This study deals with numerical modeling and experimental validation of hybrid fluidized bed-infrared drying of bulk grain. A mathematical model of simultaneous heat and mass transfer for the aforementioned dryer was developed: first single phase model was used to establish heat and mass transfer equations over the fluidized bed, then the effect of infrared heating was incorporated into the single phase model as a source term to develop the model for a hybrid fluidized bedinfrared dryer. The model is capable of predicting the moisture content of bulk corn as well as the drying air parameters (i.e., out let air temperature and out let air absolute humidity) during drying. The model was validated by comparison with experimentally obtained drying kinetics for different combinations of inlet air temperature, infrared power density and bed height. The results of verification test for all drying conditions indicated that the mean relative deviation for prediction of grain moisture content, out let air temperature and absolute humidity were less than 8, 11 and 7%, respectively, which reflects an acceptable accuracy (<15%). Other results showed that the application of infrared power in conjunction with fluidized bed drying to reduce corn moisture content from 0.23 to 0.12 kg H 2 O/kg dry solid led to a 45-87% saving in drying time and 36-68% saving in specific energy consumption compared to conventional fluidized bed configurations. The model indicated acceptable performance and hence the model could be suggested as a mathematical tool providing precise prognostications dealing with fluidized bed drying equipped with infrared heat source. PRACTICAL APPLICATIONSThe suggested model is an efficient method to simulate drying process of bulk grain in infrared-fluidized bed dryers. This model provides precise prognostications regarding the variations in grain moisture content, gas temperature and gas absolute humidity. Additionally the features of the model introduced in the present study might qualify it for use in automatic control of fluidized bed dryers and online prediction of drying time to reach a desired value of moisture content.

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Abbreviations used: B (baled-out residue); DAP (number of days after planting); EMG (percentage of seeds emerged on the day); ERI (emergence rate index); NA (inactive coulter); NB (non-baled residue); NRC (without row cleaner attachment); QFI (quality of feed index); RC (with row cleaner attachment).

Seed placement and failure to establish a uniform plant stand are critical problems associated with production of corn (Zea mays) following wheat (Triticum aestivum) in a conservation agriculture system in Iran. Our objectives were to evaluate the performance of a corn row- crop planter equipped with two planter attachments (smooth/toothed coulters) at six wheat residue management systems (three tillage systems and two levels of surface residue) at two forward speeds of 5 and 7 km h-1. Residue retained after planting, seeding depth, emergence rate index (ERI) and seed spacing indices were determined. The baled residue plots tilled by chisel plow followed by disc harrow (BRCD) resulted in minimum residue after planting as compared to other residue treatments. Furthermore, the maximum values of the ERI and uniformity of plant spacing pertained to this treatment. Other results showed that the ERI increased up to 18% for the toothed coulter as compared to the smooth coulter. The toothed coulter also established a deeper seed placement as compared to the smooth coulter. Planting at forward speed of 5 km h-1 resulted in deeper seeding depth as compared to a forward speed of 7 km h-1. However, lower values of miss and precision indices were obtained at forward speed of 7 km h-1, indicating a more uniformity of plant spacing. Results of this study showed that equipping the conventional planter with toothed coulter and planting in soil prepared under the BRCD residue management system can result in a satisfactory conservation crop production system.

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