Heat Transfer and Resistance Characteristics of Conical Spiral Tube Bundle Based on Field Synergy Principle

Conical spiral tube bundle are universally used in heat transfer enhancement in heat exchangers.The heat transfer and resistance of the tube bundle are affected greatly by the conical structure,so the analysis of it is necessary.In order to a further evaluation,the heat transfer and resistance characteristics of conical spiral tube bundle are investigated with regression analysis based on numerical simulation data.The correlations of heat transfer and pressure drop of conical spiral tube bundle are proposed both in laminar and turbulent fluid flow.On the based of the field synergy principle,the synergy of four vectors,the velocity,the velocity gradient,the temperature gradient and the pressure gradient,are calculated and discussed via the user defined function（UDF） program.The synergy angles β and θ,which respectively denote the performance of heat transfer enhancement and pressure drop of the conical spiral tube bundle,are analyzed.Finally,the comprehensive performance of the conical spiral tube is evaluated by the synergy angle γ and all of the three synergy angles of conical spiral tube bundle are compared to both bare tube and thin cylinder-interpolated tube.The analysis of the synergy angles shows that the heat transfer enhancement and pressure drop of conical spiral tube bundle are smaller than that of the thin cylinder-interpolated tube,while the comprehensive performance of conical spiral tube bundle is greater.The analysis of the heat transfer and pressure drop of conical spiral tube is valuable and instructional on the design and optimum of conical spiral tube bundle heat exchangers.

Analysis of the axial electric field in a plasma-loaded- helix travelling wave tube

A helix type slow wave structure filled with plasma is immersed in a strong longitudinal magnetic field. Taking into account the effect of the plasma and the dielectric, the system is separated radially into three regions. By means of the sheath model and Maxwell equation, the distribution of the electromagnetic field is established. Using the boundary conditions of each region, the dispersion relation of the slow wave structure is derived. The trend of change for the radial profile of the axial electric field is analysed respectively in different plasma densities, plasma column radius and dielectric constant by numerical computation. Some useful results are obtained on the basis of the discussion.

Revisiting the elastic solution for an inner-pressured functionally graded thick-walled tube within a uniform magnetic field

In this paper, the mechanical responses of a thick-walled functionally graded hollow cylinder subject to a uniform magnetic field and inner-pressurized loads are studied. Rather than directly assume the material constants as some specific function forms displayed in pre-studies, we firstly give the volume fractions of different constituents of the functionally graded material(FGM) cylinder and then determine the expressions of the material constants. With the use of the Voigt method, the corresponding analytical solutions of displacements in the radial direction, the strain and stress components, and the perturbation magnetic field vector are derived. In the numerical part, the effects of the volume fraction on the displacement, strain and stress components, and the magnetic perturbation field vector are investigated. Moreover, by some appropriate choices of the material constants, we find that the obtained results in this paper can reduce to some special cases given in the previous studies.

EFFECT OF THE MAGNETIC FIELD ON THE PULSATILE FLOW THROUGH A RIGID TUBE

This study presents the effect of the magnetic field with constant intensity on the pulsatile flow through a rigid tube. Basing on the experimental results, the influence of the magnetic field on the blood viscosity is considered The analytic solution of the pulsatile flow through a rigid tube under constant magnetic field intensitier and the effect of the magnetic field on the velocity distribution, flow and impedance in a rigid tube are given. this investigation is valuable for understanding the influence of the magnetic field on the blood circulation.

Theoretical research on the performance of a practical helix travelling wave tube

On the basis of a rigorous field theory, two different physical models of attenuator and sever have been proposed. One is named High attenuation （HATT） model in which both attenuator and sever are considered as a unified attenuator, but the sever is regarded as an area of very high loss; the other is called Sever and attenuator （SATT） model in which the sever is modelled as a drift area in which the electric and magnetic fields both vanish. A complex function is derived and potential sinking effect is also considered. Thus, a set of more practical self-consistent equations of nonlinear beam-wave interaction is formulated. Simulations are carried out under the conditions of the two different physical models, and the simulation results are compared with the experimental data. The results show that in the case of single signal drive, the unknown second harmonic should be included for predicting the saturated output power. It is also evident that the SATT model and the HATT model predict the same physical nature, whereas the results predicted by the HATT model are much closer to the experimental data than those obtained from the SATT model. Therefore, these results provide a strong theoretical basis for designing broadband and high gain helix travelling wave tubes.

