A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1985

This study describes the design and performance characteristics of an IRRI natural convection dryer based on initial observations and measurements made . The performance of the dryer was evaluated in terms of: 1) air temperature and flow patterns in the dryer, 2) the drying rates of paddy of different initial moisture contents (20, 24, 28 per cent, wb) at temperatures of 40+2 C and 50+2 C in 10 and 15 cm thick columns, and 3 ) milling quality of the-dried paddy. Drying paddy at 50 C gave a faster drying rate practically for each column thickness at all levels of initial moisture content. Comparison with shade drying as control showed that paddy drying was faster even with the least favorable combination of the experimental variables. Statistical analysis revealed that the column thickness gave the highest correlation effect on the drying rate of convection- dried paddy. The combined effects of the drying variables significantly affected the head rice recovery. But this was within a limit comparable to the head yields obtained from the shade- dried paddy . The effect of the drying air temperature and initial moisture content recorded was significant with a decrease in the head rice yield at higher temperature and when paddy is rewetted .