The drying speed is taken along a vertical axis, average moisture content is taken along a horizontal axis and the above figure is described, it will become a dry characteristic curve.
The drying speed is quantity of water evaporating in a unit time.
The drying speed has two definitions, the dry area standard Ja and the material mass standard Jm.
A: Drying area
Ms: Material mass
dmw: Water content change
dt: Time change
dw: Initial moisture content
Area based drying speed Ja = -1/A x dmw /dt = -Ms/A x dw/dt
Mass based drying speed Jm = -1/Ms x dmw /dt = -dw/dt
Relationship of area based drying speed Ja and mass based drying speed Jm
Area based drying speed Ja = Ms/A x Jm
Mass based drying speed Jm = A/Ms x Ja*The dry characteristic curve varies according to type, kind and shape of materials.