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Isogeometric analysis of coupled thermo-elastodynamic problems under cyclic thermal shock

Asghar AMANI DASHLEJEH

《结构与土木工程前沿（英文）》 2019年第13卷第2期页码 397-405 doi: 10.1007/s11709-018-0473-7

摘要： The isogeometric analysis (IGA) method was extended for the solution of the coupled thermo-elastodynamic equations. The dimensionless formulation was accepted in discretization of the uncoupled and coupled thermoelasticity equations and the Generalized Newmark method was used in the time integration procedure. First, the performance of the proposed method was verified against a two-dimensional benchmark example subjected to constant thermal shock with available exact analytical solutions. Then a two-dimensional half-space benchmark example under thermal shock was solved. Finally, cyclic thermal shock (CTS) loading was applied on the half-space problem. The results dedicated that IGA can be used as a suitable approach in the analysis of the general thermomechanical problems.

关键词： isogeometric analysis coupled thermo-elastodynamic dynamic analysis generalized newmark cyclic thermal shock

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Flow, thermal, and vibration analysis using three dimensional finite element analysis for a flux reversal

B. VIDHYA,K. N. SRINIVAS

《能源前沿（英文）》 2016年第10卷第4期页码 424-440 doi: 10.1007/s11708-016-0423-9

摘要： This paper presents the simulation of major mechanical properties of a flux reversal generator (FRG) viz., computational fluid dynamic (CFD), thermal, and vibration. A three-dimensional finite element analysis (FEA) based CFD technique for finding the spread of pressure and air velocity in air regions of the FRG is described. The results of CFD are mainly obtained to fine tune the thermal analysis. Thus, in this focus, a flow analysis assisted thermal analysis is presented to predict the steady state temperature distribution inside FRG. The heat transfer coefficient of all the heat producing inner walls of the machine are evaluated from CFD analysis, which forms the main factor for the prediction of accurate heat distribution. The vibration analysis is illustrated. Major vibration sources such as mechanical, magnetic and applied loads are covered elaborately which consists of a 3D modal analysis to find the natural frequency of FRG, a 3D static stress analysis to predict the deformation of the stator, rotor and shaft for different speeds, and an unbalanced rotor harmonic analysis to find eccentricity of rotor to make sure that the vibration of the rotor is within the acceptable limits. Harmonic analysis such as sine sweep analysis to identify the range of speeds causing high vibrations and steady state vibration at a mode frequency of 1500 Hz is presented. The vibration analysis investigates the vibration of the FRG as a whole, which forms the contribution of this paper in the FRG literature.

关键词： flux reversal generator air velocity computation fluid dynamics thermal analysis vibration analysis finite element analysis

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Risk-based probabilistic thermal-stress analysis of concrete arch dams

Narjes SOLTANI, Mohammad ALEMBAGHERI, Mohammad Houshmand KHANEGHAHI

《结构与土木工程前沿（英文）》 2019年第13卷第5期页码 1007-1019 doi: 10.1007/s11709-019-0521-y

摘要： The probabilistic risk of arch dam failure under thermal loading is studied. The incorporated uncertainties, which are defined as random variables, are associated with the most affecting structural (material) properties of concrete and thermal loading conditions. Karaj arch dam is selected as case study. The dam is numerically modeled along with its foundation in three-dimensional space; the temperature and thermal stress distribution is investigated during the operating phase. The deterministic thermal finite element analysis of the dam is combined with the structural reliability methods in order to obtain thermal response predictions, and estimate the probability of failure in the risk analysis context. The tensile overstressing failure mode is considered for the reliability analysis. The thermal loading includes ambient air and reservoir temperature variations. The effect of solar radiation is considered by an increase in the ambient temperatures. Three reliability methods are employed: the first-order second-moment method, the first-order reliability method, and the Monte-Carlo simulation with Latin Hypercube sampling. The estimated failure probabilities are discussed and the sensitivity of random variables is investigated. Although most of the studies in this line of research are used only for academic purposes, the results of this investigation can be used for both academic and engineering purposes.

