CFETR CS模型线圈NbTi导体的管内压降分析

CICC导体的压降是设计及应用过程中的重要问题。为了研究CFETR CS模型线圈NbTi的管内流体阻力性能,对模型线圈的NbTi导体进行了实验和理论的分析。压降实验采用氮气作为流体工质,测试不同流量下,导体的进出口压降。理论分析采用一种一维模型描述双通道流体,引用电缆区域及中心孔区域的摩擦因数描述流道阻力进行计算,并与测试结果作分析比较,为实际应用中的氦流体在导体中的稳态流动阻力计算提供了一种理论方法。     

40-T混合磁体外超导磁体CICC摩擦系数测定

40-T混合磁体的建设正在中科院强磁场中心进行,其外超导磁体将由管内电缆导体CICC绕制,并采用4.5K 的超临界氦迫流冷却.CICC的摩擦系数是确定各冷却通道进口压力和流量的重要依据.文中介绍了CICC压降测量平台搭建,并对40-T混合磁体外超导磁体哑缆摩擦系数进行测量;分析了该CICC内的摩擦特性,并拟合出相应的经...     

ITER TF导体压降流阻测试试验与分析

由于国际热核聚变实验堆(International Thermonuclear Experimental Reactor,简称ITER)的磁体系统运行时利用迫流氦进行冷却,迫流氦在线圈内部流动,产生一定阻力,会影响磁体线圈的正常工作,需要对磁体线圈进行压降测试。着重介绍线圈导体的流体测试试验,根据ITER纵向场(Toroidal Field,简称TF)的导体PA技术要求,搭建测试平台并在室温下进行氮气压降-流量测试实验。使用经验公式进行理论压降计算,计算结果与测量值进行对比,较为接近。同时,也利用该根导体参数进行低温下压降计算,计算结果和国外相关数据,相似。     

CFETR CS模型线圈导体铠甲低温力学性能研究

CFETR CS模型线圈采用超临界氦迫流冷却,超临界氦在导体内部流动时吸收电缆上的热负荷,使得线圈能够保持在低温下安全运行。CFETR CS模型线圈的超导体采用CICC结构,其导体外部铠甲采用氩弧焊填丝焊接连接而成。在线圈运行过程中,导体遭受的巨大电磁载荷主要依靠不锈钢铠甲承受。采用数值模拟与实验研究相结合的方法,研究了导体铠甲在磁体运行过程中的受力情况,并通过常低温拉伸实验,获得了铠甲母材与焊缝4. 2 K力学性能测试。实验结果表明,导体铠甲母材与焊缝试样机械性能,均能满足CFETR CS模型线圈超导体设计要求。     

基于VC++的校正场线圈绕制系统的建模与仿真

根据国际热核聚变试验堆校正场线圈(Correction Coil,简称CC)的绕制成形过程及高可靠性、高精度的绕制要求,通过对线圈的几何图形进行简化和分析,建立起线圈旋转过程中的运动数学模型。根据此模型,在管内电缆导体进给速度固定的条件下,得到了线圈绕制过程中各电机之间的运动关系。在此基础上,上位机基于VC++,通过对线圈CAD文件的读取以及数据信息的处理,得到各轴运动轨迹;并通过MFC对ITER校正场线圈绕制系统进行动态仿真以验证其正确性。     

ITER TF超导体焊缝的氦质谱气密性检测

国际热核聚变实验反应堆(ITER)磁体环场线圈TF导体采用CICC(cable in conduit conductor)导体结构,其导管为316LN型不锈钢套管。文中针对ITER项目对导体气密性要求,主要介绍了超导体导管焊缝的氦质谱气密性检测技术方法、检测系统、检测流程和漏率计算。     

管内电缆导体稳定性仿真分析

管内电缆导体(cable-in-conduit conductor,CICC)即铠装电缆导体,是由内冷超导体(ICS)发展演变而来的。随着超导技术的发展,CICC在大型超导核聚变实验装置及超导储能磁体中的应用具有不可比拟的优越性。CICC通常运行在大电流和快变磁场中,它的稳定性对其实际应用起着重要影响,因此对CICC稳定性研究有很大的实际意义。文中基于一维数学模型(Gandalf软件)的基础上,对ITER校正线圈(CC)CICC的稳定性进行仿真,研究了CICC的稳定性裕度与电缆的运行温度、加热长度和质量流速率之间的关系,根据仿真结果,得出了电缆运行温度、加热长度与氦的质量流速率对CICC稳定性裕度的影响,最后把仿真结果与理论分析进行对比,验证了仿真结果的正确性。     