Effect of tube size on electromagnetic tube bulging

The commercial finite code ANSYS was employed for the simulation of the electromagnetic tube bulging process. The finite element model and boundary conditions were thoroughly discussed. ANSYS/EMAG was used to model the time varying electromagnetic field in order to obtain the radial and axial magnetic pressure acting on the tube. The magnetic pressure was then used as boundary conditions to model the high velocity deformation of various length tube with ANSYS/LSDYNA. The time space distribution of magnetic pressure on various length tubes was presented. Effect of tube size on the distribution of radial magnetic pressure and axial magnetic pressure and high velocity deformation were discussed. According to the radial magnetic pressure ratio of tube end to tube center and corresponding dimensionless length ratio of tube to coil, the free electromagnetic tube bulging was studied in classification. The calculated results show good agreements with practice.

Transient out-of-plane distortion of multi-pass fillet welded tube to pipe T-joints

The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and verified experimentally. The FEM analyses consisted of thermal and mechanical analyses.Thermal analysis was validated with experimental transient temperature measurements. In the mechanical analysis, three different weld sequences and directions were considered to understand the mechanism of out-of-plane distortion in the tube to pipe T-joints. It was learnt that the welding direction plays a major role in minimizing the out-of-plane distortion. Further, during circumferential fillet welding of the tube to pipe component, the out-of-plane distortion generated in the x direction was primarily influenced by heat input due to the start and stop points, whereas the distortion in the z direction was influenced by time lag and welding direction. The FEM predicted distortion was compared with experimental measurements and the mechanism of out-of-plane distortion was confirmed.

气相旋转螺旋槽管式换热器结构优化与性能试验

粮食干燥生产中换热损失大,存在烟气热量无法高效传递,导致换热效率低等问题。本文以集管壳与列管式换热于一体的气相旋转螺旋槽管式换热器为研究对象,基于场协同与热力学理论优化螺旋槽管关键部件,探究螺旋槽管参数对换热性能的影响。以螺距、槽深及内外径比为试验因素,以努塞尔数和阻力系数为评价指标,进行三因素五水平二次正交旋转组合试验,采用多目标优化方法确定最优参数组合,当螺距为24.845 mm、槽深为1.753 mm、内外径比为0.897时,Nu为164.637,f为0.348。对优化结果进行验证试验,试验结果与优化结果基本一致。螺旋槽管平均场协同角β相较于圆管降低约2°,揭示了置于壳程内的螺旋槽管管束进口、出口及中间截面内场协同角的分布特征,整体范围内的场协同效果有所增加,结论符合场协同原理。利用强化换热综合性能指数(Performance evaluation criteria,PEC)进行评价,结果表明气相旋转螺旋槽管式换热器PEC在1.031~1.267之间,验证了螺旋槽管在换热器应用的合理性。

Conceptual Design of Beam Tube of 300 KeV Electron Electrostatic Accelerator

The column of electron electrostatic accelerator is one of the critical components in electrostatic accelerator. The geometrical design of such accelerator must be as such that in the case of applying voltage to its electrodes, not only should its equipotential surfaces and its gradient accelerate the beam particles up to desired energy, but also it should focus the beam and hinder broadening of energy distribution of accelerated particles. The immersed electrodes in the field are, geometrically, perpendicular to optical axis around the medial plane. Numerous models that can be used in the distribution of axial potential, have been presented and linear model, analytical model, double-column electrode model and polynomial electrode model are among them. In this paper, series expansions based on Bessel functions is used to obtain the axial potential distribution of immersed accelerator electrodes in double-electrode field and it is then compared to the mentioned models by solving the final equation via the least square method. Finally, by using CST Studio software and the information we obtained from the axial potential, the column of electron accelerator with its energy distribution and its optimal electron output beam radius is designed and simulated.

