Experimental and Numerical Investigations on Hydrodynamics of Nanofluid Flowing in Coiled Tubes

Abstract

A numerical model was developed to analyze the hydrodynamics of TiO₂-water nanofluids flowing through straight and coiled tubes in laminar flow regime. Pressure drop of nanofluid predicted from this model was validated with experiments for identical dimensions of tubes and process conditions. The velocity contours of flow in straight as well as coiled tube were examined. The present study revealed that there was 74% decrease in pressure drop when the straight tube diameter was increased from 0.003?m to 0.0072?m. There was 46–51% decrease in friction factor when curvature ratio (D_c/d_t) was increased from 7.54 to 12.24 for 200<De?<?850.     

Shu Fan,Chengxiong Mao,Luonan Chen,Electricity peak load forecasting with self‐organizing map and support vector regression,IEEJ Transactions on Electrical and Electronic Engineering (2006)1(3)330‐336

The original article to which this Erratum refers was published in IEEJ Transactions on Electrical and Electronic Engineering IEEJ Trans Electrical Electron Eng (2006) 1(3) 330 .     

Takahiro Jibiki,Wataru Fujii,Yasuhiro Tanaka,Development of connection systems for wind power generating plant to electric power network: Experiment at the Tomamae Winvilla power plant,IEEJ Transactions on Electrical and Electronic Engineering (2007)2(1)3‐7

The original article to which this erratum refers was published in the IEEJ Transactions on Electrical and Electronic Engineering IEEJ Trans Elec Electron Eng(2007) 2(1) 3     

数值模拟在锅炉安全运行中的应用

四角切圆燃烧锅炉在运行中遇到的诸多问题如炉膛结渣、水冷壁爆管、过热器区域的左、右温度偏差、燃烧稳定性等均与炉膛温度分布密不可分。炉膛温度分布是否合理,炉膛配风至关重要。炉膛配风若不合理,严重影响锅炉的安全运行。炉膛的配风调整十分复杂,通过空气动力场试验获得的数据比较有限,同时需要花费大量的人力物力。以元宝山电厂3号炉为例,利用应用软件GAMBIT和FLU-ENT,模拟切圆燃烧锅炉的配风。通过模拟不同工况下炉内配风,分析不同工况下炉内空气动力场,得到一二次风的最佳配比,获得良好的炉内动力场分布。数值模拟为锅炉的安全运行提供参考的数据,为优化锅炉的安全经济运行提供参考方案,同时节约大量的人力物力,数值模拟在锅炉安全运行中必将会得到广泛的应用。     

Numerical simulation of blow‐down closed‐cycle disk MHD generator

Numerical simulations of the closed‐cycle disk MHD generation experiment with Tokyo Institute of Technology's Fuji‐1 blow‐down facility are performed. In the calculations, the r–z two‐dimensional time‐dependent simulation code developed by the authors that can take the effect of water contamination into account is used, and the experimental conditions of Run A4109 operated by Disk‐F4 generator are selected as the numerical conditions. When the water contamination is the lowest level realized in the experiments, the simulation results coincide with the experimental results reasonably well, though there exist some discrepancies caused by inaccuracy of used basic plasma parameters, limitations of the two‐dimensional approximation, and so on. The voltage–current curve is almost linear, indicating that the MHD interaction is relatively weak and the flow field is mainly determined by the back‐pressure. The increase of the water contamination level results in decreased seed ionization rate at the generator channel inlet, leading to the steep deterioration of the generator performance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 46–54, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10335     

Numerical analysis of a DAR IMPATT diode

The analysis and optimization of the n ⁺ pvnp ⁺ avalanche diode structure that includes two avalanche regions have been realized on basis of the nonlinear model and special optimization procedure. The admittance and energy characteristics of the DAR diode were analyzed in very wide frequency band from 30 up to 360 GHz. Output power level was optimized for the second frequency band near the 220 GHz.     

Numerical analysis of transit conduction current in an insulating liquid with added ionic electrolyte

We simulated the phenomena of transit conduction in an insulating liquid with added ionic molecules such as surfactant, by using the charge‐injection model with dissociation‐recombination. When the parameters of C_i (density of injected charge) and C₀ (density of created charge in the liquid) are C_i>C₀ in this simulation, the waveform of current density showed an injection type with a peak, and when C_i<C₀, it showed a dissociation‐recombination type. A decreasing characteristic appeared in the low electric field, maximum one in the middle field, and saturating one in the high field. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 10– 16, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20327     

Bifurcation and chaos in multi-parallel-connected current-mode controlled boost DC-DC converters

