Evaluation of frictional pressure drop correlations for air-water and air-oil two-phase flow in pipeline-riser system

Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to pipeline-riser flow needs evaluation since the flow condition in pipeline-riser is quite different from the original data where they were derived from. In the present study, a comprehensive evaluation of 24prevailing correlation in predicting frictional pressure drop is carried out based on experimentally measured data of air-water and air-oil two-phase flows in pipeline-riser. Experiments are performed in a system having different configuration of pipeline-riser with the inclination of the downcomer varied from-2°to-5°to investigated the effect of the elbow on the frictional pressure drop in the riser. The inlet gas velocity ranges from 0.03 to 6.2 m/s, and liquid velocity varies from 0.02 to 1.3 m/s. A total of885 experimental data points including 782 on air-water flows and 103 on air-oil flows are obtained and used to access the prediction ability of the correlations. Comparison of the predicted results with the measured data indicate that a majority of the investigated correlations under-predict the pressure drop on severe slugging. The result of this study highlights the requirement of new method considering the effect of pipe layout on the frictional pressure drop.

Developing Flow Pressure Drop and Friction Factor of Water in Copper Microchannels

Experiments of de-ionized water flowing in microchannels made in copper blocks were carried out to obtain pressure drop and friction factor and to investigate any possible discrepancies from conventional theory. Three channels with widths of 0.5 mm, 1.0 mm, 1.71 mm, a depth of 0.39 mm and a length of 62 mm were tested. For adiabatic tests, the temperature of the working fluid was maintained at 30 ℃, 60 ℃ and 90 ℃ without any heat fluxes supplied to the test section. The experimental conditions covered a range of Reynolds numbers from 234 to 3,430. For non-adiabatic tests, the inlet temperature and heat flux applied were 30 ℃ and 147 kW/m2 and only for the 0.635 mm channel. The friction factors obtained for the widest channel （Dh = 0.635 mm） are reported for both adiabatic and non-adiabatic experiments to assess possible temperature effects. The paper focuses on the effect of hydraulic diameter on pressure drop and friction factor over the experimental conditions. The pressure drop was found to decrease as the inlet temperature was increased, while the friction factors for the three test sections did not show significant differences. The experimental friction factors were in reasonable agreement with conventional developing flow theory. The effect of temperature on friction factor was not considerable as the friction factor with and without heat flux was almost the same.

The Relation between the Coefficient of Friction and Pressure Drop by Using the Different Reynolds Number in a Circular Tube

This study explains the relationship between friction coefficient and pressure change at a range of Reynolds (21,056 - 28,574) and (0 - 1.4) solid loading ratio of two-phase flow (gas-solid) inside a circular copper pipe by using laboratory apparatus and solving the equations mathematically. An experimentally relationship of friction coefficient and pressure change with Reynolds number and flow velocity obtained also the relationship between the Solid loading ratio with friction coefficient and pressure change has been done for a Limit range of Reynolds number. It was noticed that the increase in friction coefficient and pressure change for two-phase flow was occurred when solid loading ratio increased. Also the relationship between pressure change and Reynolds number was direct proportion while the relationship between friction coefficient and Reynolds Number was inversely related.

ERRATUM TO “CHARACTERISTICS OF PRESSURE DROP AND CORRELATION OF FRICTION FACTORS FOR SINGLE-PHASE FLOW IN ROLLING HORIZONTAL PIPE”

This is the erratum to the article [zhang Jin-hong, Yan Chang-qi, Gao Pu-zhen, Journal of Hydrodynamics, 2009, 21(5)]. The Fig.5 is corrected.

CHARACTERISTICS OF PRESSURE DROP AND CORRELATION OF FRICTION FACTORS FOR SINGLE-PHASE FLOW IN ROLLING HORIZONTAL PIPE

Gas-liquid two-phase flow occurs increasingly in some dynamic devices operating in the oceanic condition. The relative data are limited with respect to flow characteristics, so the present study is to investigate systematically single-phase pressure drop, and to develop the theory for frictional factor under the roiling condition. Using deionized water as the test fluid, a series of experiments of single-phase flow were conducted in pipe with the inner diameter of 34.5 ram. The test section was horizontally settled on the rolling apparatus, and its regularity was similar to simple harmonic motion. It is found that the pressure drop during rolling motion fluctuate with the change of the rolling period and rolling angle, which is significantly different from fluid motion in a steady state. By the contrast between experiment results and stable-state theory values, existing correlations can not predict present frictional factor very well. Therefore, in the present article, the single-phase frictional factor is correlated with the Reynolds number for rolling motion, and its computated results agree well with experimental data.

