Effects of Discharge Fan on the Drying Efficiency in Flat-bed type Dryer
— The study of interaction among the grain, moisture, and the surrounding space (air) is key to understanding the grain-drying process. In Iran, rice (mostly Indica type) is dried by flat bed type dryer until the final MC reaches to 6 to 8%. The experiments were conducted to examine the effect of application of discharge fan with different heights of paddy on the drying efficiency. Experiments were designed based on two different configurations of the drying methods; with and without discharge fan with three different heights of paddy including; 5, 10, and 15 cm. The humid heated air will be going out immediately by the suction of discharge fan. The drying time is established upon the average final MC to achieve about 8%. To save energy and reduce the drying time, the distribution of temperature between layers should be fast and uniform with minimum difference; otherwise the difference of MC gradient between layers will be high and will induce grain breakage. The difference of final MC between layers in the two methods was 48-73%. The steady state of temperature between the two methods has saved time in the range of 10-20%, and the efficiency of temperature distribution increased 17-26% by the use of discharge fan.
PREDICTION OF MOISTURE CONTENT OF GRAINS DURING RE-WETTING PROCESS FOR MILLING
The main objectives of the present research work were to study the effects of moisture content on some characteristics of grains, the method could be used by grain industry to sequence be have moisture content during rewetting processing and to predict moisture content by calibration of electric resistance of grains to increase grain quality in order to minimize grain.Corn variety 10, Wheat variety Giza 168 and Rice variety Sakha 103 grains were used in the experiments as re-wetting process and measurements. Grains were with the initial moisture content of about 12.5% , 12% and 11% (b.d) for corn, wheat and rice grains.The grains were milled using hammer mill. The following most tmprtant results conclusions were found, 1) The suitable moisture content was 16, 15.5 and 16.5 % of corn, wheat and rice grains, respectively at about 1.5 h of re-wetting time. Which lead to increase weight of 1000 grains was 470, 43 and 26 g , and water absorbed of grains were 0.0279, 0.0023 and 0.0017g. Meanwhile, the electric resistance of grains was decreased, which were 35.95, 35.1 and 32.2 Omme and terminal velocity was 70.5, 45.9 and 28.9 m/s, and hardness of grains was decreased, which was 189, 37.5 and 24 N of corn, wheat and rice grains, respectively 2) By increasing the moisture content of corn, wheat and rice grains during rewetting process. The weight and water absorbed were increased. Meanwhile, the hardness and electric resistance were decreased. 3) The correlation factor between the moisture content and electric resistancewas 0.98, 0.97 and 0.97 for corn, wheat and paddy rice grains during re-wetting process, respectively. That is mean the correlation factorwas ranged between r = 0.97 – 0.98 which is considered that the correlation relationship between the moisture content and electric resistance more significant and high. 1-Senior Researcher, Agric. Eng. Res. Institute, Agric.Res.Center, Dokki, Egypt. 2-Head of Researchers, Agric. Eng. Res. Institute, Agric.Res.Center, Dokki, Egypt. Misr J. Ag. Eng., 34 (1): 385 402
A simulation model for solar thin-layer drying process
ABSTRACT A mathematical formulation of the physical process of solar drying based on conventional heat and mass transfer equations is presented. The model Includes: a a technique of estimating the solar radiation on a south-facing tilted panel using the meteorological and geographical parameters for a typical location; b the procedures for obtaining the thermal performance of a solar air-heater for a flat-plate flow-over-absorber design; c an analysis of the drying process based on the Lewis analogy and the Equilibrium Moisture Content concept. Results predicted by the simulation model are presented.