关键词： arch dams probabilistic analysis thermal stress sensitivity reliability

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Thermal fluid-structure interaction and coupled thermal-stress analysis in a cable stayed bridge exposed

Nazim Abdul NARIMAN

《结构与土木工程前沿（英文）》 2018年第12卷第4期页码 609-628 doi: 10.1007/s11709-018-0452-z

摘要： In this paper, thermal fluid structure-interaction (TFSI) and coupled thermal-stress analysis are utilized to identify the effects of transient and steady-state heat-transfer on the vortex induced vibration and fatigue of a segmental bridge deck due to fire incidents. Numerical simulations of TFSI models of the deck are dedicated to calculate the lift and drag forces in addition to determining the lock-in regions once using fluid-structure interaction (FSI) models and another using TFSI models. Vorticity and thermal convection fields of three fire scenarios are simulated and analyzed. Simiu and Scanlan benchmark is used to validate the TFSI models, where a good agreement was manifested between the two results. Extended finite element method (XFEM) is adopted to create 3D models of the cable stayed bridge to simulate the fatigue of the deck considering three fire scenarios. Choi and Shin benchmark is used to validate the damaged models of the deck in which a good coincide was seen between them. The results revealed that TFSI models and coupled thermal-stress models are significant in detecting earlier vortex induced vibration and lock-in regions in addition to predicting damages and fatigue of the deck due to fire incidents.

关键词： fire scenario transient heat transfer TFSI model coupled thermal-stress XFEM

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Thermal analysis of lubricated three-dimensional contact bodies considering interface roughness

《机械工程前沿（英文）》 2022年第17卷第2期 doi: 10.1007/s11465-022-0672-8

摘要： Surface roughness and thermal action are of remarkable importance in the lubrication performance of mechanical components, especially in extreme conditions. However, available studies mainly focus on the full-film lubrication conditions without considering temperature rise and real 3D surface roughness due to the complexity of surface topography and temperature characteristics. Moreover, studies on the interfacial thermal behaviors of 3D rough surface lubricated contact in an extended range of working conditions remain limited. In this paper, a deterministic mixed thermal elastohydrodynamic lubrication model considering real 3D surface roughness and thermal effects is proposed. In this model, pressure and temperature are coupled with each other, the computation of elastic deformation is accelerated through the discrete convolution and fast Fourier transform method, the temperature field is calculated with the column sweeping technique, and the semi-system method is introduced to improve convergence and numerical stability under severe conditions. The model is validated by comparing its results with available published numerical and experimental results. The thermal behaviors of the contact interface are studied in a wide range of working conditions. The influences of surface roughness and thermal effect on lubrication performance are revealed. The results show that the proposed model can be used as a powerful analysis tool for lubrication performance and temperature prediction in various heavy-load, high-speed lubricated components over a wide range of lubrication conditions.

关键词： thermal elastohydrodynamic lubrication surface roughness effect thermal effect temperature characteristics severe conditions

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Variation in humic and fulvic acids during thermal sludge treatment assessed by size fractionation, elementaryanalysis, and spectroscopic methods

Yuning YANG,Huan LI,Jinyi LI

《环境科学与工程前沿（英文）》 2014年第8卷第6期页码 854-862 doi: 10.1007/s11783-014-0755-9

摘要： Thermal pretreatment can be applied to sludge anaerobic digestion or dewatering. To analyze the variation in humic substances during thermal sludge treatment, sludge humic and fulvic acids were extracted before and after 30-min thermal treatment at 180°C, and then their contents, molecular weight distributions, elementary compositions, and spectral characteristics were compared. The results showed that the total contents of humic and fulvic acids in the sludge almost remained constant during thermal treatment, but 35% of humic and fulvic acids were dissolved from the sludge solids. Moreover, both humic and fulvic acids were partly decomposed and 32% of humic acids were converted to fulvic acids. The median value of the molecular weights of humic acids decreased from 81 to 41 kDa and that of fulvic acids decreased from 15 to 2 kDa. Besides the reduction in molecular size, the chemical structures of humic and fulvic acids also exhibited a slight change, i.e. some oxygen functional groups disappeared and aromatic structures increased after thermal sludge treatment.

关键词： sludge thermal treatment humic acids fulvic acids

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Equivalent thermal conductivity of heat pipes

LU Zesheng, MA Binghui

《机械工程前沿（英文）》 2008年第3卷第4期页码 462-466 doi: 10.1007/s11465-008-0087-1

摘要： In precision machining, the machining error from thermal distortion carries a high proportion of the total errors. If a precision machining tool can transfer heat fast, the thermal distortion will be reduced and the machining precision will be improved. A heat pipe working based on phase transitions of the inner working liquid transfers heat with high efficiency and is widely applied in spaceflight and chemical industries. In mechanics, applications of heat pipes are correspondingly less. When a heat pipe is applied to a hydrostatic motorized spindle, the thermal distortion cannot be solved during the heat transfer process because thermal conductivity or equivalent thermal conductivity should be provided first for special application in mechanics. An equivalent thermal conductivity model based on equivalent thermal resistances is established. Performance tests for a screen wick pipe, gravity pipe, and rotation heat pipe are done to validate the efficiency of the equivalent thermal conductivity model. The proposed model provides a calculation method for the thermal distortion analysis of heat pipes applied in the motorized spindle.

