GRAIN DRYING USING CONTINUOUS AND PULSED MICROWAVE ENERGY

Abstract

A laboratory microwave oven was used to dry high-moisture corn samples. The microwave oven was operated in both continuous and pulsed modes at 250 W of magnetron power setting. In the pulsed mode, two magnetron power-on times of 10 s and 15 s were used each with different power-off times in the range of 20 s to 75 s. Drying was more rapid in the continuous mode than in the pulsed mode. But, the continuous mode required much higher total magnetron power-on times. In the pulsed mode, longer power-on times generally resulted in slightly faster drying; and the power-off times did not strongly influence the drying rate. Longer power-on times should be followed by relatively longer power-off times. For a given on-time, increase in power-off time helps to decrease the total power-on time required for drying. When the microwave oven was operated at 10 s of power-on and 75 s of power-off pulsing, it resulted in the lowest total power-on time.