needs.

Effect of dry / wet steam outlet area ratio on the performance of supersonic separator

Industrial boilers are critical in various industries, transforming fuel’s chemical energy into heat energy in the form of steam. These equipment primarily serve sectors such as power generation, chemicals, metallurgy, and paper production, providing essential heat and steam. Time-series analysis of boiler parameters offers valuable insights into the interactions of various operational factors, enabling optimization of settings and extending the equipment’s service life. However, due to the challenging operational environments and data transmission issues, sensors often record incomplete or erroneous data. This study focuses on collecting operational data from a coal-fired boiler at a chemical plant in Zhejiang. By preprocessing this flawed data, we generate a high-dimensional time-series dataset that includes key operational parameters like pressure, temperature, flow rate, and oxygen levels. Using the boiler outlet steam temperature as a key indicator of equipment condition, the dataset also reveals long-tailed distribution, offering a foundation for addressing long-tailed issues in industrial equipment analytics.

Nuclear steam supply systems (NSSSs) are critical to achieving safe, efficient, and flexible nuclear power generation. While deep reinforcement learning (DRL) has shown potential in optimizing NSSS control, existing single-agent approaches apply the same optimization strategies to all subsystems. This simplification ignores subsystem-specific control requirements and limits both optimization efficacy and adaptability. To resolve this gap, we propose a multi-agent reinforcement learning (MARL) framework that independently optimizes each subsystem while ensuring global coordination. Our approach extends the current NSSS optimization framework from a single-agent model to a multi-agent one and introduces a novel MARL method to foster effective exploration and stability during optimization. Experimental findings demonstrate that our method significantly outperforms DRL-based approaches in optimizing thermal power and outlet steam temperature control. This research pioneers the application of MARL to NSSS optimization, paving the way for advanced nuclear power control systems.

A novel model was proposed for U-Tube Steam Generators in Pressurized Water Reactors to be utilized in dynamics and control studies. The steam generator was divided into 14 nodes and investigated by applying mass and energy conservation equations in differential form. A system of nonlinear differential equations was obtained. This equation system was numerically simulated using the Julia programming language through a fourth order Runge–Kutta method. Accurate values for thermodynamic properties were taken from the Coolprop library, eliminating the need to take constant values or linear interpolations. A three-element proportional and integral control was applied as the control system in the model. Changes in feedwater flow rate, steam outlet flow rate, primary inlet flow rate, feedwater inlet temperature and primary inlet temperature were investigated, and the response of the steam generator was simulated using the developed model. It was observed that the proposed model gives results for U-Tube Steam Generators comparable to those in the literature and that it can be used in dynamic model and control simulations.

Development of hybrid first principles – Artificial intelligence models for transient modeling of power plant superheaters under load-following operation

Abstract Coal-fired power plants are commonly used as adjustable power sources to complement the fluctuating output of wind and solar energy. The investigation is required to determine the flexible peak-shaving capabilities of coal-fired boilers. A modified scheme for a lignite-fired power plant to further improve the primary air temperature using the outlet steam from the low-temperature reheater is studied while increasing the inlet flue gas temperature of the air preheater is considered the conventional scheme. Thermodynamic models of the power plant are constructed using ebsilon software. The operational characteristics of both schemes are compared under 30% turbine heat acceptance (THA)–100%THA conditions and the economic performance of the modified scheme is also evaluated. Results indicate that the modified scheme exhibits superior thermodynamic and economic performances compared to the conventional scheme. The disparity in power generation efficiency between the conventional and modified schemes reaches a maximum of 0.23 percentage points under 75%THA conditions. The net present value of the modified scheme amounts to 4.51 million dollars over the power plant lifespan of 30 years. The modified scheme allows the conventional denitrification catalyst to maintain an optimal temperature range even under 30%THA conditions, resulting in a power generation efficiency only 4.8 percentage points lower than that under 100%THA conditions, thus demonstrating remarkable operational flexibility. This study presents an efficient, cost-effective, and adaptable approach for lignite-fired power plants.

