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Optimization of cold-end system of thermal power plants based on entropy generation minimization

《能源前沿（英文）》 2022年 第16卷 第6期   页码 956-972 doi: 10.1007/s11708-021-0785-5

摘要： Cold-end systems are heat sinks of thermal power cycles, which have an essential effect on the overall performance of thermal power plants. To enhance the efficiency of thermal power plants, multi-pressure condensers have been applied in some large-capacity thermal power plants. However, little attention has been paid to the optimization of the cold-end system with multi-pressure condensers which have multiple parameters to be identified. Therefore, the design optimization methods of cold-end systems with single- and multi-pressure condensers are developed based on the entropy generation rate, and the genetic algorithm (GA) is used to optimize multiple parameters. Multiple parameters, including heat transfer area of multi-pressure condensers, steam distribution in condensers, and cooling water mass flow rate, are optimized while considering detailed entropy generation rate of the cold-end systems. The results show that the entropy generation rate of the multi-pressure cold-end system is less than that of the single-pressure cold-end system when the total condenser area is constant. Moreover, the economic performance can be improved with the adoption of the multi-pressure cold-end system. When compared with the single-pressure cold-end system, the excess revenues gained by using dual- and quadruple-pressure cold-end systems are 575 and 580 k$/a, respectively.

关键词： cold-end system     entropy generation minimization     optimization     economic analysis     genetic algorithm (GA)    

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Optimization of turbine cold-end system based on BP neural network and genetic algorithm

Chang CHEN,Danmei XIE,Yangheng XIONG,Hengliang ZHANG

《能源前沿（英文）》 2014年 第8卷 第4期   页码 459-463 doi: 10.1007/s11708-014-0335-5

摘要： The operation condition of the cold-end system of a steam turbine has a direct impact on the economy and security of the unit as it is an indispensible auxiliary system of the thermal power unit. Many factors influence the cold-end operation of a steam turbine; therefore, the operation mode needs to be optimized. The optimization analysis of a 1000 MW ultra-supercritical (USC) unit, the turbine cold-end system, was performed utilizing the back propagation (BP) neural network method with genetic algorithm (GA) optimization analysis. The optimized condenser pressure under different conditions was obtained, and it turned out that the optimized parameters were of significance to the performance and economic operation of the system.

关键词： optimization     turbine     cold-end system     BP neural network     genetic algorithm    

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Optimization of cold end system of steam turbine

ZHAO Bin, LIU Ling, ZHANG Wenbing

《能源前沿（英文）》 2008年 第2卷 第3期   页码 348-353 doi: 10.1007/s11708-008-0036-z

摘要： An optimization of the movement characteristic of the cold end system of the steam turbine was conducted from an overall consideration of the condenser and the circulation water pump. An analysis method based on thermodynamics theory

关键词： circulation     characteristic     analysis     optimization     condenser    

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Polyamines and antioxidant defense system are associated with cold tolerance in centipedegrass

Jingjing CHEN, Junyang FANG, Zhenfei GUO, Shaoyun LU

《农业科学与工程前沿（英文）》 2018年 第5卷 第1期   页码 129-138 doi: 10.15302/J-FASE-2017197

摘要： Physiological responses to low temperature were analyzed in a chilling-tolerant centipedegrass ( ) accession, Shao Guan (SG), in comparison to the commercial cultivar, Common. Lower levels of ion leakage and higher chlorophyll (Chl) concentration were observed in SG than in Common during chilling stress. The maximum photochemical efficiency, the actual photosystem II (PSII) efficiency, photochemical quenching efficiency, and net photosynthetic rate were decreased during chilling stress in both genotypes, with higher levels of these parameters shown by SG than Common. In addition, higher activities of superoxide dismutase (SOD), catalase (CAT), ascorbate-peroxidase (APX) and glutathione reductase (GR), and higher concentrations of ascorbic acid (AsA) and glutathione (GSH) were observed in SG than in Common. Moreover, higher concentrations of putrescine (Put), spermidine (Spd), and spermine (Spm) were observed in SG than in Common. Correlation analysis indicated that SOD, CAT, APX and GR activities, and AsA and GSH concentrations showed high correlation to Put, while APX, GR, and AsA concentrations were correlated to Spd. Exogenous Put or Spd increased antioxidant enzyme activities and chilling tolerance. The results suggested that polyamine-regulated antioxidants are important for chilling tolerance in centipedegrass and protect plants against chilling induced oxidative damage.