ITER CB超导电缆力学性能数值模拟研究

国际热核试验堆(International Thermonuclear Experimental Reactor,简称ITER)的校正场线圈(Correction Coil,简称CC)采用校正母线(Corrector Busbar,简称CB)连接磁体线圈和电流引线,以传递整个磁体系统所需的电流。CB导体采用的主要是管内电缆导体(Cable-in-Conduit Conductor,简称CICC),而CICC导体的主要结构是由超导线与铜线经过多级绞制而成的超导电缆。利用数值模拟方法给出了CB超导电缆力学模型,并分析了CB超导电缆中超导线的应分布。     

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介绍了国内首个聚变堆用Nb3Sn超导磁体模型线圈。采用一维数学模型Gandalf对其管内电缆导体(CICC)结构的超导体稳定性进行仿真,得到了CICC稳定性裕度与磁场强度和运行电流之间的关系。这对于磁体的设计和运行都有十分重要的意义。     

HT-7U纵场磁体CICC导体设计

国家“九、五”重大科学工程HT-7U托卡马克(Tokamak)是一个全超导核聚变实验装置，装置主机包含有16个纵场(TF)超导线圈和14个极向场(PF)超导线圈．线圈采用NbTi CICC导体(Cable in-Conduit Conductor)绕制，用超临界氦迫流冷却．本介绍CICC导体的设计和导体短样的测试结果．     

自然循环加热段内摩擦阻力及对流传热的实验研究

以常压去离子水为工质,对自然循环工况下上升加热段内单相水的摩擦阻力及对流传热特性进行了实验研究.结果表明,自然循环工况下加热段内由浮升力引起的自由流动对摩擦阻力及对流传热特性有重要影响,自然循环与强制循环二种工况下加热段内的摩阻系数及对流换热系数存在明显差别;并且,自然循环工况下加热段内的摩擦阻力存在滞后现象.通过实验提出了计算自然循环工况下加热段内单相水的摩阻系数及对流换热系数的经验关系式.     

规则结构多孔填料塔两相流动特性实验研究

本文以空气和水为工质,对规则结构多孔填料塔的气-液逆向流动特性进行了可视化实验,研究了填料塔内气一液两相流动规律.实验结果表明:当液体流量一定时,随着气体流量的增加,压力损失增大;当气体流量一定时,随着液体流量的增加,气相压力损失增加.根据实验结果提出了采用水力雷诺数、韦伯数和无量纲流动参数的填料塔内气-液两相流动阻力系数实验关联式.     

Performance of shell-and-dimpled-tube heat exchangers for waste heat recovery

This paper presents an experimental study of waste heat recovery shell-and-tube heat exchangers. The exchanger heat duty, overall heat transfer coefficient, effectiveness and tubeside friction factor are investigated as functions of the tube surface geometry (plain or dimpled), the flow type (counter or parallel), the tube Reynolds number and the shellside heat capacity rate. Water and the exhaust gases of a Diesel engine are passed inside the tube and the shell, respectively.The heat transfer characteristics increase with an increase in tube Reynolds number and the shellside heat capacity rate, for all the flow types and the surface geometries examined. The counter-flow, shell-and-dimpled-tube heat exchanger, compared with that exchanger having a plain tube, increases the heat duty and the overall heat transfer coefficient by 80%, and the heat exchanger -effectiveness increases by 35%. For the parallel-flow, shell-and-dimpled-tube heat exchanger, the heat duty, the overall heat transfer coefficient and the effectiveness increase by 30, 55, and 25%, respectively. At the same time the dimpled tube increases the tubeside friction factor by 600% over that of the plain tube. The rate of waste heat recovered from the exhaust gases of the Diesel engine by the counter-flow, shell-and-dimpled-tube heat exchanger is equal to 10% of the maximum brake power of the engine running at 1500 rpm, and the tube Reynolds number equal to 8875.     

微细光滑管内气体的流动与传热特性研究

在评述当前微细管内流动和换热特性研究的基础上提出了需考虑流体压缩性对速度剖面的影响。可压缩流动守恒方程组的数值解结果表明：运动流体的压缩性不仅使管内平均流速增加，而且使速度剖面更加饱满，从而使局域阻力系数和换热系数增加。与此同时，尽管管道的长细比很大，亦不可能出现充分发展的速度和温度剖面。这是由于微细管道中由于阻力引起的压力降可以很大，它所引起的流动加速达较大马赫数时，压缩性对阻力系数和传热系数的影响就不能忽略。     

Laminar Heat Transfer Augmentation through A Square Duct and Circular Tube Fitted with Twisted Tapes

Experimental studies on friction factor and heat transfer characteristics for the laminar flow of ethylene glycol in a square duct fitted with twisted tapes of different twist ratios under nearly uniform wall temperature conditions are reported in this article. The Nusselt numbers were found to be 5.44–7.49 and 2.46–4.87 times that of plain square duct forced convection values based on constant flow rate and constant pumping power criteria, respectively, for y = 2.66. The augmented friction factor and Nusselt number for a square duct is about 1.9 and 2.10 times higher than that for an augmented circular tube.     

