2. Drying kinetics

The theory of drying is described by Lewis [16], especially during thin film drying.

The most important parameter used in process drying is the drying rate equation [17]:

$$-\frac{dX}{dt} = k(X - X\varepsilon)\tag{1}$$

$$k = 0.00719 \exp\left(-\frac{130.64}{T\_{ma}}\right) \tag{2}$$

Tch, X and Xe are respectively the moist air temperature, the instantaneous moisture content and the equilibrium moisture content of the vegetable or the wet agricultural product. According to GAB model [18, 19] Xe is expressed by:

$$Xe = \frac{W\_m \text{CKa}\_w}{(1 - Ka\_w)[1 + (C - 1)Ka\_w]} \tag{3}$$

Wm, C and K are parameters related with air temperature by the following expressions:

$$W\_m = 0.0014254 \exp\left(\frac{1193.2}{T\_k}\right) \tag{4}$$

$$C = 0.5923841 \exp\left(\frac{1072.5}{T\_k}\right) \tag{5}$$

$$K = 1.00779919 \exp\left(-\frac{43.146}{T\_k}\right) \tag{6}$$

Tk and aw are the air absolute temperature and the water activity.
