A. Exhaust
With all the filters in place, determine the total hood exhaust volume with a Shortridge meter as follows:
1.All cooking equipment should be on. If the hood has internal short circuit
2.Measuring Velocities
•Set up the Shortridge meter. Leave all holes of
Velgrid open. Do NOT tape over holes that are not over openings. The conversion factor takes this into account.
•For 20 in. (500 mm) high filters, position the grid as shown in Fig. 42 and 43. Average the two measurements.
•For 16 in. (400 mm) high filters position the grid as shown in Fig. 44.
•For 20 in. (500 mm) wide filters, position the grid over
the left and right side of the filter. Average the two |
|
measurements. | Fig. 41 |
•Take velocity readings for each filter.
3.*Calculate each filter’s volumetric flow rate by summing the flow rate of each individual filter in the hood.
4.*Calculate the total hood’s volumetric flow rate by summing the flow rate of each individual filter in the hood.
*Note: For best accuracy multiply the velocity of each filter by its conversion factor and sum the flow rates. Averaging the velocity measured for all filters may cause error.
Nominal Filter Size (H x L) | Imperial | Metric | |
Inches | Millimeters | Conversion Factor | Conversion Factor |
|
|
|
|
16 x 16 | 400 x 400 | 1.53 ft2 | .142 m2 |
16 x 20 | 400 x 500 | 2.00 ft2 | .185 m2 |
20 x 16 | 500 x 400 | 2.25 ft2 | .209 m2 |
20 x 20 | 500 x 500 | 3.00 ft2 | .279 m2 |
Example:
Measured velocities for 20 x 20 in. (500 x 500 mm) filter.
Average slot velocity |
| = | Sum of Velocity Readings |
|
|
|
| ||||
|
|
|
| Number of Readings |
|
|
|
| |||
(Imperial) |
| = | 198 + 205 |
| = | 201.5 fpm |
|
| |||
|
|
|
| 2 |
|
|
|
|
|
|
|
(Metric) |
| = | 3021 + 3749 |
| = | 3385 m/hr |
|
| |||
|
|
| 2 |
|
|
| |||||
|
|
|
|
|
|
|
|
|
|
| |
Flow rate for one filter | = | Conversion Factor x | Average Velocity |
|
|
| |||||
| = | 3.0 |
| x |
| 201.5 fpm |
| = | 604.5 cfm | ||
| = | .279 | x |
| 3385 m/hr |
| = | 944 m3/hr | |||
Total hood flow rate | = | Filter 1 | + | … | + | Filter X |
|
|
|
| |
Flow Rate | Flow Rate |
|
|
|
| ||||||
| = | 604.5 | + | 600.3 | + | 592.4 | + | 613.3 = | 2410.5 cfm | ||
|
| 944 | + | 1020 |
| 1006 | + | 1042 | = | 4012 m3/hr | |
25Canopy Hood
Fig. 42
Fig. 43
2.5 in.
Fig. 44
14.25in.
2.75in.
2.75 in.
3.25in.
14.75in.
14.25in.
2.75 in.
2.75 in.
®
