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

Thesis (M.Eng.) - Asian Institute of Technology, 1982

A series of paddy drying tests were conducted in a flat bed dryer using heated and unheated-air to compare the drying costs, moisture removal rates and the milling quality. The grain depth was 0.30 meter and the airflow rates were 7.64 and 9.16 cubic meter-min/square meter. A temperature of 43.0°c was maintained in the heated-air drying tests. The initial moisture contents of the paddy were 20.0 and 22.0% wet basis. The experimental and the simulated moisture removal rates in heated-air and unheated-air were in good agreement statistically showing that the drying models could be effectively used in the economic analysis. The heated-air drying was more economical than unheated-air drying due to the extended period of drying needed with unheated-air. It was found that a 3-horsepower engine would give the m1n1mum drying costs for the unheated-air, but heated-air drying costs always increased with increase in engine horsepower, The ratio of the unheated-air to heated-air drying cost varied in the range 2:1 to 3:1 depending on the engine horsepower applied. The quality of the paddy dried with unheated-air was significantly better than the quality of paddy obtained in the heated-air tests. However, the possible premium due to improvement of the quality dried with unheated-air was not included in the economic analysis due to the uncertainties in the present marketing practices in the Philippines.