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Thermal performance analysis of submerged combustion vaporizer at supercritical pressure

CRYOGENICS 2019年 100卷 41-52页

作者： Pan, Jie Bai, Junhua Tang, Linghong Li, Ran Wu, Gang Xian Shiyou Univ Coll Petr Engn Xian 710065 Shaanxi Peoples R China Xian Shiyou Univ Coll Mech Engn Xian 710065 Shaanxi Peoples R China

In this paper, an energy balance-based model considering icing effects was established for estimating the heat transfer of submerged combustion vaporizer (SCV) under supercritical LNG pressure, where introduces some empirical correlations to evaluate the convection heat transfer of water bath-side and LNG-side. Based on this model, the thermal performance of a typical SCV was predicted numerically, and good agreement between the predicted and actual water bath temperatures indicates that the model is reliable. The results indicated that the operation parameters, such as LNG pressure, operating load, inlet LNG temperature, have significantly different influences on the thermal performance of SCV, including required minimum water bath temperature and flue gas flow rate, and the length and average thickness of ice layer outside the LNG tube bundle. The heat transfer enhancement techniques can improve the heat transfer efficiency markedly, although they also cause an increase in flow resistance. The wire coil insert with a helix angle of 75 degrees is a better choice than the twisted tape insert with a helix angle of 45 degrees and the wire coil insert with a helix angle of 45 degrees considering its effects on both heat transfer and flow resistance.

关键词： Thermal performance SCV distributed parameter model Heat transfer tube Supercritical pressure Heat transfer enhancement

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parameter Estimation for Series Compensated Transmission LineL

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INTERNATIONAL JOURNAL OF EMERGING ELECTRIC POWER SYSTEMS 2011年第3期12卷 1-20页

作者： Du, Yan Liao, Yuan Univ Kentucky Lexington KY 40506 USA

Transmission line parameters are essential inputs to various power system analysis programs and applications such as protective relaying algorithms, and precision of line parameters is thus significant in ensuring the analysis accuracy and algorithm reliability. This paper proposes methods for estimating positive sequence parameters of a series compensated transmission line. The methods are based on distributed parameter line model and utilize voltages and currents from both terminals of the line during normal operations. In particular, based on nonlinear estimation theory, an optimal estimator is designed for deriving positive sequence line parameters. The algorithm is capable of detecting and identifying bad measurement data, and thus improving the estimation accuracy. The proposed method is independent of the operation status of the compensation device.

关键词： distributed parameter model series compensated line transmission line parameter estimation

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Developing models of Turbine Thermal Processes in Low-Steam and Motor Modes

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THERMAL ENGINEERING 2021年第8期68卷 612-618页

作者： Pikina, G. A. Arakelyan, E. K. Pashchenko, F. F. Filippov, G. A. Natl Res Univ Moscow Power Engn Inst Moscow 111250 Russia Russian Acad Sci Trapeznikov Inst Management Problems Moscow 117997 Russia

The main purpose of the motor mode is to keep the turbine in hot standby (with the boiler off) without generating electricity to the grid. To do this, the generator is switched to the engine mode, which rotates the turbine rotor, and the cooling of the flow path is performed by supplying one or two intermediate steam extractions from the extractions of the neighboring turbine. The first stages of the high-pressure cylinder run on steam from the front seals. The noted specificity of the purpose and operating conditions of the turbine in low-steam modes imposes additional requirements on the mathematical model. When developing models of a turbine stage in a motor mode, the physical media included in the object were taken into account: the steam of the flow path passing through the nozzle and working discs, participating in the conversion of its thermodynamic and kinetic energy into mechanical energy of the rotor rotation;vapor leakage into the space between the discs;steam leakage through the rotor-guide vane seal;metal of rotating devices (working disks and turbine rotor);and metal of the stator and exhaust pipes. Multipoint models are obtained with lumped parameters distributed along the length of the flow channel with values that vary depending on the ordinal number of the stage. The main part of the step models are eight ordinary differential equations or partial differential equations of physical media. The developed models are necessary for computer modeling and investigating the temperature distribution of the turbine flow path. Based on the research results, it is proposed to create a real automatic control system that ensures the implementation of restrictions on metal heating and the generation of added power.

