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modeling and simulation of an industrial falling film evaporator for alumina production

CHEMICAL ENGINEERING RESEARCH & DESIGN 2020年 154卷 303-315页

作者： Wang, Xiaoli Xiong, Pan Sun, Kaixuan Xie, Yongfang Yang, Chunhua Cent S Univ Sch Automat Changsha 410083 Peoples R China Texas A&M Univ Texas A&M Energy Inst College Stn TX 77843 USA

This paper describes a mathematical model developed by combining a lumped parameter model (LPM) and a distributed parameter model (DPM) for an industrial falling film evaporator used for the evaporation of a sodium aluminate solution (SAS) during the alumina production process. In the LPM, the dynamic equations were deduced to calculate the concentration of the evaporator outlet. The DPM was developed to study the evaporation occurring in each heating tube, in which the residence time, film thickness, liquid load of the feed, and the amount of heat transfer were established as functions of the longitudinal location from the entrance down the tube. Material properties related to the compositions, such as the density and viscosity, were fitted from industrially measured data acquired during a heat balance test. The modeling of the overall heat transfer coefficient based on fluid mechanics is discussed. The effect of scaling, which is an obstacle to accurate modeling, was considered using the industrial history data combined with the calculations of the mass and heat balance equations. The simulated concentrations of the products revealed the high accuracy of the model. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： Falling film evaporator Alumina Lumped parameter model distributed parameter model

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Distribution of brine temperature in a large-scale horizontal-tube falling film evaporator

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APPLIED THERMAL ENGINEERING 2020年 164卷 114437-000页

作者： Gong, Luyuan Zhou, Shihe Guo, Yali Shen, Shengqiang Dalian Univ Technol Key Lab Liaoning Prov Desalinat Dalian 116024 Liaoning Peoples R China

Falling film evaporator applied in multi-effect evaporation device is normally operated under small temperature differences. Considering the high sensitive of the evaporator, the distribution of the brine temperature, as one of the parameters that determines the distribution of the local temperature difference, is studied in this paper using parameter distributed model. The three-dimensional distributions of the brine temperature as well as the location of the maximum brine temperature are presented under different operating conditions. Results show that the maximum variation range of the brine temperature in the evaporator decreases with the increment of the brine inlet spray density and salinity but increases with the increment of the apparent temperature difference. In the aim of avoid design failure of the local temperature difference, the variation of the location of the maximum brine temperature as well as the thermodynamic losses in the brine film are analyzed, providing theoretical basis for the more accurate design of the falling film evaporator.

关键词： Falling film evaporator Horizontal tube bundle distributed parameter model Brine temperature distribution

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Flatness-based Heavy Rope Control: Experimental results with a 6R Industrial Manipulator

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IFAC-PapersOnLine 2022年第26期55卷 71-77页

作者： Arthur Angerer Frank Woittennek UMIT Tirol 6060 Hall in Tirol Austria

Flatness-based control schemes for a heavy rope with freely movable suspension point are compared in simulation and experiment. These schemes are based on a nonlinear distributed parameter model (DPM) of the chain and two different approximations, firstly a rigid body approximation as a physical pendulum, secondly a tangent linearization of the original model. The flat output is given by the free end of the rope for the DPMs and by the center of oscillation for the rigid body approximation. The design is achieved by prescribing a desired path for the flat output and computing the corresponding path of the suspension point. Numerical simulations are performed by means of a finite-difference approximation of the original non-linear DPM. For the experimental studies the chain is suspended from the end effector of a 6R industrial manipulator. The required joint angles of the manipulator are computed by selecting one of the eight solutions of the inverse kinematics of the robot.

关键词： heavy rope distributed parameter model flatness inverse kinematics

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Hydraulic transient modeling and analysis of the district heating network

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SUSTAINABLE ENERGY GRIDS & NETWORKS 2021年 25卷

作者： Zheng, Xuejing Xu, Boxiao Wang, Yaran You, Shijun Zhang, Huan Wei, Shen Wang, Na Tianjin Univ Sch Environm Sci & Engn Tianjin 300350 Peoples R China Tianjin Key Lab Biomass Wastes Utilizat Tianjin 300350 Peoples R China Univ Coll London UCL Bartlett Sch Construct & Project Management 1-19 Torrington Pl London WC1E 7HB England Tianjin Energy Investment Grp CO LTD Tianjin 300072 Peoples R China

