Aqueous Solutions Of Polyethylene Oxide Research Articles

Flow of dilute polymer solutions through curved pipes. 2nd report. Pressure loss in 360.DEG. bends.

Experiments on flows of water and dilute aqueous solution of polyethylene oxide are carried out over the Reynolds number range of 103 to 5×104. Concentration of polymer solutions is varried from 1 ppm to 100 ppm. The ratios of curvature radius to pipe radius R/a are 18.7, 34.3 and 47.3. Measured pressure distributions along a bend axis are classified in three types by their patterns. Flow property of each pattern is clarified by using the method of flow visualization. Drag reduction in bend flow is smaller than that in straight pipe flow. Pressure loss coefficients are correlated with the Reynolds number, the ratio of radius R/a, and the Wissenberg number. The empirical formulas presented for the bend loss coefficient are useful from an enginnering viewpoint.

Heat transfer and critical heat fluxes in the boiling of aqueous solutions of polyethylene oxide at reduced pressures under natural-convection conditions

Experimental data are presented on heat transfer and critical heat fluxes in the boiling of aqueous solutions of polyethylene oxide of different concentrations under conditions of natural convection at atmospheric and reduced temperatures.

Long-range attractive forces between two mica surfaces in an aqueous polymer solution

High polymers are widely used as flocculants in aqueous colloidal dispersions1,2. All direct investigations to date of the forces between surfaces bearing adsorbed polymers in good solvent media, however, have indicated a monotonically increasing repulsion, rather than attraction, as the surfaces approached3–8. We have now measured the interactions between two smooth mica surfaces immersed in an aqueous solution of polyethylene oxide (a good solvent system) in the range 0–300 nm apart, and find that at low adsorbance of the polymer on the mica there is a reversible, time-independent, long-range (∼2.5 Rg, the unperturbed radius of gyration of the polymer) attraction as the surfaces approach. On permitting equilibrium adsorption of the polymer to take place, the attraction disappears, to be replaced by monotonically increasing, long-range repulsion.

Effect of solvent chemistry on critical weissenberg numbers

The critical Weissenberg number for the friction factor was earlier reported to be approx. 5–10 for turbulent pipe flow of 1000 wppm polyacrylamide dissolved in Chicago tap water, while the corresponding critical Weissenberg number for the dimensionless heat transfer coefficient, j H , was found to be approx. 200–250 for this same solution. It is known that the chemistry of the solvent generally influences the friction and heat transfer behavior of a polymer solution. Experiments have been performed using 100 wppm sodium hydroxide as an additive to the aqueous polyacrylamide solution (Separan 1000 wppm) and reveal that the critical Weissenberg numbers are unaffected. It is tentatively concluded that the chemistry of the solvent does not influence the critical Weissenberg numbers for aqueous polyacrylamide solutions. Preliminary measurements using aqueous solution of polyethylene oxide (Polyox 5000 wppm) yield critical Weissenberg numbers which are in reasonable agreement with the values reported earlier for aqueous solutions of polyacrylamide.

The turbulent diffusion of drag-reducing polymer solutions from a point source in flow through a pipe

Solutions containing salt(NaCI) were injected into water flow through a fine tube at the centre of a pipe. Tests were made to ensure that the flow was turbulent and well developed at the injection point; and that neither the injection process nor the injector caused any appreciable flow disturbance. Radial concentration profiles were measured at various downstream distances by withdrawing samples from the flow and measuring their electrical conductivity. A comparison was made between water, and aqueous solutions of polyethyleneoxide and polyacrylamide. Results for the eddy diffusivity in water agreed with those from previous investigations. Turbulent diffusivities were found to be greatly reduced in the polymer solutions (even after allowance had been made for the reduced wall shear stress) compared to the values for water alone. There were detailed differences in the effects of the two different kinds of polymer and these were attributed to their different viscoelasdc properties in the concentration ranges studied.

Solvent effects on drag reduction of polyox solutions in square duct and capillary tube flows

Experimental friction factor results for laminar and turbulent flows in a square duct of 1 cm × 1 cm cross-section and in a capillary tube of 0.1172 cm I.D. are presented for dilute aqueous solutions of polyethylene oxide (WSR-301). The addition of very small amounts of chemicals such as NaOH, NH4OH,H3PO4,etc. to the water solvent resulted in significant decreases in the turbulent flow pressure drop in a once-through square duct system. This phenomenon was also observed in a capillary tube, suggesting that the solvent chemistry plays an important role in the friction factor (and inferentially, the heat transfer) performance of aqueous dilute solutions of high molecular weight polymers irrespective of the channel geometry.