Thermal performance enhancement in tubes using helically twisted tape with alternate axis inserts

This article presents an investigation on heat transfer enhancement in a round tube inserted with a helically twisted tape. The effects of a helically twisted tape with alternate axis (HTT-A) on heat transfer, friction factor, and thermal performance factor behaviours are reported for the turbulent regime. HTT-A geometries are tape pitch to tube diameter, P/D = 1.0, 1.5, and 2.0; alternate length to pitch length, l/P = 1.0, 1.5, and 2.0; twisted length to tape width, y/W = 3.0; and tape width to tube diameter, w/D = 0.2. The experiment has been performed by varying the volumetric air flow rate in order to adjust Reynolds number ranging from 6 000 to 20 000. The wall of the testing tube is uniformly heated as a constant heat flux while the tests are covered with thermal insulations to reduce heat loss to surroundings. Thermal performance is evaluated by comparing the present experimental results with the results of the modified HTT-A and also those obtained from previous study (conventional helically twisted tape, HTT). The thermal performance of tested tube with HTT-A is evaluated to obtain the degree of heat transfer enhancement and friction factor induced by HTT-A with respect to the plain tube under the same test conditions. Evenly, it is interesting to observe that the tube with HTT-A consistently possesses higher heat transfer and thermal performance factor than those with the HTT around 14.1% and 1.9%, respectively. The HTT-A with the smaller pitch ratio and adjacent twist length provides higher heat transfer rate and friction factor than the one with larger pitch ratio and alternate length as a result of a larger contact surface area, stronger swirl intensity and, thus, better fluid mixing near the tube wall. In the range determined, the tubes with the largest pitch ratio (P/D = 2.0) and smallest alternate length (l/P = 1.0) give the highest thermal performance factor at around 1.35. In addition, the empirical correlations of the Nusselt number, friction factor, and thermal performance factor are also described.     

Period-adding bifurcations and chaos in a bubble column

We obtained period-adding bifurcations in a bubble formation experiment. Using the air flow rate as the control parameter in this experiment, the bubble emission from the nozzle in a viscous fluid undergoes from single bubbling to a sequence of periodic bifurcations of k to k+1 periods, occasionally interspersed with some chaotic regions. Our main assumption is that this period-adding bifurcation in bubble formation depends on flow rate variations in the chamber under the nozzle. This assumption was experimentally tested by placing a tube between the air reservoir and the chamber under the nozzle in the bubble column experiment. By increasing the tube length, more period-adding bifurcations were observed. We associated two main types of bubble growth to the flow rate fluctuations inside the chamber for different bubbling regimes. We also studied the properties of piecewise nonlinear maps obtained from the experimental reconstructed attractors, and we concluded that this experiment is a spatially extended system.     

椭圆形和圆形翅片管流动与传热的数值研究

对椭圆管椭圆翅片间的流动与传热规律进行了三维数值研究,分析了不同翅片间距、迎面风速对表面换热系数和流动阻力的影响;与具有相同结构参数(相同的基管当量直径和翅片厚度、表面积)的圆管圆翅片进行比较表明,在相同条件下,两者的表面换热系数相差不大,但椭圆管椭圆翅片间流动阻力却有明显的减小.场协同分析表明,翅片迎风侧的换热要优于背风侧;通过适当增加迎风侧翅片面积,减小背风侧翅片面积,可以在强化换热的同时,减小流动阻力.     

竖直圆管内液氮流动沸腾流动压降的分析

文中对竖直圆管内液氮流动沸腾压降进行实验研究,分析热流密度、质量流量对液氮两相流动摩擦压降的影响以及热流密度对测试段总压降的影响。在本实验工况范围内,两相流摩擦压降随着热流密度和质量流速的增加而变大,且测试段总压降随着热流密度的增加而降低。分别利用均相模型、L-M模型和Chisholm B系数模型对实验结果进行预测,并比较了预测值与实验值,结果表明本实验工况下均相模型预测效果最好。     

扁平管外蛇形翅片空间的流动换热性能数值模拟

扁平管外纤焊蛇形翅片是直接空冷凝汽器翅片管的一种常见形式,研究扁平管外蛇行翅片空间的空气流速和温度分布规律,对指导直接空冷凝汽器的设计和运行具有重要意义.针对不同空冷凝汽器管束夹角、不同空气温度以及不同空气入口流速,分别对空气侧流场和温度场进行了数值模拟,得到了空冷器外流场和温度场,以及对流换热Nu和摩擦系数f随Re和空冷器夹角的变化规律.数值模拟结果表明,不同的空冷器管束夹角显著影响其流动和换热特性,夹角越大,凝汽器空冷效果越好.