Indirect Forced Convection Batch-in Bin Solar Dryer

The study attempts to construct and evaluate an indirect forced convection solar batch-bin dryer with stirring device to dry wheat. The main components of the system are(1)three arrays of a single pass solar air heater with double glass cover, the artificial roughness absorber plate is used to increase efficiency of the air heater,and then more heat energy gain by the flowing air with minimum surface area of the solar collector,(2)the second component is cylindrical shape heat storage tank, sand is used as sensible heat materials to extend the period of utilization beyond the sunshine hours,(3) circulating batch-bin dryer with stirring device(vertical auger) which is used to circulate the grain during drying process and discharge the Grain when desired average moisture content is obtained, three phase motor is used to rotate the auger. Swivel is installed in the top of the auger to switch between loading and uploading position, centrifugal fan with high power is used to push the hot air inside the dryer and to overcome static pressure, the hot air distributor is put in the middle of the dryer to insure uniform air distribution across the grain.To evaluate performance of the system the energy analysis is conducted to estimate the ratios of energy utilization and amount of energy gained from the solar collector,to optimize the solar air heater efficiency four different air flow rates of 1.38 kg/min,2.4 kg/min, 3.19 kg/min and 3.48 kg/min were adopted. The higher efficiency was found to be at higher air flow rate. The amount of heat that can be stored by heat storage material is considered as well, and estimate storage duration, and effect of various air velocity on drying time. For describing the drying behaviour fourteen thin layers drying equations can be fitted by applying regression analysis and the best model will be determined by comparing the root mean square error(RMSE), chisquare(x2), coefficient of determination between observed and predicted moisture ratio. Also the economic analysis was conducted using life-cycle saving method for determination the least cost of meeting the energy need, by considering both solar and auxiliary equipment, and takes into account the time value of the money, and eventually the amount of different fossil fuel saved due to use of solar energy was estimated, and time needed for the cumulative fuel savings to equal the initial investment.