The effect of different drying conditions on effective moisture diffusivity, specific energy consumption and extraction efficiency of Melissa officinalis essential oil

The aim of this study was to investigate the effect of temperature and air displacement rate on effective moisture diffusivity, specific energy consumption, drying rate, moisture ratio, and the extraction efficiency of Melissa officinalis essential oil in hybrid dryer as thin layer. This paper presents the thin layer drying behavior of Tarragon (Melissa officinalis) by a solar hybrid dryer. Experiments were carried out at the air temperatures of 40ºC, 50ºC, 60ºC, 70ºC and air velocity of 1m/s, 1.5 and 2 m/s. Effective moisture diffusivity values were achieved to be in the range of 7.1×10−12-1.05×10−11 m2/s. Specific energy consumption values were achieved to be in the range of 75.65-326.76 (MJ/kg). Also the effect of the air velocity on the drying time at a low temperature is greater than that at a high temperature. The highest amount of essential oil related to a temperature of 40°C and air velocity of 1-1.5 m/s was achieved with approximately 0.5 cc (v/w) and by increasing the temperature from 40°C to 70°C the amount of essential oil was decreased Significantly.