This paper studied the bifurcation and chaos phenomenon in a multi-parallel-connected current-mode controlled boost DC-DC converter system with the use of nonlinear mapping bifurcation theory of two dimensions, and the changing rules of the bifurcation charts with the increase of the control parallels and control parameters were concluded. The method of discrete mapping modeling was utilized to construct the difference equations of the system operating in continuous conduction mode (CCM). Analyses and computer emulations were made. __________ Translated from Journal of Proceedings of the Chinese Society for Blectrical Engineering, 2005, 25(6): 67–70 (in Chinese)     

微油点火燃烧器建模及数值计算方法的研究

为了深入掌握微油点火燃烧器内部的流场数据及颗粒场数据,结合某电厂微油点火燃烧器的实际工况,分析了对流扩散方程的离散化方法及辐射模型和气体燃烧模型对燃烧器数值计算的影响,并通过CFX软件建立了一个比较完善的数学模型。研究结果表明:采用High Resolution离散化方法、Discrete Transfer辐射模型和Eddy Dissipation气体燃烧模型,对微油点火燃烧器的计算有较大帮助。     

A new approach for numerical simulation of quantum transport in double-gate SOI

Numerical simulation of nanoscale double-gate SOI (Silicon-on-Insulator) greatly depends on the accurate representation of quantum mechanical effects. These effects include, mainly, the quantum confinement of carriers by gate-oxides in the direction normal to the interfaces, and the quantum transport of carriers along the channel. In a previous work, the use of transfer matrix method (TMM) was proposed for the simulation of the first effect. In this work, TMM is proposed to be used for the solution of Schrodinger equation with open boundary conditions to simulate the second quantum-mechanical effect. Transport properties such as transmission probability, carrier concentration, and I–V characteristics resulting from quantum transport simulation using TMM are compared with that using the traditional tight-binding model (TBM). Comparison showed that, when the same mesh size is used in both methods, TMM gives more accurate results than TBM. Copyright © 2007 John Wiley & Sons, Ltd.     

Numerical modeling and optimization of laser soldering for Micro‐USB electric connector

The laser soldering process was introduced in Micro‐USB electronic packaging in this paper. Numerical modeling and analysis was used for laser process parameter design, because experimental measurements of peak temperature and soldering stress are expensive and often intractable. Accurate knowledge of the residual stress and distortion is a prerequisite for the reliability of the electric connector. The present work proposes a three‐dimensional transient heat transfer model of Micro‐USB package laser soldering process. The calculated thermal cycles and distribution are subsequently used to calculate the distortion and thermal stresses. Meanwhile, the effect of process parameters on residual stress and pin distortion was discussed, and the tensile strength, microstructure, and residual stresses of laser soldering were tested. It can be concluded that the proper laser soldering parameters and power can improve the mechanical property of solder joints on Micro‐USB connector. Copyright © 2014 John Wiley & Sons, Ltd.     

Rotor broken-bar fault diagnosis of induction motor based on HHT of the startup electromagnetic torque

This paper presents a new method for rotor broken-bar fault diagnosis of induction motors. The asymmetry of the rotor caused by broken-bar fault will give rise to the appearance of additional frequency component of 2sf _s (s is slip and f _s is supply frequency) in the electromagnetic torque spectrum. The startup electromagnetic torque signal is decomposed into several intrinsic mode function (IMF) with empirical mode decomposition (EMD) based on the Hilbert-Huang Transform. Then, using the instantaneous frequency extraction principle of the Hilbert Transform, the rotor broken-bar fault characteristic frequency of 2sf _s can be exactly extracted from the IMF component, which includes the rotor fault information. Moreover, the magnitude of the IMF which includes the rotor fault information can also give the number of rotor broken bars. Experimental results demonstrate that the proposed electromagnetic torque-based fault diagnosis method is feasible. __________ Translated from Proceedings of the Chinese Society for Electrical Engineering, 2005, 25(11):107–112 (in Chinese)     

Mapping of circuit variables into two‐port network variables in basic amplifier structures: identifying new topologies

In this paper, we report on a unique observation which enables the unification of the analysis for different amplifier structures. In particular, we report that the change from one type of amplifier to the other can be understood via a mapping of source‐load circuit variables (V_s, R_s, I_i, I_o, I_L, V_o) into two‐port network variables (V₁, V₂, I₁, I₂). As such, unified expressions for (A_v,Z_i,A_i,Z_o) are derived. Further, a Matlab code is written to search for all valid mappings out of 3⁸ different possibilities. Copyright © 2013 John Wiley & Sons, Ltd.     

