70
E. Balasubramanian et al.
where, γ = shear rate in screw channel in s
−1 , D is diameter of the screw, N is speed
of the screw and h is the channel depth [15].
In a round die channel (rod or strand for compounding), the shear rate is obtained
using the following Eq. (2),
γ (Round channel) =
4 × Q
π × R 3
(2)
where, γ is the shear rate in the screw channel, R is the radius of the channel, and Q
is the volumetric flow rate.
Based on the preliminary experiments, the volumetric flow rate has been calculated
as 9.06287 × 10
−9 m
3 /s for the radius of the channel 0.00075 m, the corresponding
shear rate is determined as 24.78 s
−1 . Similarly, for the value of volumetric flow rate
of 9.06287 × 10
−9 m
3 /s and radius of the channel 0.00155 m, shear rate in the screw
channel at inlet is calculated as 3.0987 s
−1 .
3.2 Viscosity
The instantaneous viscosity of the slurry was measured using Bohlin Gemini II
Rheometer and it is plotted with respect to shear rate which is shown in Fig. 12.
The instantaneous viscosity at the outlet nozzle and screw is obtained as:
η nozzle ≈ 51 Pas and η screw ≈ 180 Pas.
Fig. 12 Determination of shear rate from experiments