The hydraulic transients are obvious during the operation and adjustment of large-scale district heating (DH) network. Hydraulic transient modeling and simulation methods can provide basis for efficient operation of the DH network. In this paper, two hydraulic transient models, the distributed parameter model (DPM) and lumped parameter model (LPM), were established for DH network. Efficient numerical algorithms were presented for the two models. The proposed DPM and LPM were both applied to a DH network to simulate and analyze the network hydraulic transients caused by the valve and pump operations. Results indicate that with the increase of the distance from the adjustment location, the transient time for the flow rate and pressure gets longer. As the adjustment duration decreases, the transient time increases. Comparison of the simulation performances between the two models indicates that the DPM can capture the high-frequency hydraulic transients subtly. With the decrease of adjustment duration, more severe high-frequency hydraulic transients will occur. However, only the average hydraulic fluctuations can be described by LPM. The computation time of LPM is shorter than DPM because of the vectorizable calculation procedure and the less data to record, since the LPM neglects the pressure waves and the fluid compressibility. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： District heating network Hydraulic transient distributed parameter model Lumped parameter model Transient time

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Upgraded parameter model of frame pin-supported wall structures

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STRUCTURAL DESIGN OF TALL AND SPECIAL BUILDINGS 2021年第8期30卷 e1852-e1852页

作者： Zhou, Ying Yao, Dansheng Chen, Yue Li, Qingqian Tongji Univ State Key Lab Disaster Reduct Civil Engn Shanghai Peoples R China Ningbo Univ Technol Zhejiang Engn Technol Res Ctr Civil Engn Ind Cons Ningbo 315211 Peoples R China

A frame pin-supported wall structure (FPWS) is a typical rocking structure that releases constraints at the bottom of the wall. The existing studies have demonstrated that FPWSs can control the structural deformation effectively. A distributed parameter model (DPM), which consists of a flexural beam and a shear beam connected by infinitely rigid links, is used to describe the performance of FPWSs. The flexural and the shear beams represent the wall and the frame, respectively. However, there are several flaws in the DPM. For instance, (1) it is not appropriate to simplify the frame into a shear beam, (2) the infinitely rigid links cannot demonstrate the interaction between the frame and the wall properly, and (3) the stiffness variation along the height of the frame is not considered. In this study, an upgraded parameter model (UPM) was proposed to simulate the FPWS based on the DPM. Specifically, (1) a lumped mass model is employed to simulate the frame instead of the shear beam;(2) the pin-supported wall (PW) and the frame are connected only at several positions, that is, at the floor levels;and (3) the variation of the stiffness is also considered in the UPM. The results via the UPM were compared with those using DPM and OpenSees model. A parametric analysis was then carried out using the UPM. The results indicated that the proposed UPM can describe the behavior of FPWSs accurately.

关键词： distributed parameter model drift concentration factor frame parametric analysis pin‐ supported wall upgraded parameter model

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Improved genetic algorithm-based prediction of a CO2 micro-channel gas-cooler against experimental data in automobile air conditioning system

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INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID 2019年 106卷 517-525页

作者： Yang, Jingye Yu, Binbin Chen, Jiangping Shanghai Jiao Tong Univ Inst Refrigerat & Cryogen Shanghai 200240 Peoples R China

For the prevailing CO2 micro-channel gas-cooler (MCGC) mathematical modeling research, a big challenge for an efficient numerical model is the trade-off between fast calculation and high-precision considering the specific properties of CO2. The main purpose of this work is to propose a regression method with multiple variables for CO2 MCGC model based on the combination of distributed parameter model (DPM) and Genetic algorithm (GA). The GA based prediction model of MCGC is established, which takes correlation coefficients and mean squared error into consideration. A test rig of CO2 MCGC is developed, and the experimental data used to validate the MCGC model are collected. The fixed-point iteration algorithm is utilized to reduce the complexity of simulation to accelerate the iteration speed. Moreover, an improved Taylor series expansion-based method for fast calculation of working fluid properties was proposed. The model precision was analyzed by comparing the prediction results with conducted experimental data. The improved CO2-to-air MCGC model enables to predict refrigerant outlet temperature and pressure drop within a maximum deviation of 1.2 degrees C and 2 kPa against the experimental data. (C) 2019 Elsevier Ltd and IIR. All rights reserved.

