Thermolec Application &Technical Notes - Manual (Page 13)

THREE EASY STEPS
STEP 2 - (continued)
Using the Air flow requirement curve above, find 21.66 on the vertical scale.
Read the minimum velocity required on the horizontal axis, which is approx. 1150 FPM.
If it is a 2 stage heater then KW per square foot per stage =
65 KW
= 10.83
3 sq.ft. x 2 stages
In this case 750 FPM are required.
C
If it is an SCR Controlled heater then 300 FPM are required. E
D
Example:
Find the minimum air flow requirement for a 65 KW 1 stage heater in a 24” wide by 18” high duct.
Calculate duct area in square feet.
Calculate KW per square foot per stage.
Duct Area =
24” x 18”
= 3 square feet
144
A
KW per square foot
=
65 KW
= 21.66
per stage 3 sq.ft. x 1 stage
B
Please refer to the table on page 16 for tubular elements.