The Slot Area and Slot Loss Coefficient fields are normally to be used for compound hoods. (See Figure 1 at right)
The Slot Area field is the actual open area of the slot or slots in a hood.
The Slot Loss Coefficient is the slot entry loss factor, Fs, and would have values in the range of 1.00 to 1.78 (if unknown use 1.78 value)
The system has a preset value for the Slot velocity of 200 fpm.
The Hood Loss Coefficient is the hood loss factor, Fh, when used for compound hoods.
Hood Loss Factor |
||
| α | Conical | Rectangular |
| 90 | 0.93 | 0.93 |
| 80 | 0.11 | 0.19 |
| 70 | 0.06 | 0.13 |
| 60 | 0.08 | 0.16 |
| 50 | 0.12 | 0.21 |
| 45 | 0.15 | 0.25 |
| 40 | 0.18 | 0.28 |
| 30 | 0.25 | 0.35 |
| 20 | 0.34 | 0.43 |
| 10 | 0.44 | 0.52 |
| 0 | 0.56 | 0.64 |
Note: 0° values represent round ducts butted into back of booth or hood without a rectangular to round transition.
If your hood is not considered a slotted hood the Hood Loss Coefficient is the only required value. The Slot Area and Slot Loss Coefficient are to be set to zero. The Acceleration Factor is to be set to 1. (See Figure 2 below)
When the hood is considered a compound hood all of the values are to be populated. The Acceleration Factor is to be set to 1. (See Figure 3 below)
