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在立式蒸汽发生器垂直管束间的气液两相流中,截面含气率是其中一个重要参数。使用γ射线法对高温高压下垂直管束间气液两相流截面含气率的分布规律进行了实验研究。实验压力分别为5、7、9 MPa,质量流速为300 kg/(m~2·s),热力学干度的范围为0.003~0.4。实验得到了垂直管束间截面含气率随热力学干度、体积含气率和压力的变化关系;并与经典公式的计算结果对比发现,在低干度区域,实验结果与Miropolskii模型、Smith模型和Armand模型偏差较大,均大于30%,在高干度区域偏差较小;基于Armand理论,通过多元线性回归法拟合出本文工况下平均截面含气率的计算关联式,与日本核动力工程公司(NUPEC)的实验数据偏差小于15%。本研究对蒸汽发生器的结构设计和流动特性研究具有重要意义。 相似文献
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为提高电容器对含水率测量的能力,设计与其相匹配的旋转分相单元,以实现气液两相流含水率的起旋分相式电容测量。在电容传感器的测量单元基础上,增加旋转分相单元,利用气液两相流体力学理论对其结构进行设计优化,并根据实际应用条件确定分离圈数,保证气液分相效率。旋转分相单元克服了气液两相流流动形态的多样性,将体积含水率信息转换成液膜厚度信息及截面含水率信息进行测量。经实验验证,Lockhart-Martinelli截面含气率模型与实验中电容器测量截面含气率具有良好的一致性,其能够实现对体积含水率20%以内的气液两相流有效测量,体积含水率的绝对误差在±2%以内。 相似文献
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起伏振动下气液两相流含气率的准确预测对漂浮核电站的安全稳定运行有重要意义。实验研究了不同振动和流动工况下垂直上升管气液两相流的含气率特性。结果表明,起伏振动对泡状流下的含气率影响比较明显,对弹状流、搅混流和环状流的影响较弱。整体来看,起伏振动导致泡状流的含气率增加,其他三种流型下的含气率减小。对静止管道内常用的含气率计算模型进行评价,发现现有含气率计算模型比较适用于起伏振动下含气率的计算,但对泡状流和弹状流下含气率的预测误差较大。考虑振动的影响,引入了液相Froude数,建立了考虑流型的含气率计算关系式,显著提高了起伏振动下含气率的预测准确度。 相似文献
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为提高电容器对含水率测量的能力,设计与其相匹配的旋转分相单元,以实现气液两相流含水率的起旋分相式电容测量。在电容传感器的测量单元基础上,增加旋转分相单元,利用气液两相流体力学理论对其结构进行设计优化,并根据实际应用条件确定分离圈数,保证气液分相效率。旋转分相单元克服了气液两相流流动形态的多样性,将体积含水率信息转换成液膜厚度信息及截面含水率信息进行测量。经实验验证,Lockhart-Martinelli截面含气率模型与实验中电容器测量截面含气率具有良好的一致性,其能够实现对体积含水率20%以内的气液两相流有效测量,体积含水率的绝对误差在±2%以内。 相似文献
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为探究不同操作参数及结构下矩形截面螺旋细通道内气液两相流的液相分布及压降特性,建立了光滑螺旋通道及内置矩形涡发生器的螺旋通道2种模型,在进口速度u_(in)=0.22~0.32 m/s,进口含气率α=0.55~0.59的条件下,以空气-水两相流为工质进行了数值模拟。结果表明,在研究的范围内通道内液体受离心力的影响被甩向螺旋通道外侧,而气体分布于通道内侧。进口含气率的增加会减少通道外壁面的液膜厚度。通道内置的矩形涡发生器可使内部工质产生二次流从而增强混合,有效提升截面含气率。除此之外,进口速度的增大、进口含气率的减小及矩形涡发生器的加入均会使矩形螺旋细通道内两相压降增大。 相似文献
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底吹钢包两相区两段模型 总被引:1,自引:0,他引:1
在考虑雷诺应力的基础上,建立了底吹钢包中气液两相区流体流动的两段模型。这一模型可用于计算近喷嘴处和浮羽流区各截面处两相流的平均速度、速度分布、流股直径和平均含气率等.数值计算表明:理论含气率与实验值符合很好.计算还表明:平均含气率和平均速度随高度的增大而减小,但流股直径随高度的增大而增大.另一方面,平均速度随初始供气量的增大而增大,而抽引比则随供气量增大而减小.通过两段模型可很好地描述喷嘴处气液流的行为. 相似文献
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引 言在研究两相流的流型转换、摩擦压降等性能时 ,两相流截面含汽率是一个极其重要的参数 ,一旦知道了两相流的截面含汽率便可求得两相混合物的平均密度、计算压力梯度、分析管内流动状况等 .它的测量是否准确直接关系到计算结果的正确性和设备运行的可靠性 .光纤传感器是纤维光学领域中的新技术 ,利用其对汽水折射率不同的特点可进行截面含汽率的测量 .光纤探针有很好的响应和性能 ,在高性能的数据采集板和计算机帮助下 ,对信号的处理也很方便 .本文应用法国RBI公司耐高温高压的光纤探针测量圆管含汽率的变化规律 .应用光纤探针测得管… 相似文献
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通过搭建可视化分体管壳式余热锅炉实验平台,对其下部管壳内汽液两相横向冲刷水平管束时摩擦及局部压降的计算进行了研究。在测量竖直上升管内截面含汽率时,将粒子图像测速(PIV)技术与传统压差法相结合,针对上升管中出现的泡状流型,给出了计算截面含汽率的新方法;在竖直上升管内定义了一种泡状-段塞流的新流型,并分析得出将质量含汽率x=10-4作为区分泡状流与泡状-段塞流的边界。根据汽液两相横向冲刷管束时摩擦压降与局部压降类似的产生规律,将两者作为整体分析,通过借鉴Chisholm计算方法对实验数据进行处理,重点对汽液两相横向冲刷管束时摩擦及局部压降的计算进行研究,得到了可用于计算摩擦及局部压降的关联式。对所得实验数据验证计算后发现,误差在±20%以内,能够较好地满足工程计算需要。 相似文献
