DRYING OF CUCUMBER SEEDS USING A FORCED AIR CABINET SOLAR DRAYER

Abstract

This research work aims at studying the factors affecting the solar drying of cucumber seeds using a cabinet solar dryer. The experimental work was conducted on the roof of Agricultural Engineering Research Institute (latitude angle of 30o 2' 35.2N and longitude angle of 31o 12' 20E) during summer season of 2015. Three different layers thickness of cucumber seeds (5, 10, and 15 mm thick) were functioned during the experimental work. The thermal performance analysis of the cabinet solar dryer (forced convection system) was evaluated. The obtained results revealed that, the daily average solar radiation recorded on the horizontal surface during the experimental period was 7.215 kWh/m2 while, the actual solar radiation recorded on the tilted surface of the cabinet solar dryer was 10.220 kWh/m2. Accordingly, the stationary non-tracking cabinet solar dryer increased the actual received solar radiation during that period by 41.65%. The daily average solar radiation recorded outside and inside the cabinet solar dryer was 7.215 and 5.740 kWh/m2, respectively, with cover effective transmittance of 79.56%. The solar radiation available inside the cabinet solar dryer was converted into useful heat gain for the drying process, resulting in increasing the dying air temperatures above the outdoor air (31.8oC) by 16.2oC, and reduce the air relative humidity under the outside (60.5%) by 20.4%. The daily average overall thermal efficiency of the cabinet solar dryer during the drying period was 46.64%, accordingly, 53.36% of the solar energy available was lost. The obtained results also showed that, the germination percentage of cucumber seeds dried by cabinet solar dryer was ranged between 97.1 and 97.4% under different drying times, drying air temperature, and air relative humidity. The minimum drying cost (292 LE/ton) was obtained by the dryer operated at layer thickness of 5 mm.