Valves Selection

In liquid medium

In the formula:
Q —— Liquid flow, m3/h
S —— Liquid specific gravity. When the water is at 15℃, the specific gravity is 1Kg/dm3
△P —— Pressure drop of two sides of the valve, P1-P2
KV —— Flow factor. The flow (m3/h) of the liquid per hour when the valve is fully open and the pressure drop of the inlet and outlet equals to 1bar.

e.g. Valve selection of differential pressure by-pass valve in air-conditioning system.
Outlet pressure of the chilled water pump in heavy system: 3bar
Max. flow: 400 m3/h
Pressure drop of the evaporator of water chiller: 0.7bar
Pressure drop of the differential pressure by-pass valve: △PV
Outlet pressure of the chilled water pump: P’
Pressure drop of the evaporator: △PE
Pressure drop the pipes in chiller room: △PP
Solution:

In the formula:
W —— Steam flow: Kg/h
△P —— Pressure drop of two sides of the valve, P1-P2
P1 —— Inlet absolute pressure, bar
P2 —— Outlet absolute pressure, bar
K —— Modified coefficient of the overheated steam vs saturated steam
KV —— Flow factor. The flow (m3/h) of the liquid per hour when the valve is fully open and the pressure drop of the inlet and outlet equals to 1bar.