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1.
The effects of tube diameter, coil diameter, helix angle and liquid viscosity on flow patterns, pressure drop and holdup for cocurrent gas-liquid flow in helically coiled tubes have been investigated. Nine coils of varying coil diameter and helix angle have been used with liquids of three different viscosities and air at varying pressures. The effect of tube diameter on pressure drop and holdup was determined by using tubes of diameters up to 2-in. Flow patterns were adequately predicted for all the systems by Baker's plot. Small helix angles were found to have no effect on pressure drop or holdup in coiled tubes. Both pressure drop and holdup could be adequately correlated using the Lockhart-Martinelli approach with modified correlating parameters. 相似文献
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Flow boiling in inclined tubes is encountered in solar collectors, but there is no literature on inclined flow boiling on which to base their design. Experimental studies have been carried out on heat transfer, pressure drop and flow maps for flow boiling of water in a circular tube. The angle of inclination was varied from 0° to 90°. The inclination was found to influence the transport processes in the bubbly and the intermittent flow regimes. The correlation of Chen (1966) has been extended to correlate the heat-transfer data to account for the angle of inclination. The Baroczy (1965) and the Lockhart-Martinelli (1949) correlations were adapted to correlate the frictional pressure gradient in the inclined flow boiling. The observed flow patterns were presented as flow maps. 相似文献
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HUO Xiaoqian XU Ying WANG Jinghan ZHANG Tao MAIMAITI Aikebaier WANG Xigang 《化工学报》2021,71(12):5506-5514
Considering the influence of swirl attenuation, the pressure drop characteristics of gas-liquid spiral annular flow are studied, and the pressure drop prediction model of spiral annular flow is deduced. The swirl-straight ratio of pressure drop is defined as the ratio of pressure drop of swirl flow to straight flow, used to characterize the effect of swirl decay on pressure drop. The expression of swirl-straight ratio of pressure drop is derived by the method of dimensional analysis, and it has a strongly dependence on Lockhart-Martinelli coefficient and gas phase Froude number. Finally, the prediction model of pressure drop for gas-liquid swirl annular flow is obtained. The pressure drop characteristics of the swirl annular flow are experimentally studied in a horizontal tube with an inner diameter of 50 mm. The range of the gas superficial velocity is 10—16 m/s and the range of the liquid volume fraction (LVF) is 0.6%—4.8%. Through comparison with experimental data, the relative error of the pressure drop prediction model is within ±15%, which provides a method reference for engineering applications. 相似文献
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考虑旋流衰减的影响,对气液螺旋环状流的压降特性进行研究并推导出了螺旋环状流压降预测模型。定义压降旋-直比系数为气液两相螺旋环状流和气液两相直流的压降之比,以此来表征旋流衰减对压降的影响。基于量纲分析的方法对压降旋-直比系数进行分析,推导出其表达式,压降旋-直比系数依赖于Lockhart-Martinelli 参数和气相Froude数变化。最终,得出了气液两相螺旋环状流的压降预测模型。在50 mm内径的水平管内对螺旋环状流的压降特性进行了实验研究,其中气相表观流速变化范围为10~16 m/s,体积含液率(LVF)变化范围为0.6%~4.8%。通过与实验数据进行对比,压降预测模型的相对误差在±15%以内,为工程应用提供了参考。 相似文献
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Two-phase gas-liquid flow has been investigated in a 1-inch internal diameter vertical tube coil containing two risers and a downcomer all connected by “U” bends. Pressure drop, holdup and flow pattern data were successfully obtained simultaneously in the three vertical tubes, each 17.30 ft. long, for five different air-liquid systems at about 25 psia and 50°F-80°F over flow ranges of 0–700 lbm air/min-ft2 and 140--25300 lbm liquid/min-ft2. Pressure drops and liquid holdups were plotted against gas volume flowrate with liquid flowrate as a parameter. From these plots it was found that for a combination of an increase in liquid viscosity and density, and a decrease in surface tension, the frictional pressure drop increased in down flow and decreased in upflow. Holdup, on the other hand, increased for both types of vertical flow with respect to the same combination of parameters. The Lockhart-Martinelli scheme was satisfactory in correlating frictional pressure drop and holdup in all the flow regimes except the frothy-slug regime in upflow. In downflow however, the Lockhart-Martinelli scheme met with limited success because of a strong influence of liquid flowrate, physical properties and pipe orientation. Holdup in the falling film and falling bubbly film regimes in downflow were satisfactorily treated by the drift flux approach which emphasizes the relative motion of the two phases. 相似文献
6.
