100/180 mm PAPERLESS GRAPHIC RECORDER: USER GUIDE
HA028910
Issue 13 Sep 16
User Guide
Page 114
4.3.11 FUNCTION (Cont.)
LINEAR MASS FLOW
Note: The overall accuracy of a fl ow measurement installation depends on a number of factors
outside the control of the recorder manufacturer. For this reason, the recorder manufacturer takes
no responsibility for the accuracy of the results obtained using the mass fl ow equations imple-
mented in the maths pack.
The equations solved is:
where, QM
t
= Mass fl ow (in kg/sec), at time ‘t’
K = Scaling factor (see below)
Rg = Specifi c gas constant in J/kg-K (see below)
Z = Compressibility factor (see below)
Flow
t
= Measured value from the fl ow meter at time ‘t’
AbsP
t
= Absolute pressure of the fl uid at time ‘t’ in kPa(A)
Temp = Temperature of the fl uid in Kelvins
Scaling factor
This is determined from an assumed value of Qm at a known Flow, AbsP and Temp.
The value is chosen to give an output within the range low scale to high scale.
Specifi c gas constant The specifi c gas constant for any gas is available from published tables. For conven-
ience, the value for a number of common gases is given in table 4.3.11a, below.
Table 4.3.11a Common gas constants
Air
Ammonia
Carbon dioxide
Carbon monoxide
Ethylene
Hydrogen
Methane
Nitrogen
Oxygen
Propane
Steam
287.1
488.2
188.9
296.8
296.4
4116.0
518.4
296.8
259.8
188.5
461.4
RG
(J/kg-K)
Gas
QM
t
!
K
Rg
$
Z
$
Flow
t
$
AbsP
t
Temp