DEVELOPMENT A MECHANICAL STIRRING UNIT FOR DRYING RICE GRAINS

Abstract

The present study was carried out to develop and evaluate the performance of a mechanical stirring unit for rice crop after harvesting for drying to increase stirring efficiency and decrease both power and cost requirements. The aim of this study is to develop a mechanical stirring-unit for drying rough rice-grains after harvesting. The performance of the developed stirring unit was studied as a function of change in screw paddles speed of (120, 180 and 300 rpm ), paddle inclination angle of( zero, 15 and 30deg) with two paddle shapes (trapezoid and rectangle) and a unit wheel width of (4 and 10 cm). The developed unit performance was evaluated in terms of unit capacity, stirring efficiency and required power. The results showed that the screw trapezoid paddle with inclination angle of 300 decreased specific power by 15.79 % and 20.83 % by increasing paddle speed from 120 to 180 rpm and from 180 to 300 rpm, respectively. While, under the same conditions, stirring efficiency increased by 4.39 %, and volumetric capacity decreased by 8.8 % and 17.6 % under conditions of increasing inclination angle from zero to 150 and to 300, respectively at the same screw pitch of 20 cm with layer height of 7.0 cm. Total costs with the use of the developed stirring unit decreased by 48.2% comparing to the traditional method (by feet) according to hiring laborers with recent prices