3.4. Energy efficiency
Fig. 6 shows the variation of energy efficiency with drying time
for microwave drying of apple samples. The energy efficiency
was very high during the initial phase of the drying which resulted
in a higher absorption of microwave power. Following
moisture reduction, the energy absorbed by the product decreased
and the reflected power increased. The best result with
regard to energy efficiency was obtained from 600 W microwave
power levels among all microwave power. Average energy
efficiency of apple samples ranged from 17.42% to
54.34% for the output microwave power.