In this paper we design and testing solar dryer performance that made of three main part, which were solar collector, box dryer and chimney. The solar collector was made in trapezoid shape the bigger base down, the collector were inclined with thirty degree, the upper base connected with box dyer, that let the hot air reach to box dryer, which were
making hotter by black rock effect in the solar collector to the box dryer and the tray. The last was the chimney. The aim of the chimney is to replace the moist air by dryer air and prevent the air turbulent movement, satisfying the continuity equation, the chimney was
open to with diameter of (D=21cm).
The drying process was in summer season of (100 gm of Okra), were selected and studying the daily efficiency of drying, which reach (35%) the maximum value at 12:00 pm in 24/7/2012, and the minimum value at 12:00 pm in 26/7/2012 reach (16%).
For the same day the reduction reason in efficiency was due to sun set down gradually but depending on observed heat in black rock.
To improving and increasing the drying efficiency process the fan was applied at the chimney outlet to take the air out and increasing the velocity of its movement, and changing the free air movement to forced movement inside the solar dryer. (now the movement will be mixed by free and forced).In natural convection the velocity was (V=0.1m/s) at the solar collector input, while after the fan applying in the chimney outlet the velocity in the solar collector input has become (V=0.3m/s). After calculating the efficiency we notice that the value increase to
(52%) at 10/8/2012 between the 2:00 pm and 4:00 pm, which means the efficiency, was increased by (14%). The efficiency increasing percentage got from this process is a high good value in indirect solar dryer depending on changing the heat type from solar radiation to observed
heat and then heating the air of drying process.