B. Supply (If Applicable):
Example for Perforated Face Supply
1.Hood set up
If the
2.Measure Velocities
Divide the perforated face panel into a grid of equal areas, each approximately 4 in. (100 mm) square.
Measure the velocity at the center of each grid area. A digital 2.75 in. (70 mm) rotating vane anemometer or equivalent is suggested. The center of the anemometer should be held tight to the face of the panel, and parallel to the filter. Both squareness and distance are important for accuracy. Calculate the average velocity of the panel.
3.Measure the length, height, and width of the perforated face panel.
4.Calculate the perforated face panel volume in CFM by using the following formula:
Volume | = | Avg. Velocity | * | Length (in.) | * | Height (in.) | * | 0.005 |
Volume | = | Avg. Velocity | * | Length (m) | * | Height (m) | * | 0.72 |
5.Calculate the system’s volume by repeating the process for the remaining panels and adding the individual panel volumes together.
Filter Readings (fpm)
260 | 250 | 255 | 260 | 250 | 255 | 265 |
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270 | 275 | 270 | 280 | 265 | 265 | 270 |
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290 | 285 | 280 | 280 | 275 | 290 | 295 |
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285 | 275 | 280 | 260 | 270 | 265 | 260 |
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Filter Readings (m/hr)
4755 4572 4663 4755 4572 4663 4846
4938 5029 4938 5121 4846 4846 4938
5304 5212 5121 5121 5029 5304 5395
5212 5029 5121 4755 4938 4846 4755
Example: Face Supply Hood with three 28 in. (.711 m) Perforated Panels |
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Measured velocities in FPM for one perforated panel |
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Average Velocity | = | Sum of Velocity Readings |
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(Imperial) | = | 260 + 250 + … + 265 + 260 | = | 270.7 fpm |
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(Metric) | = | 4755 + 4572 + … + 4846 + 4755 | = 4951 m/hr |
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Measure Length and Height = 28 in. (.711 m) long perforated panels x 16 in. (.406 m) high | ||||||||||||
Volume for one panel | = | Conversion | x | Average |
| x | Length | x | Height |
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Velocity |
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| = | 0.005 | x | 270.7 fpm | x | 28 | x | 16 | = |
| 606.4 cfm | |
| = | 0.72 | x | 4951 m/hr | x | .711 | x | .406 | = | 1029 m3/hr | ||
Total system volume | = (Panel 1 Volume) + (Panel 2 Volume) + (Panel 3 Volume) |
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| = | 606.4 |
| + | 614.3 | + |
| 593.8 |
| = | 1814.5 cfm | |
| = | 1029 |
| + | 1044 | + |
| 1009 |
| = | 3082 m3/hr | |
20 Canopy Hood
®
