Eclipse ImmersoJet v2.20 Design Guide 330, 10/02
Blower
The rating of the blower must match the system requirements.
You can find all the blower data in Bulletin 610.
Follow these steps:
1. Calculate the outlet pressure.
When calculating the outlet pressure of the blower, the total
of these pressures must be calculated.
•
the static air pressure required at the burner
•
the total pressure drop in the piping
•
the total of the pressure drops across the valves
•
the pressure in the immersion tube
•
recommend a minimum safety margin of 10%
2. Calculate the required flow
The blower output is the air flow delivered under standard
atmospheric conditions. It must be enough to feed all the burners
in the system at high fire.
Combustion air blowers are normally rated in terms of standard
cubic feet per hour (scfh) of air.
An example calculation follows the information tables below:
Series SMJ turbo blower
C
OMBUSTION
A
IR
S
YSTEM
(
CONTINUED
)
D
ESCRIPTION
U
NIT
OF
MEASURE
F
ORMULA
SYMBOL
Total system heat input
Btu/hr
Q
Number of burners
-
-
Type of fuel
-
-
Gross heating value of fuel
Btu/ft
3
q
Desired excess air percentage
percent
%
(Typical excess air percentage
@ high fire is 15%)
Air/Gas ratio
-
α
(Fuel specific, see table below)
Air flow
scfh
V
air
Gas flow
scfh
V
gas
Figure 3.4
Required calculation information
* Stoichiometric: No excess air. The precise amount of air and gas are present
for complete combustion.
Figure 3.5
Fuel gas heating values
F
UEL
GAS
S
TOICHIOMETRIC
*
AIR
/
GAS
RATIO
α
α
α
α
α
(
ft
3
air
/
ft
3
gas
)
G
ROSS
HEATING
VALUE
q (Btu/ft
3
)
Natural gas
(Birmingham, AL)
9.41/1
1,002
Propane
23.82/1
2,572
Butane
30.47/1
3,225
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