The process
Large sheds shed heat through the ridge with roof extractors and draw fresh air through louvers or supply fans. Evaporative cooling is added where the process heat is high.
The gas
Ambient air carrying light dust from the surroundings, enough to settle on blades over months but not to erode them. Inlet screens and a wheel that sheds deposit are the usual precautions.
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 factory shed ventilation
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.