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Determining the optimum economic insulation thickness of double pipes buried in the soil for district

Fating LI, Pengfei JIE, Zhou FANG, Zhimei WEN

《能源前沿(英文)》 2021年 第15卷 第1期   页码 170-185 doi: 10.1007/s11708-020-0680-5

摘要: The insulation thickness (IT) of double pipes buried in the soil (DPBIS) for district heating (DH) systems was optimized to minimize the annual total cost of DPBIS for DH systems. An optimization model to obtain the optimum insulation thickness (OIT) and minimum annual total cost (MATC) of DPBIS for DH systems was established. The zero point theorem and fsolve function were used to solve the optimization model. Three types of heat sources, four operating strategies, three kinds of insulation materials, three buried depth (BD) values, and seven nominal pipe size (NPS) values were considered in the calculation of the OIT and MATC of DPBIS for DH systems, respectively. The optimization results for the above factors were compared. The results show that the OIT and MATC of DPBIS for DH systems can be obtained by using the optimization model. Sensitivity analysis was conducted to investigate the impact of some economic parameters, i.e., unit heating cost, insulation material price, interest rate, and insulation material lifetime, on optimization results. It is found out that the impact of sensitivity factors on the OIT and MATC of DPBIS for DH systems is different.

关键词: double pipes     optimization model     optimum insulation thickness     minimum annual total cost    

Optimizing environmental insulation thickness of buildings with CHP-based district heating system based

Yumei ZHANG, Pengfei JIE, Chunhua LIU, Jing LI

《能源前沿(英文)》   页码 613-628 doi: 10.1007/s11708-020-0700-5

摘要: The increase of insulation thickness (IT) results in the decrease of the heat demand and heat medium temperature. A mathematical model on the optimum environmental insulation thickness (OEIT) for minimizing the annual total environmental impact was established based on the amount of energy and energy grade reduction. Besides, a case study was conducted based on a residential community with a combined heat and power (CHP)-based district heating system (DHS) in Tianjin, China. Moreover, the effect of IT on heat demand, heat medium temperature, exhaust heat, extracted heat, coal consumption, carbon dioxide (CO ) emissions and sulfur dioxide (SO ) emissions as well as the effect of three types of insulation materials (i.e., expanded polystyrene, rock wool and glass wool) on the OEIT and minimum annual total environmental impact were studied. The results reveal that the optimization model can be used to determine the OEIT. When the OEIT of expanded polystyrene, rock wool and glass wool is used, the annual total environmental impact can be reduced by 84.563%, 83.211%, and 86.104%, respectively. It can be found that glass wool is more beneficial to the environment compared with expanded polystyrene and rock wool.

关键词: optimum environmental insulation thickness     heat medium temperature     energy grade     extracted heat     exhaust heat    

A novel algorithm for frequency dependent modeling of ferrite ring and its optimum design to study VFTO

Mehrdad MAJIDI, Hamid JAVADI, Moein MANBACHI

《能源前沿(英文)》 2014年 第8卷 第1期   页码 90-100 doi: 10.1007/s11708-013-0286-2

摘要: One of the fundamental issues in gas insulated substations (GIS) which has destructive effects on GIS equipment is the very fast transient over-voltages (VFTOs). This paper models a 400/230 kV substation in order to study the effects of VFTO extensively implemented on EMTP-RV. In addition, the application of ferrite rings for suppressing VFTOs is assessed thoroughly. The main advantage of this paper is its new proposed algorithm according to the ferrite ring frequency dependent modeling that is validated with experimental results. This paper examines the effects of three compositions of the ferrite ring on VFTO suppression. Moreover, it estimates the dimension of the ferrite ring based on the SF6 gas insulation withstand and the maximum effect of ferrite rings on VFTO suppression constraint with the COMSOL multiphysics software. Furthermore, it gains VFTO attenuated percentages due to the installation of the ferrite ring in different GIS nodes. Finally, it analyzes the offered VFTO amendment technique in various GIS switching scenarios.

