25
DETERMINATION OF GAS VOLUME FOR THE INSTALLATION
Specifications on natural gas, town gas and biogas vary. For more exact
information please contact the gas distributor.
Example how to calculate the gas volume (natural gas)
V
=
Gas volume Nm
3
/h
Q
=
Boiler output 120 kW
H
u
=
Calorific value of the gas A. 37 144 kJ/Nm
3
, B. 10.3 kWh/ Nm
3
η
=
Expected efficiency 90%
Ex. A
Ex. B
If the barometer height, pressure and temperature of the gas deviate con-
siderably from the normal values this must be taken into account as follows:
f
=
t
=
Temperature of the gas at the gas meter (15°C)
B
=
Barometer height (945 mbar)
P
u
=
Pressure of the gas at the gas meter (15,0 mbar)
f
=
f
≈
1.11
The gas volume read on the gas meter actually reads 1,11
.
12,9 = 14,4 m
3
/h.
172 205 16 03-01
Net calorific value
Gas quality
kWh/Nm
3
kJ/Nm
3
kcal/Nm
3
Natural gas
10.3
37 144
8 865
Propane
26.0
93 647
22 350
Butane
34.3
123 571
29 492
Town gas
4.9
17 653
4 213
Biogas
7.0
25 219
6 019
273+15
273
. 1013,25
945+15
V
=
120
10,3 · 0,90
≈
12,9 Nm
3
/h
B+P
u
273+t
273
. 1013,25
120 . 3 600
37 144 . 0,90
V
=
Q .3 600
H
u
·
η
=
≈
12,9 Nm
3
/h
