Effect of drag reducing polymers on the rate of mass transfer in relation to their use as corrosion inhibitors in pipelines under turbulent flow conditions

Rates of mass transfer between a turbulently flowing fluid containing CMC drag reducing polymer and the wall of a tube were measured in the mass transfer entry region using the electrochemical technique. Variables studied were polymer concentration, surface roughness and solution flow rate. Carboxymethyl cellulose (CMC) was found to reduce the mass transfer coefficient by an amount ranging from 15 to 37% depending on the operating conditions. The percentage decrease in the mass transfer coefficient becomes greater with increasing CMC concentration and Reynolds number. CMC was found to reduce the rate of mass transfer at rough surfaces (e ⁺>3) by an amount higher than that at a smooth surface. The possibility of using large polymers as drag reducers and corrosion inhibitors simultaneously in pipelines is indicated.Nomenclature I limiting current (A) - Z number of electrons involved in the reaction - F Faraday's constant - A projected (geometrical) area of the cathode (cm²) - K mass transfer coefficient (cm s^–1) - C concentration of ferricyanide ion (mole cm^–3) - e roughness height (cm) - d tube diameter (cm) - L length of transfer surface (cm) - St Stanton number (K/V) - Re Reynolds number (Vd/u) - Sc Schmidt number (v/D) - e ⁺ dimensionless height (eu ^*/v) - u ^* friction velocity [V(f/2)^1/2] (cm s^–1) - V solution velocity (cm s^–1) - f friction factor - v kinematic viscosity (cm² s^–1) - u viscosity (poise) - density (g cm^–3) - D diffusivity (cm²s^–1)     

Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions

The present study aimed to investigate the corrosion behavior of a pipeline carrying dilute pulp fiber suspensions (0.1–0.3% consistency). To examine the role played by pulp fibers on the rate of diffusion controlled corrosion of metals an accelerated test which involved the diffusion controlled dissolution of copper in acidified dichromate was used under turbulent flow conditions. Different concentrations of pulp fibers at different solution velocities were studied. The rate of mass transfer controlled corrosion of copper was found to increase by increasing solution velocity and decrease by increasing pulp consistency. The data in the presence and absence of the pulp slurry were correlated by dimensionless equations.     

Pipeline scale-up in drag reducing turbulent flow

Models available in literature for predicting drag reduction scale-up are inadequate as they have been successful only over a narrow range of diameters. A new scale-up model is presented which equates dampening of turbulent velocity fluctuations by drag reducing additives to a reduction in the Prandtl mixing length. Flow and pressure drop data from a laboratory scale pipe along with shear viscosity measurements are sufficient to predict drag reduction scale-up in bigger diameter pipes. Using this approach, scale-up was successfully predicted over a diameter range of 7 to 154 mm for a surfactant-water system and 26.6 to 1194 mm for a polymer-oil system.     

Purification of corundum by calcination under controlled reducing conditions

The alkaline impurities detract from the mechanical properties of corundum materials, specially at high temperatures. So it is important that they are minimized. This paper describes a new purification method of aluminas by calcination at high temperatures (>l200°C) in controlled reducing atmospheres (P_O2∼10⁻¹⁵ atm). Under these conditions, alkaline impurities are removed by reduction to volatile species. Over 95% of Na₂O existing in the alumina can be removed in this way. SiO₂ and Fe₂O₃ can also be removed with these treatments.     

Developing and fully developed turbulent flow of drag reducing fluids in an annular duct

Velocity profiles for the inner and outer flow regions of annuli are proposed for the turbulent flow of drag reducing fluids. Theoretical expressions for friction factors are developed. From the shear stress equations and the velocity profiles, estimates for the entrance lengths are given.     

Review on the applications and developments of drag reducing polymer in turbulent pipe flow

Drag reduction phenomenon in pipelines has received lots of attention during the past decades due to its potential engineering applications, especially in fluid transporting industries. Various methods to enhance drag reduction have been developed throughout the years and divided into two categories;non-additives method and additives method. Both categories have different types of methods, with different formulations and applications which will generally be discussed in this review. Among all the methods discussed, drag reduction using polymer additive is as one of the most enticing and desirable methods. It has been the subject of research in this field and has been studied extensively for quite some time. It is due to its ability to reduce drag up to 80% when added in minute concentrations. Reducing drag in the pipe will require less pumping power thus offering economic relieves to the industries. So, this paper will be focusing more on the use of polymer additives as drag reducing agent, the general formulations of the additives, major issues involving the use of drag reducing polymers, and the potential applications of it. However, despite the extensive works of drag reduction polymer, there are still no models that accurately explain the mechanism of drag reduction. More studies needed to be done to have a better understanding of the phenomenon. Therefore, future research areas and potential approaches are proposed for future work.     