关键词: comsol multiphysics     EMTP-RV     ferrite ring     gas insulated substations (GIS)     transient over-voltage     insulation coordination    

Effects of sheet thickness and material on the mechanical properties of flat clinched joint

Chao CHEN, Huiyang ZHANG, Shengdun ZHAO, Xiaoqiang REN

《机械工程前沿(英文)》 2021年 第16卷 第2期   页码 410-419 doi: 10.1007/s11465-020-0618-y

摘要: The flat clinching process is attracting a growing attention in the joining field of lightweight materials because it avoids the geometric protrusion that appears in the conventional clinching process. In this paper, the effects of sheet thickness and material on the mechanical properties of the clinched joint were studied. Al1060 and Al2024 sheets with 2 mm thickness were employed to develop the clinched joint by using different material configurations, and Al1060 sheets with 2.5- and 1.5-mm thicknesses were used to produce the clinched joint by using different thickness configurations. The clinched joints using various sheet configurations were sectioned, and dimensional analysis was conducted. Cross-tensile and shearing tests were carried out to analyze the mechanical properties of the clinched joint, including tensile strength, shearing strength, and absorbed energy. In addition, the failure modes of the clinched joints were discussed. Results indicated that the clinched joint with a stiff top sheet had increased static strength regardless of the test type. The clinched joint with a thick top sheet demonstrated lower static strength than the joint with a thick bottom sheet in the cross-tensile test. However, this result was reversed in the shearing tests. The flat clinching process has a great potential in joining dissimilar and various thickness materials.

关键词: clinched joint     flat clinching process     thickness configuration     material configuration     mechanical property    

Influence of envelope insulation materials on building energy consumption

Junlan YANG, Jiabao TANG

《能源前沿(英文)》 2017年 第11卷 第4期   页码 575-581 doi: 10.1007/s11708-017-0473-7

摘要: In this paper, the influence of different external wall insulation materials on the energy consumption of a newly built apartment in Germany is investigated. Three types of insulation materials commonly used in Germany including mineral fiber, polyurethane, and vacuum insulation panel are chosen for the case studies. An energy analysis model is established to clarify the primary energy use for production of the insulation materials and for building space heating. The calculation results show that the energy consumption for insulation material production increases with the insulation thickness, whereas the energy use for space heating decreases with the insulation thickness. Thus, there exists an optimum thickness to get the lowest total energy consumption for each kind of insulation material. The ascending order of the total energy consumption of the three materials is mineral fiber, polyurethane, and vacuum insulation panel. However, the optimum insulation thicknesses for the three insulation materials show a verse order at a certain heat transfer coefficient of the base envelope. The energy payback time (EPT) is proposed to calculate the payback time of the primary energy use for insulation material production. Mineral fiber has the shortest time, followed by polyurethane and vacuum insulation panel. The EPTS is 10, 19 and 21 years, respectively when the heat transfer coefficient of the base envelope is 0.2 W/(m ·K). In addition, the simulated results show that the theoretical value and the simulated value are basically identical.

关键词: building envelope     insulation materials     energy consumption     payback time    

A concept of capillary active, dynamic insulation integrated with heating, cooling and ventilation, air

Mark BOMBERG

《结构与土木工程前沿(英文)》 2010年 第4卷 第4期   页码 431-437 doi: 10.1007/s11709-010-0071-9

摘要: When a historic fa?ade needs to be preserved or when the seismic considerations favor use of a concrete wall system and fire considerations limit exterior thermal insulation, one needs to use interior thermal insulation systems. Interior thermal insulation systems are less effective than the exterior systems and will not reduce the effect of thermal bridges. Yet they may be successfully used and, in many instances, are recommended as a complement to the exterior insulation. This paper presents one of these cases. It is focused on the most successful applications of capillary active, dynamic interior thermal insulation. This happens when such insulation is integrated with heating, cooling and ventilation, air conditioning (HVAC) system. Starting with a pioneering work of the Technical University in Dresden in development of capillary active interior insulations, we propose a next generation, namely, a bio-fiber thermal insulation. When completing the review, this paper proposes a concept of a joint research project to be undertaken by partners from the US (where improvement of indoor climate in exposed coastal areas is needed), China (indoor climate in non-air conditioned concrete buildings is an issue), and Germany (where the bio-fiber technology has been developed).

