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Influence of Filling Ratio and working Fluid Thermal Properties on Starting up and Heat Transferring Performance of Closed Loop Plate Oscillating Heat Pipe with Parallel Channels

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Journal of Thermal Science 2017年第1期26卷 73-81页

作者： SHI Weixiu PAN Lisheng School of Environment and Energy Engineering Beijing University of Civil Engineering and Architecture Beijing Key Lab of Heating Gas SupplyVentilating and Air Conditioning Engineering State Key Laboratory of High-temperature Gas Dynamics Institute of MechanicsChinese Academy of Sciences

Using ethanol or acetone as the working fluid, the performance of starting up and heat transfer of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying filling ratio, inclination, working fluids and heating power. The performance of the tested pulsating heat pipe was mainly evaluated by thermal resistance and wall temperature. Heating copper block and cold water bath were adopted in the experimental investigations. It was found that oscillating heat pipe with filling ratio of 50% started up earlier than that with 70% when heating input was 159.4 W, however, it has similar starting up performance with filling ratio of 50% as compared to 70% on the condition of heat input of 205.4 W. And heat pipe with filling ratio of 10% could not start up but directly transit to dry burning. A reasonable filling ratio range of 35%-70% was needed in order to achieve better performance, and there are different optimal filling ratios with different heating inputs- the more heating input, the higher optimal filling ratio, and vice versa. However, the dry burning appeared easily with low filling ratio, especially at very low filling ratio, such as 10%. And higher filling ratio, such as 70%, resulted in higher heat transfer( dry burning) limit. With filling ratio of 70% and inclination of 75°, oscillating heat pipe with acetone started up with heating input of just 24 W, but for ethanol, it needed to be achieved 68 W, Furthermore, the start time with acetone was similar as compared to that with ethanol. For steady operating state, the heating input with acetone was about 80 W, but it transited to dry burning state when heating input was greater than 160 W. However, for ethanol, the heating input was in vicinity of 160 W. Furthermore, thermal resistance with acetone was lower than that with ethanol at the same heating input of 120 W.

关键词： closed loop with parallel channels, plate pulsating heat pipe, filling ratio, working fluid thermalproperties, start up, heat transfer performance

Spatial-temporal variation features and law of gas concentration in the fully mechanized working face under the condition of intermittent ventilation

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International Journal of Mining Science and Technology 2019年第6期29卷 963-969页

作者： Yinpin Cao Yimin Li Zhongning Zhou School of Electrical and Power Engineering China University of Mining & Technology

Based on the fluid mechanics and mass transfer theory,a mathematical model of the spatial-temporal variation of gas was derived to avoid the gas accident caused by the main fan stopping ventilation under the condition of intermittent ventilation in the *** to the actual parameters of the tunnel,a numerical calculation model was *** spatial-temporal variation of gas concentration in the fully mechanized working face under the condition of intermittent ventilation was calculated by using the commercial package Fluent,and the correctness of the calculated results was verified by the actual monitoring data of the ***,the gas concentration was calculated under different wind velocities at driving face in coal tunnel,and the result showed that the gas can be carried effectively by the wind when the wind velocity is about 1.8 m/***,the distributions of wind velocity and gas concentration at driving face were studied at 1.8 m/s,and the result showed the gas concentration increased gradually with the distance close to the outlet,but the gas concentration almost kept constant at the height of driving ***,the distribution of gas concentration was investigated with time after the ventilation was stopped and restarted,*** gas concentration of test point gradually increased with the increment of downtime,when the downtime was 40 min,the gas concentration of test point 3 reached the maximum *** gas concentration increased gradually and reached the maximum after10 min of restart,then sharply decreased and kept constant.

关键词： Fully mechanized working face Intermittent ventilation Gas concentration

Carbon Dioxide as working Fluids in Transcritical Rankine Cycle for Diesel Engine Multiple Waste Heat Recovery in Comparison to Hydrocarbons

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Journal of Thermal Science 2019年第3期28卷 494-504页

作者： LIU Peng SHU Gequn TIAN Hua State Key Laboratory of Engines Tianjin University

In consideration of the high-temperature characteristic of engine's waste heat and stricter environmental regulations, natural substance, including CO_2 and hydrocarbons, have been treated as promising working fluid for diesel engine waste heat recovery due to its environment friendly and excellent physical and chemical properties. This paper presented a comprehensive performance analysis on transcritical Rankine cycles for diesel engine multiple waste heat recovery using hydrocarbons and CO_2 as working fluid. The optimal turbine inlet pressures corresponding to maximum net power output, maximum exergy efficiency and minimum electricity production cost(EPC) were obtained. The effect of working fluid on these optimal pressures has been discussed. For fluids with low critical temperature, the optimal pressure corresponding to maximum net power output is lower than the one for maximum exergy efficiency, while the opposite results can be found for fluid with high critical temperature. Then, the effect of various working fluid properties in transcritical cycle performance is discussed. Comparison results show that CO_2 obtains only more power output than Ethane, Propane and Propene, but CO_2 is capable of absorbing more energy from engine coolant and regeneration heat with comparable total heat transfer areas and has an advantage in turbine size, particularly for hydrocarbons with high critical temperature.