关键词： antioxidants     centipedegrass     chilling     photosynthesis     polyamines    

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Establishment of the Comprehensive Evaluation System of Cold Stamping Die Quality

LU Xiao-chun, GUO Sheng, RUAN Feng

《机械工程前沿（英文）》 2006年 第1卷 第1期   页码 80-84 doi: 10.1007/s11465-005-0021-8

摘要：

A comprehensive evaluation system of die quality, a multiplayer hierarchical amendment index system according to the characteristics of cold stamping die production, an evaluation standard referring to the technique and design rules of dies, and a scientific evaluation by using the multiplayer hierarchical and the fuzzy comprehensive evaluation methods are presented in this paper. The applications show that the system can be used to evaluate the die quality objectively, fairly, and reasonably.

关键词： scientific evaluation     stamping     multiplayer hierarchical     technique     evaluation standard    

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A simplified model of direct-contact heat transfer in desalination system utilizing LNG cold energy

Qingqing SHEN, Wensheng LIN, Anzhong GU, Yonglin JU

《能源前沿（英文）》 2012年 第6卷 第2期   页码 122-128 doi: 10.1007/s11708-012-0175-0

摘要： With the increasingly extensive utilization of liquefied natural gas (LNG) in China today, sustainable and effective using of LNG cold energy is becoming increasingly important. In this paper, the utilization of LNG cold energy in seawater desalination system is proposed and analyzed. In this system, the cold energy of the LNG is first transferred to a kind of refrigerant, i.e., butane, which is immiscible with water. The cold refrigerant is then directly injected into the seawater. As a result, the refrigerant droplet is continuously heated and vaporized, and in consequence some of the seawater is simultaneously frozen. The formed ice crystal contains much less salt than that in the original seawater. A simplified model of the direct-contact heat transfer in this desalination system is proposed and theoretical analyses are conducted, taking into account both energy balance and population balance. The number density distribution of two-phase bubbles, the heat transfer between the two immiscible fluids, and the temperature variation are then deduced. The influences of initial size of dispersed phase droplets, the initial temperature of continuous phase, and the volumetric heat transfer coefficient are also clarified. The calculated results are in reasonable agreement with the available experimental data of the R114/water system.

关键词： liquefied natural gas (LNG)     cold energy utilization     desalination     direct-contact heat transfer    

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Radial electromagnetic type unbalance vibration self-recovery regulation system for high-end grinding

《机械工程前沿（英文）》 2023年 第18卷 第3期 doi: 10.1007/s11465-023-0763-1

摘要： Modern rotating machines, which are represented by high-end grinding machines, have developed toward high precision, intelligence, and high durability in recent years. As the core components of grinding machine spindles, grinding wheels greatly affect the vibration level during operation. The unbalance vibration self-recovery regulation (UVSRR) system is proposed to suppress the vibration of grinding wheels during workpiece processing, eliminating or minimizing the imbalance. First, technical principles and the system composition are introduced. Second, the balancing actuator in the UVSRR system is analyzed in detail. The advanced nature of the improved structure is presented through structure introduction and advantage analysis. The performance of the balancing actuator is mutually verified by the theoretical calculation of torque and software simulation. Results show that the self-locking torque satisfies the actual demand, and the driving torque is increased by 1.73 times compared with the traditional structure. Finally, the engineering application value of the UVSRR system is verified by laboratory performance comparison and actual factory application. The balancing speed and effect of the UVSRR system are better than those of an international mainstream product and, the quality of the workpieces machined in the factory improved by 40%.

