EXERGY ANALYSIS OF SOLAR DRYER WITH A BACKUP INCINERATOR

Solar dryer with backup incinerator was fabricated with the aim of improving the efficiency of the drying rate of selected agricultural products. The dryer consist of three main parts, the collector, the drying chamber and the incinerator. 1000g of chill pepper was sun dried and 1000g was charged into the dryer for the experiment. Drying using solar drying process was carried out during clear weather while incinerator drying process was carried out during cloudy weather and at nights The collector, dryer and incinerator energy efficiencies were determined and reported elsewhere. Exergy analysis of the dryer was carried out for both solar drying and incinerator drying using the experimental values. The average exergy inflow and outflow during solar drying was found to be 266.97 KJ/Kg and 20.85 KJ/Kg respectively. The average exergy loss at airflow velocity of 2.7 m/s was found to be 269.3 KJ/Kg for incinerator drying. The exergy efficiency of the incinerator fluctuates as it starts from 7.9, 11.1, 5.2, 13.5, 8.0 and 3.6 % for 8.00, 10.00, 12.00, 14.00, 16.00, 18.00 hrs respectively. The result also shows exergy efficiency of 83.1, 85.9, 91.7, 92.4, 89.0 and 73.4 % for 8.00, 10.00, 12.00, 14.00, 16.00, 18.00 hrs respectively during solar drying. The experimental and analytical temperatures values were observed to be solar radiation intensity dependants and are directly proportional with it. Although the heat losses are high for both drying processes, the dryer is suitable for drying agricultural produce during clear, cloudy weather and at nights.