Determining the optimal performance conditions in the drying process of rosemary plant using a hybrid conveyor belt drying system equipped with infrared lamps with photovoltaic source

The current research used a hybrid conveyor belt drying system, including a solar water heater and solar-powered infrared lamps, to dry rosemary leaves. Its performance characteristics were evaluated regarding drying time, total energy consumption, solar energy ratio and energy efficiency. In each experiment, 300 g of freshly harvested rosemary leaves at a drying air temperature of 50 °C and different values of inlet air velocity (7, 8 and 9 m/s) and infrared lamp power (0, 150 and 300 W) were fed into in the drying system. The optimum point for the working of the drying system was determined using Response Surface Method (RSM) by selecting the appropriate values for the inlet air velocity and infrared power based on these criteria: to minimize drying time, to minimize total energy consumption, to maximize energy efficiency, and to maximize solar energy ratio. Accordingly, the selected optimum point included infrared power of 300 W and an air velocity of 8.85 m/s. Under the defined conditions, the performance characteristics of the drying system, including drying time, total energy consumption, energy efficiency and solar ratio, were equal to 149.13 minutes, 3868.91 kJ, 52.37% and 0.75, respectively. According to the findings of this study, it can be concluded that using a developed drying system can significantly reduce the need for fossil fuel resources and lead to an acceptable performance efficiency in the drying process of medical plants.