关键词: capillary active insulation     integrated heating     cooling and ventilation     air conditioning (HVAC) and building enclosure     dynamic insulation     switchable thermal resistance     variable U-value walls    

旅客机环境控制系统优化研究

方林,王浚

《中国工程科学》 2006年 第8卷 第1期   页码 77-80

摘要:

为了选择经济高效的旅客机环境控制系统,对现役各种旅客机采用的环境控制系统方案进行了优化设计和比较,分别建立了二轮简单式低压除水系统、三轮升压式高压除水系统和四轮升压式高压除水系统(又称冷凝循环制冷系统)的优化设计数学模型,以起飞燃油质量代偿损失为目标函数,采用广义乘子法结合单纯形加速法求解,优化结果可作为设计研究旅客机环境控制系统的理论依据。

关键词: 旅客机     环境控制     优化设计    

Lamellar thickness transition of melt-crystallized polybuten-1 tetragonal phase: configurational change

Motoi YAMASHITA

《化学科学与工程前沿(英文)》 2009年 第3卷 第1期   页码 26-32 doi: 10.1007/s11705-009-0002-2

摘要: Lamellar crystal thickness of isotactic polybutene-1 ( -PB1) have been investigated for crystallization in the melt over a wide range of crystallization temperature from 40°C to 90°C by small angle X-ray scattering experiments and density measurements. The crystal thickness demonstrates two linear dependences on inverse supercooling and a transition from one dependence to the other has been observed around = 65°C. Each of the two dependences obeys the nucleation theory in the high and low supercooling ranges, respectively. Chain folding free energy determined from the low supercooling range is larger than that determined from the high supercooling range. Possible mechanisms for the transition are discussed taking account of entropy of chain folding directions.

关键词: isotactic polybutene-1     tetragonal phase     crystal thickness     melt growth     chain folding     small angle X-ray scattering     nucleation theory     end surface free energy    

Modeling of the minimum cutting thickness in micro cutting with consideration of the friction around

Tianfeng ZHOU, Ying WANG, Benshuai RUAN, Zhiqiang LIANG, Xibin WANG

《机械工程前沿(英文)》 2020年 第15卷 第1期   页码 81-88 doi: 10.1007/s11465-019-0561-y

摘要: Friction modeling between the tool and the workpiece plays an important role in predicting the minimum cutting thickness during TC4 micro machining and finite element method (FEM) cutting simulation. In this study, a new three-region friction modeling is proposed to illustrate the material flow mechanism around the friction zone in micro cutting; estimate the stress distributions on the rake, edge, and clearance faces of the tool; and predict the stagnation point location and the minimum cutting thickness. The friction modeling is established by determining the distribution of normal and shear stress. Then, it is applied to calculate the stagnation point location on the edge face and predict the minimum cutting thickness. The stagnation point and the minimum cutting thickness are also observed and illustrated in the FEM simulation. Micro cutting experiments are conducted to validate the accuracy of the friction and the minimum cutting thickness modeling. Comparison results show that the proposed friction model illustrates the relationship between the normal and sheer stress on the tool surface, thereby validating the modeling method of the minimum cutting thickness in micro cutting.