关键词： UVSRR system     radial electromagnetic type     vibration suppression     performance simulation     engineering application    

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Evaluation of the performance of a centralized ground-water heat pump system in cold climate region

Shilei LU,Zhe CAI,Li ZHANG,Yiran LI

《能源前沿（英文）》 2014年 第8卷 第3期   页码 394-402 doi: 10.1007/s11708-014-0310-1

摘要： The aim of this study is to evaluate the performance of a centralized open-loop ground-water heat pump (GWHP) system for climate conditioning in Beijing with a cold climate in China. Thus, a long-time test was conducted on a running GWHP system for the heating season from December 2011 to March 2012. The analysis of the testing data indicates that the average heat-pump coefficient of performance (COP) and the COP of the system (COPs) are 4.27 and 2.59. The low value and large fluctuation in the range of COP are found to be caused by the heat transfixion in the aquifer and the bypass in the circulation loop. Therefore, some suggestions are proposed to improve the performance for GWHPs in the cold climate region in China.

关键词： ground-water heat pump (GWHP)     actual coefficient of performance     heat transfixion    

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End-to-end delay analysis for networked systems

Jie SHEN,Wen-bo HE,Xue LIU,Zhi-bo WANG,Zhi WANG,Jian-guo YAO

《信息与电子工程前沿（英文）》 2015年 第16卷 第9期   页码 732-743 doi: 10.1631/FITEE.1400414

摘要： End-to-end delay measurement has been an essential element in the deployment of real-time services in networked systems. Traditional methods of delay measurement based on time domain analysis, however, are not efficient as the network scale and the complexity increase. We propose a novel theoretical framework to analyze the end-to-end delay distributions of networked systems from the frequency domain. We use a signal flow graph to model the delay distribution of a networked system and prove that the end-to-end delay distribution is indeed the inverse Laplace transform of the transfer function of the signal flow graph. Two efficient methods, Cramer’s rule-based method and the Mason gain rule-based method, are adopted to obtain the transfer function. By analyzing the time responses of the transfer function, we obtain the end-to-end delay distribution. Based on our framework, we propose an efficient method using the dominant poles of the transfer function to work out the bottleneck links of the network. Moreover, we use the framework to study the network protocol performance. Theoretical analysis and extensive evaluations show the effectiveness of the proposed approach.

关键词： Networked system     End-to-end     Delay distribution    

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Heating energy savings potential from retrofitting old apartments with an advanced double-skin façade systemin cold climate

Yeo Beom YOON, Byeongmo SEO, Brian Baewon KOH, Soolyeon CHO

《能源前沿（英文）》 2020年 第14卷 第2期   页码 224-240 doi: 10.1007/s11708-020-0801-1

摘要： Apartments account for over 60% of total residential buildings and consume a significant portion of primary energy in South Korea. Various energy efficiency measures have been implemented for both new apartment constructions and existing apartment retrofits. Old apartment structures have poor thermal performances, resulting in a high energy consumption. The South Korean government initiated retrofitting projects to improve the energy efficiency in old apartments. Apartment owners typically replace old windows with high-performance windows; however, there is still a demand for better and more innovative retrofit methods for a highly improved energy efficiency. This paper proposes an advanced double-skin façade (DSF) system to replace existing balcony windows in old apartments. Considering the cold climate conditions of Seoul, South Korea, it mainly discusses heating energy savings. Three case models were developed: Base-Case with existing apartment, Case-1 with typical retrofitting, and Case-2 with the proposed DSF system. The EnergyPlus simulation program was used to develop simulation models for a floor radiant heating system. A typical gas boiler was selected for low-temperature radiant system modeling. The air flow network method was used to model the proposed DSF system. Five heating months, i.e., November to March, and one representative day, i.e., January 24, were selected for detailed analysis. The main heat loss areas consist of windows, walls, and infiltration. The results reveal that the apartment with the DSF retrofit saves 38.8% on the annual heating energy compared to the Base-Case and 35.2% compared to Case-1.