Experimental study on steam-water two-phase flow frictional pressure drops in helical coils

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不同流向上小流道加热管内超临界CO_(2)的压降特性

针对不同流动方向上超临界CO_(2)流体在小流道加热管径为0.75mm内的压降特性进行了实验研究。结果表明,不同流动(水平流动、垂直向上流动以及垂直向下流动)方向上,实验总压降、摩擦压降以及加速度压降均随着系统压力的升高而逐渐减小,而随着质量流量的增大、加热功率以及进口温度的升高而增大。然而,在垂直流动方向上重力压降随着系统压力的升高以及质量流量的增大而逐渐增大,但随着加热功率以及进口温度的升高而逐渐减小。当系统压力、质量流量、加热功率以及进口温度保持恒定时,不同流动方向上超临界CO_(2)流体的摩擦压降均在实验总压降中所占有的比例最大,而重力压降在实验总压降中所占有的比例最小。通过两种测试管径的压降数据比较可知,超临界CO_(2)流体在不同流动方向上实验总压降的变化趋势始终保持一致,并且小管径的实验总压降远大于大管径的实验总压降,从而说明测试管径的尺寸大小对实验总压降的变化有着显著影响。

并联通道中超临界RP-3航空煤油流量分配特性数值研究

针对热流偏差下空-油换热器的应用,进行了三种类型并联通道中超临界压力RP-3航空煤油流量分配数值研究,探究了进口压力、进口温度、进口总流量、进出口布置对双通道流量分配的影响机制。通过摩擦压降和加速压降的演变机制揭示了流量非对称分配的原因,讨论了通道质量流速和温度的分布特征及其对换热的影响,进行了(火积)耗散效应分析。根据热流密度比值和运行参数提出了流量偏差的预测准则,预测偏差处于±15%范围内。结果表明:随着双通道热流差别增大,两者流量偏差增大,源于加速压降和摩擦压降的平衡机制。热流比值小于1时,摩擦压降主导流量分配;热流比值大于1时,加速压降主导流量分配。热流比值等于1时,双通道流量等量分配。提高进口压力、进口温度、进口总流量双通道流量偏差均受到抑制。高热流偏差下通道出现流量不连续和偏差管温度反向分层问题。相对流量偏差和(火积)耗散偏差的变化规律一致,I型布置相比U型和Z型布置更好。

R513A在水平管内流动沸腾传热特性的研究

全球变暖已成为各国关注的全球性问题,因此第4代新型环保制冷剂的研究迫在眉睫。制冷剂在蒸发器内的沸腾传热特性直接关系到该制冷剂的应用。R513A是R134a的替代制冷剂,通过实验研究R513A和R134a在12.7 mm水平光滑管和内螺纹管内的沸腾传热特性,分析质量流速、蒸发温度、热流密度和内螺纹结构对传热系数及压降变化的机理。实验工况:制冷剂的质量流速为100~200 kg/(m^(2)·s),蒸发温度为5~10℃。结果表明:沸腾传热系数随着热流密度的增大发生显著变化;随着质量流速的增加,沸腾传热系数增大15.06%~42.33%,压降增大26.16%~61.83%;随着蒸发温度升高,沸腾传热系数增大13.27%~38.25%,压降减小19.53%~33.27%;内螺纹管的传热系数显著高于光滑管,强化倍率最大为2倍。相同工况下,R513A的沸腾传热系数比R134a增大约25.61%~30.74%,R134a内螺纹管内压降比R513A平均高约12.33%;随着热流密度的增加,R513A的流型转变较R134a提前,此时沸腾传热系数急剧下降。

超薄空间复杂边界条件下气体流动压降实验

随着超薄热管等元件进一步超薄化,蒸汽腔厚度减小导致蒸汽流动压降急剧增大,传热热阻增加,传输极限降低。搭建了超薄受限空间气体流动压降实验装置,开展空气流动实验,获得了不同通道高度(0.1~0.5 mm)、不同表面丝网孔径(0.036~0.104 mm)和不同流速(1~10 m/s)下的压降变化。结果表明:通道高度和流速对压降产生显著影响,而表面丝网孔径并不会;3个影响因素按显著程度依次为通道高度、流速、表面丝网孔径;随表面丝网孔径的减小,压降逐渐增大;随通道高度的减小,压降先缓慢增大,在减至0.3 mm后压降开始剧烈上升;随流速的增加,压降增大且近似呈正比例变化关系。最后基于实验数据修正了微通道层流情况下沿程阻力系数相关性预测关联式,以便更准确地预测气体压降。