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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主要对自主设计的渐缩管、渐扩渐缩管、螺旋管和四孔管进行水-空气两相流混合顶吹实验,并得出了扰流型喷管的管内流型变化规律。实验通过对可视化特殊喷管内的气液两相进行高速拍摄,并调节水与空气两相各自的体积流量,获取不同喷管中出现的特殊流型照片及视频。实验结果表明:在表观气速和表观液速变化时,除渐缩管外,其他特殊喷管的流型转变均有一定规律性;渐扩渐缩管内截面半径变化较大,易产生环状-搅拌流,并有典型泡状流出现,螺旋管由于轴向环流速度的影响,会产生大密度泡状流并逐渐过渡到有旋流趋势的环状流型,特殊结构的四孔管中流型较稳定,短暂出现泡状流、弹状流后形成稳定环状流。四孔管的设计最利于冶金熔炉中柴油-氮气混合两相流喷吹,形成的气泡群中单个气泡直径较小,柴油被充分细化打散,渣层中的还原反应更充分,能有效提高柴油对渣层中磁性铁的还原率。 相似文献
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槽式孔板是一种新型气液两相流量传感器,目前尚未发现能够应用于槽式孔板的两相流压降相关式,结合空气/水两相流实验数据,比较了五类典型的标准节流元件两相流压降相关式对槽式孔板测量数据的计算结果,分析了这些相关式的适用范围和误差原因。基于不同的建模思想,综合考虑洛—马参数、介质压力、气相流量等参数的作用,建立了三种相对准确的槽式孔板两相流压降相关式,并将其应用于低含液率的凝析天然气计量技术研究,计算结果表明三种相关式均能达到工业计量的精度要求。 相似文献
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螺旋扭扁管强化传热与阻力性能的模拟分析 总被引:5,自引:0,他引:5
运用数值模拟的方法对螺旋扭扁管的传热与阻力性能进行了分析与研究,并与普通椭圆直管相比较,研究了管内流体的Re、Pr以及管子几何尺寸对其管内传热与流动性能的影响。结果表明,螺旋扭扁管是一种较好的强化传热元件,尤其对具有高Pr数的大粘度流体在低Re数的层流或过渡流时具有较好的强化传热效果。根据数值模拟的结果,利用多元线性回归的方法给出了努塞尔数Nu和阻力系数f的准则公式。 相似文献
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Characteristics of gas penetration and polymer melt flow in gas-assisted injection molded spiral tubes was investigated by simulations and experiments. Distribution of the skin melt thickness along the gas flow direction was measured, and gas penetration in the primary and secondary stages was identified. An algorithm based on the control-volume/tiniteelement method combined with a particle-tracing scheme using a dual-filling-parameter technique is utilized to predict the advancements of both melt front and gas from during the molding process. The simulated distribution of gas penetration shows reasonably good coincidence with experimental observations. © 1995 John Wiley & Sons, Inc. 相似文献
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静态混合器气液两相流压降的研究 总被引:2,自引:0,他引:2
在气相和液相均为湍流的情况下,测定了SK10,SK25,SV20,SV25静态混合器的压降。采用Lockhart-Martinelli关联方法,对不同类型的静态混合器,得出X_a~φ_L线和X_U和φ_L的经验关联式。 相似文献
15.
