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Effects of thermocline on performance of underwater glider’s power system propelled by ocean thermal

Hai YANG, Jie MA,

《能源前沿(英文)》 2009年 第3卷 第4期   页码 472-479 doi: 10.1007/s11708-009-0052-7

摘要: The thermal glider’s changeable volume produces propelling force to power the glider’s descending and ascending through the thermocline. The different depth, thickness, and intensity of the thermocline at different seasons and locations affect the working processes of the glider’s power system. Based on the enthalpy method, a mathematical model of the underwater glider’s power system was established and the time efficiency of operation was introduced, so that the effects of different thermoclines on the underwater glider’s power system were analyzed theoretically. The simulation result shows that the thermocline affects the transition time of the phase change processes of working fluids within the thermal engine tubes. There exist the threshold values of the thermocline’s depth and upper thickness for the power system’s operation. A depth or upper thickness of the thermocline less than the corresponding threshold leads the power system to work abnormally. To keep the power system working efficiently, a glider must be kept in warm surface water for a certain period before it moves through cold water, so that the time efficiency of operation is reduced. A less time efficiency of operation is unfavorable to the thermal glider to penetrate through the ocean currents.

关键词: mathematical     underwater glider     system working     certain     corresponding threshold    

Manufacturing system modeling and performance evaluation based on improved stochastic statechart

ZHANG Guojun, HE Jiabing, ZHU Haiping, CHEN Xuan

《机械工程前沿(英文)》 2007年 第2卷 第4期   页码 453-458 doi: 10.1007/s11465-007-0078-7

摘要: Stochastic statecharts are widely used in modeling systems. Considering that the comparability between different subsystems can streamline the modeling process, a stochastic statechart is improved by using the abstract sub-system and general system chart to express the comparability and integrity of a stochastic statechart respectively. Per formance data can be obtained by using a continuous-time Markov chain, which is transformed from a manufacturing system model described by the improved stochastic statechart. The case study shows that the improved stochastic statechart can effectively simplify the modeling and performance evaluation process and the results are useful to the configuration and optimization of a manufacturing system.

关键词: performance evaluation     different     configuration     improved     continuous-time    

Discrete-event stochastic systems with correlated inputs: Modeling and performance evaluation

《工程管理前沿(英文)》 2022年 第9卷 第2期   页码 214-220 doi: 10.1007/s42524-022-0192-6

摘要: In the majority of the previous works on discrete-event stochastic systems, they have been assumed to have independent input processes. However, in many applications, these input processes can be highly correlated. Furthermore, the performance measures of the systems with correlated inputs can be significantly different from those with independent inputs. In this paper, we provide an overview on some commonly used methods for modeling correlated input processes, and we discuss the difficulties and possible future research topics in the study of discrete-event stochastic systems with correlated inputs.

关键词: discrete-event stochastic system     correlated input     performance evaluation    

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    

Performance analysis of solar absorption-subcooled compression hybrid refrigeration system in subtropical

Xiangyang YE,Liming LIU,Zeyu LI

《能源前沿(英文)》 2019年 第13卷 第1期   页码 185-192 doi: 10.1007/s11708-017-0452-z

摘要: Solar absorption-subcooled compression hybrid refrigeration system is a new type of efficient and economical solar refrigeration device which always meets the demand of cooling load with the change of solar irradiance. The performance of the hybrid system is higher due to the improvement of evaporator temperature of absorption subsystem. But simultaneously, the variation of working process as well as performance is complicated since the absorption and compression subsystems are coupled strongly. Based on the measured meteorological data of Guangzhou, a subtropical city in south China, a corresponding parametric model has been developed for the hybrid refrigeration system, and a program written by Fortran has been used to analyze the performance of the hybrid system under different external conditions. As the condensation temperature ranges from 38°C to 50°C, the working time fraction of the absorption subsystem increases from 75% to 85%. Besides, the energy saving fraction also increases from 5.31% to 6.02%. The average COP of the absorption subsystem is improved from 0.366 to 0.407. However, when the temperature of the absorption increases from 36°C to 48°C, the average COP of hybrid system decreases from 2.703 to 2.312. Moreover, the working time fraction of the absorption subsystem decreases from 80% to 71.7%. The energy saving fraction falls from 5.67% to 5.08%. In addition, when the evaporate temperature increases from 4°C to 14°C, the average COP of the absorption subsystem decreases from 0.384 to 0.365. The work of the compressor decreases from 48.2 kW to 32.8 kW and the corresponding average COP of the absorption subsystem is improved from 2.591 to 3.082.