关键词: tool friction     minimum cutting thickness     finite element method     tool edge radius     micro cutting    

系统非优分析理论及方法

何平

《中国工程科学》 2003年 第5卷 第7期   页码 40-46

摘要:

对系统非优分析理论做了较为详细的论述。指出寻求不确定系统优化的主要问题,关键是缺少对系统的非优分析。在系统非优范畴的基础上建立了征兆群与经验分析,提出了系统非优度量以及从非优追踪到系统自组织等问题。

关键词: 系统非优范畴     非优征兆群     非优度量     系统自组织    

Numerical simulation of compaction parameters for sand-filled embankment using large thickness sand filling

Wentao WANG, Chongzhi TU, Rong LUO

《结构与土木工程前沿(英文)》 2018年 第12卷 第4期   页码 568-576 doi: 10.1007/s11709-017-0444-4

摘要: The study uses the finite element method to simulate a new technique of highway sand embankment filling in Jianghan Plain district, which can raise the thickness of sand-filled layer from 30 cm to 70 cm and can significantly shorten the construction period based on the guarantee of sand embankment construction quality. After simulating the three compacting proposals carried out on the field test, the study uses COMSOL software to research on the compacting effects of sand-filled layers in larger thicknesses by 22 ton vibratory roller alone, and then to investigate the steady compacting effect of 12 ton vibratory roller. The simulation results indicate that the sand-filled layer thickness of 70 cm is suitable for the new sand filling technique, and the sand-filled embankment project with tight construction period is suggested to choose the 12 ton vibration roller for steady compaction.

关键词: sand embankment     compaction in large thickness     numerical simulation     small size vibratory roller     steady compaction    

Genome-wide association study of the backfat thickness trait in two pig populations

Dandan ZHU,Xiaolei LIU,Rothschild MAX,Zhiwu ZHANG,Shuhong ZHAO,Bin FAN

《农业科学与工程前沿(英文)》 2014年 第1卷 第2期   页码 91-95 doi: 10.15302/J-FASE-2014005

摘要: Backfat thickness is a good predictor of carcass lean content, an economically important trait, and a main breeding target in pig improvement. In this study, the candidate genes and genomic regions associated with the tenth rib backfat thickness trait were identified in two independent pig populations, using a genome-wide association study of porcine 60K SNP genotype data applying the compressed mixed linear model (CMLM) statistical method. For each population, 30 most significant single-nucleotide polymorphisms (SNPs) were selected and SNP annotation implemented using Build 10.2. In the first population, 25 significant SNPs were distributed on seven chromosomes, and SNPs on SSC1 and SSC7 showed great significance for fat deposition. The most significant SNP (ALGA0006623) was located on SSC1, upstream of the gene. In the second population, 27 significant SNPs were recognized by annotation, and 12 SNPs on SSC12 were related to fat deposition. Two haplotype blocks, M1GA0016251-MARC0075799 and ALGA0065251-MARC0014203-M1GA0016298-ALGA0065308, were detected in significant regions where the and genes were identified as contributing to fat metabolism. The results indicated that genetic mechanism regulating backfat thickness is complex, and that genome-wide associations can be affected by populations with different genetic backgrounds.

关键词: backfat thickness     SNP chip     genome-wide association study     compressed mixed linear model     pig    

Estimation of optimum design of structural systems via machine learning

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1441-1452 doi: 10.1007/s11709-021-0774-0

摘要: Three different structural engineering designs were investigated to determine optimum design variables, and then to estimate design parameters and the main objective function of designs directly, speedily, and effectively. Two different optimization operations were carried out: One used the harmony search (HS) algorithm, combining different ranges of both HS parameters and iteration with population numbers. The other used an estimation application that was done via artificial neural networks (ANN) to find out the estimated values of parameters. To explore the estimation success of ANN models, different test cases were proposed for the three structural designs. Outcomes of the study suggest that ANN estimation for structures is an effective, successful, and speedy tool to forecast and determine the real optimum results for any design model.