Measurement of forces between two mica surfaces in aqueous polyethylene oxide solution

The force as a function of distance between two curved mica surfaces immersed in a solution of 0.01% polyethylene oxide (molecular weight 150,000) in 0.04 M MgSO4 (a good solvent) has been measured with precision by an interferometric technique. The most striking features of this study are the long-range nature of the interaction (i.e., many times the free coil diameter) and the marked hysteretic behavior. Our results indicate (1) the existence of a dilute long-range polymer layer forming on mica surfaces, probably possessing gel-like properties; (2) that even though the forces may be monotonically repulsive on approach, once significant overlap occurs there is sticking, probably through polymer bridging, resulting in effective adhesion; and (3) as the rate of segmental rearrangement toward equilibrium is very slow (> 1 hr) the effective forces between colloidal particles with adsorbed polymers of high molecular weight may often be determined by non-equilibrium relaxation mechanisms.

An Increase in Base Pressure by Polymer Solutions Added to Separated Shear Layers

The change in the base pressure of a semicircular cylinder whose round side faced to the approaching stream was experimentally studied when the aqueous solutions of polyethyleneoxide (PEO) and polyacrylamide (PAM) were added to the boundary layer which eventually separated from the surface of the cylinder. The experiments were performed at a Reynolds number of 2.0 × 105, based on the base height of the cylinder. The base pressure was found to increase by 15 percent at its maximum by the injection of the polymer solutions as compared with the case of no injection. Saturation of the base-pressure increase was observed to exist with regard to the concentration of the polymer solutions and their velocity of injection.

Chemical effects in the flow of dilute polymer solutions

Experimental results are presented for the pressure drop of a dilute aqueous solution of polyethylene oxide (Polyox) for various chemical additives to the water solvent. These results suggest that the pressure drop and heat transfer behavior of dilute acqueous solutions of high molecular weight polymers is very sensitive to the chemistry of the water solvent.

Influence of temperature on the hydrodynamic resistance reduction effect

The effect of temperature on hydrodynamic resistance of aqueous solutions of polyethylene oxide is established experimentally.

On scale-dependent effect in laminar flow of dilute polymer solution in tubes

Presented are the results obtained in experiments on viscous flow of dilute aqueous solutions of polyethylene oxide in tubes of inner diameter ranging from 0.2 to 8.0 mm. Ostwald viscometers, horizontal capillary viscometers, and two special viscometric setups were used in the measurements. Results have shown that the solution viscosity varies with the changing tube diameter. This effect is not associated with the shear rate dependence or degradation. Laser Doppler anemometers were used to measure the velocity of polymer solutions in thin capillaries. No deviation from the Poiseuille profile was observed. Thus, it is not possible to explain the reduction of viscosity in thin capillaries by means of wall effect. Relationship between scale-dependent effect of viscosity and existence of large macromolecular aggregates is proposed. Anomalies of viscosity are responsible for the ambiguity in the intrinsic viscosity. Intrinsic viscosity, in particular, may be determined by means of the maximum or minimum viscosity. Difference between the maximum and minimum intrinsic viscosities changes with the molecular weight of dissolved polymer. Such differences were not noticed for low-molecular polymers.

Determination of rheological constants of an elastico-viscous fluid by kinematical analysis of oscillatory motions

This paper contains experimental and theoretical work on a rotatory oscillatory flow of an elastico-viscous fluid. Assuming a linear constitutive equation, the motion of the fluid contained in a spherical or circular cylindrical vessel is computed. In particular, the limited height of the cylinder is taken into account for the boundary conditions. The solutions yield the velocities of the fluid particles as functions of the constitutive equation parameters, everywhere in the flow field. The experimental study is essentially based upon quantitative vizualisation techniques with solid particles: the amplitude and phase of the displacements of the tracers suspended in the fluid are obtained from an analysis of the photographs. Using the above-mentioned theoretical results we deduce the measurement of characteristic coefficients and functions of the materials tested. An experimental investigation of moderately concentrated aqueous solutions of polyethylene oxide is carried out.

Turbulent Characteristics Of Drag-Reducing Flows

Turbulence measurements were made in water and in a polyethylene oxide aqueous solution, using hot-film anemometry. Mean velocities, turbulence intensities, energy spectra and energy-dissipation rates were measured in a turbulent smooth-pipe flow. Mean flow structure showed that the mean velocity follows Virk's interactive-layer profile, and that the wall shear velocity is the proper velocity scale for polymer flows. Using Lumley's concept of an effective viscosity, the polymer spectra were cast into universal form and compared with Newtonian spectra. Results coincide reasonably well with the universal equilibrium theory. The major effect of the polymer additive appears to be an increase of the dissipative scales of the turbulence without significantly altering the basic structure of the flow, except near the wall.

Turbulent dispersion in drag‐reducing fluids

AbstractTurbulent pipe flow was examined by measuring the radial dispersion of dyed fluid introduced at an axial point source within the flow. From the classical theoretical results of G. I. Taylor it was possible thereby to calculate various parameters that characterize the structure of the turbulent flow field. A comparison was made between water, and aqueous solutions of polyethylene oxide (Polyox) at concentrations up to 50 ppm (by weight). Results indicate that Polyox affects the turbulence in the following ways: (1) intensity is reduced, (2) the energy spectrum is shifted toward low frequency, (3) dispersion occurs largely through large scale motion, and intermittency is increased. Indication is also seen that a simple exponential form for the Lagrangian correlation coefficient is superior to other often recommended models.

