Pressure

When the flow is known as all points, the pressure loss depending on friction can be calculated. The pressure loss as a consequence of friction is calculated using the following formula:

If there is an individual pressure loss in the pipe, this is calculated as follows:

Where:

ΔP      =       Pressure [Pa

ρ        =       Density [kg/m³

L        =       Pipe length [m

λ        =       Friction factor [ -

D        =       Internal diameter of pipe [m

v        =       Flow rate [m/s

g        =       Gravitation constant [m/s²

z_d       =       Level downstream [m/s

z_u       =       Level upstream [m/s

ξ        =       Individual pressure loss coefficient

K1      =       Calibration factor 1

K2      =       Calibration factor 2 [ m^-1

 

The total pressure loss is the sum of pressure loss due to friction and individual pressure losses.

The friction factor is calculated on the basis of the Colebrook and White formula:

 

 

Where:

k        =       Roughness in the pipe [m

Re      =       Reynolds number [ -

µ        =       Viscosity [kg/(ms)

D        =       Internal diameter of pipe [m

For small Reynolds numbers (< 2300), the friction factor is calculated as:

If a valve or pump is placed at the end of the pipe, this is incorporated in the pressure loss calculation. The pressure loss or pressure increase is added directly to the pressure at the pipe end.