稠油井内衬保温油管热损失分析及开采参数优化

针对塔河油田稠油开采过程中原油热量损失大、资源浪费的问题,开展内衬保温油管开采技术研究。基于井筒稳态热传递与地层非稳态热传递理论,建立了稠油井井筒热传递数学模型,评价了不同内衬材料油管的保温性能,揭示了含水率、日产液量及内衬保温油管下深对井筒温度的影响规律。研究表明:内衬聚酮防腐层与气凝胶保温层的保温油管保温性能最佳,日产液量和保温油管下深对井口温度影响较大,含水率对井口温度的影响较小;日产液量大于72 t/d且保温油管下深大于3 500 m时,可满足稠油开采的温度要求。该研究明确了内衬保温油管保温的可行性,可为油田保温油管内衬的选材、稠油开采工艺参数的制订提供技术依据。

激波管模拟产生近场爆炸冲击波

激波管可以在实验室环境下模拟爆炸产生冲击波,具有参数易于控制和测量手段准确多样等优势,在爆炸冲击效应的研究中被广泛应用。但与真实爆炸相比,尤其是近场爆炸,激波管产生的冲击波存在正压作用时间难以缩短、超压峰值难以提升的困难。通过对激波管运行理论和数值模拟分析发现:缩短正压作用时间的关键是让反射稀疏波尽快追上入射激波;提升超压峰值的关键是提高驱动气体的驱动能力。为此,设计了一种驱动段为锥形截面的激波管,使得反射稀疏波更快地追上入射激波,从而有效减小激波管设备长度并缩短正压作用时间;同时,采用正向爆轰驱动技术,利用化学能代替高压空气驱动提高驱动气体声速,在低爆轰初始压力下可以获得高的超压峰值。数值计算结果表明,在入射激波马赫数(MS=2.0)相同条件下,相对于等截面驱动方式,采用锥形截面驱动方式时,激波管长度可以减少近2/3,正压作用时间可以缩短近1/2。激波管实验结果表明,锥形截面驱动激波管产生的超压曲线满足近场爆炸冲击波形要求,并获得了超压峰值为64.7~813.4 kPa、正压作用时间为1.7~4.8 ms的爆炸冲击波波形。该研究可为近场爆炸冲击波致伤及装备防护效应评价实验提供参考。

大口径爆炸激波管出口冲击波流场图像测量

为了获取大视场下爆炸冲击波的纹影图像以及冲击波与被测模型相互作用后的流场演化特征,开展了基于聚焦纹影的反射式高速纹影测试。利用激光光源和高反射膜建立了系统所需的光源输入,并通过简化刀口栅设计,实现了远距离大口径爆炸激波管出口冲击波流场图像演化特征以及与固体模型相互作用的高时空分辨特征。研究结果表明,设计的聚焦式反射纹影系统在80 m以上距离处获取了大口径大当量爆炸激波管出口处6 m×3 m视场的冲击波特征,以及与固体相互作用的高时空分辨图像和状态数据;相比传统聚焦纹影系统,该系统具有结构简单、可实现性强、测试距离远,覆盖视场大等特点;通过设计不同光源输入,探讨了激光光源在远距离拍摄中的优势;通过冲击波阵面与固体模型的相互作用特征,揭示了冲击波作用于被测固体模型后的形成、演化和绕流状态。该测量结果能够为武器装备在受到冲击波作用后的状态评估和响应特性分析提供直观的图像数据支撑。

