Yokogawa 415 Steam and Gas - Manual (Page 26)

3.2.2 General Gas
For general gases, the compressibility is calculated using the Redlich-Kwong
equation. In order to calculate the compressibility of a gas, it is necessary to
know the critical temperature and pressure. From these parameters, the
compressibility factors Z
B
and Z
F
are calculated for a gas.
A list of common gases with specific gravity and critical temperatures &
pressures is given in the appendix to this manual.
The equations 1 to 9 are then used to calculate both corrected volume and mass
flow.
Example 6
It is required to measure Hydrogen via an orifice plate using
compressibility. Find the critical temperature and pressure which
need to be programmed and the specific weight.
From the table, in the appendix,
T
C
= -239.9 C
P
c
= 1296.9 kPa
G = 0.0696
24 Operation