9
Eclipse TFB, V2, Design Guide 310, 11/14/2014
Figure 3.6.
The effective tube length required is a function of the
efficiency chosen. The effective length of a tube is the total
length of straight tube covered by liquid. Add 13" for each
90° bend.
Calculate the gross burner input
Calculate the gross burner input in (BTU/hr) with this
formula:
Compare the gross burner input
Compare the gross burner input with the maximum tube
input. If the gross burner input is greater than the
maximum tube input from the table below, then the size of
the immersion tube must be increased.
Exceeding these inputs may result in burner pulsation or
other operational problems.
Sizing Example
Application parameters
• Net heat release required to tank: 1,000,000 BTU/hr
• Efficiency: 70%
• Effective tube length: (Figure 3.6) 37'
• Gross Burner Input: 1,000,000 / .70 = 1,428,571
BTU/hr
• 200TFB Burner: 2,000,000 BTU/hr maximum
capacity
• Minimum Tube I.D. : (Table 3.3) = 8"
• Tube Surface Area/sq. in. = O.D. x x L
O.D. = 8.625
= 3.142
L = Total effective tube length in inches =
(37 x 12) = 444"
8.625 x 3.142 x 44 = 12,032.3 sq. in.
• BTU/hr/sq.in = Net heat release to tank /
sq.in. surface area
1,000,000 / 12.032.3 = 83.1 BTU/sq.in./hr
NOTE: If the medium to be heated in the above example
was cooking oil, it would be necessary to increase tube
length or select a larger tube. It is recommended that you
not exceed 50 BTU/hr/sq.in. for cooking oil.
Air Tube Length
The air tube length should be as short as possible to
maximize the exposure of the immersion tube to the
flame.
■ Any section of immersion tube that extends
beyond the nozzle, must be submerged in the
liquid. Dimension B must be greater than
Dimension A.
Figure 3.7. Air Tube Length
Choose the shortest tube length (Dimension B) that is
greater than Dimension A. You can find the air tube
lengths (dim. B) that are available in the appropriate 310
Datasheet series.
net heat release to the tank
= gross burner input
tube efficiency
Table 3.3 Maximum Tube Input
Tube ID (inches) Maximum Input (1000 BTU/hr)
4 300
5 600
6 900
8 1500
10 2500
12 3500
Net Heat Release to Tank (Btu/hr x 1000)
0
0
10
20
30
40
50
60
Effective Tube Length (feet)
75%
70%
65%
60%
Efficiency
Effective Tube Length
200 400 600 800 1000 1200 1400 1600 1800 2000
CAUTION
A
B
Correct
Incorrect
B
A
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