基于响应面法的钢管混凝土系杆拱桥有限元模型修正

为探讨将钢管混凝土系杆拱桥有限元模型修正方法应用于实际工程性能评估的有效性,以某80 m单拱面钢管混凝土系杆拱桥为工程背景,采用Midas Civil与ANSYS有限元软件分别建立全桥梁格模型与拱脚精细化数值模型,基于径向基函数网络的响应面法对此多尺度模型进行修正。首先根据结构特点和实桥试验选取修正参数与目标函数,以中心复合试验设计构造不同修正水平下的修正参数样本,通过桥梁有限元模型计算得到对应的目标函数样本,并利用F检验法对修正参数的显著性水平进行判断;然后,以修正参数样本与目标函数样本分别作为响应面的输入输出,对径向基函数网络进行拟合训练;最后在修正范围内随机生成修正参数样本,并利用训练好的径向基网络预测对应的目标函数,采用期望度函数D进行优化处理以完成有限元模型的修正。研究结果表明:对于单拱面钢管混凝土系杆拱桥的有限元模型,可以通过径向基函数网络的响应面法进行修正,对比实测数据,修正后的模型误差有明显下降,可作为结构再分析的基准模型;对于使用不同程序建立的多尺度桥梁有限元模型,模型修正方法依旧有效,修正后的参数具有明确的物理意义,其误差可降到工程实践接受范围之内。研究结果为建立与修正钢管混凝土系杆拱桥的有限元模型提供参考。

水声材料声学参数测试技术的进展

水声材料是水下声系统能力形成和发展的基础,其声学参数测试技术是确保水声材料构件功能实现的重要保障,然而目前水声材料构件的测试技术面临着低频拓展及高压拓展等方面带来的技术挑战。水声材料构件的声管测试技术可分为驻波管法、脉冲管法和行波管法,此3种方法在适用性方面相互补充,但存在测试构件尺寸小难以阐明结构的整体特性、构件与管壁间的缝隙造成测量失准的问题。自由场测试技术及压力罐测试技术是大面积水声材料测试的有效手段,但存在测试构件边缘衍射造成测量准确性降低的问题。对目前采用的水声材料测试技术及其研究现状进行了综述,讨论了各类测试技术存在的困难和挑战,并展望了水声材料构件测试技术未来的发展方向。

变截面半圆通道内超临界二氧化碳热工水力性能研究

建立了不同半圆通道的数学和物理模型,并通过与实验数据的比较,验证了所建立模型的准确性。研究了超临界二氧化碳(S-CO_(2))在等截面半圆通道、渐扩型和渐缩型通道内的热工水力换热性能,并分析了不同通道和压力对S-CO_(2)在变截面半圆通道内的热工水力性能的影响。结果表明:相较于均匀截面半圆通道,渐扩型通道恶化传热,渐缩型通道强化传热;入口和出口半径比为1.0:0.5的渐缩型半圆通道的总体换热系数最大提升了39.93%,流动传热综合性能评价因子PEC最大为1.346;当压力越靠近临界压力或热通量较低时,传热性能越高。最后,从场协同性和湍动能分布的角度解释了渐缩型变截面通道强化传热的原因。研究结果可为S-CO_(2)循环系统冷却器的设计与优化提供新的思路和理论指导。

漳州市芗城区2012—2023年人间布鲁氏菌病实验室检测结果分析

目的调查分析漳州市芗城区2012年布鲁氏菌病(以下简称布病)局部暴发的原因、流行特征、连续3年监测点监测结果以及2016—2023年漳州市芗城区出现的布病病例,为预测布病流行趋势、科学预防和控制提供有力依据。方法采用现场流行病学调查、人间布病监测、采样、哨点医院监测及实验室血清学试管凝集试验(serum agglutination test,SAT)对芗城区发生布病及疫情进行调查处置。结果2012—2015年监测点共检测血清标本479份,平均布病抗体阳性率为4.87%,各年度依次为14.43%(14/97)、3.33%(5/150)、1.72%(2/116)、0%(0/116)。哨点医院检测血清标本90份,布病抗体平均阳性率为24.44%,2013年为46.67%(14/30),2014年为16.67%(5/30),2015年为10.00%(3/30)。2016—2023年确诊病例9例。其中2016年2例,2017—2023年各1例。结论2012年漳州市芗城区人间布病疫情的暴发主要与牲畜的屠宰、加工、收购、销售有关。疫情处置后,2013—2023年抗体阳性率逐年走低,所以应继续加强动物间及人间布病跟踪监测,加大宣传教育力度,加强综合防治,严防人间布病的流行。

