Drag-reducing Surfactant Research Articles

Effect of Molar Ratio of Counter-Ions to Cationic Surfactants Treating Trimethylolethane Hydrate Slurries

Experimental studies on flow characteristics and particle size distributions of trimethylolethane (TME) hydrate slurries treated with drag-reducing surfactants have been conducted to investigate the effect of the molar ratio of counter-ions to surfactants. Oleylbishydroxyethylmethylammonium chloride is used as the drag-reducing surfactants. The molar ratio of sodium salicylate supplying counter-ions to surfactants is adjusted from 0 to 100 while the concentrations of TME in water and of surfactants remains constant at 25 wt% and at 2000 ppm, respectively. Results unexpectedly indicate that the drag reduction is greatest when the molar ratio of the counterions to surfactants is 20 against the fact that the higher molar ratio shows the higher drag reduction in water case. This indicates that some interaction between the counter-ions and TME molecules occurs and that it disturbs the formation of rod-like micellar structures causing the drag reduction. Thus, a molar ratio of counterions to surfactants of 20 is concluded to be the optimum for the drag reduction although it has a detrimental effect on the particle size under the present experimental conditions used.

Drag reducing surfactants for district heating

An application of specific surfactants in district heating and cooling systems can give notable economical benefits due to a reduction in friction and heat transfer attributed to a formation of an additional viscous sublayer along the pipe walls, buffering the turbulence. A mathematical three-layer model of water velocity profile is composed for the calculation of drag reduction and flow-capacity increase. At a properly chosen surfactant and concentration, the local drag can be reduced up to 80%. A computer simulation and optimization for a selected district heating network model with additive shows 4% saving in total costs because smaller pipes and weaker pumps are required.

Small-angle neutron scattering study of shearing effects on drag-reducing surfactant solutions

Drag-reducing surfactant solutions are very sensitive to shear. Shear can induce nanostructural transitions which affect drag reduction effectiveness and rheological properties. Literature reports on the effects of shear on different micellar solutions are inconsistent. In this paper, the effects of shear on three cationic drag-reducing surfactant solutions each with very different nanostructures and rheological behaviors, Arquad 16-50/sodium salicylate (NaSal) (5 mM/5 mM) (has thread-like micelles, shear-induced structure and large first normal stress ( N 1)), Arquad S-50/NaSal (5 mM/12.5 mM) (has branched micelles, no shear-induced structure and first normal stress is about zero) and Arquad 16-50/sodium 3,4-dimethyl-benzoate (5 mM/5 mM) (has vesicles and thread-like micelles, shear-induced structure and high first normal stress ( N 1)) are studied by small-angle neutron scattering (SANS), together with their rheological properties, drag reduction behavior and nanostructures by cryogenic-temperature transmission electron microscopy(cryo-TEM). The differences in the rheological behavior and the SANS data of the solutions are explained by the different responses of the nanostructures to shear based on a two-step response to shear.

Friction and heat transfer in drag-reducing surfactant solution flow through curved pipes and elbows

A study of drag-reducing flow in curved pipes was conducted. In contrast to earlier studies we show that if we use a modified definition of drag reduction that includes only the turbulence effects, we observe indeed the same level of drag reduction in both coiled and straight pipes. More complex results showing reduced drag reduction compared to curved pipes were achieved with elbows. Two elbows of different size and type were tested in turbulent flow of both water and drag-reducing surfactant solution. A more elaborate analysis was conducted for a half-inch threaded elbow with a ratio of curvature radius to diameter of 1.2. The pressure drop and heat transfer were measured in a section downstream from the elbow over a distance of x/ D = 130 in order to investigate the hydrodynamic and thermal developments of the flow. The pressure drop coefficient of the elbow was calculated for water and a surfactant solution, based on the total increase in pressure drop in the system due to the presence of the elbow. For a larger welded elbow of 6″ diameter some drag reduction was measured for the surfactant solution.

