Page 47 - Valve Selection Handbook
P. 47
34 Valve Selection Handbook
where
G = specific gravity
This relationship is contained in the IEC Publication 534-1 19 and
applies to single-phase and fully turbulent flow of Newtonian liquids.
For other flow conditions, refer to IEC Publication 534-2, Parts 1 and 2,
or to manufacturers' catalogs.
Flow Coefficient A v
The flow coefficient A v is a version of the flow coefficient K v in
coherent SI units. A v states the number of cubic meters per second of
water at a temperature between 5° and 40°C that will flow through the
valve with a pressure loss of one Pascal at a specific opening position, as
defined by the equation:
where
3
Q = flow rate, m /s
p = operational differential pressure, Pa
p = density of Newtonian liquid, kg/m 3
A v is derived from Equation 2-8, which may be presented in the fol-
lowing forms:
where
v = flow velocity of fluid, m/s
A = cross-sectional area, m 2
(2} m
The expression A — is replaced in Equation 2 -16 by a single
expression A v . VW