关键词： proposed distortion analysis hydrostatic motorized motorized spindle Performance

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Influence evaluation of loading conditions during pressurized thermal shock transients based on thermal-hydraulics

Jinya KATSUYAMA, Shumpei UNO, Tadashi WATANABE, Yinsheng LI

《机械工程前沿（英文）》 2018年第13卷第4期页码 563-570 doi: 10.1007/s11465-018-0487-9

摘要：

The thermal hydraulic (TH) behavior of coo-lant water is a key factor in the structural integrity assessments on reactor pressure vessels (RPVs) of pressurized water reactors (PWRs) under pressurized thermal shock (PTS) events, because the TH behavior may affect the loading conditions in the assessment. From the viewpoint of TH behavior, configuration of plant equipment and their dimensions, and operator action time considerably influence various parameters, such as the temperature and flow rate of coolant water and inner pressure. In this study, to investigate the influence of the operator action time on TH behavior during a PTS event, we developed an analysis model for a typical Japanese PWR plant, including the RPV and the main components of both primary and secondary systems, and performed TH analyses by using a system analysis code called RELAP5. We applied two different operator action times based on the Japanese and the United States (US) rules: Operators may act after 10 min (Japanese rules) and 30 min (the US rules) after the occurrence of PTS events. Based on the results of TH analysis with different operator action times, we also performed structural analyses for evaluating thermal-stress distributions in the RPV during PTS events as loading conditions in the structural integrity assessment. From the analysis results, it was clarified that differences in operator action times significantly affect TH behavior and loading conditions, as the Japanese rule may lead to lower stresses than that under the US rule because an earlier operator action caused lower pressure in the RPV.

关键词： structural integrity reactor pressure vessel pressurized thermal shock thermal hydraulic analysis pressurized water reactor weld residual stress

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A modified zone model for estimating equivalent room thermal capacity

Hua CHEN, Xiaolin WANG

《能源前沿（英文）》 2013年第7卷第3期页码 351-357 doi: 10.1007/s11708-013-0254-x

摘要： The zone model has been widely applied in control analysis of heating, ventilation and air conditioning (HVAC) systems to achieve a high building efficiency. This paper proposed a modified zone model which is much simpler in the HVAC system simulation and has the similar accuracy to the complicated simulation model. The proposed model took into consideration the effect of envelop heat reservoir on the room indoor temperature by introducing the thermal admittance of the inner surfaces of the building enclosure. The thermal admittance for the building enclosure was developed based on the building thermal network analytical theory and transfer function method. The efficacy of the proposed model was demonstrated by comparing it with the complicated model — heat balance method (HTB2 program). The predicted results from the proposed model well agreed with those from the complicated simulation. The proposed model can then make the HVAC system dynamic simulation much faster and more acceptable for control design due to its simplicity and efficiency.

关键词： room model thermal network analysis transfer function heating ventilation and air conditioning (HVAC) system simulation

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Steady-state thermal-hydraulic analysis of SCWR assembly

LIU Xiaojing, CHENG Xu

《能源前沿（英文）》 2008年第2卷第4期页码 475-478 doi: 10.1007/s11708-008-0093-3

摘要： Among the six gen-IV reactor concepts recommended by the gen-IV international forum (GIF), supercritical water-cooled reactor (SCWR), the only reactor with water as coolant, achieves a high thermal efficiency and, subsequently, has economic advantages over the existing reactors due to its high outlet temperature. A thermal-hydraulic analysis of the SCWR assembly is performed in this paper using the modified COBRA-IV code. Two approaches to reduce the hot channel factor are investigated: decreasing the moderator mass flow and increasing the thermal resistance between moderator channel and its adjacent sub-channels. It is shown that heat transfer deterioration cannot be avoided in SCWR fuel assembly. It is, therefore, highly required to calculate the cladding temperature accurately and to preserve the fuel rod cladding integrity under heat transfer deterioration conditions.