Turbulence statistics and structures of drag-reducing turbulent boundary layer in homogeneous aqueous surfactant solutions

In our earlier work [Itoh et al., Phys. Fluids 17, 075107 (2005)], the additional maximum of the streamwise turbulence intensity near the center of the drag-reducing turbulent boundary layer was found in the homogeneous dilute aqueous surfactant solution which was a mixture of cetyltrimethyl ammonium chloride with sodium salicylate as counterion. In this work, we systematically investigated the influence of the drag-reducing surfactant on the velocity fields of the turbulent boundary layer at various Reynolds numbers Reθ from 301 to 1437 and the drag reduction ratio DR from 8% to 74% under different streamwise locations and concentration and temperature of solutions using a two-component laser-Doppler velocimetry (LDV) system. It was revealed that all data on DR versus the wall-shear rate obtained here were collapsed on a single curve. We verified the existence of the additional maximum of the streamwise turbulence intensity near the center of the boundary layer which appeared at relatively large drag reduction ratios and small Reynolds numbers. It was found that the additional maximum of streamwise turbulence intensity and its wall-normal location were independent of the streamwise location, wall-shear rate, Reynolds number, and drag reduction ratio. The additional maximum could be explained by the bilayered structure model proposed, in which the flow in the near-wall region is in shear-induced structure (SIS) and viscoelastic, whereas the flow in the region away from the wall is in non-SIS and nonviscoelastic. This model was based on measurements of the shear viscosity. We also performed particle image velocimetry measurements, which revealed that the fluctuating velocity vector fields showed two situations, with low and high activity. In low activity, the velocity fluctuations were attenuated largely across the turbulent boundary layer. In high activity, fluctuating velocity vectors were almost parallel to the wall and relatively large in both regions near the wall and the center of the boundary layer, which seemed to be a bilayered structure and supported the bilayered structure model.

Evaluation of the role of a cationic surfactant on the flow characteristics of fly ash slurry

Transportation of fly ash is a major problem in its efficient disposal. The main problem associated with fly ash transportation is that the particles settle down sooner than desired. The primary objective of this research is that not only the fly ash particles should remain floated till it reaches the end but also settle down after that. In this investigation the role of a drag-reducing cationic surfactant and a counter-ion has been evaluated to achieve the objectives. The experimental results show encouraging trends of surfactant helping fly ash particles to remain water-borne. The material exhibited Newtonian behavior. This paper describes these in term of shear rates, shear stress, temperature, concentration and viscosity. Rheological tests were conducted using Advanced Computerized Rheometer. Zeta potential was measured to test the stability of the colloidal fly ash particles using Malvern Zeta Sizer instrument. Surface tension was also measured to know the drag reduction behavior of the fly ash slurry by using Surface Tensiometer. The test results and flow diagrams were generated using Rheoplus software and are presented in this paper. Surfactant concentration of 0%, 0.1%, 0.2%, 0.3%, 0.4% and 0.5% by weight was mixed with equal amount of counter-ion and the slurry was prepared by adding fly ash with ordinary tap water to achieve the desired solid concentration of 20% (by weight).

0504 抵抗低減化界面活性剤溶液のマルチ構造に関する研究(OS5-1 非ニュートン流体の流動現象,オーガナイズドセッション)

Experimental study on the contribution from the surfactant structure to the shear stress characteristics of drag-reducing cationic surfactant solution has been performed. The contributions from each structure were estimated while the surfactant concentration and the counter-ion molar ratio to the surfactants were widely changed. From the results, it was found that the structure having shortest relaxation time well corresponds to the shear stress characteristics. Form the comparison with the drag reduction occurrence map, the shortest relaxation structure was concluded to be the main cause of drag reduction occurrence.

553 抵抗低減界面活性剤水溶液の乱流境界層流れにおける乱れ構造に関する実験的研究(GS流体工学(抵抗低減など))

553 抵抗低減界面活性剤水溶液の乱流境界層流れにおける乱れ構造に関する実験的研究(GS流体工学(抵抗低減など))

Effects of Temperature and Concentration on Rheological Characteristics of Surfactant Additive Solutions

The shear viscosity of turbulent drag-reducing surfactant solution was measured as a function of concentration, shear rate and temperature by using an AG-G2 rheometer (TA Instruments, New Castle, USA). The experimental results showed complicated rheological behavior with the concentration in large. The Bird-Carreau model was found to fit well to the measured rheological results. The characteristics for the parameters η 0, η ∞ and λ dependence on temperature were also studied.

Experimental study on the effects of shear induced structure in a drag-reducing surfactant solution flow

In this paper, The drag reduction characteristics of surfactant solutions have been experimentally studied, as well as, the shear viscosities of turbulent drag-reducing surfactant solution have been measured as a function of concentration, shear rate and temperature by using AG-G2 (TA Instruments, New Castle, USA) rheometer. In comparison the rheological property with the macroscopic behavior of the solutions in turbulent channel flow, a deeper insight into the mechanisms of drag-reducing surfactant solution has been obtained. For no shear induced structure of surfactant solutions they just show features shear thinning, but the drag reduction is very significant phenomenon. Surfactant solution of the shear induced structure is not a surfactant fluid drag reduction of the necessary elements.