Degradation of drag reducing polymers in aqueous solutions

The performance of drag reducing polymers in turbulent flow is restricted by their mechanical degradation. This study examines how the working fluid can affect the degradation behavior of diluted drag reducing polymeric solutions. Solutions having different proportions of tap water and de-ionized water served as the working fluids. Three commercially available water soluble polymeric agents, namely, an anionic copolymer of polyacrylamide, xanthan gum, and polyethylene oxide, were then added to these solutions. All experiments had identical flow rates corresponding to turbulent conditions in a laboratory scale pipe line. Variation of pressure drop in the pipe line was then measured for 2 hours. It was found that polymer degradation is accelerated in tap water solutions compared to that in de-ionized water solutions. However, this is dependent on the specification of the polymer used, namely, the molecular weight of the polymer and the rigidity of its molecular backbone. Furthermore, a new mathematical relation has been developed to investigate degradation of the polymers over time.     

Flow visualization studies of a turbulent drag reducing solution

A nondisturbing photochromic dye trace technique has been employed to study the flow profiles of water-alcohol solutions containing the drag reducing polymer Polyox at concentrations of 0.55 to 5.5 ppm. Drag reductions of from 33 to 75% were observed in a smooth glass pipe. The dye traces show a thicker wall layer for the drag reducing solutions than that for the solvent alone. The core region is relatively unaffected by the polymer at 0.55 ppm and at 5.5 ppm the relative thickness of the turbulent core region has been greatly reduced. Earlier, unpublished work of Corinthios shows effectively no core at 33 ppm. Mean velocity and apparent axial turbulence intensity profiles obtained are in general agreement with previous data in the literature obtained with other methods and in the wall region the low frequency intensity is greater than that of the pure solvent. This is consistent with the results of Spangler but not those of Seyer. Higher low frequency intensities measured in the wall region suggest that higher frequency fluctuations are suppressed and/or that the time stability of eddies is increased as indicated by the reduced frequency of wall ejections in drag reducing solutions.     

Thermo‐responsive polymers for drag reduction in turbulent Taylor–Couette flow

The addition of a small amount of high molecular weight polymer to a solvent can substantially decrease friction losses by approximately 80%. This phenomenon known as drag reduction (DR) is used extensively in oil recovery during hydraulic fracturing and in many other applications to reduce the pumping costs. However, because of long chain length, these polymers get adsorbed on the surface of reservoir, diminishing the effectiveness of fracking. In the current study, a thermo‐responsive polymer, i.e., poly(N‐isopropylacrylamide) (PNIPAM) is investigated as a drag reducing agent (DRA), which collapses reversibly above 33 °C known as lower critical solution temperature (LCST), thereby preventing it from getting adsorbed beyond this temperature. Free radical polymerization was used to synthesize the PNIPAM and a Taylor–Couette (TC) setup with a rotating inner cylinder was utilized for measuring the DR. The effect of concentration, Reynolds number (Re), and temperature on DR were studied and a maximum of 50% DR was observed at 400 PPM concentration. PNIPAM demonstrated significant decrease in DR beyond LCST, validating its thermo‐responsive nature that could be beneficial for DR in oil recovery or in providing a control modality to DR technologies.DR versus temperature for PNIPAM solution (500 PPM) at Re = 100,000 demonstrating responsive behavior with temperature © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44191.     

Effects of drag reducing polymers on initiation of atherosclerosis

Results from two pilot studies using White Carneau pigeons on high cholesterol diets have demonstrated substantial reduction in arterial plaque accumulations when the birds were periodically injected with dilute aqueous solutions of a drag reducing polymer (Separan AP-30) so as to maintain circulating blood concentrations of approximately 60 ppm. Initiation of arterial plaque formation may be fluid-mechanically motivated such that regions subjected to fluid turbulence, rapidly developing boundary layers, and alternate separation and reattachment, arc; the most prone lo attack. Viscoelastic fluid response, as seen in drag reducing media, is known to alter such phenomena. Comparative documentation of plaque deposition in experimental as well as control birds shows significant differences in both the aortas and coronary arteries, at optical magnifications from 20 to 15000X.     

