The flow behavior index n' may be assumed independent of temperature and concentration for small changes in these conditions. It does not rapidly change with either temperature or concentration of dissolved material.
To predict whether flow will be laminar or turbulent, it is necessary to explore the characteristics of flow in both the laminar and turbulent state (Roberson et al, 1993). Laminar flow is the resistance due to viscous forces only and is independent of roughness of the pipe surface (Hampden Engineering, Corp., 1992). With this type of flow at every point both instantaneous and time- averaged velocities are the same (Vogel, 1994). Laminar flow is devoid of the intense mixing phenomena and eddies common to turbulent flow. The flow has a very smooth appearance.(Roberson et al, 1993).
The critical or transitional Reynolds number is dependent on the amplitude of the disturbance (caused by roughness or fittings). This critical Reynolds number is often taken to be 2100. Experimental work has shown that flow will be laminar below Re = 2000, even in the presence of large disturbances. Above roughly Re = 4000, the flow will likely be turbulent (Simpson, 1968).
Non-Newtonian Fluid Flow
All fluids for which the flow curve is not linear through the origin at a given temperature and pressure are said to be non- Newtonian (Skelland, 1967).
In solving engineering problems with non-Newtonian fluids, the engineers must first have information about the relationship between shear stress and shear rate. This relationship must be determined experimentally in the way that viscosity is found for a Newtonian liguid (Simpson, 1968).