Effects of Concentration of Surfactant Solutions on Drag-Reducing Turbulent Boundary Layer

In this study, the influence of a drag-reducing surfactant on the turbulent boundary layer was extensively investigated under different solution concentrations using a two-component laser-Doppler velocimetry system. The surfactant solution used here was a mixture of cetyltrimethyl ammonium chloride (CTAC) with sodium salicylate as counterion, which was dissolved in tap water. The concentrations tested were 100 and 150 ppm, and the previous data on surfactant solution of 65 ppm were also used.The temperature of surfactant solution was T=20°C.It is found that the drag reduction ratio DR becomes larger downstream, and decreases with the increase of concentration from C=65 to 150 ppm. Regardless of solution concentrations, the value of the mean velocity scaled by the friction velocity increases with increasing the amount of drag reduction, while the mean velocity scaled by the free-stream velocity, which are collapsed for the different Reynolds number and drag reduction ratio, are about in the middle between the mean velocity profile of water and the Blasius laminar profile. For the present experimental conditions tested, the maximum of streamwise turbulence intensity near the wall is not related to the amount of DR directly and seems to be affected by the low Reynolds number effect strongly, while the location of the maximum becomes more distant from the wall with the increase of DR. The additional maximum of streamwise turbulence intensity near the center of the boundary layer, which is observed for all the concentration tested, and the wall-normal location of additional maximum are almost constant and are independent of the amount of drag reduction.

Measurement of temperature profiles in turbulent pipe flow of polymer and surfactant drag-reducing solutions

A device was built to measure temperature profiles of turbulent pipe flows of various drag-reducing fluids. It is easy to use and reliable. We measured temperature profiles over a range of conditions leading to accurate measurements down to y+≈10, for tests carried over Reynolds numbers (Re) between 10 000 and 90 000. The effects of high heat fluxes and buoyancy, in particular, were quantified to ascertain the parameter range for accurate measurements. Temperature profiles measured for type-A polymer solution and for cationic surfactant solutions allowed us to see strong similarity between velocity and temperature profiles for drag-reducing surfactant solutions. A comparison between the slopes of the thermal and velocity buffer layers resulted in calculated turbulent Prandtl numbers between 6 and 9 for those drag-reducing solutions. We also used this tool to investigate drag reduction for a nonionic surfactant solution, which showed a significantly different fan-type profile, and also for a type-B drag-reducing polymer solution (Xanthan gum).

Temporary degradation and recovery of drag-reducing surfactant solutions

We have investigated the intentional temporary degradation and the subsequent recovery of the drag-reducing properties of surfactant solutions. Degradation was achieved by exposing the fluid to mechanical stresses after which it showed significantly reduced drag reduction capability. The recovery time varies from a fraction of second to several minutes, depending on the surfactant concentration, the counter-ion concentration and the temperature. The recovery process generally showed a linear increase of the drag reduction level with time, with the rate of recovery being essentially independent of the flow velocity and the initial level of degradation, though the recovery at rest is considerably slower than the recovery under turbulent flow conditions. The recovery time decreases sharply with increasing concentration and temperature, and with increasing counter-ion concentration for the cationic surfactant. The mechanical degradation apparently affects not only the shear-induced structure but also the rod-like micelles themselves.

Effect of a shear-thickening rheological behaviour on the friction coefficient in a plane channel flow: A study by Direct Numerical Simulation

The aim of this paper is to study by direct numerical simulation the effect of a shear-thickening behaviour of a surfactant solution, on the fluid flow, and especially on the friction coefficient in a plane channel flow. A three-dimensional model named Surfactant Drag Reduction Study (SUDRES3D) [S. Guillou, R. Makhloufi, Direct numerical simulation of an incompressible channel flow in presence of an additive, in: J. Sobota, R. Verhoeven (Eds.), Proc. 11th International Conference Transport and Sedimentation of Solid Particles, AXA, Wroclam, 2002, pp. 151–158] was developed to apply to DNS. The shear-thickening rheological behaviour of an aqueous surfactant solution (Ethoquad O/12 (500 ppm) + NaSal (330 ppm)), studied previously by Usui et al. [H. Usui, T. Itoh, T. Saeki, On pipe diameter effects in surfactant drag-reducing pipe flows, Rheol. Acta 37 (1998) 122–128], is modelled here by a combination of two shear-thinning Carreau laws, which is later referred to as composed law. The calculations are performed first separately with the two shear-thinning Carreau laws and the composed law for different Reynolds numbers either in laminar and turbulent flows. The results are compared between them. It appears that for the set of parameters used, corresponding to the experimental data, the shear-thickening has no major effect on the wall friction and then no Drag Reduction occurs. Secondly, some calculations are performed with a chosen set of parameters. They show that such kind of behaviour may have a positive effect on the friction coefficient and a drag reduction phenomenon appears, but under restrictive conditions.

