Modeling and Optimization of Energy Parameters in Rosmarinus officinalis Drying with Microwave Pretreatment

Today, the use of pretreatment operations has been considered to reduce the time and energy with the aim of reducing the cost of agricultural products drying, such as medicinal plants. In this research, the modeling and optimization of energy parameters in the Rosmarinus officinalis drying with microwave pretreatment was evaluated using response surface methodology in three treatments (90 W for 5 min, 180 W for 2.5 min and 360 W for 1.5 min) and control (without pretreatment) in a convection dryer at temperatures of 40, 50 and 60 oC and the constant air flow velocity of 0.4 m/s. The results showed that with increasing power (from 90 to 360 W) and temperature (from 40 to 60 °C), the amount of drying coefficient increased quadratically. The value of energy efficiency, drying efficiency, thermal efficiency and convective efficiency increased by increasing of power and temperature from 90 to 180 W and 40 to 50 oC, respectively, but these amounts decreased by increasing of power and temperature from 180 to 360 W and 50 to 60oC, respectively. The increasing of the power (from 90 to 360 W) and temperature (from 40 to 50 °C) increased the amount of specific heat, specific power and specific energy consumption, while with increasing of temperatures from 50 to 60 °C, these values were reduced during quadratic equation. Based on modeling using RSM, optimum conditions for obtaining of the best energy parameters were determined to be microwave power of 360 W and drying temperature of 60 oC with desirability 99.5%.