Influence of drag reducing polymers on turbulent mass transfer to a pipe wall

McConaghy, G. A.; Hanratty, Thomas J.

doi:10.1002/aic.690230414

Cited by 27 publications

(14 citation statements)

References 20 publications

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“…The local mass transfer coefficient K ( t ) was determined by measuring the current to platinum wires located flush with the cathode surface. These were a t a dimensionless distance of x > 3,000 from the upstream edge of the cathode so as to insure that the concentration boundary layer was fully developed (McConaghy and Hanratty, 1977). An electronic circuit was used to measure and eliminate the mean current from the local electrodes and to amplify the fluctuating component.…”

Section: Methodsmentioning

confidence: 99%

“…The test fluid was an aqueous solution of iodine, potassium iodide, and a high molecular weight polyacrylamide, Separan AP-30, with concentration of 50, 150, and 325 ppm. The test loop and the experimental techniques are described in papers by Shaw and Hanratty (1977) and by McConaghy and Hanratty (1977).…”

Section: Methodsmentioning

confidence: 99%

“…An electronic circuit was used to measure and eliminate the mean current from the local electrodes and to amplify the fluctuating component. Details regarding the fabrication of the test section and the measuring techniques are given by Vassiliadou (1983), andMcConaghy (1974), and in previously cited papers.…”

Section: Methodsmentioning

confidence: 99%

“…It is based on measurements presented in theses by McConaghy (1974) and Vassiliadou (1983). The motivation for this paper is the testing of ideas that have emerged from recent numerical experiments that simulated turbulent mass transfer at a wall (Campbell and Hanratty, 1983).…”

Section: Scopementioning

confidence: 98%

“…A paper by McConaghy and Hanratty (1977) presents results of the effect of dilute polymer solutions of Separan AP-30 on measurements of average mass transfer coefficients between a turbulent fluid and a pipe wall for fully developed velocity and concentration fields. They found that the decrease in the mass transfer rate, caused by the addition of polymers, at a given volumetric flow rate, is greater than the percent change in the pressure gradient, and that the use of an analogy between momentum and mass transfer overpredicts the amount by which the mass transfer rate is decreased.…”

Section: Scopementioning

confidence: 99%

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Effect of drag‐reducing polymers on mass transfer fluctuations

1986

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Electrochemical techniques are used to show that drag-reducing polymers decrease the magnitude and the frequency of mass transfer fluctuations. Measurements of the frequency spectrum of the mass transfer fluctuations allow calculation of the normal component of velocity fluctuations in the immediate vicinity of the wall. This information is used to interpret the observed effect of drag-reducing polymers on the rate of mass transfer. Eleni Vassiliadou SCOPEA paper by McConaghy and Hanratty (1977) presents results of the effect of dilute polymer solutions of Separan AP-30 on measurements of average mass transfer coefficients between a turbulent fluid and a pipe wall for fully developed velocity and concentration fields. They found that the decrease in the mass transfer rate, caused by the addition of polymers, at a given volumetric flow rate, is greater than the percent change in the pressure gradient, and that the use of an analogy between momentum and mass transfer overpredicts the amount by which the mass transfer rate is decreased.This paper shows how drag-reducing polymers affect the fluctuations in the mass transfer coefficient. It is based on measurements presented in theses by McConaghy (1974) and Vassiliadou (1983). The motivation for this paper is the testing of ideas that have emerged from recent numerical experiments that simulated turbulent mass transfer at a wall (Campbell and Hanratty, 1983). CONCLUSIONS AND SIGNIFICANCEDrag-reducing polymers cause a large decrease in_the magnitude of the mass transfer fluctuations, (P)''*/K, and change the character of the function describing the fluctuating mass transfer coefficient, k(t). The function does not have the large pulses found for a Newtonian fluid, and is described reasonably well by a Gaussian distribution. Furthermore, the frequency characterizing k(t), made dimensionless with wall parameters, is less than for a Newtonian fluid.Campbell and Hanratty (1983) transfer is the zero frequency value of the dimensionless spectral density function, W,(O), characterizing the normal component of velocity fluctuations in the immediate vicinity of the wall. This quantity is calculated from the measurements of the spectral function of the mass transfer fluctuations that are presented. It is found to decrease with increasing drag-reduction.The dependence of the time-averaged mass transfer coefficient on W,(O) is found to be the same as predicted in the numerical experiments of Campbell and Hanratty. However (k2)"'/E is found to be more strongly dependent on WB(0). This suggests that other hydrodynamic variables than W,(O) need to be considered.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Scopementioning

confidence: 98%

Section: Scopementioning

confidence: 99%

See 3 more Smart Citations

Effect of drag‐reducing polymers on mass transfer fluctuations

1986

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Wall region heat and mass transfer with newtonian and viscoelastic fluids in turbulent flow

Hughmark¹

1979

AIChE Journal

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Baton Rouge, Louisiana 70821Heat and mass transfer models that represent the experimental range of Prandtl and Schmidt numbers with turbulent flow include empirical wall region models (Churchill, 1977; Hughmark, 1975b). Shaw and Hanratty (1977) reported experimental data to rule out the plausible limiting expressions for eddy diffusivity close to a wall. Lau, Lee, and Hanratty (1977) interpret additional experimental data to indicate that the region y + < about 4 cannot be represented by a pseudo steady state assumption. Hughmark (1972Hughmark ( , 1973 analyzed experimental data to indicate that the core and transition regions can be represented by pseudo steady state models. This communication utilizes the models for the core and transition region with a range of experimental heat and mass transfer data to estimate the boundary layer contribution at the wall. Data for viscoelastic fluids in turbulent flow are also considered with respect to these models. NEWTONIAN FLUIDSThe prior work related to steady state models for the core and transition region show that eddy transport in the core of a circular pipe is represented by and for the transition region by k + E T = 0.0615 NsC-% (2) Equation (2) represents the penetration model with the contact time consistent with the wall frequency relationshipAlso, in the prior work, eddy diffusivity for heat and mass for the transition region was correlated by 2-= 0.0094 y+2 (4) V Integration of the eddy diffusivity with the upper limit as y + = 34.6 to represent the boundary with the turbulent core shows that the lower limit is y+ = 5.5 to correspond to the eddy transport of Equation (2). This is in reasonable agreement with y+ = about 4 value reported by Lau et al, as the limit of the wall boundary layer that cannot be represented by a pseudo steady state assumption.The sum of the eddy diffusivity from Equation (4) and the molecular difhsivity for heat or mass can be Figure 1 shows the data of Debrule and Sabersky (1974), Friend and Metzner (1958), Harriott and Hamilton (1965), Malina and Sparrow (1964), and Shaw and H a n r a 3 (7)which is consistent with the Shaw and Hanratty observation that the observed wall region value rules out the plausible limiting expressions for eddy dsusivity close to a wall. Figure 1 is interesting in that the Harriott and Hamilton data are correlated by Equation (7) for Nsc < 3000 but show significantly higher coefficients at the higher Schmidt numbers. The Harriott and Hamilton data were obtained by the wall solution method and the Shaw and Hanratty data by the electrochemical method. VJSCOELASTIC FLUIDSHughmark ( 1 9 7 5~) showed that the wall region frequency for a viscoelastic fluid in turbulent flow could be related to the drag reduction of the fluid with a 00w behavior index of unity fN = 0.0206 a2I3 (8) f E which corresponds to k+ET = 1.13 a-% Nsc-"~ (9) for the penetration model with this wall region frequency. The dimensionless variable a is a function of the Deborah number as shown by the reference. Similarly, the eddy diffusivity f...

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