Local shear stress measurements with microelectrodes in turbulent flow of drag reducing surfactant solutions

The local wall shear stress, in turbulent flow of drag reducing and corrosion inhibiting surfactant solutions, was measured from polarographic mass transfer experiments using microelectrodes. A good agreement was observed between these values and those obtained by pressure drop measurements in a rectangular channel of high aspect ratio (10:1). Irreversible degradation was not observed in these systems at variance with polymer solutions.

106 非イオン性界面活性剤水溶液の乱流境界層流れに関する実験的研究(2)(OS1-2 流れの抵抗低減,OS1 流れの抵抗抵減,オーガナイズドセッション)

Surfactant additives have been attractive as practical drag-reducing additives because they were not affected by the degradation due to mechanical shear action and they could apply to the circulatory system. There are only a few studies on drag-reducing effect of nonionic surfactant solutions, although a lot of studies for cationic surfactant solutions have been performed so far. The influence of drag-reducing nonionic surfactant solution at 4000 ppm and 6000 ppm on the pipe flow and turbulent boundary layer was investigated.

Heat Transfer Reduction by Drag-Reducing Surfactant Solutions in a Higher Temperature Range

Drag reduction caused by surfactant solutions is considered to be an effective way to reduce the running cost in closed-loop district heating and cooling systems. Conversely, much research has pointed out that heat transfer reduction occurs simultaneously for drag reducing flows. In this study, drag reduction and heat transfer characteristics were measured for drag-reducing additives with two cationic surfactants of different concentrations, particularly in a higher temperature range, that cross the upper limit temperature of drag reducing solutions. Information on what occurs at this higher temperature range is necessary for design and operation with considering heating processes.

Influence of Surfactant on the Elementary Motions in Turbulent Flow

To investigate the effect of drag-reducing surfactant on typical elementary motions in turbulent flows, direct numerical simulation was carried out for a pair of streamwise vortices and a single low-speed streak. The surfactant solution was represented by a modified Bird-Carreau model. In surfactant solution, the streamwise vortices were inhibited immediately. On the other hand, the low-speed streak was less affected. Secondary streamwise vortices generated by low-speed streak were inhibited at downstream of surfactant solution. In such a sense, maintainance mechanism of low-speed streak was changed. In order to clarify the factor of modification of the elementary motions in turbulence, the energy budget was estimated. The inhibition of streamwise vortices resulted from strong viscous diffusion due to non-Newtonian effect. The influence of surfactant on the low-speed streak motion is mainly caused by the change in magnitude of energy redistribution. This is an indirect effect of streamwise vortices around a streak.

On the mitigation of erosion–corrosion of copper by a drag-reducing cationic surfactant in turbulent flow conditions using a rotating cage

Erosion–corrosion is a complex materials degradation mechanism involving the combined effects of mechanical erosion and electrochemical corrosion. It is known to be induced by high shear stresses in strong flows. One way to mitigate this phenomenon is to use additives reducing the turbulent Reynolds stresses. Oleyltrimethyl ammonium cationic surfactant and sodium salicylate as counter-ion known to form thread-like micelles behaving as drag reducers were tested in this work and successfully imaged by using AFM technique. A shear stress mapping in the rotating cage using an electrochemical method was implemented in the absence and in the presence of surfactant, showing drag reduction amounts up to 65%. In a second step, erosion corrosion of Cu in Na 2SO 4 0.1 M in the presence of small amounts of NaCl (1 mM) was investigated on Cu microelectrodes located at different positions on plastic coupons in the cage. The surfactant effect was found to be beneficial by preventing the removal of the pre-existing oxide films, otherwise observed in the absence of surfactant. Tests performed with benzotriazole known as a good corrosion inhibitor for Cu, could not prevent either the breaking of the oxide film in strong flow conditions.

Synthesis of aminimides derived from oleic acid: a new family of drag-reducing surfactants

Large-scale syntheses of aminimide surfactants that serve as low temperature drag-reducing agents in ethylene glycol–water mixtures are described. Preliminary drag reduction results are presented and the susceptibility of the surfactants to methanolysis is discussed.