| Ventilator technology is indispensable for drying and conditioning agricultural products. Axial ventilators are put to frequent use here. Characteristic of axial ventilators is that the air flows in the longitudinal direction of the shaft of the ventilator motor.
An axial ventilator comprises a ring with a motor and
an impeller. Many factors play a role in determining the correct axial ventilator for your specific situation - the people at Agratechniek are pleased to provide you with sound advice regarding this. | 
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Counterpressure in Pa
Based on the conventional standards that apply to drying technology, a rough classification can be made of three main groups for the counterpressure in Pa (Pascal):
* low pressure: 0-75 Pa, the ventilator blows into an open space
* medium pressure: 75-250 Pa, for flower bulbs, potatoes, garlic and shallots
* high pressure: 250-800 Pa, for onions (stored loosely), seeds and cereals.
 | Available versions
Many versions of axial ventilators are available:
Impeller diameter: 630,710,800,900,1000,1120 - Ø in mm
Motor power: 0.55 kW through 22 kW - P in kW
No. of vanes per impeller: 4,5,8,10 - x vane position (angle with respect to shaft): between 25o and 45o - ino rotational speed of the motor: 720,960,1440 - in rpm (or double-speed motor) in the case of very high counterpressure: use fixed blades
Other ventilators
* Condensation ventilators
* Ceiling-mounted ventilators
* Low-pressure ventilators.
Detail: changing the direction of rotation of the motor reverses the airflow through the product. |
Custom-made solutions
Axial ventilators are constructed in such a way that the correct ventilator can be selected for every situation.
The following table indicates the effect of changing the diameter, the number of vanes, the motor power and the rotational speed in that order.
* Regarding diameter:
A smaller impeller diameter results in a lower air delivery, especially in the case of high counterpressure (see Table 1)
* Regarding the number of vanes:
In the case of low/medium counterpressure, fewer vanes per ventilator results in a higher air delivery; in the case of high counterpressure, more vanes per ventilator results in a high air delivery - as the ventilator diameter increases, the difference also increases (see Tables 2 and 2a)
* Regarding motor power:
A higher motor power in kW results in a higher air delivery - as the ventilator diameter increases, the difference also increases (see Tables 3 and 3a)
* Regarding rotational speed:
The use of a double-speed motor results in a flexible air delivery - Table 4 clearly indicates the relationship between rotational speed, air delivery and motor power.
Air delivery, counterpressure and motor power are calculated as follows (in this example we are operating at 1440 rpm, i.e. high speed):
* Changing down from 1440 to 720 rpm imples 25,920m_/h
for 200 Pa reduced to: 720/1440x25920="12960m_/h
Counterpressure is: (720/1440)_x200Pa="50Pa
Power consumption is: (720/1440)_x3kW="0.375kW
* Changing down from 1440 to 960 rpm implies 25,920m3/h
for 200 Pa reduced to: 960/1440x25920="17280m3/h
Counterpressure is: (960/1440)3x200 Pa="88.89Pa
Power consumption is: (960/1440)3x3kW="0.9" kW
Conclusion:
* When the rotational speed is reduced, the volume of air drops proportionately
* The counterpressure is also reduced by a factor of 2
* The motor power is reduced to the power of 3.
Table
* The correct setting of the angle of the vanes results in optimum air delivery without overloading the motor.
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