Numerical simulation of coupled heat and moisture transfer process in ultrasonic pre-dehydration of carrot

For further understanding the effect of ultrasonic on moisture transfer process in wet porous material, the experiment on pre-dehydration process of carrot slice under ultrasonic irradiation was performed, the coupled heat and moisture transfer model for ultrasonic pre-dehydration process of carrot slice was also established. In this model, the effective moisture diffusion coefficient under ultrasonic irradiation was derived considering the influences of ultrasonic cavitations and mechanical vibration on removal rate of water molecule. The effects of ultrasonic intensity on dehydration rate and temperature variation of carrot were analyzed and discussed. The results showed that ultrasonic irradiation accelerates the moisture transfer process in carrot slice, both the effective moisture diffusion coefficient and dehydration rate of carrot slice increased gradually with intensifying of ultrasonic intensity. Compared with the dehydration process of sample untreated with ultrasonic vibration, the dehydration rate increased by 3.9 times at ultrasound intensity of 1.5 W/cm2. The temperature rising at the center of sample induced by the thermal effect of ultrasound was lower than 4℃ at ultrasound intensity of 1.0 W/cm2 after 5 400 s. The ultrasonic irradiation could be an effective method for enhancing the moisture transfer in wet porous material with non-thermal factor.