Utilization of Solar Energy for Drying Sugar Beet Tops

Abstract

A study was carried out to test and evaluate a green house type solar dryer for drying sugar beet tops under three different levels of air velocity (0.4, 0.8, and 1.2 m/sec), three different lengths of beet tops (3, 6, 9 cm) and two different treating conditions (with crushing, and without crushing). The changes in sugar beet tops moisture content was monitored versus the drying time until reaching the proper moisture content of about (12-13 % w.b.). Solar radiation flux incident, bulk temperature of tops, air temperature and relative humidity, overall thermal efficiency of the dryer and the protein content of the dried tops were determined. The results showed that, the hourly average available solar radiations ranged from 598.26 to 663.85 W/m 2 during the experimental work. Also, the solar collector of the dryer could increase the air temperature by about 12.6, 12.31 and 12.81 o C and decrease the air relative humidity by about 26.06, 23.67 and 20.97 % for air velocity of 0.4, 0.8, and 1.2 m/sec respectively. The reduction rate in moisture content of sugar beet tops was varied and increased with the increase of drying air velocity, decrease of chopping length and for the crushed samples in comparison with the not crushed samples. Also, the constant drying rate period was not detected for all studied levels of drying air velocity, while all the drying process occurred during the falling rate-drying period. The result also show that the use of the green-house type solar dryer with chopping and crushing of the green tops could decrease the drying time of sugar beet tops by about 47 to 59 h in comparison with the traditional drying method which has been taken about 78 hours. The thermal efficiency of the dryer ranged from 34.12 to 22.96 % and the protein content of the dried tops ranged from 12.57 to 14.52 % on DM basis.

Thermal Performance of Different Solar Dryers and Application in Jew's Mallow Drying

“…The greenhouse dryer minimizes the shortcomings of the cabinet dryer such as capacity of full load operation, expenditure, and moisture condensation under the glass surface (Kumar et al, 2014). Studying the possibility of using the greenhouse as a solar dryer for some agricultural crops under Egyptian climatic conditions has been investigated by many investigators (Radwan, 2002;Abu-Habaga et al, 2010;Abdellatif et al, 2010;Kishk et al, 2018). Radwan (2002) evaluated a greenhouse solar dryer for drying fresh grapes compared with natural sun drying.…”