关键词: optimization     metaheuristic algorithms     harmony search     structural designs     machine learning     artificial neural networks    

Unified cycle model of a class of internal combustion engines and their optimum performance characteristics

Shiyan ZHENG

《能源前沿(英文)》 2011年 第5卷 第4期   页码 367-375 doi: 10.1007/s11708-011-0170-x

摘要: The unified cycle model of a class of internal combustion engines is presented, in which the influence of the multi-irreversibilities mainly resulting from the adiabatic processes, finite-time processes and heat leak loss through the cylinder wall on the performance of the cycle are taken into account. Based on the thermodynamic analysis method, the mathematical expressions of the power output and efficiency of the cycle are calculated and some important characteristic curves are given. The influence of the various design parameters such as the high-low pressure ratio, the high-low temperature ratio, the compression and expansion isentropic efficiencies etc. on the performance of the cycle is analyzed. The optimum criteria of some important parameters such as the power output, efficiency and pressure ratio are derived. The results obtained from this unified cycle model are very general and useful, from which the optimal performance of the Atkinson, Otto, Diesel, Dual and Miller heat engines and some new heat engines can be directly derived.

关键词: internal combustion engine     irreversibility     power output     efficiency     optimization    

The ITZ microstructure, thickness, porosity and its relation with compressive and flexural strength of

《结构与土木工程前沿(英文)》   页码 191-201 doi: 10.1007/s11709-021-0792-y

摘要: A new insight into the interfacial transition zone (ITZ) in cement mortar specimens (CMSs) that is influenced by cement fineness is reported. The importance of cement fineness in ITZ characterizations such as morphology and thickness is elucidated by backscattered electron images and by consequences to the compressive (Fc) and flexural strength (Ff), and porosity at various water/cement ratios. The findings indicate that by increasing the cement fineness the calcium silicate hydrate formation in the ITZ is favored and that this can refine the pore structures and create a denser and more homogeneous microstructure. By increasing cement fineness by about 25% of, the ITZ thickness of CMSs was reduced by about 30% and Fc was increased by 7%–52% and Ff by 19%–40%. These findings illustrate that the influence of ITZ features on the mechanical strength of CMSs is mostly related to the cement fineness and ITZ microstructure.

关键词: cement fineness     interfacial transition zone     compressive and flexural strength    

标题 作者 时间 类型 操作

Determining the optimum economic insulation thickness of double pipes buried in the soil for district

Fating LI, Pengfei JIE, Zhou FANG, Zhimei WEN

期刊论文

Optimizing environmental insulation thickness of buildings with CHP-based district heating system based

Yumei ZHANG, Pengfei JIE, Chunhua LIU, Jing LI

期刊论文

A novel algorithm for frequency dependent modeling of ferrite ring and its optimum design to study VFTO

Mehrdad MAJIDI, Hamid JAVADI, Moein MANBACHI

期刊论文

Effects of sheet thickness and material on the mechanical properties of flat clinched joint

Chao CHEN, Huiyang ZHANG, Shengdun ZHAO, Xiaoqiang REN

期刊论文

Influence of envelope insulation materials on building energy consumption

Junlan YANG, Jiabao TANG

期刊论文

A concept of capillary active, dynamic insulation integrated with heating, cooling and ventilation, air

Mark BOMBERG

期刊论文

旅客机环境控制系统优化研究

方林,王浚

期刊论文

Lamellar thickness transition of melt-crystallized polybuten-1 tetragonal phase: configurational change

Motoi YAMASHITA

期刊论文

Modeling of the minimum cutting thickness in micro cutting with consideration of the friction around

Tianfeng ZHOU, Ying WANG, Benshuai RUAN, Zhiqiang LIANG, Xibin WANG

期刊论文

系统非优分析理论及方法

何平

期刊论文

Numerical simulation of compaction parameters for sand-filled embankment using large thickness sand filling

Wentao WANG, Chongzhi TU, Rong LUO

期刊论文

Genome-wide association study of the backfat thickness trait in two pig populations

Dandan ZHU,Xiaolei LIU,Rothschild MAX,Zhiwu ZHANG,Shuhong ZHAO,Bin FAN

期刊论文

Estimation of optimum design of structural systems via machine learning

期刊论文

Unified cycle model of a class of internal combustion engines and their optimum performance characteristics

Shiyan ZHENG

期刊论文

The ITZ microstructure, thickness, porosity and its relation with compressive and flexural strength of

期刊论文