This paper had investigated the effects of surface wettability on the frictional resistance of turbulent horizontal flow for tap water in five pipes made of various materials and four kinds of liquids in a polytetrafl...This paper had investigated the effects of surface wettability on the frictional resistance of turbulent horizontal flow for tap water in five pipes made of various materials and four kinds of liquids in a polytetrafluoroethylene(PTFE) pipe,with the same inner diameter of 14 mm. Pressure drops were measured under different flow rates through an experimental flow loop. The contact angles and adhesion work of liquids in contact with pipe surfaces were determined using a contact angle meter. Based on the dimension and regression analyses, two kinds of modified relationships between the frictional coefficient and the surface wettability were established according to the measured results corresponding to tap water in five pipes and four liquids in PTFE pipe. The experimental results show that the surface wettability has some influence on frictional coefficient of the studied liquids flowing in macroscale pipes, and the frictional coefficient decreases with the increase of the contact angle at the same Reynolds number. Meanwhile the effect of wettability on the hydrophobic surface is greater than that on the hydrophilic one. The frictional coefficients predicted by the modified formulas have verified to be in good agreement with the experimental values, the relative errors of which are within ±6% and ±3% for the tap water flowing in five different pipes and four kinds of liquids flowing in PTFE pipe, respectively.展开更多
Adhesion of oil at rock surface plays an important role in the liberation of oil from micro-/nano-pores,especially for heavy oil that has extremely high viscosity.Although molecular dynamics simulation is widely used ...Adhesion of oil at rock surface plays an important role in the liberation of oil from micro-/nano-pores,especially for heavy oil that has extremely high viscosity.Although molecular dynamics simulation is widely used to study the interfacial interaction for some specific oil-water-rock systems,experimental measurements provide more realistic and reliable evidence.In this work,we propose a dynamic wettability characterization method to indirectly measure resistant forces at oil-surfactant-rock interfaces,including frictional force,wettability hysteresis force,and viscous force,which are parallel with the oil-solid interface.The adhesive force,which is normal to the oil-solid interface is calculated through measurement of work of adhesion.The results show that work of adhesion instead of contact angle can better describe the adhesion of oil at solid surface.The effect of surfactant concentration on work of adhesion is different for water-wet and oil-wet surfaces.Moreover,average viscous forces are calculated through force analysis on oil drops moving along solid surface in different surfactant environments.It is found that viscous force has a magnitude comparable to the frictional force during the movement,while the wettability hysteresis force is negligible.On the other hand,the adhesive force calculated from the work of adhesion is also comparable to the viscous force.Therefore,both the resistant forces parallel with and normal to the oil-solid interface should be minimized for the liberation of oil from rock surface.This work proposes a simple method to evaluate the wetting capability of different surfactants and measure the adhesive force between heavy oil and rock surfaces indirectly,which provides insight into the adhesion of heavy oil at rock surface and would be valuable for the development of surfactant-based oil recovery methods.展开更多
针对传统方法的不足,提出了泡沫溶胶控制煤尘技术,并对泡沫溶胶湿润和黏附煤尘的特性进行了研究。基于湿润性动态接触角模型,分别对水性泡沫、泡沫溶胶和去离子水的湿润性和黏附功进行了对比分析;利用Zisman图对浸湿煤尘的湿润剂临界表...针对传统方法的不足,提出了泡沫溶胶控制煤尘技术,并对泡沫溶胶湿润和黏附煤尘的特性进行了研究。基于湿润性动态接触角模型,分别对水性泡沫、泡沫溶胶和去离子水的湿润性和黏附功进行了对比分析;利用Zisman图对浸湿煤尘的湿润剂临界表面张力值进行了分析。研究得出泡沫溶胶具有较好的煤尘湿润性,起泡能力和较强的黏附功;当润湿剂的表面张力值小于28.32 m N/m,可完全浸湿煤尘,当润湿剂的表面张力值大于73.77 m N/m,不能浸湿煤尘。研究得出在捕捉动态煤尘时,泡沫溶胶的捕尘效果应明显优于水性泡沫和去离子水。展开更多
基金supported by the National Major Science&Technology Project of China(No.2016ZX05025004-005)the Science&Technology Project of Sichuan Province(Grant No.2015JY0099)
文摘This paper had investigated the effects of surface wettability on the frictional resistance of turbulent horizontal flow for tap water in five pipes made of various materials and four kinds of liquids in a polytetrafluoroethylene(PTFE) pipe,with the same inner diameter of 14 mm. Pressure drops were measured under different flow rates through an experimental flow loop. The contact angles and adhesion work of liquids in contact with pipe surfaces were determined using a contact angle meter. Based on the dimension and regression analyses, two kinds of modified relationships between the frictional coefficient and the surface wettability were established according to the measured results corresponding to tap water in five pipes and four liquids in PTFE pipe. The experimental results show that the surface wettability has some influence on frictional coefficient of the studied liquids flowing in macroscale pipes, and the frictional coefficient decreases with the increase of the contact angle at the same Reynolds number. Meanwhile the effect of wettability on the hydrophobic surface is greater than that on the hydrophilic one. The frictional coefficients predicted by the modified formulas have verified to be in good agreement with the experimental values, the relative errors of which are within ±6% and ±3% for the tap water flowing in five different pipes and four kinds of liquids flowing in PTFE pipe, respectively.
基金funded by the National Key R&D Program of China(No.2018YFA0702400).
文摘Adhesion of oil at rock surface plays an important role in the liberation of oil from micro-/nano-pores,especially for heavy oil that has extremely high viscosity.Although molecular dynamics simulation is widely used to study the interfacial interaction for some specific oil-water-rock systems,experimental measurements provide more realistic and reliable evidence.In this work,we propose a dynamic wettability characterization method to indirectly measure resistant forces at oil-surfactant-rock interfaces,including frictional force,wettability hysteresis force,and viscous force,which are parallel with the oil-solid interface.The adhesive force,which is normal to the oil-solid interface is calculated through measurement of work of adhesion.The results show that work of adhesion instead of contact angle can better describe the adhesion of oil at solid surface.The effect of surfactant concentration on work of adhesion is different for water-wet and oil-wet surfaces.Moreover,average viscous forces are calculated through force analysis on oil drops moving along solid surface in different surfactant environments.It is found that viscous force has a magnitude comparable to the frictional force during the movement,while the wettability hysteresis force is negligible.On the other hand,the adhesive force calculated from the work of adhesion is also comparable to the viscous force.Therefore,both the resistant forces parallel with and normal to the oil-solid interface should be minimized for the liberation of oil from rock surface.This work proposes a simple method to evaluate the wetting capability of different surfactants and measure the adhesive force between heavy oil and rock surfaces indirectly,which provides insight into the adhesion of heavy oil at rock surface and would be valuable for the development of surfactant-based oil recovery methods.
文摘针对传统方法的不足,提出了泡沫溶胶控制煤尘技术,并对泡沫溶胶湿润和黏附煤尘的特性进行了研究。基于湿润性动态接触角模型,分别对水性泡沫、泡沫溶胶和去离子水的湿润性和黏附功进行了对比分析;利用Zisman图对浸湿煤尘的湿润剂临界表面张力值进行了分析。研究得出泡沫溶胶具有较好的煤尘湿润性,起泡能力和较强的黏附功;当润湿剂的表面张力值小于28.32 m N/m,可完全浸湿煤尘,当润湿剂的表面张力值大于73.77 m N/m,不能浸湿煤尘。研究得出在捕捉动态煤尘时,泡沫溶胶的捕尘效果应明显优于水性泡沫和去离子水。
