摘要:

Fluid flow rates of gases, liquids, suspensions, and particulate solids were measured through right cylindrical capillaries (microopenings) having diameters from 0.5 to 60 μm and lengths in the range of 100–4000 diameter. The results showed that gases passing through microopenings with diameters from 5 through 60 μm and lengths of 100 times the diameter or more obey Darcy's Equation. For microopenings with diameters from 0.6 to 1.7 μm and lengths of at least 200 times the diameter, the measured flow rates of gases exceed those predicted by the Darcy Equation by a factor of approximately three. Water and low‐viscosity aqueous solutions flowing in 1 μm diameter or larger microopenings having lengths of at least 100 diameter appeared generally to follow Poiseuille's Law, although at low pressure drops in the smaller sizes, the flow rates suddenly became considerably lower than those predicted. Polystyrene latex suspensions flowing in microopenings from 25 through 50 μm in diameter flowed as predicted by the Poiseuille Equation until the suspension particles plugged the hole. Metallic and polymer powders could not be made to flow through the microopenings, and aerosolized particles of a free‐flowing organic powder deposited on the upstream face of a microopening rather than flow through it.

ISSN:0148-6055    

DOI:10.1122/1.549474

出版商:The Society of Rheology    

年代:1978

数据来源: AIP

摘要:

A transparent channel was constructed of Plexiglas and droplets of known volume were injected into the reservoir upstream of the channel, through which a suspending medium (i.e., continuous phase) was pumped at a constant flow rate. The deformation patterns of the droplets were recorded on still and movie films as they approached the die entrance and passed through the fully developed region of the channel. The suspending fluids were glycerin as Newtonian medium, and aqueous solutions of polyacrylamide (Separan AP30) at various concentrations (0.6, 2.0, 4.0, and 6.0 wt %) as viscoelastic medium. Droplets were formed of both viscoelastic and Newtonian fluids. For the viscoelastic droplets, polyisobutylene dissolved in decalin (0.6, 2.0, 6.0, and 10.0 wt %) was used, and for Newtonian droplets, low molecular weight polybutene (Indopols L50 and H25) was used. It was observed that at wall shear rates of a suspending medium below a certain critical value, the droplets, initially spherical when upstream in the reservoir, elongated very much at the die entrance and then recoiled somewhat in the fully developed region downstream of the channel. However, at wall shear rates of a suspending medium higher than a certain critical value, a deformed droplet broke up into smaller droplets. The phenomenon of breakup of viscoelastic droplets was observed as being somewhat different from that of Newtonian droplets. Independent measurements were taken of the rheological properties and interfacial tension of the fluids tested, and were used to explain the deformation and breakup phenomenon of the liquid droplets.

ISSN:0148-6055    

DOI:10.1122/1.549475

出版商:The Society of Rheology    

年代:1978

数据来源: AIP

摘要:

A visual study of the dynamics of plasticating screw extrusion was undertaken by using a 1‐in.‐diameter(L/D=20)extruder with a transparent barrel. The extrudate consisted of frozen pellets of a 40% solution of polystyrene in diethylphthalate plasticizer. Blue and red colored pellets of the same material were added in ratios of 1:120 and 1:40, respectively. This was done in order to mark the flow of material in the screw channel. The flow was recorded on color movie film taken at both 15 and 90 frames/sec. Films of the unsteady state as well as of the steady state, flow were obtained. Unsteady conditions in the flow were induced by introducing step changes in screw speed which were in the range of 60–75 rpm. Analysis of the steady state films revealed that the steady melting mechanism, as described by past workers, is valid. Under transient conditions involving a step‐up in screw speed, a rupture in the solid bed occurred. This phenomenon was related to the rheological characteristics of the viscoelastic liquid extrudate. It was hypothesized that this occurred because of a difference in the response times of the liquid polymer at various points along the screw axis. Variation in liquid polymer temperature was assumed to result from the near adiabatic mode of extruder operation employed, which in turn gave rise to the large differences in the liquid response time. Solid bed profiles of the extrudate in the melting zone under transient conditions were also constructed from the films. These profiles showed departures of the flow regime from that under steady state conditions. Defects in the solid bed were seen to propagate in the screw down‐channel direction. Those defects undoubtedly contributed to fluctuations in the flow rate and to the lack of good mixing observed in the product.

ISSN:0148-6055    

DOI:10.1122/1.549476

出版商:The Society of Rheology    

年代:1978

数据来源: AIP

摘要:

A device for producing a Fano extensional flow with a total pressure drop of more than 1 atm has been designed and tested with Newtonian fluids. It was found that the shape of the Fano column profile was best fit by the equationDi/D=C1 exp(C2z/L),whereC1andC2are constants,Diis the inside diameter of the Fano nozzle,Lis the total height of the column, andDis the diameter of the column at heightz. Extensional viscosity calculations for glycerine Fano columns produced values equal to approximately three times the shear viscosity.

ISSN:0148-6055    

DOI:10.1122/1.549477

出版商:The Society of Rheology    

年代:1978

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549479

出版商:The Society of Rheology    

年代:1978

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549501

出版商:The Society of Rheology    

年代:1978

数据来源: AIP