Atypical Flow Propertis of Aqueous Kaolin Suspensions

0444679 - ÚCHP 2016 SK eng C - Conference Paper (international conference)
Pěnkavová, Věra - Tihon, Jaroslav - Wein, Ondřej
Atypical Flow Propertis of Aqueous Kaolin Suspensions.
Proceedings of the 42nd International Conference of SSCHE. Bratislava: Slovak Society of Chemical Engineering, 2015 - (Markoš, J.), s. 114. ISBN 978-80-89475-14-8.
[International Conference of Slovak Society of Chemical Engineering /42./. Tatranské Matliare (SK), 25.05.2015-29.05.2015]
R&D Projects: GA MŠMT(CZ) LD13018
Institutional support: RVO:67985858
Keywords : rheology * apparent wall slip * kaolin suspensions
Subject RIV: CI - Industrial Chemistry, Chemical Engineering

Flow of colloidal suspensions can be accompanied by the flow anomaly in proximity of the solid wall. A thin layer (in tens micrometers), depleted of the disperse phase, can establish along the solid wall due to steric or electrochemical interactions. Therefore, a steeper velocity gradient, developed in this thin layer due to locally higher fluidity, can establish. This phenomenon, called apparent wall slip (AWS), is usually represented by an apparent slip velocity at the wall. In analogy to fluidity of suspension, where velocity gradient is a function of shear stress, the slip function (Navier slip coefficient), where slip velocity is a function of shear stress, can be used to characterize quantitatively the AWS effect. The fluidity and slip functions of aqueous kaolin suspensions were obtained from the results of viscosity measurements. These measurements were carried out over a wide range of shear stresses for several flow geometries (differing in the hydraulic radius). Both the material functions were determined via nonlinear regression, using appropriate empirical models. The fluidity was found to decrease with concentration and also, which is surprising, with temperature. The Navier slip coefficient rises both with concentration and temperature.
Permanent Link: http://hdl.handle.net/11104/0247196