Pressure drop calculation - theory
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In this calculator well known equations have been used. Here
you can find all of them for your review.
First of all, pressure drop through the pipe due to friction and local losses can
be calculated as follows:
where is:
Dp - pressure drop
rho - fluid density view table
Q - volumetric flow rate
D - pipe diameter
lambda - friction coefficient
L - pipe length
sum ksi - the sum of minor losses coefficient
To calculate mass flow rate following equation has been used:
where is:
G - mass flow rate
For pressure drop calculation because of friction, viscosity of fluid has to be known.
Relation between dynamic and kinematics viscosity is as follows:
where is:
mi - dynamic viscosity view table
ni - kinematic viscosity view table
Velocity of flowing fluid is calculated based on the continuity equation:
where the cross section of round pipe is:
To find out if the flow is laminar or turbulent, Reynolds number must
be calculated:
Friction coefficient for laminar flow is:
for flow in hydraulically smooth pipe (Blasius equation):
for turbulent flow with Re<100 000 (Prandtl equation):
for turbulent flow with Re>100 000 (Karman equation):
The boundary layer thickness (delta) can be calculated based on the Prandtl
equation as:
and when the boundary layer thickness is bigger than pipe roughness
and if the flow is turbulent, than it can be considered as flow
in hydraulically smooth pipe and Blasius equation is used.
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