Numerical simulation of intermediate‐temperature disk type seal‐less SOFC fed with partially reformed methane

Since natural gas containing methane as major component is the most promising fuel for the solid oxide fuel cell (SOFC), development of a numerical simulation code of the intermediate‐temperature disk‐type seal‐less SOFC for methane fuel case is considered to be very useful. In this study, therefore, we develop a new simulation code for the single cell unit of this type of SOFC fed with partially reformed methane as the fuel gas, based on the existing simulation code for pure hydrogen. We calculate the current density versus single cell voltage (i–V ) curves of the single cell unit for various cases with a wide range of the cell temperature and prereformer temperature conditions and compare them with the corresponding experimental results. From the results, we confirm that the numerically obtained i–V curves coincide very well with the corresponding experimental ones in all cases. The variations of the i–V curves, which depend not only on the cell temperature but also on the prereformer temperature, are successfully simulated with a sufficiently high accuracy, indicating the validity of the newly developed simulation code. We also investigate the detailed influence of the cell temperature and prereformer temperature on the cell performance on the basis of the numerically obtained gaseous partial pressure profiles in the fuel channel and Nernst potential profiles in the cell, and clarify the reason why the prereformer temperature has obvious influence on the cell performance when the cell temperature is low, though the cell performance is almost independent of the prereformer temperature when the cell temperature is high. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Biomedical Engineering in China

Biomedical engineering has had a remarkable growth in the past decade in China. With the significant increase in research funding in the past several years, our Chinese colleagues have enjoyed good times for biomedical engineering research and development. This special issue includes a collection of articles contributed by groups, which cover the broad spectrum of biomedical engineering research, including molecular imaging, cancer detection and treatment, health information technology, neural engineering, electrophysiology, and biomedical imaging.     

Numerical simulation of hole transport in silicon nanostructures

In order to study the trade-off between accuracy and computational costs in p-type device simulation, we have simulated hole transport in one-dimensional Si p⁺pp⁺ structures within a nonequilibrium Green’s function formalism combining with three different types of methods for band structure calculation; an empirical sp³d⁵s* tight-binding method, k⋅p two-band approximation, and effective-mass approximation.     

A novel PWM scheme to eliminate the diode freewheeling In the Inactive phase in BLDC motor

The brushless DC motor (BLDCM) with trapezoidal electromotive force (back-EMF) waveform is used widely. In principle, when the motor runs in the 120° conduction mode, two of the three phases are active while the other phase is inactive at all times. However, a ripple current occurs in the inactive phase due to the diode freewheeling during the non-commutation period in the traditional pulse width modulation (PWM) methods, which aggravates the torque ripples. A new PWM method is proposed in this paper to eliminate the diode freewheeling during the non-commutation period in the inactive phase. As a result, the torque ripple is suppressed using the proposed method. The simulation and experimental results are demonstrated to verify the validity of the proposed PWM method. __________ Translated from Proceedings of the Chinese Society for Electrical Engineering, 2005, 25(7): 104–108 (in Chinese)     

Induction motor rotor fault diagnosis method based on double PQ transformation

This paper presents a new rotor fault diagnosis method for induction motors which is based on the double PQ transformation. We construct the PQ transformation matrix with the positive sequence fundamental voltage components and their Hilbert transformation as elements. The active power P and the reactive power Q are obtained through the PQ transformation of the stator currents. As both P and Q are constant for a healthy motor, they are represented by a dot on the PQ plane. Whereas the P and Q for a rotor broken bar motor are represented by an ellipse because they comprise an additional frequency component 2sf _s (s is the slip and f _s is the supply frequency). Thus, by distinguishing these two different patterns, the rotor broken bar fault is detected. We use the major radius of the ellipse as the fault indicator and the distance between the point of no-load condition and the center of the ellipse on the PQ plane as its normalization value. We thus arrive at the fault severity factor which is fairly independent of the load level and the inertia value of the induction motors. Experimental results have demonstrated that the proposed method is effective in identifying the rotor-broken-bars fault and at determining the severity of the fault. Translated from Proceedings of the Chinese Society for Electrical Engineering, 2006, 26(13): 135–140 [译自: 中国电机工程学报]     

导电排固定搭接的数值分析

通过数学模型对导电排固定搭接的电流场与温度场进行了计算,并结合试验研究,对导电排固定搭接进行了数值分析.     

大型火电机组微机成套保护装置的研究

本文介绍了一种由ＳＴＤ总线Ｖ４０系统工控机实现的火电机组保护装置，该装置具有主从式工业局域网结构。作为从站的各保护微机子系统合理配置保护种类可对大型机组的发电机，主变和厂变同时控制完善的保护，并且具有级的故障冗能力。作为主站的管理微机子系统具有良好的人机界面和完善的服务功能。