minor losses in the pipelines, fittings, valves… for waterReading time:
Special case: pipe emerging from a large tank
Special case: pipe entering into a large tank
friction loss (∆h1)
Evaluate pressure drop ∆h1', in a cylindrical pipe of the same length and having a section equal to the large section :
head loss by detachment (∆h2)
Values for K (table 57) :
Elbow delivering into a closed tank (K total)
sharp bends :
It is assumed as follows :
- branch pipes have the same diameter as the main pipe;
- couplings have sharp angles.
outgoing branch pipe
inlet branch pipe
symmetrical T, flow separation: (welded steel T)
symmetrical T, converging flows
valves and taps
rotating or butterfly valves
The head loss coefficient according on the valve opening angle depends on the hydraulic profile of the butterfly: for guidance, table 63 provides a few typical values; however, it is advisable to refer to manufacturer tables for greater clarification.
open valves and couplings
valve coefficient Cv
The normal practice consists in allocating a flow coefficient Cv to the different openings. By definition, Cv is the water flow at 15°C expressed in US gpm that travels through the constricted section for a 1 psi head loss, which is more or less equivalent to the water flow expressed in litres per minute, creating a head loss of 5 mbar or 0.05 m of WC .
Therefore, for water, we have :