Roles of drag reducing polymers in single- and multi-phase flows

It has become a well-known fact that finding sustainable solutions to the unavoidable high pressure losses accompanying pipeline flows to increase the pumping capacity without necessarily adding more pump stations is inevitable. Polymers, as one of the drag reducing agents which have been found to offer such an economic relieve, is the most widely investigated and most often employed in industries because they can produce drag reduction up to 80% when they are added in minute concentrations. In addition, polymer additives modify the flow configurations of multiphase flows to such an extent that stratification of individual phases is enhanced thereby making the separation of the phases at the fluid destination much easier. The achievements so far made and the challenges facing the use of polymers as drag reducers in turbulent single and multiphase flows are comprehensively reviewed. This review discusses the experimental studies of the effects of polymer additives in turbulent flows, the analytical studies, and the proposed models as well as the suggested mechanisms that explain the drag reduction. Likewise, specific areas of interest in the review include phenomena of drag reduction by polymers, factors influencing the effectiveness of the drag reducing polymers, methods of injecting the polymers into the base fluids, degradation of the polymers and industrial applications of polymers as drag reducing agents. The current and future research interests are also addressed. Although finding reveals that there are quite a lot of research in this area, most of the experimental and theoretical works are devoted to single phase flows while the remaining ones are mostly directed towards gas–liquid flows except in very recent time when investigation into the use of polymers in liquid–liquid flows is being focused. Despite this voluminous works on drag reducing polymers, there are no universally accepted models and hence the mechanisms of drag reductions by polymers.     

Electrochemical evaluation of aminotriazole corrosion inhibitor under flow conditions

The primary purpose of this study was to investigate the effect that turbulent pipe flow has on the electrochemical behaviour of a 3-amino-1,2,4-triazole (aminotriazole or 3-AT)-based corrosion inhibitor. The experiments were carried out in a 4-L laboratory pipe loop. A metallic ring made of API X52 pipeline steel was located in a linear segment of the pipe loop and acted as a test electrode. The test environment used in all experiments was a 3% NaCl solution saturated with CO₂ at 20 °C. The range of Reynolds number studied was from 6518 to 32118, assuring turbulent flow conditions in the pipe loop. Electrochemical impedance spectroscopy (EIS) was used to determine the electrochemical behavior of the steel in the environment at different flow rates and inhibitor concentrations. It was found that the electrochemical impedance of the system is dependent on both exposure time and flow conditions (Reynolds number). It was also detected that EIS data can give information on the persistence of the inhibitor film formed upon the metal surface. Therefore, in order to qualify the performance of the corrosion inhibitor, it is necessary to define the flow conditions at which it is intended to work.     

Experimental research on drag reduction by polymer additives in a turbulent pipe flow

In order to investigate the effects of injection position on drag reduction as well as further the effects of polymer additives on turbulent structures, LDA measurements of turbulent pipe flows were conducted. The results show that the amount of drag reduction grows with the increase of the Reynolds number, and injecting the polymer at the centre of pipe is more effective than at the wall. Due to the addition of polymer solution, the axial, radial r.m.s. velocity fluctuations and Reynolds stress decrease over the entire pipe cross‐section, the time auto‐correlation coefficients of axial and radial velocity fluctuation at the centre of pipe decay more slowly, the number of spectrum peaks is decreased, and the peak shifts towards lower wave numbers. The results also reveal that, due to the addition of polymer solution, the large‐scale vortices are enhanced and small‐scale vortices are suppressed.     

Momentum/heat transfer analogy for drag reducing fluids during turbulent boundary layer flow with small pressure gradients

There have been many attempts in the literature to develop analogies for momentum, heat and mass transfer to drag reducing fluids; however, none have considered the presence of a pressure gradient when formulating the analogies. In the present work, a momentum/heat transfer analogy has been developed under the influence of small pressure gradient for drag reducing fluids using the Nakayama et al. (1984) solution methodology for Newtonian fluids. The results of the present analysis have been found to compare well with existing theoretical expressions.     