关键词： CO2 Micro channel gas cooler distributed parameter model Genetic algorithm Interpolation method Heat transfer performance

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modelING THE DRYING OF WHEAT SEEDS IN A FLUIDIZED BED USING A SPATIALLY RESOLVED model

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APPLIED ENGINEERING IN AGRICULTURE 2019年第4期35卷 551-559页

作者： Hemis, M. Watson, D. G. Raghavan, V Univ Khemis Miliana Fac Sci & Technol Dept Technol Ain Defla Algeria Southern Illinois Univ Dept Plant Soil & Agr Syst Carbondale IL USA McGill Univ Bioresource Engn Ste Anne De Bellevue PQ H9X 3V9 Canada

A mathematical model for simulating heat and mass transfer during fluidized-bed drying of wheat grains has been developed, combining two transfer steps;a movement of moisture inside the grain and outside the grain. Empirical equations have been used for material properties as well as for transfer processes. The developed model is composed of two models coupled to each other;the distributed parameter model (DPM or Luikov model) and the convective model. The coupled mathematical model was solved numerically by a finite difference method after discretization of equilibrium equations distributed in space. The DPM model made it possible to predict the quantity of water extracted from the grain under the effect of known drying conditions. Results showed that the drying rate of wheat increased when air temperature was increased;and that the rates were higher in the first few minutes of drying, achieving 2.6 x 10(-5) and 1.7 x 10(-5) kg water kg(-1 )[d.b.].s(-1) for temperatures of 66.7 degrees C and 58.6 degrees C, respectively. A comparison of experimental and predicted results gave good agreement, and the use of the distributed model improved the predictive capabilities of wheat grain drying in fluidized beds.

关键词： Canada Western Red Spring distributed parameter model Fluidized-bed dryer Mathematical modeling Wheat seeds

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Impact of the geometric parameters on the thermal performance of a large-scale falling film evaporator for desalination

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DESALINATION AND WATER TREATMENT 2019年第0期157卷 281-289页

作者： Gong, Luyuan Guo, Yali Mu, Xingsen Shen, Shengqiang Dalian Univ Technol Natl United Engn Res Ctr Thermal Energy Integrat Key Lab Liaoning Prov Desalinat Dalian 116024 Liaoning Peoples R China

Based on a validated distributed parameter model, the thermal performance of a large-scale falling film evaporator was simulated under different geometric parameters including the tube length and the row-column ratio of the tube bundle. On considering that the falling film evaporators applied in the multi-effect evaporation are operated under small temperature difference thus sensitive to the temperature variation inside the evaporator, the variation of the local temperature difference is presented in detail. The distributions of the local heat transfer coefficient and heat flux were also exhibited under different geometric parameters. Results show that both the tube length and tube bundle row-column ratio have significant impact on the distribution of thermodynamic parameters in the falling film evaporator. The maximum value of the average heat flux of the evaporator is obtained when the length of the tube is 7 m. The maximum heat flux of the evaporator is obtained when the tube bundle row-column ratio is 2.5.

关键词： Falling film evaporator Horizontal tube bundle distributed parameter model Geometric parameters Thermal performance

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Thermal performance analysis of submerged combustion vaporizer at supercritical pressure

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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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A modified lumped parameter model of distribution transformer winding

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Global Energy Interconnection 2020年第2期3卷 158-165页

作者： Qingqing Ding Yao Yao Bingqian Wang Jingwei Fu Wei Zhang Chao Zeng Xiaoping Li Stanimir Valtchev State Key Laboratory of Power System Department of Electrical EngineeringTsinghua UniversityHaidian DistrictBeijing100084P.R.China State Grid Hubei Electric Power Co. Research Institute(HBEPRI)Hongshan DistrictWuhan 430077P.R.China Flexible Transmission Engineering Department Nari-Relays Electric Company210003 NanjingP.R.China State Grid Hubei Electric Power Co. LtdHongshan District430077 WuhanP.R.China Department of Electrical and Computer Engineering Faculty of Science and TechnologyUNLPortugal

The modelling of the distribution transformer winding is the starting point and serves as important basis for the transformer characteristics analysis and the lightning pulse response prediction.A distributed parameters model can depict the winding characteristics accurately,but it requires complex *** parameter model requires less calculations,but its applicable frequency range is not *** paper studies the amplitude-frequency characteristics of the lightning wave,compares the transformer modelling methods and finally proposes a modified lumped parameter model,based on the above *** proposed model minimizes the errors provoked by the lumped parameter approximation,and the hyperbolic functions of the distributed parameter *** this modification it becomes possible to accurately describe the winding characteristics and rapidly obtain the node voltage *** proposed model can provide theoretical and experimental support to lightning protection of the distribution transformer.

关键词： Wide band frequency response distributed parameter model Lumped parameter model Distribution transformer Lightning protection

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