How to use the DRYIT semi-continuous tray dryer
Practical Action
that temperature.
From point A follow an adiabatic cooling line to the 100% saturation line. This is point C. It
tells you that the equivalent wet bulb temperature is approximately 13°C. (see figure 7)
Figure 7: Graph to show temperature of dry bulb against humidity
Read across to the absolute humidity axis (Point D):
0.009kg moisture/kg air
Point D - Point B = Potential of the ambient air to pick up moisture.
0.009 - 0.007 = 0.002kg moisture per kg air
After heating the air to 50°C.
From point A take a line horizontally across to the 50°C point. This is Point E.
Follow adiabatic cooling line to 100% saturation (Point F).
Read off absolute humidity from right hand axis (Point G): 0.017kg/kg. Subtract the ambient
dry air humidity (point B) from this figure to give the potential ability of the heated air to pick
up water vapour.
0.017-0.007 = 0.01kg/kg i.e. 5 times greater than the ambient air potential.
Assume a pick-up factor of 50% for herbaceous materials. This gives a potential moisture
pick up of: 0.005kg/kg
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