关键词： double-skin façade     retrofitting     high-rise apartment     heating energy     building simulation    

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Topology-independent end-to-end learning model for improving the voltage profile in microgrids-integrated

《能源前沿（英文）》 2023年 第17卷 第2期   页码 211-227 doi: 10.1007/s11708-022-0847-3

摘要： With multiple microgrids (MGs) integrated into power distribution networks in a distributed manner, the penetration of renewable energy like photovoltaic (PV) power generation surges. However, the operation of power distribution networks is challenged by the issues of multiple power flow directions and voltage security. Accordingly, an efficient voltage control strategy is needed to ensure voltage security against ever-changing operating conditions, especially when the network topology information is absent or inaccurate. In this paper, we propose a novel data-driven voltage profile improvement model, denoted as system-wide composite adaptive network (SCAN), which depends on operational data instead of network topology details in the context of power distribution networks integrated with multiple MGs. Unlike existing studies that realize topology identification and decision-making optimization in sequence, the proposed end-to-end model determines the optimal voltage control decisions in one shot. More specifically, the proposed model consists of four modules, Pre-training Network and modified interior point methods with adversarial networks (Modified IPMAN) as core modules, and discriminator generative adversarial network (Dis-GAN) and Volt convolutional neural network (Volt-CNN) as ancillary modules. In particular, the generator in SCAN is trained by the core modules in sequence so as to form an end-to-end mode from data to decision. Numerical experiments based on IEEE 33-bus and 123-bus systems have validated the effectiveness and efficiency of the proposed method.

关键词： end-to-end learning     microgrids     voltage profile improvement     generative adversarial network    

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review on technologies with electricity generation potentials using liquified natural gas regasification cold

《能源前沿（英文）》 2023年 第17卷 第3期   页码 332-379 doi: 10.1007/s11708-023-0863-y

摘要： In modern times, worldwide requirements to curb greenhouse gas emissions, and increment in energy demand due to the progress of humanity, have become a serious concern. In such scenarios, the effective and efficient utilization of the liquified natural gas (LNG) regasification cold energy (RCE), in the economically and environmentally viable methods, could present a great opportunity in tackling the core issues related to global warming across the world. In this paper, the technologies that are widely used to harness the LNG RCE for electrical power have been reviewed. The systems incorporating, the Rankine cycles, Stirling engines, Kalina cycles, Brayton cycles, Allam cycles, and fuel cells have been considered. Additionally, the economic and environmental studies apart from the thermal studies have also been reviewed. Moreover, the discussion regarding the systems with respect to the regassification pressure of the LNG has also been provided. The aim of this paper is to provide guidelines for the prospective researchers and policy makers in their decision making.

关键词： liquified natural gas     cold energy     power generation    

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耗散陀螺系统的李雅普诺夫函数构造：剩余能量函数方法 Personal View

Cem CİVELEK, Özge CİHANBEĞENDİ

《信息与电子工程前沿（英文）》 2020年 第21卷 第4期   页码 629-634 doi: 10.1631/FITEE.1900014

摘要： 在自由度为4、张量有逆变（右上标）和协变（右下标）形式的耗散陀螺系统中，使用二阶线性微分方程建立拉格朗日耗散模型，即{L, D}模型。通过系统的{L, D}模型确定广义元素。满足勒让德变换先决条件时，可得哈密顿量。剩余能量函数（REF）由哈密顿量及损耗或耗散能量（为负）之和组成，将其作为李雅普诺夫函数，可通过李雅普诺夫第二方法作稳定性分析，并从数学上推导出稳定性条件。

关键词： 李雅普诺夫函数；剩余能量函数；耗散陀螺系统稳定性    

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Current understanding and applications of the cold sintering process

Tong Yu, Jiang Cheng, Lu Li, Benshuang Sun, Xujin Bao, Hongtao Zhang

《化学科学与工程前沿（英文）》 2019年 第13卷 第4期   页码 654-664 doi: 10.1007/s11705-019-1832-1

摘要： In traditional ceramic processing techniques, high sintering temperature is necessary to achieve fully dense microstructures. But it can cause various problems including warpage, overfiring, element evaporation, and polymorphic transformation. To overcome these drawbacks, a novel processing technique called “cold sintering process (CSP)” has been explored by Randall et al. CSP enables densification of ceramics at ultra-low temperature (≤300°C) with the assistance of transient aqueous solution and applied pressure. In CSP, the processing conditions including aqueous solution, pressure, temperature, and sintering duration play critical roles in the densification and properties of ceramics, which will be reviewed. The review will also include the applications of CSP in solid-state rechargeable batteries. Finally, the perspectives about CSP is proposed.

