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AWS Viscosimetry of Microdispersions - Detection of Apparent Wall Slip
Pěnkavová, Věra ; Večeř, M. ; Wein, Ondřej
The rheometric data measured using three various sensor geometries (PP60, ZZ40DIN and KK-sensor) are compared in this contribution at the case of water solution of polymer welan. The KK-sensor, constructed at our department, combines advantages of geometry both plate-plate and concentric cylinder geometry. It is shown that KK-sensor is comparable to commercial sensors. It is presented for water kaolin dispersions that apparent wall slip does not disappeared neither for low consistent dispersions. The values of slip coefficients are even higher in the case of less consistent samples.
Fulltext:  PDF
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Effect of Surface Quality in Viscometry of Aqueous Polymer Solutions
Večeř, M. ; Wein, Ondřej
The proposed paper is focused on experimental viscometric study of AWS effect of aqueous polymer solutions: 1.5% wt solution of Na salt of Carboxymethylcellulose, 0.4%wt of Welan Gum and 1% wt of Polyacrylamide was chosen as the tested liquids. Four viscometric sensors (type KK) with different quality of surface (Stainless steel, Titanium, Alloy of Aluminum and Magnesium, as well as Stainless steel with surface roughened by sandblasting) have been used. It is documented that the extent of AWS effect strongly depends both on the sensor material and type of solution.
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Electrodiffusion Diagnostics of Apparent Wall Slip in Polymer Solutions
Wein, Ondřej ; Tovčigrečko, Valentin ; Večeř, M. ; Sobolík, Václav
Two substantially improved experimental methods, the apparent wall slip (AWS) rotational viscometry with a Morse-taper sensor and electrodiffusion (ED) flow diagnostics with autocalibrated friction probes, are used to study near-to-wall velocity profiles in aqueous solutions of high-molecular polysaccharides under viscometric flow conditions. By comparing the velocity data from the both methods, estimates of the depleted layer thickness in dependence on wall shear stress are obtained. The ED data support the two-layer model of AWS effect, with the constant enhanced fluidity across the depleted layer.
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Teorie elektrodifuzních čidel třeni v mikrodisperzních kapalinách 8. Vliv zdánlivého skluzu na směrové charakteristiky
Wein, Ondřej
Insulated insertions between individual segments of direction-sensitive electrodiffusion friction probes attenuate the directionalsensitivity. Quantitative study of this effect by Wein and Wichterle (1989) for Newtonian liquids has been extended in a recent research report (Wein 2007) for the microdisperse liquids, displaying the Apparent Wall Slip, i.e. a non-linear velocity profile close to solid surfaces. In the present research report, this theory is used to the simulation calculations of directional characteristics for a class of 3-segment electrodiffusion friction probes with the insulating insertions. Rather realistic model of non-ideal 3-segment direction-specific probes is tested by comparison of the predictions with experimental data about an actual 3-segment probe in both homogeneous and microdisperse liquids.
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Koncové efekty v rotační viskometrii za přítomnosti zdánlivého skluzu
Wein, Ondřej ; Večeř, Marek ; Havlica, Jaromír
Common methods of treating primary data from rotational viscometry are tested using numerical simulations of primary circular flow of shear-thinning liquids in an actual sensor Z40 DIN according to ISO 3219 and a new KK (Morse-taper) sensor, suggested for rotational viscometry under slip effect. Theory of the sensors is presented, including the conversion of primary data into fluidity and slip viscometric material functions, as well as a statistical analysis of their relevance. The data treatment, based on the concept of local filtration, is illustrated on several aqueous solutions of Hercules CMC and Welan gum.
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Computer Treatment of the Viscometric Data Displaying Apparent Wall Slip Effect
Večeř, Marek ; Wein, Ondřej
In the present poster and a PC show, we demonstrate such software designe to support all available sensors (Z,PP, and CP) of HAAKE RS rotational rheometres, and including one novel (KK) sensor, designed specially for the liquids displaying AWS effect. The primary data, including the related calibration parameters, are extracted from the HAAKE RheoWin ASCII export and further treated in a plot-supportin dialogue mode, including selection/discrimination of a new 8-parameter model, representing the Fluidity&Slip viscometric material functions.
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