蛇形微通道内绝热和沸腾流动气液两相压降的实验研究

蛇形微通道因结构紧凑和换热能力强的特点在高新技术领域中具有较大的研究价值,目前对微细尺度蛇形通道内全流型演变过程中的压降研究分析相对较少。通过实验的方法研究了当量直径为0.65 mm和弯管段曲率半径为1.2、1.8、2.4 mm的蛇形微通道内绝热流动和沸腾流动气液两相压降变化规律。根据实验计算了质量流速为600 kg/(m^(2)·s)时压降的占比情况,分析了质量流速为600、1200、1800、2400 kg/(m^(2)·s)时压降的变化情况,并与文献中压降经验关联式进行对比,发现文献中大部分已有关联式并不适用于蛇形微通道内气液两相流型的预测。

受热通道内超临界R134a流动阻力特性试验研究

以超临界R134a流体为工质,测试其在内径2 mm圆管内,流体压强p=4.3~4.9 MPa,质量流速G=550~1650 kg/(m^(2)·s),热流密度q=25~75 kW/m^(2)(电加热模拟热源)工况条件下的流动阻力。根据摩擦压降曲线特征,将其划分为类液相区、类两相区和类气相区3个区域。分析压强、质量流速和热流密度等工况参数对3个区域内的摩擦压降和摩擦因子的影响规律。在类两相区,摩擦因子曲线存在一个明显的峰值特性。将试验数据与已有的摩擦因子关联式进行对比,并进行定量评价。结果显示,已有关联式的预测误差普遍偏大,尤其是在类两相区域。为此,提出一个同时包含密度、黏度和平均普朗特数修正的超临界流体摩擦因子关联式,与试验数据对比显示,97%预测数据均处于±20%的误差范围内。

Lockhart-Martinelli两相流摩擦压降模型与典型均相流模型的验证对比分析

两相流摩擦压降的计算对于两相流设备与管道的设计选型和流阻分析至关重要。在已有的两相流摩擦压降模型中,均相流模型和Lockhart-Martinelli模型(L-M模型)是比较常用的两相流摩擦阻力压降计算模型。两相流压力对两相流摩擦压降影响很大,然而,之前的模型验证分析并未分析这些模型在不同压力条件下的计算精度。L-M模型是否适用于中高压两相流,均相流模型在什么压力范围内适用,并未有相关验证分析及结论。本研究对比了均相流模型和L-M模型计算值与文献中公开发表的两相流摩擦压降数据,主要包括OuldDidi的制冷剂两相流摩擦压降数据、GASPARI的7 MPa两相流摩擦压降数据及陈听宽的高压两相流摩擦压降实验数据。通过验证对比分析发现在中高压条件下,L-M模型计算误差非常大,压力越高,模型计算误差越大。而均相流模型,对于高压两相流,特别是对高压低质量含气率两相流有比较好的预测精度。

液态二氧化碳压裂管流摩阻计算与分析

液态二氧化碳压裂技术中采用无水纯液态二氧化碳,液态二氧化碳压裂管流摩阻的精准预测对于压裂的顺利进行具有极为重要的意义。针对该问题,对评价液态二氧化碳压裂管流摩阻的计算公式进行了研究。引入了液态二氧化碳压裂井口施工压力公式,在液态二氧化碳压裂管流摩阻压降计算模型中建立了摩阻系数与雷诺数之间的关系式来评价其摩阻系数。在液态二氧化碳压裂管流摩阻梯度计算模型中,对比分析了其相关摩阻计算方法。基于现场实测数据,通过得出的摩阻计算公式建立了不同管径和排量条件下的液态二氧化碳管流摩阻梯度曲线。研究结果表明,尼古拉兹系数清水摩阻计算式更为精确,相同排量下,摩阻随管径的增大而减小,套管注入方式的摩阻小于油管注入方式。采用相同管径的注入条件下,摩阻随施工排量增大而增大,研究结果对压裂施工的成功实施具有一定的指导意义。

钻具旋转时同心窄间隙环空流动的数值模拟

钻井过程中,当循环钻井液在井眼环空中作轴向流动时,由于钻具旋转而导致周向运动的出现,整个环空中因此形成螺旋流动,从而可能会对环空(特别是窄间隙)摩擦压降存在潜在的影响。对此,本文借助数值模拟软件,对同心窄间隙环空中钻具旋转下的层流流动进行直接数值模拟计算并分析。其中,钻具理想化为钻杆或圆柱体;钻井液则选用3种不同流变参数的宾汉流体。当前数值模拟计算结果表明,在不同钻具/杆转速下,PLR(压损比)几乎保持不变;这就表明,钻具/杆旋转过程中,并不会引起环空中摩擦压降的显著变化;然而,对比一些经验公式后发现,除了Ooms(1999)的公式能与当前计算吻合外,其余公式均不能反应该现象。进一步地,通过观察环空压力沿径向的变化过程时,结果表明,在当前180 rad/min范围内,压力沿径向几乎不变;即使当转速增大到600 rad/min,这种径向变化也十分有限,占比大约是2×10^(-5)量级。因此,在当前工程应用范围(钻具转速在180 rad/min以内)内,钻具旋转既不会导致轴向摩擦压降增大,也不会引起压力沿着径向显著变化。本文研究结果为实际钻井过程中对钻具旋转引起的摩擦压降的估算提供了一些参考,有助于优化钻井工艺和设备设计,提高钻进效率和安全性。