关键词: solar     absorption-subcooled     compression hybrid     dynamic simulation     performance analysis    

Micromixing performance of the teethed high shear mixer under semi-batch operation

《化学科学与工程前沿(英文)》 2022年 第16卷 第4期   页码 546-559 doi: 10.1007/s11705-021-2069-3

摘要: Semi-batch operated reaction processes are necessary for some competitive reaction systems to achieve a desirable process selectivity and productivity of fine chemical products. Herein the structural and operating parameters of the teethed high shear mixers were adjusted to study the micromixing performance in the semi-batch operated system, using the Villermaux/Dushman reaction system. The results indicate that the rising of the rotor speed and the number of rotor teeth, the decrease of the width of the shear gap and the radial distance between the feed position and the inner wall of stator can enhance the micromixing level and lead to the decrease of the segregation index. Additionally, computational fluid dynamics calculations were carried out to disclose the evolution of the flow pattern and turbulent energy dissipation rate of the semi-batch operated high shear mixer. Furthermore, the correlation was established with a mean relative error of 8.05% and R2 of 0.955 to fit the segregation index and the parameters studied in this work, which can provide valuable guidance on the design and optimization of the semi-batch operated high shear mixers in practical applications.

关键词: high shear mixer     semi-batch operation     micromixing performance     Villermaux/Dushman system     segregation index    

西部交通科技项目绩效评价体系研究及系统设计初探

赵杰华,康厚荣

《中国工程科学》 2008年 第10卷 第12期   页码 73-78

摘要:

在明确交通科技项目实施流程的基础上,站在后评价视角分析项目的社会经济效益,制订出一套相对完善的项目评价标准,同时应用Microsoft Visual Basic 6.0和Access 2003搭建系统框架,充分实现交通科技项目评价的科学性、有效性、合理性,促进决策过程的程序化、科学化。

关键词: 西部交通科技项目     绩效评价     后评价指标体系    

某奥运体育场馆排烟系统和补风系统性能化设计

付强,张和平,朱五八,谢启源

《中国工程科学》 2007年 第9卷 第12期   页码 21-25

摘要:

采用NFPA92B所提供的烟气控制计算公式对某奥运体育场馆的排烟量进行计算,并利用CFD数值模拟软件对排烟系统及补风系统进行优化设计,研究在该体育场馆内机械排烟,机械补风,自然补风三者之间的内在联系以及机械补风量对某馆排烟系统的影响。对该奥运体育场馆排烟系统以及补风系统的优化设计提供了理论依据。

关键词: 体育馆     排烟系统     补风系统     性能化    

Optimization and performance prediction of a new near-zero emission coal utilization system with combined

GUAN Jian, WANG Qinhui, LI Xiaomin, LUO Zhongyang, CEN Kefa

《能源前沿(英文)》 2007年 第1卷 第1期   页码 113-119 doi: 10.1007/s11708-007-0013-y

摘要: In accordance with the new near-zero emission coal utilization system with combined gasification and combustion, which is based on the CO acceptor gasification process, the product gas composition of the gasifier and the combustor was calculated by means of thermodynamic equilibrium calculation software FactSage 5.2. Based on these calculations, the whole system efficiency calculation method that complies with the mass and energy conservation principle was established. To enhance the system efficiency, the system pressure and the gasifier carbon conversion ratio were optimized. The results indicate that the system efficiency increases with increasing pressure and gasifier carbon conversion ratio. After taking into consideration the influence of the pressure and carbon conversion ratio on the performance of the system, the gasifier and the combustor were synthetically studied. The optimum system pressure and carbon conversion ratio were obtained as 2.5 MPa and 0.7, respectively. The system efficiency could reach around 62.1% when operated in these two optimum parameters. If the advanced ion transport membrane (ITM) air separation technology is used, there would be an increase of another 1.3%.

关键词: influence     efficiency calculation     optimum     software FactSage     transport    

A reliable and practical reference objective for the deviation diagnosis of energy system parameters

Liping LI, Zheng LI,

《能源前沿(英文)》 2009年 第3卷 第4期   页码 440-445 doi: 10.1007/s11708-009-0051-8

摘要: The core objective to optimize a complex energy system is to set the reference target to guide the parameter adjustment of system operation. In this paper, a new case-based approach is proposed based on an online performance assessment program and its long-term operation data for a large power unit. The online model of a coal-fired power unit’s performance assessment is demonstrated, and the distribution pattern of the performance index is revealed by statistical analysis of the abundant data. The fundamental issues (representation of the similarity of two thermal processes, similarity measure, etc.) are tackled. The key sections and key parameters for the completion of similarity determination are proposed, which are essential to realize a case-based strategy. A full-scope simulator of power unit is used to test the availability of the method. The advantage of the case-based approach is the integrality of information over other methods.

