The process
Basement car parks and tunnels use jet fans and extract fans rated for smoke extract, with silencers at the discharge. The fans run on carbon monoxide sensors in normal operation and at full speed in a fire.
The gas
Ambient air with vehicle exhaust, moved by jet fans and extract fans, with the smoke extract case setting the high temperature rating of the motor.
Selection for this process
| Impeller | PAG or die-cast aluminium impeller for low power, fixed or variable pitch |
| Form | Tube axial for low pressure; vane axial where the pressure or the downstream distribution calls for it; bifurcated where the motor must be out of hot or contaminated air |
| Density at the fan | At about 35°C the gas density is close to 1.15 kg/m³, 95% of standard air. Pressure developed and power drawn fall in the same ratio, so the selection is made at this density and the motor is checked at cold start. |
Types, construction and performance of the axial fans.
Industries
Fans in car parks and tunnels
Axial Fans in other processes
Information needed to select or quote
- Gas volume and temperature. Actual flow at the inlet, normal and upset temperature, moisture.
- Dust or pollutant. Inlet loading, particle size distribution, whether it is abrasive, sticky, hygroscopic or combustible; for gases, the species and concentration.
- Required outlet. The emission limit or clean gas concentration the unit must meet.
- Site. Available space and height, material of construction preferences, and how the collected material is to be discharged.