关键词： turbine low steam and motor modes thermal processes multipoint models distributed parameter model partial differential equations lumped parameter model ordinary differential equations

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Nonlinear model Predictive Control for the Superfluid Helium Cryogenic Circuit of the Large Hadron Collider

Nonlinear Model Predictive Control for the Superfluid Helium...

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IEEE International Conference on Control Applications Part of 2010 IEEE Multi-Conference on Systems and Control

作者： Noga, Rafal Ohtsuka, Toshiyuki de Prada Moraga, Cesar Vinuela, Enrique Blanco Cubillos, Juan Casas Osaka Univ 1-3 Machikaneyama Osaka 5608531 Japan Univ Valladolid E-47011 Valladolid Spain CERN European Org Nuclear Res CH-1211 Geneva Switzerland

ISBN: (纸本)9781424453634

Superfluid helium is used in the cryogenic circuit that cools down and stabilizes temperature of more than 1600 high performance, main superconducting magnets of the Large Hadron Collider (LHC) - the new particle accelerator at European Organization for Nuclear Research (CERN). This paper presents a simulation study of the application of Nonlinear model Predictive Control (NMPC) to the Superfluid Helium Cryogenic Circuit. First, the new first principles, distributed parameter model of the circuit to be used in online optimization is reviewed. Then stabilization of the superconducting magnets temperature using NMPC based on the model and Continuation/Generalized Minimum Residual (C/GMRES) algorithm is described. Finally the small computational cost of C/GMRES solution/approximation method and resulting real-time feasibility are highlighted.

关键词： European Organization for Nuclear Research accelerator control systems accelerator magnets circuit optimisation continuation-generalized minimum residual algorithm cryogenic electronics distributed parameter model distributed parameter systems large hadron collider liquid helium nonlinear control systems nonlinear model predictive control online optimization particle accelerators predictive control superconducting magnet superconducting magnets superfluid helium cryogenic circuit superfluidity synchrotrons temperature control

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Study of Transient Spectrum in Transmission Lines

Study of Transient Spectrum in Transmission Lines

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General Meeting of the IEEE-Power-and-Energy-Society

作者： Wang, X. G. Huang, S. F. Liu, Q. K. N China Elect Power Univ Key Lab Power Syst Protect & Dynam Secur Monitori Minist Educ Beijing Peoples R China

ISBN: (纸本)9781424419050

When faults occur in transmission lines, the high frequency signals are caused by fault generated traveling waves and the spectrum is a series of harmonic in frequency domain. This paper utilizes lumped and distributed parameter models to express transmission tines respectively, analyzes the character of nature frequencies. Different influencing factors including different fault conditions, source impedance, bus capacitance, series compensated capacitance and shunt reactor are discussed in this paper. The results have been proven by ATP procedure in a typical 500-kv power transmission line.

关键词： Transmission line Nature frequencies High frequency signals Traveling wave Lumped parameter model distributed parameter model Spectrum

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A multi-loop vibration control of a torsional plant

A multi-loop vibration control of a torsional plant

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IEEE International Conference on Mechatronics (ICM)

作者： Kang, BS Oloomi, H Purdue Univ Ft Wayne IN 46805 USA

ISBN: (纸本)0780389980

This paper addresses the problem of suppressing torsional vibration induced by a disturbance torque in a high performance two-disk system. The plant consists of two inertia disks connected by a weakly damped link and is driven by a brushless DC motor connected to one of the disks. A distributed parameter model of the system is developed and a lumped parameter model including the dominant torsional modes is then extracted. A multi-loop controller is designed on the basis of the lumped parameter model and is shown to be capable of suppressing the vibration to a reasonable level and over a wide frequency range.

关键词： torsional plant vibration control distributed parameter model multi-loop control disturbance suppression

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A Fast Full-line Tripping Distance Protection Method for HVDC Transmission Line

A Fast Full-line Tripping Distance Protection Method for HVD...