Natural convective heat-transfer from a vertical surface of uniform heat flux to a non-newtonian sutterby fluid

This paper deals with the laminar natural convection of a non-Newtonian fluid along a vertical surface with uniform heat flux. The boundary layer equations for a Sutterby fluid are solved numerically, and the typical results for the local Nusselt number Nu x, are represented graphically. From the results an approximate expression of Nu x, is proposed as Nu x = 0.62(Gr ∗ oxPr o) 0.2(1+m ∗ where m ∗ = 0.06Pr o −0.28A 3.7 pr o -0.34Z ∗ o 0.35A0.66 , Gr ∗ 0x and Pr 0 are Grashof and Prandtl numbers based on zero viscosity respectively, and A and Z ∗ 0 are non-Newtonian parameters. Local heat-transfer coefficients are obtained by experiments with aqueous solutions ofpolyethyleneoxide (PEO) and carboxymethylcellulose (CMC). The experimental results are in excellent agreement with the theoretical predictions.

Natural convective heat transfer from a vertical isothermal surface to a non-Newtonian Sutterby fluid

This paper deals with the laminar natural convection of a non-Newtonian fluid along a vertical isothermal surface. The boundary-layer equations for a Sutterby fluid are solved numerically, and several characteristics of the non-similarity solution are represented graphically. An approximate expression of local Nusselt number Nu x is proposed as Nu x = 0·.50(Gr 0xPr 0) 0·.25(1+m) , where m= 0−04 Pr 0 0.23 A 3·7 Pr 0 −0.34 Z 0 0·63A 0.66 Gr 0 x and Pr 0 are Grashof number and Prandtl number based on zero viscosity respectively, and A and Z 0 are non-Newtonian parameters. Local heat-transfer coefficients are obtained by experiments with aqueous solutions of polyethyleneoxide (PEO) and carboxymethylcellulose (CMC). The experimental results are in excellent agreement with the theoretical ones.

Effects of Polyethylene-Oxide Solutions on the Performance of a Small Propeller

Thrust and torque were measured and efficiency calculated for a 14.6-cm diam, two-bladed propeller in aqueous solutions of polyethylene oxide, WSR-301, with concentrations ranging from 0 to 75 wppm. For the propeller operating under heavily loaded conditions (advance coefficients from 0.04 to 02.), the thrust decreased with increasing concentration while the torque passed through a minimum at 10 wppm. The net result was that the propeller efficiency remained essentially constant except for a small increase of a few percent at 10 wppm. Acoustic measurements demonstrated that the polymer greatly reduced the rate of propeller cavitation but did not influence the rotational speed at which cavitation was first noticed. The polymer had no effect on the sound pressure level (SPL) of the fundamental blade line.

Drag reduction in capillary tubes as a function of polymer concentration and molecular weight

An equation derived from Virk's universal drag reduction relation has been shown to adequately describe the drag reduction of aqueous solutions of polyethylene oxide condensates over a wide range of molecular weight and concentration. Virk's intrinsic concentration was found to be an inverse function of polymer molecular weight. The limit of usefulness of polymer critical concentration as a normalizing aid in the treatment of drag reduction is indicated and the polymer aggregation hypothesis for drag reduction is briefly discussed.

The radiation induced reactions of aqueous polyethylene oxide solutions. V. Systems containing dioxane

AbstractThe radiation induced variations in intrinsic viscosity for concentrated aqueous solutions of polyethylene oxide containing relatively high proportions of dioxane show features which may be indicative of additive effect on water‐polymer interactions. In solutions more dilute in polymer and dioxane, the data can be treated in terms of competition between polymer and additive for hydrogen abstracting radicals and competition between dioxanyl radicals and the crosslinking process for macroradicals.

The radiation induced reactions of aqueous polyethylene oxide solutions. I. Theory of gelation

AbstractDilute deaerated aqueous polyethylene oxide solutions have been irradiated with 60Co γ‐rays. The concentration dependence of the gel dose, the dose required for gelation, was found to vary with the initial molecular weight of the polymer used. For low molecular weight polymer, with increasing polymer concentration the gel dose fell rapidly to its lowest value at the critical concentration, ccrit, and thereafter increased. High molecular weight material showed similar behaviour below ccrit, but the gel dose varied little with addition of polymer for concentrations not far above ccrit. These results are interpreted in terms of a proposed theory which considers the intermolecular crosslinking process to be diffusion controlled below ccrit, and to depend on the packing of discrete, non‐interpenetrating polymer molecules not far above ccrit. Literature data on the radiation induced gelation of deaerated aqueous polyvinyl alcohol solutions can also be satisfactorily treated with the proposed theory.