Identification of Kinetic Energy Contribution &
Viscous Dissipation Contribution
Thin Thin Swe
The non-dimensional form of the total mechanical energy balance is given by the following equation.
Therefore, the kinetic energy is
Using the above equations, a plot of the excess pressure drop
(KL) versus Reynolds number can be seen in figure 3 in a log-log
plot. Figure 3 details the contributions due to the kinetic energy change, viscous
dissipation, and the total excess pressure drop (KL). Pressure drop is mainly due to viscous
dissipation in the fully developed regions of the large and small channels,
plus the extra viscous dissipation due to the expansion and kinetic energy change.
Since figure 3 is graphed in a log-log plot, the curves do not have additive
properties.
Figure3. Laminar flow excess pressure drop for a 3:1 expansion in a circular channel.
(Delta-p is the total pressure minus the fully developed
pressure drop in the large and small channels.)