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Asia-Pacific Power and Energy Engineering Conference (APPEEC)

作者： Zhang, Jiankang Suonan, Jiale Jiao, Zaibin Song, Guobing Su, Xiaohua Xi An Jiao Tong Univ Sch Elect Engn Xian 710049 Peoples R China Northwest China Grid Co Ltd Xian Peoples R China

ISBN: (纸本)9781457705472;9781457705465

Though distance protection has been successfully used for AC transmission line, there is no practical application of it for HVDC transmission line. For distance protection, it is essential to measure accurately at the zone boundary to distinguish internal fault from external correctly, and high measurement accuracy at any part of the full line is unnecessary. Besides, HVDC transmission line is generally connected with smoothing reactor at two ends and it can be regarded as the operating boundary of distance protection. Considering these features, a fast full-line tripping distance protection method for HVDC transmission line is introduced in this paper. Based on distributed parameter model, the voltage and current at the end-point are calculated accurately using those at the relay point. After that, the line between the end-point and fault point is simplified as lumped parameter RL model and the fault distance is obtained with differential equations. In this way, high calculation accuracy at the zone boundary is attained and which contributes greatly to the improvement of protection performance. Simulation results show that this method is capable of protecting the whole line with high rapidity, and can be used as primary protection for HVDC transmission.

关键词： HVDC transmission line distance protection distributed parameter model RL model primary protection

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Numerical simulation of operating performance of heat exchangers in a residential split air-conditioner

Numerical simulation of operating performance of heat exchan...

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1st International Conference on Civil Engineering, Architecture and Building Materials (CEABM 2011)

作者： Su, Shunyu Tian, Tian Chen, Jian Wuhan Univ Sci & Technol Coll Urban Construct Wuhan 430070 Peoples R China

ISBN: (纸本)9783037851272

The mechanism of fluid flow and heat transfer in the heat exchangers was investigated in this paper. Using R22 as the working fluid, the steady distributed parameter models of condenser and evaporator in a residential split air-conditioner were established based on thermophysical laws such as mass, momentum and energy conservation equations. The regions of two-phase fluid and superheated gas in evaporator and the regions of superheated gas, two-phase fluid and subcooled liquid in condenser were respectively simulated under designed conditions of air-conditioning system. Based on the calculated results, the flow and heat transfer performances of heat exchangers were analyzed. The results show that the two-phase fluid regions in both evaporator and condenser have great influence on the fluid flow and heat transfer performances in it.

关键词： distributed parameter model Heat exchanger Air-conditioner Conservation equation

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modeling of Converters and Devices with distributed RC-parameters with the Required Accuracy in the Specified Frequency Range 2

Modeling of Converters and Devices with Distributed RC-param...

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2nd International Conference on Industrial Engineering, Applications and Manufacturing (ICIEAM)

作者： Sukhinets, Zh. A. Gulin, A., I Ufa State Aviat Tech Univ Ufa Russia

ISBN: (纸本)9781509013227

The paper considers application of the method of conversion functions for modeling converters and devices with distributed RC - parameters, including those consisting of non-linear elements, for a given frequency band that satisfy the requirements of attenuation and the input(output) immittance. It proposes analytical expressions and the method of calculating the minimum required number of links in the model. The expressions and formulas allow simulation of devices with distributed RC - parameters with the required accuracy in the given frequency range.

关键词： ladder structure the transformation function distributed parameter model frequency error

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Theoretical study of monolithic pyroelectric sensor arrays by thermal diffusion equation 4

Theoretical study of monolithic pyroelectric sensor arrays b...

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4th International Conference on Thin Film Physics and Applications

作者： Yu, J Ling, YN Sun, JL Meng, XJ Chu, JH Tang, DY Chinese Acad Sci Shanghai Inst Tech Phys Natl Lab Infrared Phys Shanghai 200083 Peoples R China

ISBN: (纸本)0819437298

distributed parameter model is used for computation of the performances of single pixel of PZT ferroelectric thin Mm infrared uncooled focal plane array(IR-UFPA) with two kinds of thermal isolation structures. The detector performances are found to be related closely to the thermal isolation structure. The preferred thickness of pyroelectric thin film is in the region of 0.3-2 mum for pixel dimensions 50x50 and 100x100 mum(2). And the preamplifier current noise is the dominant noise when it more than 10(-16)A . Hz(-1/2) in PZT-UFPA device.

关键词： UFPA performance distributed parameter model PZT

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