Comparative Experimental Investigation Between Parabolic Dish and Flat Plate Collector Based Solar Dryer for Saw Dust Briquette Production

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Addis Ababa University


From different types of briquette drying technology, the open sun drying system is the most widely used, which is found in many developing countries including Ethiopia. For this type of convectional drying process, the time required to remove moisture from the product is too long. In average it requires 3 to 4 days with available sufficient solar radiation. Beside that the recent improved type solar driers (flat plate-based driers) have still inefficiency regarding to the drying time. This happened due to the low drying air temperature effect that limits the drying time and efficiency. The main objective of this project was to design, construct and test more efficient solar drier compare to the recent developed dryer type. To prove the new type of drier performance, the experiment has been done by comparing the performance of the parabolic dish based drier (PDSCD) with the Flat plate based drier (FPSCD). The comparative assessment has been done with scientific experiment using different measuring methods and tools discussed in this paper. The experiment was conducted in the Addis Ababa Institutes of Technology compound free field area for both solar driers. The drying air temperature has been increased using concentrator collectors. The PDSCD and FPSCD absorber surface temperature, drying air temperature, air speed at the outlet of the drying chamber, moisture content variation, the relative humidity at ambient and inside the drying chamber were measured with unloaded and loaded setup using direct and indirect measuring methods. The amount of moisture removed from the drying chamber of PDSCD and FPSCD is 0.039 kg and 0.022 Kg respectively. The measured result indicates that performance PDSCD has a better moisture removing capacity rate than FPSCD. After analysis of the measured result, the thermal efficiency parabolic dish collector and Flat plate collector is determined 31.55% and 8.95 % respectively. And the overall drying system efficiency of the PDSCD and FPSCD is 31.55 % and 8.95 % respectively where the PDSCD has better performance than FPSCD.



Solar thermal Energy, Solar dryer, parabolic dish solar collector, Drying chamber