Effect of Rough Rice Temperature and Air Velocity on Grain Crack during Infrared Radiation Drying

Experimental infrared dryer was used to study the effect of rough rice temperature and air velocity on grain crack during infrared radiation and convection drying. Factorial experiment with Completely Randomize Block design was applied to the experiment at three temperature levels of 45، 60 and 75°C (equal to radiation intensities of 0. 19، 0. 39 and 0. 58 W/cm2) and two inlet air velocity levels of 0. 4 and 0. 6 m/s. The result showed that the rough rice temperature (radiation intensity) and air velocity had significant effect on crack losses. Increasing the radiation intensity and decreasing air velocity caused to increase of crack percentage during drying of rough rice samples. The comparison of infrared and convectional drying method showed that grain cracks with infrared drying energy at 60 and 75 °C (0. 39 and 0. 58 W/cm2) were less than that with convection drying at the same temperatures. But it did not have a significant difference at 45 °C (0. 19 W/cm2). The mathematical model relationship of grain crack percentage with rough rice temperature and air flow velocity was derived. Also the result show that the effect of rough rice temperature was more than air velocity on grain crack in infrared radiation drying.