La curva del sistema e la curva de la bomba
Curva del sistema 2 Suplemento

The equation of Darcy-Weisbach allows to determine the pressure loss of straight piping and bends. Darcy Friction Factor is calculated by the law of Hagen-Poiseulle for laminar flow. For transition zone and turbulent flow Darcy Friction Factor is calculated by the equation of Colebrook (Moody). Laminar flow through bends is calculated according to Ghia, non-laminar flow according to Krüger. Data for suction side and pressure side is collected separately to determine the pressure rise accross the pump. Absolute pressure on the pumps suction side must stay below its NPSH value to avoid cavitation caused by evaporation inside the pump. We start with choosing the roughness of the inner pipe wall. Click the link roughness for help.

Flow coefficient cv of a component equals its water flow in [gal/min] at a pressure loss of 1 [psi]. Flow coefficient kv equals its water flow in [m³/h] at a pressure loss of 1 [bar]. The tab above the entry area leads to kv values of various valves. Flow coefficients cv can be converted to kv - see link kv or choose the calculator from the main menue. More theory as always on the left corner of the entry area.

Friction Factor K is the proportional factor of the Darcy-Weisbach equation. Click the tab above the entry area for K values of various valves. More theory as always on the left corner of the entry area.

Sometimes neither a cv value nor a friction factor is known for the component in question. But pressure loss and flow for one point of operation. This data can be used as reference the same way we use cv values. Darcy-Weisbach equation allows the conversion to different flows, pressure losss and densities.