Investigation of flow resistance characteristics of endothermic hydrocarbon fuel under supercritical pressures

The characteristics of flow resistance of a typical hydrocarbon fuel(RP-3)flowthrough adiabatic horizontal miniature tubes at supercritical pressures are experimentallyinvestigated for both laminar and turbulent flow.The experiments are conducted by using along tube measuring section and a short tube measuring section simultaneously in order toeliminate the effect of local pressure drop.In these experiments,the temperature of RP-3changes from(295 to 789)K and the reduced pressure(P/Pc,Pc=2.33 MPa)ranges from 1 to2.58,the mass flux is up to 1572.7 kg/(m^(2).s).Test results indicate that frictional pressuredrops for various supercritical pressures at the same mass flux can be considered as equalwith each other when the reduced temperature Tb/Tpc<0.95.When Tb/Tpc>0.95,differenceappears and increases with the increase of Tb/Tpc.Additionally,the friction factor(f)of thesupercritical fluid for turbulent flow has a critical value at Tb/Tpc=1,the values of f at thispoint for all pressures and mass fluxes are equal with each other.Moreover,at the same massflux,there are two comresponding friction factors for the same Re,one is in the region of Tb/Tpc<1,the other is in the region of Tb/Tpc> 1.Finally, classical conelations of frictionfactor is inapplicable when Tb/Tpc>0.95 at supercritical pressure and a new coelation hasbeen obtained based on the experimental data.

摇摆状态下竖直管内单相水阻力特性实验研究

在3种不同摇摆周期(5s、10s、15s)、2种不同摇摆角度(10°、20°)的情况下,分别对3种不同管径(15mm、25mm、34.5mm)的竖直光滑有机玻璃管管内单相水的阻力特性进行了实验研究。经实验研究发现,试验段内的摩擦阻力系数随时间变化有明显的周期性,雷诺数增加导致摩擦阻力系数的波动幅值降低、平均值减小,管径越粗使得摩擦阻力系数λ的波动幅度越大。在任意时刻,摩擦阻力系数的瞬态值随周期的变长而增加,但是摇摆角度的变化对摩擦阻力系数的影响不是很显著。

水平管内油气水三相流分流型阻力特性实验研究

对水平管内油气水三相流的摩擦阻力压降特性进行了实验研究,水平管实验段由有机玻璃管制成,内径为40mm,所用的实验工质为:46#机械油,自来水和空气。油、气、水三相的折算速度范围分别为:0.05-0.51m／s、0.05-1.51m／s、0.02-50.6 m／s。按照气液界面总体特征将水平管内油气水三相流的流型分为泡状流、间歇流(段塞流和弹状流)、分层流及环状流。对各种典型流型下的摩擦阻力压降应用改进的Chisholm关系式及油水两相压降关系式进行分析,对Chisholm关系式中的参数C进行了重新定义。发现改进的Chisholm关系式能够较好地对管内油气水三相摩阻压降进行预测,因此改进Chisholm关系式可以作为摩擦压降计算的通用关系式。

不同截面形状微肋片内流动阻力特性

以去离子水为工质,实验研究了横截面形状为圆形、椭圆及菱形的叉排微肋片组成的流道内的流动阻力特性。结果表明,3种形状肋片流道内压降随流量增大而增大。受微/小尺度下层流边界层的影响,流量较低时微肋形状对流动影响较弱,椭圆形肋片与菱形肋片内压降几乎相同,而圆形截面肋片内由于流动距离较长导致流动阻力最大;当流量较大时,椭圆形肋片内压降最小。Re较小时,长短轴一致的菱形肋片内的流动阻力系数f比椭圆形肋片略低,但在Re较高时,椭圆形肋片内的f值仍然最低。研究还表明,在现有各种关联式中,只有菱形微肋片关联计算值与本实验值较吻合。

管内两相流摩擦压力损失计算研究进展

管内两相流摩擦压力损失计算广泛应用于各种工业领域,一直是热流体科学的重要研究方向。本文对管内两相流摩擦压降计算的研究成果进行了全面总结与归纳,系统综述了分相摩擦倍增因子方法、全相摩擦倍增因子方法以及均相模型方法,并且对各模型进行了评价和分析,可为相关研究提供参考。