关键词： cold sintering process     processing variables     solid-state rechargeable batteries    

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Application of cold spraying for flux-free brazing of aluminium alloy 6060

Kirsten BOBZIN, Lidong ZHAO, Thomas SCHLAEFER, Thomas WARDA,

《机械工程前沿（英文）》 2010年 第5卷 第3期   页码 256-260 doi: 10.1007/s11465-010-0095-9

摘要： In the present study, samples of aluminium alloy 6060 were coated by cold spraying with a powder of brazing alloy Al12Si. The influence of the process gas temperature on particle velocities and coating build-up was investigated. The coated samples were heat-treated in air and under argon atmosphere to investigate the wetting behaviour of the deposited Al12Si and the diffusion processes between Al12Si coatings and substrates. Coated samples were brazed flux-free under argon atmosphere by an induction heating system. The microstructure of the coated, heat-treated, and brazed samples was investigated. The shear strength of the brazed joints was determined. The results show that the brazing alloy Al12Si could be very well deposited on the substrate by cold spraying. The particle velocity increased with increasing process temperature. Correspondingly, the thickness of Al12Si coatings increased with increasing process temperature. The heat treatments showed that a very good metallurgical bond between the Al12Si coatings and the substrate could be realized by the deposition using cold spraying. The coated samples could be well brazed without fluxes. The coating thickness and overlap width influenced the shear strength of the brazed joints. The highest shear strength of brazed joints amounts to 80 MPa.

关键词： aluminium alloy     flux-free brazing     cold spraying     shear strength    

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标题 作者 时间 类型 操作

Optimization of cold-end system of thermal power plants based on entropy generation minimization

期刊论文

Optimization of turbine cold-end system based on BP neural network and genetic algorithm

Chang CHEN,Danmei XIE,Yangheng XIONG,Hengliang ZHANG

期刊论文

Optimization of cold end system of steam turbine

ZHAO Bin, LIU Ling, ZHANG Wenbing

期刊论文

Polyamines and antioxidant defense system are associated with cold tolerance in centipedegrass

Jingjing CHEN, Junyang FANG, Zhenfei GUO, Shaoyun LU

期刊论文

Establishment of the Comprehensive Evaluation System of Cold Stamping Die Quality

LU Xiao-chun, GUO Sheng, RUAN Feng

期刊论文

A simplified model of direct-contact heat transfer in desalination system utilizing LNG cold energy

Qingqing SHEN, Wensheng LIN, Anzhong GU, Yonglin JU

期刊论文

Radial electromagnetic type unbalance vibration self-recovery regulation system for high-end grinding

期刊论文

Evaluation of the performance of a centralized ground-water heat pump system in cold climate region

Shilei LU,Zhe CAI,Li ZHANG,Yiran LI

期刊论文

End-to-end delay analysis for networked systems

Jie SHEN,Wen-bo HE,Xue LIU,Zhi-bo WANG,Zhi WANG,Jian-guo YAO

期刊论文

Heating energy savings potential from retrofitting old apartments with an advanced double-skin façade systemin cold climate

Yeo Beom YOON, Byeongmo SEO, Brian Baewon KOH, Soolyeon CHO

期刊论文

Topology-independent end-to-end learning model for improving the voltage profile in microgrids-integrated

期刊论文

review on technologies with electricity generation potentials using liquified natural gas regasification cold

期刊论文

耗散陀螺系统的李雅普诺夫函数构造：剩余能量函数方法

Cem CİVELEK, Özge CİHANBEĞENDİ

期刊论文

Current understanding and applications of the cold sintering process

Tong Yu, Jiang Cheng, Lu Li, Benshuang Sun, Xujin Bao, Hongtao Zhang

期刊论文

Application of cold spraying for flux-free brazing of aluminium alloy 6060

Kirsten BOBZIN, Lidong ZHAO, Thomas SCHLAEFER, Thomas WARDA,

期刊论文