RHEOLOGICAL PROPERTIES AND STRUCTURE OF THE LIQUID IN NANOTUBES - Foundations of Nanotechnology: Pore Size in Carbon-Based Nano-Adsorbents - page 195

FIGURE 3.7 Flow rate effect of shearing stress (triangle) and viscosity (square).

It should be noted that even though the equation for viscosity is based on the
theory of the continuum, it can be extended to a complex flow to determine the
effective viscosity of the nanotube.
Figure 3.7 shows dependence of h on v inside of the nanotube (20, 20). It is
shown that h decreases sharply with increasing flow rate and begins to approach
a definite value when v >150 m/sec. For the current pipe size and flow rate ranges
of

h , this trend is because of τ - v , contained in Fig. 3.7. According to Fig.
3.6, high-speed effects are negligible.
One can easily see that the dependence of viscosity on the size and speed is
consistent qualitatively with the results of molecular dynamic simulations. In all
studied cases, the viscosity is much smaller than its macroscopic analogy. As the
radius of the pores varies from about 1 nm to 10 nm, then the value of the effective
viscosity increases by an order of magnitude. A more significant change occurs
when increasing the speed of 0.1 mm/min up to 100 mm/min. This results in a
change in the value of viscosity h, respectively, by 3-4 orders. The discrepancy
between simulation and test data can be associated with differences in the struc-
ture of the nanopores and liquid phase.
Figure 3.8 shows the viscosity dependence of water (calculated by the method
of DM, the diameter of the CNT). The viscosity of water, as shown in the Fig. 8,
increases monotonically with increasing diameter of the CNT.

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