关键词: energy system     case-based     optimization     power unit operation     performance    

and permeability reducing admixtures having different action mechanisms on mechanical and durability performance

《结构与土木工程前沿(英文)》 2021年 第15卷 第5期   页码 1277-1291 doi: 10.1007/s11709-021-1752-2

摘要: In this paper, the effect of usage of the permeability reducing admixture (PRA) having different action mechanisms on hardened state properties of cementitious systems containing mineral additives is examined. For this aim, three commercial PRAs were used during investigation. The effective parameters in the first and third PRAs were air-entraining and high-rate air-entraining, respectively. The second one contained the insoluble calcium carbonate residue and had a small amount of the air-entraining property. Mortar mixes with binary and ternary cementitious systems were prepared by partially replacing cement with fly ash and metakaolin. The hardened state properties of mortar mixtures such as compressive strength, ultrasonic pulse velocity, water absorption, drying shrinkage and freeze–thaw resistance were investigated. The ternary cement-based mixture having both fly ash and metakaolin was selected as the most successful mineral-additive bearing mix in regard to hardened state properties. In this sense, PRA-B, with both insoluble residues and a small amount of air-entraining properties, showed the best performance among the mixtures containing PRA. The combined use of mineral additive and PRA had a more positive effect on the properties of the mixes.

关键词: cementitious system     mineral additive     permeability reducing admixture     mechanical properties     durability performance    

Influence of aeration intensity on the performance of A/O-type sequencing batch MBR system treating azo

Xinhua WANG, Jingmei LI, Xiufen LI, Guocheng DU

《环境科学与工程前沿(英文)》 2011年 第5卷 第4期   页码 615-622 doi: 10.1007/s11783-011-0362-y

摘要: Among the numerous parameters affecting the membrane bioreactor (MBR) performance, the aeration intensity is one of the most important factors. In the present investigation, an anoxic/aerobic-type (A/O-type) sequencing batch MBR system, added anoxic process as a pretreatment to improve the biodegradability of azo dye wastewater, was investigated under different aeration intensities and the impact of the aeration intensity on effluent quantity, sludge properties, extracellular polymeric substances (EPS) amount generated as well as the change of permeation flux were examined. Neither lower nor higher aeration intensities could improve A/O-type sequencing batch MBR performances. The results showed 0.15 m ·h aeration intensity was promising for treatment of azo dye wastewater under the conditions examined. Under this aeration intensity, chemical oxygen demand (COD), ammonium nitrogen and color removal as well as membrane flux amounted to 97.8%, 96.5%, 98.7% and 6.21 L·m ·h , respectively. The effluent quality, with 25.0 mg·L COD, 0.84 mg·L ammonium nitrogen and 8 chroma, could directly meet the reuse standard in China. In the meantime, the sludge relative hydrophobicity, the bound EPS, soluble EPS and EPS amounts contained in the membrane fouling layer were 70.3%, 52.0 mg·g VSS, 38.8 mg·g VSS and 90.8 mg·g VSS, respectively, which showed close relationships to both pollutant removals and membrane flux.

关键词: batch membrane bioreactor     azo dye     aeration intensity     extracellular polymeric substances     sludge properties    

Sustainability performance analysis of environment innovation systems using a two-stage network DEA model

《工程管理前沿(英文)》   页码 425-438 doi: 10.1007/s42524-022-0205-5

摘要: The term environmental innovation system refers to an innovation network composed of enterprises, universities, and research institutions involved in the development and diffusion of environmental technology, with the participation of a government. An environmental innovation system not only exerts important impact on the achievement of carbon neutrality but also affects social and economic activities. Investigations on environmental innovation system performance constantly assume a single-stage independent system while ignoring its internal structure. However, such systems are composed of environmental innovation research and development (R&D) and environmental innovation conversion subsystems. A two-stage data envelopment analysis (DEA) model is developed in this study to analyze the efficiency of Chinese regional environmental innovation system by opening the “black box” and considering shared resources. Empirical results indicated that China presents high overall environmental innovation efficiency although some regions need to improve. Regions with low efficiencies in both environmental innovation R&D (EIR) and environmental innovation conversion (EIC) subsystems should expand their investment in and strengthen the management of environmental innovation resources. Regions with low EIR efficiency should improve the absorption and transformation of environmental innovation achievements. Regions with low EIC efficiency should increase investment in the commercialization of environmental innovation achievements and encourage green economy industries, such as new energy, art, tourism, and environmental protection.