输毛管中流场状态对纤维丝束开松处理效果的影响

纤维输毛管的设计对粘胶纤维或Lyocell短纤维丝束的开松效果至关重要。为了探究纤维丝束在输毛管中的开松机理以及管道内流场状态对纤维运动状态的影响,采用三维建模软件建立输毛管流场模型,在商用软件Cradle CFD中建立纤维丝束模型结合流场进行耦合计算,研究分析了2000根长度为38 mm纤维丝束在输毛管中的运动过程。结果表明:在输毛管中纤维丝束受到流场作用的差异形成了纤维丝束运动的速度差,这是纤维丝束开松的主要原因;输毛管的竖直圆形管道处存在较大的压力梯度,使纤维丝束整体受到压力差异,也为纤维开松创造条件;输毛管的锥型管位置处的速度场较复杂,有利于纤维丝束开松;管径的变化导致产生漩涡,阻碍了纤维的输送。研究结果可为化纤与纺织行业输毛管设计提供参考。

固井趾端滑套研制与现场试验

针对水平井桥塞射孔联作分压工艺首段采用连续油管传输射孔,存在施工费用高、作业时间长、特殊井况连续油管无法下入等问题,开展了固井趾端滑套技术研究。趾端滑套与油层套管一起下入固井完井,通过井口憋压开启即可进行首段压裂作业,同时为后续层段桥塞泵送提供液体通道。文章设计了趾端滑套完井压裂工具,抗内压强度132 MPa,开启压力可调,具有开启可靠、便于压裂等优点。室内试验合格后,在新疆油田玛湖地区超长水平井开展现场试验,完井作业过程中趾端滑套承压可靠,顺利完成固井施工;压裂作业过程中趾端滑套成功开启并完成首段压裂施工,解决了连续油管无法下入射孔的问题,同时节约作业时间1 d。结果表明,研制的固井趾端滑套可以满足现场作业需求,为水平井安全效益改造提供了一种有效手段。

CO_(2)激光作用玻璃管的热效应

激光对单一玻璃管进行热熔封接的过程中,加工质量与玻璃管内的温度分布有密不可分的联系。在考虑表面热辐射、材料内部热传导和空气热对流的情况下,使用COMSOL Multiphysics有限元仿真软件对CO_(2)激光作用高硼硅酸盐玻璃管的温度场进行模拟仿真,分析了温度场分布随时间的变化规律,比较了激光功率、激光光斑半径和旋转速度对玻璃管温度分布的影响。仿真结果表明,激光功率越大,光斑半径越小,玻璃管旋转速度越低,玻璃管温度越高。根据仿真结果,选择合适的加工参数能够达到高硼硅酸盐玻璃管进行激光加工的工艺要求,此项研究为后续玻璃管激光热熔封接的工艺参数选择提供了重要理论依据。

短管直径对短管蜂窝夹套传热性能的影响

基于某工程中1台干燥机的短管蜂窝夹套结构形式,通过将短管尺寸由Ф90 mm×5 mm逐渐增大到Ф135 mm×7.5 mm,建立了模型1~模型6共6种夹套流场计算有限元模型,模拟分析了各模型速度场和温度场分布特性,计算并对比了各模型在不同体积流量下的总传热系数。模拟数据表明,随着短管尺寸的增大,夹套流体域内最大流速呈持续递减趋势。随着短管尺寸的增大,夹套流体域内温度场均匀性先升后降,模型5温度场分布均匀性最佳,总传热系数最大。随着体积流量的增加,夹套总传热系数持续增大。随着短管直径的增大,夹套总传热系数先升后降,模型5总传热系数最大。综合分析表明,在一定范围内增大短管的直径,能够强化夹套传热效果。