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The moisture dependent physical properties of different lathyrus varieties namely NLK-40, Pratik and Ratan were studied at moisture content of 7.33 to 30.29, 6.75 to 29.95 and 7.90 to 30.90% (d.b.), respectively. The grain size, thousand grain weight, angle of repose, grain volume and surface area were found increased linearly. The grain size was found increased from 4.43 to 4.70, 4.96 to 5.32 and 5.08 to 5.49 mm. Thousand grain weight was found increased from 64.6 to 103.5, 69.1 to 105.3 and 85.3 to 125.6 g. The angle repose was increased from 28.3 to 35.4, 29.5 to 35.8 and 26.9 to 33.5°. The grain volume was increased from 9.13 to 10.38,11.73 to 13.24 and 12.22 to 14.15 mm(3) whereas, surface area increased from 54.78 to 62.29, 70.38 to 79.45 and 73.31 to 84.88 mm(2),respectively with the corresponding increase in moisture content, for NLK-40, Pratik and Ratan. The sphericity and porosity increased initially and then found decreased with increase in further moisture content. The bulk density values decreased linearly from 827.5 to 697.2, 851.3 to 726.3 and 856.0 to 727.4 kg/m(3). The true density values were found decreased from 1288.3 to 1074.3, 1324.0 to 1118.4 and 1277.7 to 1102.5 kg/m(3), respectively for these varieties with the corresponding increase in moisture content.

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A b s t r a c t. Resistance of material to airflow is an important factor to consider in the design of a dryer or an aeration system. The airflow resistance of soybean was determined with the modified airflow resistance apparatus. It was found that pressure drop increased with increase in airflow rate, bulk density, bed depth and decreased with moisture content. Modified Shedd equation, Hukill and Ives equation and modified Ergun equation were examined for pressure drop prediction. Airflow resistance was accurately described by modified Shedd equation followed by Hukill and Ives equation and modified Ergun equation. The developed statistical model comprised of airflow rate, moisture content and bulk density could fit pressure drop data reasonably well.K e y w o r d s: airflow resistance, pressure drop, soybean, models INTRODUCTIONThe soybean (Glycine max L.) has been reported to have originated in Eastern Asia. It contains about 20% oil and 40% protein. Soybean protein is rich in the valuable amino acid lycine (5%). A large number of Indian and Western dishes such as bread, chapati, milk, sweets, pastries etc. can be prepared with soybean. Production of soybean in India at present is restricted mainly to Madhya Pradesh, Uttar Pradesh, Maharashtra and Rajasthan. It is also grown on a small acreage in Andhra Pradesh, Karnataka, Nagaland and Gujarat. In India during 2007-08 area, production and yield of soybean is recorded as 8.88 mln ha, 9.99 mln t and 1 124 kg ha -1 , respectively (ISO, 2007).The relationship between a drop in pressure and the rate of airflow through an agricultural product is important in the design of drying or aeration systems. Resistance to airflow is a function of both product and air properties (Khatchatourian and Oliveira, 2006). The air pressure, required to force air through a bed of grain, is dissipated continuously due to friction and turbulence. The pressure drop for airflow through any particulate system depends on the rate and direction of airflow, surface and shape characteristics of the grain, the number, size and configuration of the voids, the particle size range, bulk density, depth of product bed, method of filling bin, fines concentration and moisture content. The data on the airflow-static pressure relationship of a number of agricultural grains have been published (ASABE, 2007). Most of researchers have reported airflow resistance data for agricultural grains but for low ranges of airflow. The data on airflow resistance of agricultural crops are scarce for high airflow range as reported by Nimkar and Khobragade (2006).The phenomenon of pressure drop in airflow through agricultural products has been widely investigated for various grains (Nimkar and Chattopadhyay, 2003;Rajabipour et al., 2001) and root vegetables and other crops (Kashaninejad and Tabil, 2009;Reed et al., 2001;Shahbazi and Rajabipour, 2008;Verboven et al., 2004). In most cases, data were analyzed by means of Shedd (1953) and Hukill and Ives (1955) equations. Both the models have been widely used because they ...

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