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Eclipse ThermJet Design Guide No. 205, 3/5/07
Application example:
A batch furnace requires a gross heat input of 2,900,000 btu/hr
(based on 45% efficency). The designer decides to provide the
required heat input with four burners operating on natural gas using
15% excess air.
e
xample
bloWer
CalCulatioN
Calculation example:
a. Decide which ThermJet burner model is appropriate:
• Select 4 Model TJ075 ThermJet burners based on the
required heat input of 725,000 Btu/hr for each burner.
b. Calculate required gas flow:
• Gas flow of 2,894
ft
3
/hr
is required
c. Calculate required stoichiometric air flow:
V
air-Stoichiometric
=
a
(
air/gas ratio)
x V
gas
=
9.41 x 2,894 ft
3
/hr
= 27,235 ft
3
/hr
• Stoichiometric air flow of 27,235 scfh required
d. Calculate final blower air flow requirement based on the
desired amout of excess air:
V
air
=
(1 + excess air %)
x V
air-Stoichiometric
=
(1 + 0.15 )
x
27,235 ft
3
/hr = 31,320 ft
3
/hr
•
For this example, final blower air flow requirement is
31,320 scfh at 15% excess air.
Q
q
V
gas
=
=
2,9000,000 btu/hr
1,002 Btu/ft
3
=
2,894 ft
3
/hr
Q (total heat input) of 2,900,000 btu/hr
4 burners
=
725,000 Btu/hr/burner
Note:
It is common practice to add an additional 10% to the final
blower air flow requirement as a safety margin.
Find the blower model number and motor horsepower (hp).
With the output pressure and the specific flow, you can find
the blower catalog number and the motor hp in Bulletin /
Info Guide 610.
Eclipse Combustion recommends that you select a Totally
Enclosed Fan Cooled (TEFC) motor.
Select the other parameters:
Inlet filter or inlet grille
Inlet size (frame size)
Voltage, number of phases, frequency
Blower outlet location, and rotation direction Clockwise
(CW) or Counter Clockwise (CCW).
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