Midco Blue Flame Series, Инструкция по установке и обслуживанию

Страница: 7 / 18

Midco International Inc.
7
8471 34
Installation
Net Pro fi le Area = Rated Fan (SCFM) ÷ Pro fi le Velocity (SFPM)
The Pro fi le Velocity should be determined based on the burner fi ring rates. If we choose to fi re the
burner at 675,000 BTU/hr/ft then the pro fi le opening should be sized for a pressure drop of 0.8 ″
W.C. across the burner. If the fi ring rate is 450,000 BTU/hr/ft then the pro fi le opening should be
sized for a pressure drop of 0.4 ″ W.C. across the burner. The corresponding pro fi le velocity across
the burner should be determined from Chart 4 or use the following equation.
For the 675,000 BTU/hr/ft
Net Pro fi le Area = 5000 (SCFM) ÷ 3086 (SFPM)=1.62 ft 2
For the 450,000 BTU/hr/ft
Net Pro fi le Area = 5000 (SCFM) ÷ 2182 (SFPM)=2.29 ft 2
To calculate the pro fi le area needed for both cases:
Pro fi le Area = Net Pro fi le Area + Total Burner Area
For the 675,000 BTU/hr/ft
Pro fi le Area = 1.62 + 0.650 = 2.27 ft
2
For the 450,000 BTU/hr/ft
Pro fi le Area = 2.29 + 0.975 = 3.265 ft 2
To calculate the length of the pro fi le opening add burner length to the desired clearance:
For the 675,000 BTU/hr/ft case
12 inch + 4 inch (2 inches on each side) = 16 inch (1.3 ft)
For the 450,000 BTU/hr/ft case
18 inch + 4 inch (2 inches on each side) = 22 inch (1.83 ft)
To calculate the height of the pro fi le opening divide the pro fi le area by the pro fi le length:
For the 675,000 BTU/hr/ft case
2.27 ft 2 ÷ 1.3 ft = 1.75 ft (21 inch)
For the 450,000 BTU/hr/ft case
3.265 ft 2 ÷ 1.83 ft = 1.78 ft (21.5 inch)
1. Conversion of SCFM to Actual CFM of air
SCFM = CFM x ρ
_____
0.075
2. Air density as a function of Temperature -- ρ = 1.35 x Barometric Pressure (in Hg)
T
(out)
+ 460
3. Change in Standard Barometric Pressure as a function of Altitude
Barometric Pressure (in.Hg) = 29.921x (1-6.8753 x 0.000001x altitude (ft))^5.2559
4. Temperature di ff erence -- Temperature Rise = T
(out)
- T
(in)
5. Energy equation - - BTU/hr = SCFM x Temperature Rise x 1.08 / 0.92
Where: 1.08 is a sensible heat equation constant
1.08 = 0.2397
(
BTU
)
x 60
(
min
)
x 0.075
(
lb
)
____ ___ ___
lb H Ft 3
___________________________________
Pro fi le Setup Example
Continued
Profile Velocity
075 0
945
P
Δ
=
.
Profile Velocity
075 0
945
=
.
0
.
8
= 3086(SFPM)
Profile Velocity
075 0
945
=
.
0
.
4
= 2182(SFPM)