How to use the DRYIT semi-continuous tray dryer
Practical Action
From knowledge of the quantity of air passed it then becomes possible to calculate the
theoretical drying times for this particular drying condition. (See next box).
To calculate how much water can be removed over time
Using the large tray Dryer and diesel fired heater: The heater has a fan which moves 2800m3
air per hour: To convert this to a weight of air it is necessary to know the density of the
ambient air. This can be calculated from the psychrometric chart:
The surrounding air has a temperature of 18°C and an RH of 60%. On the chart below this
corresponds to the value at Point H: 0.84 = specific volume (m3/kg) Therefore weight of air
per hour moving through the Dryer:
Weight =
Volume
Specific Volume
= 2800
0.84
= 3333kg air per hour
From the above box, the heated air can pick up 0.005kg moisture per kg of air.
Therefore air can remove:
= 3333kg/hr x 0.005kg/kg
= 16.66kg moisture per hour
= Rate of moisture loss
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