Dispersion of gases in laminar flow through a circular tube

1961 ◽  
Vol 261 (1305) ◽  
pp. 227-236 ◽  
Keyword(s):  
Molecular Weight ◽  
Laminar Flow ◽  
Molecular Diffusion ◽  
Circular Tube ◽  
Ultra Violet ◽  
Narrow Beam ◽  
Violet Light ◽  
Maximum Value ◽  
Flow Through ◽  
Mean Concentration

The longitudinal dispersion of a finite slug of gas has been measured at various velocities by using a gas (1,3-butadiene) that absorbs in the ultra-violet region and passing the dispersed slug through a narrow beam of ultra-violet light of wavelength 250mμ. To avoid effects of differences in gas density, the second gas (1-butyne) was chosen to have the same molecular weight as butadiene. The range of applicability of Sir Geoffrey Taylor’s virtual coefficient of diffusivity has been discussed. The experimental observation that the peak mean concentration passes through a maximum value with velocity has been explained by considering the relative rates of dispersion by convection, longitudinal molecular diffusion and radial molecular diffusion.

Dispersion in Laminar Flow Through Tubes by Simultaneous Diffusion and Convection

1981 ◽  
Vol 48 (2) ◽  
pp. 217-223 ◽  
Author(s):  
J. S. Yu
Keyword(s):  
Laminar Flow ◽  
Molecular Diffusion ◽  
Solute Concentration ◽  
Dimensionless Time ◽  
Mean Flow ◽  
Round Tube ◽  
Flow Through ◽  
The Mean ◽  
Time Required ◽  
Mean Concentration

The dispersion of a small quantity of a solute initially injected into a round tube in which steady-state laminar flow exists is critically examined. It is shown that the mean solute concentration profile is far from being symmetric at small dimensionless times after injection. The mean concentration and the axial location at the peak of the profile are presented in detail as functions of time for flow with various Peclet numbers. It is suggested that such results may be useful for determining either the molecular diffusion coefficient or the mean flow velocity or both from experimental measurements. A previously established criterion in terms of the Peclet number for determining the minimum dimensionless time required for applying Taylor’s theory of dispersion is graphically illustrated. Although the complete generalized dispersion equation of Gill’s model is exact, the truncated two-term form of it with time-dependent coefficients is exact only asymptotically at large values of time; however, at small Peclet numbers, the two-term approximation is shown graphically to be reasonably satisfactory over all values of time. The exact series solution is compared with the solution of Tseng and Besant through the use of Fourier transform.

Dispersion of matter in non-Newtonian laminar flow through a circular tube

1966 ◽  
Vol 292 (1429) ◽  
pp. 203-208 ◽  
Keyword(s):  
Laminar Flow ◽  
Newtonian Fluid ◽  
Circular Tube ◽  
Newtonian Fluids ◽  
Parallel Plane ◽  
Bingham Plastic ◽  
Ellis Model ◽  
Model Fluid ◽  
Flow Through

Taylor’s analyses of the dispersion of Newtonian fluids in laminar flow in a circular tube are extended to the flow of the Bingham plastic and Ellis model fluid. The previous results for the Newtonian fluid and power-low fluid can be deduced from the results of this work. It is indicated that Aris’s modification of Taylor’s analyses can be naturally applied to the non-Newtonian fluid. Results obtained for laminar flow between two parallel plane walls are given in the appendix.

Hot-Wire Measurements of Turbulence Correlations in a Triangular Duct

1962 ◽  
Vol 29 (4) ◽  
pp. 609-614 ◽  
Author(s):  
C. J. Cremers ◽  
E. R. G. Eckert
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Cross Section ◽  
Circular Tube ◽  
Turbulent Transport ◽  
Circular Cross Section ◽  
Hot Wire ◽  
Round Tube ◽  
Flow Through ◽  
Hot Wires

Previous studies by flow visualization have indicated that the flow through a duct of triangular cross section is in its characteristics quite different from flow through a duct with circular cross section. They revealed among others that purely laminar flow exists in the corners of the duct even though the bulk of the fluid moves in turbulent motion. Heat-transfer measurements in such a duct appear to indicate that the turbulent transport in the direction of the height of the duct is considerably smaller than expected from circular tube measurements. The present paper reports the measurements of turbulent correlations for turbulent flow through such a duct. These measurements have been made with hot wires of very small dimensions. They again reveal the existence of a laminar corner region. In the bulk of the fluid, the differences of the correlations to those in a round tube turned out to be smaller than originally suspected.

A numerical solution for the dispersion in laminar flow through a circular tube

1990 ◽  
Vol 68 (2) ◽  
pp. 191-196 ◽  
Author(s):  
Teruo Takahashi ◽  
Takashi Korenaga ◽  
Fenghua Shen
Keyword(s):  
Laminar Flow ◽  
Numerical Solution ◽  
Circular Tube ◽  
Flow Through

The photolysis of polymethylvinylketone. I. Reactions and kinetics

1955 ◽  
Vol 233 (1193) ◽  
pp. 153-172 ◽  
Keyword(s):  
Molecular Weight ◽  
Ultra Violet ◽  
Type I ◽  
Type Ii ◽  
Weight Changes ◽  
Violet Light ◽  
Aliphatic Ketones ◽  
Primary Reactions ◽  
Acetyl Radical ◽  
Kinetics Of

The photolysis of polymethylvinylketone has been studied in solution. The two primary reactions which occur upon absorption of a quantum of ultra-violet light by the carbonyl group have been shown to be similar to those which occur with simple aliphatic ketones; namely, the type I split to form a polymer radical and a free methyl or acetyl radical, and the type II split at the C—C linkage α — β to the carbonyl which results in a decrease in the molecular weight of the polymer and the formation of a double bond. The kinetics of the molecular weight changes have been followed by viscosity, osmotic pressure and ultracentrifuge measurements on the degraded polymers, and it is shown that these can be explained on the basis of a competing reaction which opposes the breakdown by type II. A mechanism is proposed for this reaction which involves a ‘repolymerization’ due to the addition of free radicals to the double bonds formed by type II.

Friction and Thermal Characteristics of Laminar Flow of Viscous Oil Through a Circular Tube Having Axial Corrugations and Fitted With Helical Screw-Tape Inserts

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Sujoy Kumar Saha ◽  
Bikram Narayan Swain ◽  
G. L. Dayanidhi
Keyword(s):  
Nusselt Number ◽  
Laminar Flow ◽  
Friction Factor ◽  
Circular Tube ◽  
Thermal Characteristics ◽  
Circular Duct ◽  
Viscous Oil ◽  
Flow Through ◽  
The Individual ◽  
Better Than

The experimental friction factor and Nusselt number data for a laminar flow through a circular duct having axial corrugation and fitted with helical screw-tape inserts have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the helical screw-tape inserts, in combination with axial corrugation, perform better than the individual enhancement technique acting alone for laminar flow through a circular duct.

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