بررسی سینتیک خشک شدن زیره سبز در یک خشک کن خورشیدی در دو حالت تابش مختلط و غیرمستقیم

In this work, a cabinet solar dryer for thin layer drying of Cuminum cyminum was evaluated in two conditions (Indirect and Mixed). Four levels of drying air flow rates (three active and one passive) were adopted. The experiments were performed in a completely randomized Block design pattern in three replications. Drying durations were kept constant (90 min) for all the experiments. Average initial moisture content of Cuminum cyminum was 43.5 %( db) and the product was set to be dried for 90min in the solar dryer (average 8%d.b). The effects of the drying air flow rates and modes of drying were highly significant in final moisture content of Cuminum cyminum. Duncan test was selected to evaluate the effects of different factors on average moisture content of the samples. The results showed that the passive air flow system in mixed mode drying conditions for drying the Cuminum cyminum was best. The drying duration for the mentioned condition was 55min to dry the product from 43.5% to 8 %( db). The experiments were conducted each sunny day of August-September 2007 from 11.30 till 13.The average solar irradiance was recorded 750 W/m2 average ambient air temperature was32°C and average ambient relative humidity was20%. Using the dryer in the best selected conditions reduced the moisture content of the product from 43.5% to 4.95% after 90 min.