ABSTRACT The cascade heat pump (CHP) system shows significant potential in generating high-temperature steam by upgrading the ambient heat, whose energy efficiency is constrained by the large temperature difference between the air source and terminal output. This paper integrates vapor injection (VI) technology into both low-temperature and high-temperature stages of CHP system. A thermodynamic model of the vapor injection cascade heat pump (VI-CHP) system is constructed utilizing Aspen Hysys. Furthermore, the effects of intermediate temperature, VI separators’ temperatures, evaporator superheat and condenser subcooling on COP are analyzed. Simulation results demonstrated that the VI-CHP with dual-stage VI effectively enhances efficiency, reaching a nominal COP of 2.17, which indicates 8.6% improvement over the CHP system without VI. This paper analyzes the variation of system operation at intermediate temperatures from 45°C to 65°C, low-temperature flasher outlet steam temperatures from 33°C to 45°C, high-temperature flasher outlet steam temperatures from 74°C to 86°C, and superheat and subcooling degrees from 0°C to 10°C. Sensitivity analysis shows that maximum COP can attain 2.67 under the specified operational parameters. Finally, the impact of separators’ temperatures on the exergy efficiency is discussed. It is revealed that the exergy efficiency of the proposed system can reach 2.67.

Thermal-hydraulic transient performance and dynamic characterization analysis of direct steam generation for parabolic trough solar collectors

Dynamic analysis for ultra-supercritical boiler water wall considering uneven heat flux distribution and combustion instability

Off-design performance optimization for steam-water dual heat source ORC systems

The steam heating pipeline, as a heat energy delivery method, plays an important role in petrochemical, food processing, and other industrial fields. Research on dynamic hydraulic and thermal calculation methods for steam heating pipelines is the basis for the realization of precise control and efficient operation of steam pipe networks, which is also the key to reducing the energy consumption and carbon emissions of urban heating. In this study, the coupled hydraulic–thermal model of a steam pipeline is established considering the steam state parameter changes and condensate generation, the SIMPLE algorithm is used to realize the model solution, and the accuracy of the model is verified by the actual operation data of a steam heat network. The effects of condensate, environmental temperature, and steam pipeline inlet temperature and pressure changes on the hydraulic and thermal characteristics of the steam pipeline are simulated and analyzed. Results indicate that condensate only has a large effect on the steam outlet temperature and has almost no effect on the outlet pressure. As the heat transfer coefficient of the steam pipeline increases, the effect of both condensate and environmental temperature on the steam outlet temperature increases. The effect of the steam inlet pressure on the outlet pressure is instantaneous, but there is a delay in the effect of the inlet temperature on the outlet temperature, and the time required for outlet temperature stabilization increases by about 25 s to 30 s for each additional 400 m of pipeline length. The research can be applied to the control of supply-side steam temperature and pressure parameters in actual steam heating systems. Utilizing the coupled hydraulic–thermal characteristics of the steam pipeline network, tailored parameter control strategies can be devised to enhance the burner’s combustion efficiency and minimize fuel consumption, thereby significantly augmenting operational efficiency and fostering sustainable development within the steam heating system.

Abstract Lignite‐fired boilers usually encounter the insufficient drying capacity of the pulverizer due to the inherent drawback of high moisture content in fuel. In this study, four schemes of heat sources for temperature boosting of hot primary air are proposed for an ultra‐supercritical large‐scale single reheat lignite‐fired power plant according to heat sources such as inlet flue gas of air preheater (Scheme 1), the third stage extraction steam (Scheme 2), outlet steam of low‐temperature reheater (Scheme 3), and inlet flue gas of economizer (Scheme 4). The thermodynamic system models are built by using EBSILON Professional software. The thermodynamic performance of the four schemes is analyzed and compared from the perspectives of the first and second laws of thermodynamics. First law analysis indicates that the power generation standard coal consumption of Scheme 3 is reduced by 0.87, 0.42, and 0.04 g·kW−1·h−1 compared with Schemes 1, 2, and 4, respectively. Second law analysis indicates that the exergy loss of Schemes 2–4 is 3.7, 7.6, and 7.5 MW lower than that of Scheme 1. The present study may provide guidance for the energy efficiency improvement of lignite‐fired power plants.