关键词: data envelopment analysis     environmental efficiency     environmental innovation system     shared resources     two-stage structure    

Recent advances in system reliability optimization driven by importance measures

Shubin SI, Jiangbin ZHAO, Zhiqiang CAI, Hongyan DUI

《工程管理前沿(英文)》 2020年 第7卷 第3期   页码 335-358 doi: 10.1007/s42524-020-0112-6

摘要: System reliability optimization problems have been widely discussed to maximize system reliability with resource constraints. Birnbaum importance is a well-known method for evaluating the effect of component reliability on system reliability. Many importance measures (IMs) are extended for binary, multistate, and continuous systems from different aspects based on the Birnbaum importance. Recently, these IMs have been applied in allocating limited resources to the component to maximize system performance. Therefore, the significance of Birnbaum importance is illustrated from the perspective of probability principle and gradient geometrical sense. Furthermore, the equations of various extended IMs are provided subsequently. The rules for simple optimization problems are summarized to enhance system reliability by using ranking or heuristic methods based on IMs. The importance-based optimization algorithms for complex or large-scale systems are generalized to obtain remarkable solutions by using IM-based local search or simplification methods. Furthermore, a general framework driven by IM is developed to solve optimization problems. Finally, some challenges in system reliability optimization that need to be solved in the future are presented.

关键词: importance measure     system performance     reliability optimization     optimization rules     optimization algorithms    

Viability of a concentrated solar power system in a low sun belt prefecture

Rahul BHATTACHARJEE, Subhadeep BHATTACHARJEE

《能源前沿(英文)》 2020年 第14卷 第4期   页码 850-866 doi: 10.1007/s11708-020-0664-5

摘要: Concentrating solar power (CSP) is considered as a comparatively economical, more efficient, and large capacity type of renewable energy technology. However, CSP generation is found restricted only to high solar radiation belt and installed where high direct normal irradiance is available. This paper examines the viability of the adoption of the CSP system in a low sun belt region with a lower direct normal irradiance (DNI). Various critical analyses and plant economics have been evaluated with a lesser DNI state. The obtained results out of the designed system, subjected to low DNI are not found below par, but comparable to some extent with the performance results of such CSP plants at a higher DNI. The analysis indicates that incorporation of the thermal energy storage reduces the levelized cost of energy (LCOE) and augments the plant capacity factor. The capacity factor, the plant efficiency, and the LCOE are found to be 32.50%, 17.56%, and 0.1952 $/kWh, respectively.

关键词: concentrated solar power     direct normal irradiance     plant performance     plant economics     thermal energy storage    

标题 作者 时间 类型 操作

Effects of thermocline on performance of underwater glider’s power system propelled by ocean thermal

Hai YANG, Jie MA,

期刊论文

Manufacturing system modeling and performance evaluation based on improved stochastic statechart

ZHANG Guojun, HE Jiabing, ZHU Haiping, CHEN Xuan

期刊论文

Discrete-event stochastic systems with correlated inputs: Modeling and performance evaluation

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

Performance analysis of solar absorption-subcooled compression hybrid refrigeration system in subtropical

Xiangyang YE,Liming LIU,Zeyu LI

期刊论文

Micromixing performance of the teethed high shear mixer under semi-batch operation

期刊论文

西部交通科技项目绩效评价体系研究及系统设计初探

赵杰华,康厚荣

期刊论文

某奥运体育场馆排烟系统和补风系统性能化设计

付强,张和平,朱五八,谢启源

期刊论文

Optimization and performance prediction of a new near-zero emission coal utilization system with combined

GUAN Jian, WANG Qinhui, LI Xiaomin, LUO Zhongyang, CEN Kefa

期刊论文

A reliable and practical reference objective for the deviation diagnosis of energy system parameters

Liping LI, Zheng LI,

期刊论文

and permeability reducing admixtures having different action mechanisms on mechanical and durability performance

期刊论文

Influence of aeration intensity on the performance of A/O-type sequencing batch MBR system treating azo

Xinhua WANG, Jingmei LI, Xiufen LI, Guocheng DU

期刊论文

Sustainability performance analysis of environment innovation systems using a two-stage network DEA model

期刊论文

Recent advances in system reliability optimization driven by importance measures

Shubin SI, Jiangbin ZHAO, Zhiqiang CAI, Hongyan DUI

期刊论文

Viability of a concentrated solar power system in a low sun belt prefecture

Rahul BHATTACHARJEE, Subhadeep BHATTACHARJEE

期刊论文