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Three-sphase flow invo1ving oil-water two immiscible liquids and gas which is often foundin the fields of petroleum production has been studied in this paper.A new method with thecombination of a horizontal tube,a downward flow vertica1 tube and an orifice to measure theflowrates is presented.In this method the frictional pressure drop in the downward vertical tube isreplaced by that in the horizontal tube,the void fraction is derived from the gravitational pressuredrop,then the volume fraction of the individual phase can also be obtained.The individual flowratescan be calculated when the water fraction is known.This method is applicable for many kinds ofoil-wells to measure the flowrates of crude oil,natural gas and water.Compared with other methods,the presented method involves fewer measuring parameters.The experimental results proved quitegood accuracy of the method,with measurement deviation within 10%,and reliable results wereobtained under high Dressure conditions. 相似文献
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Equilibrium and non‐equilibrium gas–liquid two phase flow in long and short pipelines following a rupture 下载免费PDF全文
A. Nouri‐Borujerdi A. Shafiei Ghazani 《American Institute of Chemical Engineers》2017,63(7):3214-3223
The two‐phase flow following the blowdown of pipeline carrying flashing liquid is numerically investigated by using thermodynamic equilibrium and non‐equilibrium models. Model equations are solved numerically by the finite volume method. The values of fluxes at cell boundaries are obtained by AUSM+‐up. To obtain proper values for the coefficients of dissipation, both single phase liquid and two phase shock tube problems are investigated. The transient release from the pressurized pipeline is studied for two cases of long and short pipes. Comparison of the predictions against experimental data reveals non‐equilibrium model performs a little better than equilibrium model in the prediction of temporal variations of pressure and void fraction of the long pipe. However, equilibrium model totally overestimates pressure and void fraction of the short pipe. The relative error of equilibrium model in the prediction of pressure variation with time exceeds 50% and it is 20% for non‐equilibrium model. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3214–3223, 2017 相似文献
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R. Sh. Abiev 《Theoretical Foundations of Chemical Engineering》2010,44(1):86-101
A method for calculating the void fraction and relative size of bubbles at the known flow rates of phases is constructed using the mathematical model of a gas—liquid slug flow in capillaries that was developed earlier. The results of the calculations are in good agreement with the experimental data of other authors. The boundedness of linear approximations such as the Armand formula by the small values of the capillary numbers is revealed. It is shown that the void fraction depends not only on the dynamic gas holdup, but also on the capillary number and the Weber number, as well as on the direction of the flow. It is found that the