Multi-objective optimization and performance assessment of response surface methodology (RSM), artificial neural network (ANN) and adaptive neuro-fuzzy interfence system (ANFIS) for estimation of fouling in phosphoric acid/steam heat exchanger

Fusion power plants can meet the energy demands of the world. The high thermal performance of a power generation system is still a challenge and one of the developing trends with a fusion reactor due to the high outlet temperature. A combined cycle system has been optimized to work at high outlet temperature and pressure of fusion power reactor with thermal power of 2500 MWth and its input parameter has been optimized along with impact of partial load to achieve high thermal performance very first time. The combined cycle based on the concept of two stages of expansion in the closed-Brayton-cycle and two reheaters in the Rankine cycle named Schematic-IV with the higher thermal performance of 58.19% as compared to Schematic-I, II and III has been proposed for a fusion power reactor. The increase in more than one expansion stage and reheat stage is not economical because it increased the thermal performance by about half of performance as compared to one. The effect of isentropic efficiency of compressor and heat rate have been investigated to validate the thermodynamic model and calculations. The optimized thermal performance of the combined cycle is 58.19% at a feed water mass flow rate of 592 kgs−1 and steam outlet temperature of 277 °C in the combined cycle. The heat rate decreased and thermal performance increased with the mass flow rate verifying that the thermodynamic model is correct. The thermodynamic analysis of the combined cycle-based nuclear reactor provides insights for better system thermal performance and reveals the effect of key parameters on the system performance.

A modular modelling approach was adopted to build a dynamic simulation model of the moisture separation reheater on a high-precision APROS real-time platform to investigate the dynamic operating characteristics of the moisture separation reheater. The model was subjected to steady-state and step dynamic tests at different loads. The results show that the established model can correctly reflect the steam flow and heat transfer properties and can meet the requirements of the simulation. Using the one-dimensional distribution of the model, the effect of a small breakage failure in the heat exchanger bundle was further investigated. The results showed that the heat transfer tube bundle had leaks, reducing the heat transfer capacity and affecting the quality of the steam used to work in the low-pressure turbine. Simultaneously, the effect on steam outlet parameters increased with the degree of leakage in the heat exchanger.

Flue gas and steam deviation of the final reheater is an inevitable problem in the tangentially fired boiler due to the remaining gas spinning at the furnace exit. An in-house one-dimensional process simulation code coupled with comprehensive three-dimensional combustion simulation was adopted to accurate investigate the characteristics of the flue gas and steam maldistribution of the final reheater in a 600 MW supercritical tangentially fired boiler. Firstly, the combustion simulation result was validated by the in-house fire-side heat transfer calculation data, then the effect of boiler loads and reversed separated overfire air (SOFA) deflection angles on the gas temperature deviation, velocity deviation and outlet steam temperature of reheater were conducted. The results showed that the deviation of flue gas temperature and velocity increases as the boiler load decreases. The reversed SOFA deflection angle plays a crucial role in improving the gas distribution under low loads, and the deviation of flue gas temperature and velocity is the smallest when the angle is -18? under 100% boiler maximum continuous rating (BMCR), 75% and 50% turbine heat acceptance (THA), but it is the smallest when the angle is -9? under 35% BMCR load. Moreover, the maximum outlet steam temperature difference between parallel heating surfaces of the final reheater increases from 84.68 K to 106.48 K as the boiler load decreases from 100% BMCR to 75% THA, and it is mainly affected by the flue gas temperature deviation rather than the mass flow rate maldistribution when the deflection angle changes from -9? to -18?.