关键词： transcritical Rankine cycle natural working fluid multiple waste heat performance comparison

working Pressure Induced Microstructure and Stress Evolution of Sputtered ZrN Coatings

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稀有金属材料与工程 2012年第S1期41卷 429-432页

作者： Qi Zhengbing Yan Weili Hong Jinqing Zhu Fangping Sun Peng Wang Zhoucheng Wu Zhengtao Peng Dongliang Wu Chonghu Xiamen Univ Coll Chem & Chem Engn Xiamen 361005 Peoples R China China Natl R&D Ctr Tungsten Technol Xiamen 361005 Peoples R China

The influence of working pressure on microstructure and residual stress evolution of magnetron sputtered ZrN coatings were systemically *** and XRD results reveal that all as-deposited coatings at varying working pressure are stoichiometric ZrN with cubic NaCl structure.A decrease in working pressure results in preferred orientation evolution from(111)to(200).This evolution is driven by kinetics processes,such as adatom surface migration and competitive grain growth,rather than by *** explanation is also supported by morphology characterization as the surface and cross-section morphologies transition from tapered shape and columnar structure to round and non-columnar(equiaxed)structure.

关键词： ZrN coating working pressure preferred orientation residual stress microstructure

Comparisons of Exhaustive and Nonexhaustive M/M/l/N Queues with working Vacation and Threshold Policy

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Journal of Systems Science and Systems Engineering 2019年第2期28卷 154-167页

作者： Wei Sun Shiyong Li Yan Wang Naishuo Tian School of Economics and Management Yanshan UniversityQinhuangdao 066004 China College of Science Yanshan University Qinhuangdao 066004 China

This paper compares the performance of exhaustive and nonexhaustive M/M/l/N queues with working vacation and threshold policy. In an exhaustive queue, the server slows down its service rate only when no customers exist in the system, and turns to normal service until the number of customers achieves a threshold. However, in a nonexhaustive queue, the server switches service rate between a low and a high value depending on system congestion. To get equilibrium arrival rate of customers and social welfare for the two types of queues, we first derive queue length distributions and expected busy circle. Then, by making sensitivity analysis of busy circle, system cost, arrival rate and optimal social welfare, we find that customers tend to join exhaustive queues instead of nonexhaustive queues, and the optimal threshold in an exhaustive queue is probably inconsistent with the one in a nonexhaustive queue. Moreover, in general, whet her to consider system cost or not in social welfare will obviously affect the tendencies of optimal arrival rate and optimal social welfare with the threshold and system capacity for the two types of queues, especially for the nonexhaustive queues, and then affect the final decisions of social planner or system manager.

关键词： Markovian queue service discipline limited capacity working vacations threshold policy equilibrium arrival rate busy circle social welfare system cost

Review of the working Fluid Thermal Stability for Organic Rankine Cycles

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Journal of Thermal Science 2019年第4期28卷 597-607页

作者： DAI Xiaoye SHI Lin QIAN Weizhong Department of Chemical Engineering Tsinghua UniversityBeijing 100084China Department of Energy and Power Engineering Tsinghua UniversityBeijing 100084China

The organic Rankine cycle(ORC)is an efficient power generation technology and has been widely used for renewable energy utilization and industrial waste heat *** stability is a significant property of ORC working fluids and is the primary limitation for working fluid selection and system *** paper presents a review of the working fluid thermal stability for ORCs,including an analysis of the main theoretical method for thermal stability,a summary of the main experimental method for thermal stability,a summary of the decomposition experimental results for working fluids,and a discussion of the decomposition influence on ORC *** research trends of thermal stability are also discussed in this paper.