Inhibition and interfacial behaviour of novel amidine inhibitors against brass corrosion in 1 M HNO3 under flow conditions

Abstract

Amidine inhibitors for brass in 1?M HNO₃ were synthesized, and the electrochemical behaviours were investigated by different electrochemical techniques under flow conditions. This type of inhibitor can effectively overcome the fluid impact in flowing HNO₃ solutions for at least 24?h. The amidine inhibitors caused mainly cathodic curves to low current density and significantly strengthened the impedance under flow conditions. The relationship between concentration, flow conditions, and inhibition effects was investigated by weak electrochemical polarization curves, electrochemical impedance spectroscopy, and scanning electron microscopy. Adsorption thermodynamics indicated that all of the inhibitors function via chemisorption processes with Gibbs free energies of approximately -40?kJ/mol. A modified adsorption model was constructed based on the results of electrochemical experiments to explain why higher concentrations resulted in worsened inhibition effects due to fluid impact. The adsorption mechanism was identified by X-ray photoelectron spectroscopy, ATR-FTIR spectroscopy, and quantum chemical calculations. All of the chemistry analyses indicated that the amidine and heteroatoms contributed to surface adsorption.     

Synthesis of functional polymers under conditions of controlled atom-transfer radical polymerization

The major achievements in the field of controlled atom-transfer radical polymerization, the most promising method of living radical polymerization, are analyzed. The relationship between the structure of a regulating agent and its activity under the conditions of controlled radical polymerization, including the efficiency of metal-complex catalysts for the targeted synthesis of macromolecules with predetermined molecular-mass characteristics, chain structure, and properties, is examined. Main trends in the development of this area of polymer chemistry are highlighted.     

The investigation and optimization of drag reduction in turbulent flow of Newtonian fluid passing through horizontal pipelines using functionalized magnetic nanophotocatalysts and lecithin

The nanophotocatalysts were synthesized in four stages and evaluated by FTIR, FESEM and VSM analysis. The influence of nanofluids containing functionalized magnetic TiO₂ nanophotocatalyst and dipalmitoylphosphatidylcholine lecithin in drag reduction of turbulent flow in four horizontal pipelines was studied. The effective parameters on drag reduction (nanoparticle concentration, surfactant concentration, pH and Re number) were investigated and optimized in each pipeline using response surface method. The drag reduction in 1/2 galvanized, 3/4 galvanized, 1/2 five-layer and 1/2 cuprous pipelines was found 99.1%, 92.5%, 87.6% and 85.2%, respectively. The model adequacy was measured using ANOVA. Based on the high determination coefficient, more than 95% of variance of experimental data in all pipelines was described by quadratic model.     

A rheological study of laminar–turbulent transition in drag reducing polymeric solutions

Presented herein are the studies of laminar–turbulent transition in micropolar and power law fluids flowing in a circular pipe. For some parametric values of micropolar and power law fluids, both depict the drag reducing properties. The parametric values of these representations have been obtained from the experimental results of Mc-Comb. It has been observed that, in both the cases, as the drag-reducing property in the solution increases, the first transition point moves towards the walls of the pipe. It is also observed that the onset of early turbulence phenomenon occurs for the drag-reducing polymeric solutions.     

Characterization of polymer adsorption in tube flow of drag reducing fluids

Elucidation of the polymer adsorption and flow characteristics at the tube wall is essential for an understanding of turbulent drag reduction. The polymer adsorbed onto the tube wall, in the flow of dilute solutions of linear random coiling macromolecules, also produces a concentrated fluid layer at the surface of the adsorption zone, as a result of the flow of the solvent micromolecules in the porous network comprising the adsorption zone.Velocity profiles are developed and used to determine the radial variation in the adsorption zone of porosity, as well as fractional surface coverages and mean separation or interpenetration distances between macromolecules in the various adsorption layers. The polymer concentration build-up in the concentrated fluid layer is also evaluated. Predictions of the latter for aqueous Polyox WSR-301 solutions are in qualitative agreement with experimental measurements and suggest that turbulent drag reduction is related to the level of polymer build-up in the concentrated fluid layer.