A novel noninvasive approach, based on flow-induced vibration, to the online flow regime identification for wet gas flow in a horizontal pipeline is proposed. Research into the flow-induced vibration response for the wet gas flow was conducted under the conditions of pipe diameter 50 mm, pressure from 0.25 MPa to 0.35 MPa, Lockhart-Martinelli parameter from 0.02 to 0.6, and gas Froude Number from 0.5 to 2.7. The flow-induced vibration signals were measured by a transducer installed on outside wall of pipe, and then the normalized energy features from different frequency bands in the vibration signals were extracted through 4-scale wavelet package transform. A “binary tree” multi-class support vector machine(MCSVM) classifier, with the normalized feature vector as inputs, and Gaussian radial basis function as kernel function, was developed to identify the three typical flow regimes in-cluding stratified wavy flow, annular mist flow, and slug flow for wet gas flow. The results show that the method can identify effec-tively flow regimes and its identification accuracy is about 93.3%. Comparing with the other classifiers, the MCSVM classifier has higher accuracy, especially under the case of small samples. The noninvasive measurement approach has great application prospect in online flow regime identification. 相似文献
16.
The effect of tube diameter on two‐phase flow patterns was investigated in circular tubes with inner diameters of 0.6, 1.2, 1.7, 2.6, and 3.4 mm using air and water. The gas and liquid superficial velocity ranges were 0.01–50 and 0.01–3 m/s, respectively. The gas and liquid flow rates were measured and the two‐phase flow pattern images were recorded using high‐speed CMOS camera. The flow patterns observed were dispersed bubbly, bubbly, slug, slug‐annular, wavy‐annular, stratified, and annular flows. These flow patterns were not observed in all the test diameters, but were found to be unique to particular tube diameters, confirming the effect of tube diameter on the flow pattern. The data obtained were compared to existing experimental data and flow regime transition maps which show generally reasonable overall agreement at the larger diameters, but significant differences were observed with the smaller diameter tubes. 相似文献
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李强伟 《高校化学工程学报》2009,23(4)
基于电容层析成像技术和文丘里管流量计,提出改进的de Leeuw关系式来实现油气两相流质量流量测量.实际测量中应用电容层析成像技术获取两相流空隙率和流型信息,由获取的空隙率通过关联Lockhart-Martinelli参数得到质量流量含气率.该改进关系式根据不同的流型信息选择经验参数 (该参数与气相弗劳德准数有关),结合质量流量含气率及文丘里管流量计获取的差压信息实现两相流质量流量测量.油气两相流的实验结果表明所提出的改进de Leeuw关系式是有效的. 相似文献
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A precise knowledge of gas-holdup distribution and energy dissipation is essential for designing gas-liquid contactors. A semi-theoretical approach has been presented to obtain the axial distribution of gas holdup through the column for gas-non-Newtonian liquid two-phase flow system. The whole column is distinguished to have three zones based on gas holdup, viz. top, middle and bottom. The middle section where significant accumulation of bubbles takes place, contributes higher gas holdup towards the total compared to the other two sections. Energy dissipation in the column have been calculated from two-phase gas-liquid frictional losses. A comparative study shows that substantial gas holdup are observed in the present system with considerably lower energy losses. The experimental data of gas holdup have been correlated in terms of pressure drop by the modified Lockhart-Martinelli equation. 相似文献
20.
Investigating the liquid film characteristics of gas–liquid swirling flow using ultrasound doppler velocimetry
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Fachun Liang Zhaojun Fang Jing Chen Shitao Sun 《American Institute of Chemical Engineers》2017,63(6):2348-2357
A novel gas–liquid two‐phase flow metering method was proposed. A spiral vane mounted in the inner pipe was used to transform inlet flow patterns into gas–liquid swirling annular flow. The thickness and velocity profile of liquid film were measured by ultrasound Doppler velocimetry. The liquid flow rates were obtained by integrating of velocity profile during the liquid film zone. Experiments were carried out in an air–water two‐phase flow loop and an ultrasonic transducer was installed under the bottom of the test section with the Doppler angle of 70°. The flow patterns included stratified wavy, annular, and slug flows. Compared with non‐swirling flow, the liquid film thickness at the bottom reduces greatly. The measurement accuracy of liquid flow rate was independent of inlet flow patterns, gas and liquid velocities. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2348–2357, 2017 相似文献