The change of opening 81.43 to 90° caused the net Cv
to increase 4 times while the gross Cv
did not change
that much. This highlights that the contribution of the frictional pressure drop due to pipe is very significant in 90° of opening
as compared to 81.43° opening.
The contribution of the valve body in the total pressure drop of 90° opening is very less as compared to that of the pipe. It can be
said that the contribution of the pipe is ≈ 90% of the total pressure drop(Cv
is inversely proportional to square root of pressure
drop, hence the mathematical value is obtained).