تعیین ضریب اصطکاک و سرعت حد گل زعفران و اجزای آن

The terminal velocity and coefficient of friction data are necessary for designing of handling and separating equipments. The terminal velocity data are also valuable in designing pneumatic conveying, fluidized bed dryer and cleaning equipments. In this paper, the terminal velocity and coefficient of static friction of saffron flower and its components (stigma, stamina, petal and stem) were determined as a function of moisture content. The experiments were conducted on saffron flower selected from fields of Kashmar. The data was statistically analyzed using factorial experiments with completely randomized design. The results showed that the terminal velocity of the saffron flower, stigma, stamina, petal and stem at moisture content of harvesting level to 40% (w.b.) were in the range of 1.03 to 5.13 m/s. With decreasing moisture content from harvesting level to 40% the terminal velocity of the flower and stem decreased significantly but the terminal velocity of the stigma, petal and stamina were not decreased significantly. The terminal velocity of the petal was the minimum value at the three moisture content levels. The coefficient of friction of saffron flower and its components on the friction surfaces were in the range of 0.52 to 1.1. The friction coefficients of all the components except the stem were the maximum values on polyethylene surface. The coefficients of friction were the minimum values on galvanized iron surface for all of the components. With decreasing moisture content from harvesting level to 40% (w.b.) the average values of coefficient of friction increased significantly for all of the components. The coefficient of friction of the stigma and flower were the maximum and minimum values, respectively at different levels of moisture content. Generally, at moisture content of harvesting it is possible to separate the flower, petal, stamina, stigma and stem from each others with changing air stream velocity. As well, it is possible to separate the petal from the others components at moisture levels of 70% and 40% (w.b.) using wind column device.