关键词： organic Rankine cycle(ORC) working fluid thermal stability

A Fast Multi-tasking Solution: NMF-Theoretic Co-clustering for Gear Fault Diagnosis under Variable working Conditions

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Chinese Journal of Mechanical Engineering 2020年第1期33卷 182-196页

作者： Fei Shen Chao Chen Jiawen Xu Ruqiang Yan School of Instrument Science and Engineering Southeast UniversityNanjing 210096China School of Mechanical Engineering Xi’an Jiaotong UniversityXi’an 710049China

Most gear fault diagnosis(GFD)approaches su er from ine ciency when facing with multiple varying working conditions at the same *** this paper,a non-negative matrix factorization(NMF)-theoretic co-clustering strategy is proposed specially to classify more than one task at the same time using the high dimension matrix,aiming to o er a fast multi-tasking *** short-time Fourier transform(STFT)is first used to obtain the time-frequency features from the gear vibration ***,the optimal clustering numbers are estimated using the Bayesian information criterion(BIC)theory,which possesses the simultaneous assessment capability,compared with traditional validity ***,the classical/modified NMF-based co-clustering methods are carried out to obtain the classification results in both row and column ***,the parameters involved in BIC and NMF algorithms are determined using the gradient ascent(GA)strategy in order to achieve reliable diagnostic *** Spectra Quest’s Drivetrain Dynamics Simulator gear data sets were analyzed to verify the e ectiveness of the proposed approach.

关键词： Gear fault diagnosis Non-negative matrix factorization Co-clustering Varying working conditions

Analysis of working behavior of Jinping-I Arch Dam during initial impoundment

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Water Science and Engineering 2016年第3期9卷 240-248页

作者： Shi-yong Wu Wei Cao Jiang Zheng Yalong River Hydropower Development Company Ltd.

To study the stress, deformation, and seepage pressure during the initial impoundment of the Jinping-I Arch Dam, monitoring analysis and numerical calculation were used in a dam behavior analysis that focused on the working behavior of the dam during the late period of the initial impoundment up to the end of November 2014. The numerical calculation was performed based on feedback analysis of the deformation and stress of the arch dam through inversion of the elastic moduli(E) of the dam body and foundation, using a three-dimensional finite element model for the linear elastic material of the arch dam. The main monitoring indices presented insignificant changes in the late period of the initial impoundment, and the results of feedback analysis were consistent with monitoring results. Analysis results also show that the deformations of the dam body and dam foundation were within the design range; the dam stress distributions were normal, with values lower than the design control criteria; and the seepage flows through the dam body and dam foundation were lower than the design drainage capacity of the deep-well pump house, demonstrating that the Jinping-I Arch Dam was in good working condition, and the initial impoundment had been successfully completed. The results of the working behavior analysis of the Jinping-I hydropower project during the initial impoundment can provide references for safe operation of similar projects.

关键词： Dam safety monitoring working behavior Elastic modulus Dam impoundment Jinping-I hydropower project

Mechanism of rock burst caused by fracture of key strata during irregular working face mining and its prevention methods

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International Journal of Mining Science and Technology 2019年第6期29卷 889-897页

作者： Zengqiang Yang Chang Liu Hengzhong Zhu Fuxing Xie Linming Dou Jianhang Chen School of Resource and Safety Engineering China University of Mining&TechnologyBeijing 100083China State Key Laboratory of Coal Resources and Mine Safety China University of Mining&TechnologyXuzhou 221116China Science&Technology Innovation Center Coal Mining and Designing DepartmentTiandi Science&Technology Co.LtdBeijing 100013China Mine Construction Branch of Research Institute China Coal Research InstituteBeijing 100013China

To study the occurrence mechanism of rock burst during mining the irregular working face,the study took irregular panel 7447 near fault tectonic as an engineering *** spatial fracture characteristic of overlying strata was analyzed by Winkler elastic foundation beam ***,the influence law of panel width to suspended width and limit breaking span of key strata were also analyzed by thin plate *** micro-seismic monitoring,theoretical analysis,numerical simulation and working resistance of support of field measurement,this study investigated the fracture characteristic of overlying strata and mechanism of rock burst in irregular working *** results show that the fracture characteristic of overlying strata shows a spatial trapezoid structure,with the main roof being as an *** fracture form changes from vertical‘‘O-X"type to transverse‘‘O-X"type with the increase of trapezoidal *** the narrow mining face to the wide mining face,the suspended width of key strata is greater than its limit breaking width,and a strong dynamic load is produced by the fracture of key *** numerical simulation and micro-seismic monitoring results show that the initial fracture position of key strata is close to tailgate *** there is a high static load caused by fault *** dynamic and static combined load induce rock ***,a cooperative control technology was proposed,which can weaken dynamic load by hard roof directional hydraulic fracture and enhance surrounding rock by supporting system.

关键词： Rock burst Irregular working face Key strata Dynamic and static combined load Cooperative control