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< prev - next > Crop processing Drying KnO 100295_Small scale Drying technologies (Printable PDF)
Drying technology
Practical Action
Small Electric Dryers, as shown in Figure 5, can be constructed at a cost equal to or less than
the solar dryers described above. Typically, such a dryer consists of a plywood box one metre
cube, with a door to the front. Between 6 and 10 mesh trays are supported on wooden runners on
the dryer walls. Heated air is supplied by a domestic 2kw fan heater to the rear base wall. The
heater should be re-wired with an external thermostat (placed in the drying chamber) so that the
heater elements are controlled by the thermostat while the fan runs all the time. This is a simple
job that can be carried out by a competent electrician. The air exits via an opening at the top of
the rear wall. The trays should be arranged so as to cause the air to follow a zig-zag path as it
passes through the dryer as shown in Figure 5.
Figure 5: Small electric dryer. The air should follow a zigzag path.
Provided sufficient value is added by drying to cover electricity costs, such dryers offer distinct
advantages over solar dryers which include:
greater daily output
higher drying temperatures and thus considerably more rapid drying
faster drying due to the forced air flow
total independence from weather conditions
good control of the drying process.