关键词： cladding temperature assembly temperature coolant resistance

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Thermal and energy analysis of a Chinese kang

Zhi ZHUANG, Yuguo LI, Xudong YANG, Bin CHEN, Jiaping LIU,

《能源前沿（英文）》 2010年第4卷第1期页码 84-92 doi: 10.1007/s11708-010-0009-x

摘要： About 67million Chinese kangs are still used by about 175million people in China today. The kang utilizes biomass burning for space heating and hence reduces the use of commercial energy. However, the existing design of kangs is largely based on the accumulated experience of craftsmen, for lack of scientific studies and engineering design guidelines. Poor construction of kangs also leads to serious indoor air pollution. In this paper, a macroscopic smoke flow and heat transfer model of an elevated kang is integrated in a widely-used building energy analysis software in China–DeST, and the integrated software can be used for the thermal performance analysis of kang-integrated houses. A typical house with kangs in various villages of northern China is chosen as a case study. The annual performance of the kang under different insulations of building envelope and climatic conditions are discussed. Based on the simulation results, it is found that the thermal comfort requirement of the outside surface of the upper kang plate can be met by a proper construction of the kang and selection of the appropriate firing pattern. The better the insulation of the building envelope is or the better the room air tightness is, the greater the indoor air temperature rise and the greater the building heating load contribution of the kang. In the eight selected cities in northern China, the use of kang can meet 50%–80% of the house heating load.

关键词： Chinese kang elevated kang rural house thermal modeling building energy efficiency DeST

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Thermogravimetric coupled with Fourier transform infrared analysis study on thermal treatment of monopotassium

Yuheng FENG, Xuguang JIANG, Yong CHI, Xiaodong LI, Hongmei ZHU

《环境科学与工程前沿（英文）》 2011年第5卷第2期页码 186-192 doi: 10.1007/s11783-011-0322-6

摘要： In China, safe disposal of hazardous waste is more and more a necessity, urged by rapid economic development. The pyrolysis and combustion characteristics of a residue from producing monopotassium phosphate (monopotassium phosphate residue), considered as a hazardous waste, were studied using a thermogravimetric, coupled with Fourier transform infrared analyzer (TG-FTIR). Both pyrolysis and combustion runs can be subdivided into three stages: drying, thermal decomposition, and final devolatilization. The average weight loss rate during fast thermal decomposition stage in pyrolysis is higher than combustion. Acetic acid, methane, pentane, (acetyl) cyclopropane, 2,4,6-trichlorophenol, CO, and CO were distinguished in the pyrolysis process, while CO was the dominant combustion product.

关键词： hazardous waste combustion pyrolysis thermogravimetric coupled with Fourier transform infrared analysis (TG-FTIR) monopotassium phosphate residue

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高速高精度机床热分析与热设计技术

高建民,史晓军,许艾明,赵博选

《中国工程科学》 2013年第15卷第1期页码 28-33

摘要：

随着机床高速高精度的技术发展，热问题已成为影响机床特性的重要因素。从提高机床的固有热性能出发，系统介绍了机床热特性分析、热结构优化及其冷却技术的理论和方法，以及国内外研究现状，并探讨了机床“热设计”理论与技术的最新进展和未来研究重点及趋势。

关键词：高速高精度机床热特性分析热结构优化冷却技术

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航天器热控系统的可靠性设计与分析

李运泽,宁献文,王晓明,石晓波

《中国工程科学》 2007年第9卷第7期页码 53-56

摘要：

针对国内外航天器热控制、热管理技术的发展现状，在详细调研各种航天器热控系统组成原理与功能实现方式的基础上，从可靠性的角度出发，归纳、总结了航天器热控系统中串联、并联、表决、储备四种常见的可靠性设计模式及其相应的可靠性分析计算模型，介绍了其在空间站、月球探测系统、火星探测系统等典型航天器上的应用范例，为进一步的航天器热控系统可靠性设计方法与理论分析奠定了基础。

关键词：航天器热控制热管理可靠性

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Theory analysis and system identification methods on thermal dynamics characteristics of ballscrews

XIA Junyong, HU Youmin, WU Bo, SHI Tielin

《机械工程前沿（英文）》 2008年第3卷第4期页码 408-415 doi: 10.1007/s11465-008-0061-y

摘要： Empirical model of machine tools on thermal error has been widely researched, which can compensate for thermal error to some extent but not suitable for thermal dynamic errors produced by dynamic heat sources. The thermoelastic phenomenon of unidimensional heat transfer of ballscrews influenced by changeable heat sources is analyzed based on the theory of heat transfer. Two methods for system identification (the least square system identification and BP artificial neural network (ANN) system identification) are put forward to establish a dynamic characteristic model of thermal deformation of ballscrews. The model of thermal error of the axis in a feed system of DM4600 vertical miller is established with a fine identification effect. Comparing the results of the two identification methods, the BP ANN system identification is more precise than the least square system identification.

关键词： square system network vertical miller transfer ANN