The process
Withering troughs blow a large volume of ambient or warmed air through green leaf for hours. The trough fan is an axial fan at low pressure, often with a hot air mixer, run for long hours and cleaned often.
The gas at the fan
Warm, humid air through withering troughs and dryers with light leaf dust. Large volume at low pressure; the fan is cleaned often, so access matters.
Selection for this duty
| Impeller | Coated aluminium or stainless steel impeller, stainless or coated casing |
| 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 60°C the gas density is close to 1.06 kg/m³, 88% 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. |
Blows a large volume of ambient or warmed air through the bed of green leaf on a withering trough. Low pressure, long running hours, and a fan that must be easy to clean. Client-stated blade types for the Trough Fan in general: Axial.
Industries
Other fans in tea withering troughs
Trough Fan in other processes
Information needed to select or quote
- Duty point. Volume flow and static pressure at the fan inlet, with the gas density and temperature or the conditions to derive it.
- Operating conditions. Site altitude, normal operating temperature and continuous or intermittent duty.
- Gas stream. Dust loading and particle size, corrosive species, moisture, upset temperature and any tendency of the material to deposit on the impeller.
- Mechanical. Rotation viewed from the drive end, discharge orientation and motor power.