Direct calculations of unsteady-state Weymouth equations for gas volumetric flow rate occur more frequently in the design and operation analysis of natural gas systems. Most of the existing gas pipelines design proced...Direct calculations of unsteady-state Weymouth equations for gas volumetric flow rate occur more frequently in the design and operation analysis of natural gas systems. Most of the existing gas pipelines design procedures are based on a particular friction factor and steady-state flow analysis. This paper examined the behavior of different friction factors and the need to develop model analysis capable of calculating unsteady-state gas flow rate in horizontal and inclined pipes. The results show different variation in flow rate with Panhandle A and Panhandle B attaining stability in accurate time with initial unsteadiness at the instance of flow. Chen and Jain friction factors have opposition to flow with high flow rate: The prediction also reveals that Colebrook-White degenerated to Nikuradse friction factor at high Reynolds number. The horizontal and inclined flow equations are considerably enhanced on the usage of different friction factors with the aid of Matlab to handle these calculations.展开更多
The fabrication of superhydrophobic surfaces and the studies on water flow characteristics therein are of great significance to many industrial areas as well as to science and technology development. Experiments were ...The fabrication of superhydrophobic surfaces and the studies on water flow characteristics therein are of great significance to many industrial areas as well as to science and technology development. Experiments were car- ried out to investigate slip characteristics of water flowing in circular superhydrophobic microtubes within lam- inar flow region. The superhydrophobic microtubes of stainless steel were fabricated with chemical etching- fluorination treatment. An experimental setup was designed to measure the pressure drop as function of water flow rate. For comparison, superhydrophilic tubes were also tested. Poiseuille number Po was found to be smaller for the superhydrophobic microtubes than that for superhydrophilic ones. The pressure drop reduc- tion ranges from 8% to 31%. It decreases with increasing Reynolds number when Re 〈 900, owing to the transition from Cassie state to Wenze] state. However, it is almost unchanged with further increasing Re after Re 〉 900. The slip length in superhydrophobic microtubes also exhibits a Reynolds number dependence similarly to the pressure drop reduction. The relation between slip length and Darcy friction factor is theoretically analyzed with consideration of surface roughness effect, which was testified with the experimental results.展开更多
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 syst...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.展开更多
本文建立了R32在绝热毛细管中流动的一维均相模型,并用实验数据验证了该模型的准确性。对比了采用现有文献中5种摩擦因子关联式和4种黏度关联式不同组合时的预测性能。结果表明:f=F(Re)模型与f=F(ε/D,Re)模型在低雷诺数区域预测值相似...本文建立了R32在绝热毛细管中流动的一维均相模型,并用实验数据验证了该模型的准确性。对比了采用现有文献中5种摩擦因子关联式和4种黏度关联式不同组合时的预测性能。结果表明:f=F(Re)模型与f=F(ε/D,Re)模型在低雷诺数区域预测值相似;随着雷诺数的增加,表面粗糙度的影响使f=F(ε/D,Re)模型预测值明显大于f=F(Re)模型,同时f=F(ε/D,Re)模型对质量流量的预测精度也要优于f=F(Re)模型。在f=F(Re)模型中,Bittle and Pate-Dukler模型具有最小平均绝对偏差(6.99%),有76.92%的数据点相对偏差在±10%以内、94.87%的数据点相对偏差在±20%以内。在f=F(ε/D,Re)模型中,Moody-Dukler模型具有最小平均绝对偏差6.38%,有82.05%的数据点相对偏差在±10%以内、97.44%的数据点相对偏差在±20%以内。展开更多
文摘Direct calculations of unsteady-state Weymouth equations for gas volumetric flow rate occur more frequently in the design and operation analysis of natural gas systems. Most of the existing gas pipelines design procedures are based on a particular friction factor and steady-state flow analysis. This paper examined the behavior of different friction factors and the need to develop model analysis capable of calculating unsteady-state gas flow rate in horizontal and inclined pipes. The results show different variation in flow rate with Panhandle A and Panhandle B attaining stability in accurate time with initial unsteadiness at the instance of flow. Chen and Jain friction factors have opposition to flow with high flow rate: The prediction also reveals that Colebrook-White degenerated to Nikuradse friction factor at high Reynolds number. The horizontal and inclined flow equations are considerably enhanced on the usage of different friction factors with the aid of Matlab to handle these calculations.
基金the National Natural Science Foundation of China(20476014,51376030)
文摘The fabrication of superhydrophobic surfaces and the studies on water flow characteristics therein are of great significance to many industrial areas as well as to science and technology development. Experiments were car- ried out to investigate slip characteristics of water flowing in circular superhydrophobic microtubes within lam- inar flow region. The superhydrophobic microtubes of stainless steel were fabricated with chemical etching- fluorination treatment. An experimental setup was designed to measure the pressure drop as function of water flow rate. For comparison, superhydrophilic tubes were also tested. Poiseuille number Po was found to be smaller for the superhydrophobic microtubes than that for superhydrophilic ones. The pressure drop reduc- tion ranges from 8% to 31%. It decreases with increasing Reynolds number when Re 〈 900, owing to the transition from Cassie state to Wenze] state. However, it is almost unchanged with further increasing Re after Re 〉 900. The slip length in superhydrophobic microtubes also exhibits a Reynolds number dependence similarly to the pressure drop reduction. The relation between slip length and Darcy friction factor is theoretically analyzed with consideration of surface roughness effect, which was testified with the experimental results.
基金supported by the National Natural Science Foundation of China (Grant No.50376012)supported by the Scientific Research Foundation of Harbin Engineering University (Grant No.HEUFT07066)
文摘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.
文摘本文建立了R32在绝热毛细管中流动的一维均相模型,并用实验数据验证了该模型的准确性。对比了采用现有文献中5种摩擦因子关联式和4种黏度关联式不同组合时的预测性能。结果表明:f=F(Re)模型与f=F(ε/D,Re)模型在低雷诺数区域预测值相似;随着雷诺数的增加,表面粗糙度的影响使f=F(ε/D,Re)模型预测值明显大于f=F(Re)模型,同时f=F(ε/D,Re)模型对质量流量的预测精度也要优于f=F(Re)模型。在f=F(Re)模型中,Bittle and Pate-Dukler模型具有最小平均绝对偏差(6.99%),有76.92%的数据点相对偏差在±10%以内、94.87%的数据点相对偏差在±20%以内。在f=F(ε/D,Re)模型中,Moody-Dukler模型具有最小平均绝对偏差6.38%,有82.05%的数据点相对偏差在±10%以内、97.44%的数据点相对偏差在±20%以内。