ratio of the dynamic gas holdup to the void fraction varies from 1 to 2.5 as the capillary number increases. A tenfold error in the experimental determination of the length of liquid slugs by a simplified procedure is revealed. A simple calculation relationship that relates the dynamic gas holdup to the void fraction is derived from the Liu—Vandu—Krishna approximation. The theoretical explanation of the causes of the abnormal dependence of the void fraction on the dynamic gas holdup in microchannels with sizes of less than 100 fum is given. The specific features of a slug flow in microchannels that are caused by the disintegration of a film into drops are explained. The developed calculation method can also be applied to liquid—liquid systems. 相似文献
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Multiple size group (MUSIG) model combined with a threedimensional twofluid model were em ployed to predict subcooled boiling flow of liquid nitrogen in a vertical upward tube. Based on the mechanism of boiling heat transfer, some important bubble model parameters were amended to be applicable to the modeling of liquid nitrogen. The distribution of different discrete bubble classes was demonstrated numerically and the distribu tion patterns of void fraction in the wallheated tube were analyzed. It was found that the average void fraction in creases nonlinearly along the axial direction with wall heat flux and it decreases with inlet mass flow rate and sub cooled temperature. The local void fraction exhibited a Ushape distribution in the radial direction. The partition of the wall heat flux along the tube was obtained. The results showed that heat flux consumed on evaporation is the leading part of surface heat transfer at the rear region of subcooled boiling. The turning point in the pressure drop curve reflects the instability of bubbly flow. Good agreement was achieved on the local heat transfer coefficient aalnst experimental measurements, which demonstrated the accuracy of the numerical model. 相似文献
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过冷流动沸腾在核能、动力、化工等工业领域广泛存在,局部空泡分布特性的准确预测对构建两相流数理模型及两相流动压降和传热特性计算均具有重要意义。实验借助光学探针测量手段研究摇摆条件下圆管内过冷沸腾局部空泡分布特性,并提出多周期同相位叠加方法获得摇摆运动条件下局部瞬时空泡份额。实验结果表明:摇摆条件下圆管内局部空泡分布呈现周期性波动规律,摇摆条件下圆管轴心区及近壁区均会出现局部空泡份额峰值,且流道近壁区局部空泡份额波动幅度最大;与静止条件下不同,摇摆运动周期内过冷沸腾局部空泡份额空间分布形态随时间发生变化;摇摆周期和摇摆角度对过冷沸腾局部空泡分布特性也存在一定影响。 相似文献
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在常温常压下 ,应用电导探针对无泄漏的TEMA -E型管壳式换热器壳侧气液两相流的局部含气率进行了测量 ,研究发现在壳侧错流区折流板的迎流面和背流面附近 ,气液分布有着明显的差异 ,而且两者均不等同于错流区中心区域的气液分布。通过对局部含气率的加权体积积分得到了体积平均含气率 ,并采用马蒂内利参数及全液相佛鲁德数进行关联 ,得到的关联式与实验数据较吻合 相似文献
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采用光纤探针法和高速摄影法对垂直上升气液两相弹状流的液弹区含气率分布进行了试验研究,测试管径为15 mm。一种基于机器学习的图像处理技术用来识别气液两相界面,通过搭建气泡边界提取的神经网路系统,使用构建的气泡边界数据库对模型进行多次迭代训练,该方法可以有效地识别多种复杂类型的气泡边界。试验得到了弹状流液弹区的径向含气率分布曲线,结果表明,壁峰分布是液弹区含气率分布的主要形式,其中泰勒气泡的尾迹效应对分布形式有重要影响,尾迹的旋涡中心和含气率分布的峰值相对应。针对弹状流液弹区径向含气率分布的两个主要特征——中心局部含气率和壁峰位置,分别提出了相应的预测公式,且与本文的试验数据吻合良好。 相似文献