Abstract Drying of agricultural products has been done since ancient times in order to facilitate transportation, avoid corruption and increase the shelf life. The energy-intensive drying process of these products has led to many innovations in drying methods with the aim of reducing energy. One of these innovations is the use of infrared radiation, which has been considered by many researchers in recent years. These waves increase the vibration of food molecules in contact with them. The friction created by these vibrations raises the temperature of the food and causes water to evaporate. In this research, a return air system was designed and built to eva‎luate different drying conditions for infrared-hot air belt dryers. Then, the effect of independent variables (infrared power, temperature and velocity of air flow) on energy analysis and exergy analysis was studied. The parameters of drying kinetics, drying time, specific energy consumption, energy efficiency, specific dissipative energy, exergy efficiency, exergy loss and exergy recovery potential were eva‎luated. Experiments at three temperature levels of 50, 60 and 70 degrees Celsius, three levels of radiation power of 500, 600 and 700 watts and two levels of air flow rate over the product of 1 and 1.5 meters per second in two repetitions and for two modes without system The return air was done with the return air system. In order to study the drying kinetics, the mass of the samples was recorded every five minutes. Analysis of variance showed that the return air system had no significant effect on drying time. Using the recoil air system compared to the non-recoil air system resulted in a 23.18% energy saving. The use of high levels of infrared power and low levels of temperature and speed of passing air flow and the use of return air system increased energy efficiency by 35.74%. The specific dissipation energy was significantly affected by the velocity of the incoming air flow. The use of a return air system reduced waste energy by 45.44%. Exergy efficiency increased with increasing infrared power and temperature and decreasing inlet air velocity. The use of a return air system resulted in a 15.28% increase in exergy efficiency. Air flow velocity and infrared power showed the greatest effect on exergy loss and the use of return air system reduced exergy loss by 24.03%. Increasing the inlet air velocity and temperature and decreasing the infrared power increased the exergy healing potential. The use of a recoil air system reduced the potential for exergy recovery by 25.32%. The amount of extracted essential oil increased at a lower flow rate and decreased with decreasing temperature. The use of return air system increased the extracted essential oil by 20.96%. key words:. Drying, Infrared, Return air system, Energy analysis, Exergy analysis, Medicinal plants, Extracting essential oil

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مهرنوش جعفري، ميلاد فتحي