First experimental trials were carried out to study the
influence of ultrasonic power (0 W, 25 W, 50 W, 75 W
and 100 W) in the kinetics of the dehydration process. In
all trials the temperature and relative humidity were kept
between 24–26 C and 30–46%, respectively. The applied
static pressure was fixed at 0.06 kg/cm2
, the suction at
60 mbar and the air flow velocity and temperature at
2 m/s and 30 C, respectively. Moisture content of samples
was measured by weighing them at fixed intervals of
15 min. Fig. 6 shows the evolution of the weight percentage
(%) during the drying process of a set of thirty carrot samples
assisted by power ultrasound (+US) and without
ultrasound (US). The results clearly show the strong
influence of the acoustic intensity in the process. The curves
obtained up to a maximum power applied of 100 W reveal
a direct increase of the drying effect with the acoustic intensity
and no saturation was reached. The use of the present
prototype of ultrasonic drying system has so confirmed the
role of the main ultrasonic parameter when the other
thermo-mechanical parameters (temperature, flow rate,
suction, etc.) are kept constants.