Example Blower Calculation - Eclipse ThermJet TJ0015 Design Manual

e
xample bloWer
CalCulatioN
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.
Calculation example:
a. Decide which ThermJet burner model is appropriate:
Q (total heat input) of 2,900,000 btu/hr
4 burners
• 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:
Q
=
=
V
q
gas
• Gas flow of 2,894
c. Calculate required stoichiometric air flow:
= a
V
air-Stoichiometric
= 27,235 ft
• Stoichiometric air flow of 27,235 scfh required
d. Calculate final blower air flow requirement based on the
desired amout of excess air:
=
V
(1 + excess air %)
air
=
(1 + 0.15 )
• For this example, final blower air flow requirement is
31,320 scfh at 15% excess air.
Note:
It is common practice to add an additional 10% to the final
blower air flow requirement as a safety margin.
1. 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.
2. Eclipse Combustion recommends that you select a Totally
Enclosed Fan Cooled (TEFC) motor.
3. 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).
Eclipse ThermJet Design Guide No. 205, 3/5/07
725,000 Btu/hr/burner
=
2,9000,000 btu/hr
= 2,894 ft
1,002 Btu/ft
3
is required
ft /hr
3
=
(air/gas ratio) x V
gas
3
/hr
x V
air-Stoichiometric
3
x
27,235 ft /hr = 31,320 ft
/hr
3
3
9.41 x 2,894 ft /hr
3
/hr
1