The dryers are made of trays held
in a cabinet which is connected to a source of air heated by
Electric & Gas. The air temperature is usually controlled by a
thermostat which is normally set between 50 and 250 Deg C. The
air enters the bottom of the chamber below the trays and then
rises, through the trays of material being dried, and exits
from an opening in the top of the chamber. In the Practical
Action systems the trays are designed to force the air to
follow a longer zigzag route which increases the air /
material contact time and thus improve its efficiency. This
system also reduces back pressure which means that cheaper,
smaller fans can be used. The airflow in a typical system.
There are different size of tray
drier as per no of tray 12 tray To 192 tray.