A Feasibility Study - Aaltodoc - Aalto-yliopisto

The relative roughness is a dimensionless number which gives the ratio between the
roughness of the surface and the inner diameter of the pipe. The Reynolds number is
also a dimensionless number which describes the type of flow, whether it is laminar
(smooth and calm) with a low Reynolds number or turbulent (violent and chaotic) with
a high Reynolds number. The equation describing the Reynolds number is
where is the dynamic viscosity of water, which is 1,0049∙ 10 - kg/ms at 20 ºC.
Pressure losses also arise always when the geometry of the pipeline changes e.g. at the
intakes, outlets, valves or divisions of the pipes. A standard way to calculate the
pressure loss in each case is to use the formula
where is the loss coefficient for various geometric changes, easily obtainable from the
literature for different cases.
A pipeline can have numerous changes in its geometrics, each contributing a small
pressure loss. Therefore the following principle is usually applied. Combining
Equations 4 and 7 gives the following
Thus the pressure loss from each change in geometrics can be converted to a pressure
loss due to travelled distance. Furthermore, all pressure losses resulting from changes in
the geometrics can be summed up giving
38
(6)
(7)
(8)
(9)
∑ (10)