The results of investigations of the rheological properties of typical ceramic slurries used in the investment casting technology – the lost
wax technology are presented in the paper. Flow curves in the wide range of shear velocity were made. Moreover, viscosity of ceramic
slurries depending on shearing stresses was specified. Tests were performed under conditions of three different temperatures 25, 30 and
35oC, which are typical and important in the viewpoint of making ceramic slurries in the investment casting technology.
In the light of the performed investigations can be said that the belonging in group of Newtonian or Non – Newtonian fluid is dependent
on content of solid phase (addition of aluminum oxide) in the whole composition of liquid ceramic slurries.
This study is devoted to the instantaneous acoustic heating of a shear-thinning fluid. Apparent viscosity of a shear-thinning fluid depends on the shear rate. That feature distinguishes it from a viscous Newtonian fluid. The special linear combination of conservation equations in the differential form makes it possible to derive dynamic equations governing both the sound and non-wave entropy mode induced in the field of sound. These equations are valid in a weakly nonlinear flow of a shear-thinning fluid over an unbounded volume. They both are instantaneous, and do not require a periodic sound. An example of a sound waveform with a piecewise constant shear rate is considered as a source of acoustic heating.
The present work deals with agitation of non-Newtonian fluids in a stirred vessel by Scaba impellers. A commercial CFD package (CFX 12.0) was used to solve the 3D hydrodynamics and to characterise at every point flow patterns especially in the region swept by the impeller. A shear thinning fluid with yield stress was modelled. The influence of agitator speed, impeller location and blade size on the fluid flow and power consumption was investigated. The results obtained are compared with available experimental data and a good agreement is observed. It was found that an increase in blade size is beneficial to enlargement of the well stirred region, but that results in an increased power consumption. A short distance between the impeller and the tank walls limits the flow around the agitator and yields higher power consumption. Thus, the precise middle of the tank is the most appropriate position for this kind of impeller.