Firing Rate According To Air Density - Riello RS 200/M BLU Installation, Use And Maintenance Instructions

4.7.1

Firing rate according to air density

The burner firing rate specified in the manual applies for an
ambient temperature of 20 °C and an altitude of 0 m a.s.l.
(barometric pressure of approx. 1013 mbar).
The burner may have to operate at a higher altitude and/or with
combustion air at a higher temperature.
Both air heating and increased altitude cause air volume
expansion, i.e. air density is reduced.
Burner fan flow rate remains basically the same but oxygen
content per cu. m of air is reduced as well as the fan push (head).
Therefore, it is important to know whether burner required
maximum output at a certain pressure in the combustion
chamber remains within the burner firing rate also under different
temperature and altitude conditions.
To check this, proceed as follows:
1 find the correction factor F concerning air temperature and
altitude for the system in Tab. F.
2 Divide output Q requested from the burner by F to obtain the
equivalent output Qe:
Qe = Q : F (kW)
3 Within burner firing rate, mark the point identified by:
Qe = equivalent output
H1= pressure in combustion chamber
point A that must remain within the firing rate.
4 Draw a vertical line from point A)(Fig. 3), and calculate the
maximum pressure H2 of the firing rate.
5 Multiply H2 by F to obtain the reduced maximum pressure
H3 of the firing rate:
H3 = H2 x F (mbar)
Average
Altitude barometric
pressure
m a.s.l. mbar
0 1013
100 1000
200 989
300 978
400 966
500 955
600 944
700 932
800 921
900 910
1000 898
1200 878
1400 856
1600 836
1800 815
2000 794
2400 755
2800 714
3200 675
3600 635
4000 616
Technical description of the burner
0 5 10
1.087 1.068 1.049
1.073 1.054 1.035
1.061 1.042 1.024
1.050 1.031 1.013
1.037 1.018 1.000
1.025 1.007 0.989
1.013 0.995 0.977
1.000 0.982 0.965
0.988 0.971 0.954
0.977 0.959 0.942
0.964 0.946 0.930
0.942 0.925 0.909
0.919 0.902 0.886
0.897 0.881 0.866
0.875 0.859 0.844
0.852 0.837 0.822
0.810 0.796 0.782
0.766 0.753 0.739
0.724 0.711 0.699
0.682 0.669 0.657
0.661 0.649 0.638
11
If H3 is higher than H1)(Fig. 3), the burner can output the
requested flow rate.
If H3 is lower than H1, burner output must be reduced. Output
reduction is also combined with a reduction of the pressure in the
combustion chamber:
Qr = reduced output
H1r = reduced pressure
Qr 2
( )
H1r = H1 x
Q
Example, 5% output reduction:
Qr = Q x 0.95
H1r = H1 x (0.95)2
Using the new Qr and H1r values, repeat steps 2-5.
The combustion head must be adjusted according
to equivalent output Qe.
ATTENTION
mbar
mbar
H2
H3
H1
D388
F
Air temperature °C
15 20
1.031 1.013
1.017 1.000
1.006 0.989
0.995 0.978
0.983 0.966
0.972 0.955
0.960 0.944
0.948 0.932
0.937 0.921
0.926 0.910
0.914 0.898
0.893 0.878
0.871 0.856
0.851 0.836
0.829 0.815
0.808 0.794
0.768 0.755
0.726 0.714
0.687 0.675
0.646 0.635
0.627 0.616
GB
A
Qe
Qe
25 30
0.996 0.980 0.948
0.983 0.967 0.936
0.972 0.956 0.926
0.962 0.946 0.916
0.950 0.934 0.904
0.939 0.923 0.894
0.928 0.913 0.884
0.916 0.901 0.872
0.906 0.891 0.862
0.895 0.880 0.852
0.883 0.868 0.841
0.863 0.849 0.822
0.842 0.828 0.801
0.822 0.808 0.783
0.801 0.788 0.763
0.781 0.768 0.743
0.742 0.730 0.707
0.702 0.690 0.668
0.664 0.653 0.632
0.624 0.614 0.594
0.606 0.596 0.577
kW kg/h
Fig. 3
40
Tab. F
20152093