Abstract:
Energy and mass transfer investigations in thermal
processing of fruits serve as a
breakthrough in the design and scale up of drying s
ystems. Diffusivity characteristics and
specific energy consumption for drying of fig fruit
in a laboratory scale microwave dryer
were assessed. Several intervals for microwave powe
r intensity including 0.5, 1, 1.5, 2, and
2.5 W g
-1
, and 6 levels of power on-off stated as pulsing ra
tios of 1.5, 2, 2.5, 3, 3.5, and 4
were employed. The results showed that the drying r
ate decreased with the pulsing ratio
and increased with microwave power intensity. Effec
tive moisture diffusivity as an
indicator of mass transfer was obtained to be highe
r at elevated microwave power
intensities. Also, increased pulsing ratios had a r
educing effect on moisture diffusivity.
Using 2
nd
law of Fick, moisture diffusivity was calculated t
o be varying from 5.93E-10 to
1.42E-08 m
2
s
-1
depending on the experimental conditions. Furtherm
ore, the activation
energy of fig fruit was obtained to be in the range
of 60.094 to 92.189 kJ mol
-1
. Specific
energy consumption variations showed a positive cor
relation with pulsing ratio and
drying time. However, due to the dependence of ener
gy consumption on MW power
intensity, a multiple regression analysis with
R
2
of 0.968 was developed.
Keywords
:
Activation energy, Diffusivity, Pulsed drying, Spec
ific energy consumption.