out using direct and indirect prototype solar dryers. The two
prototypes are constructed from wood frames and have the
same dimensions as shown in Figs. 1 and 2. The direct proto-
type solar dryer was covered by transparent polyethylene film;
while black polyethylene film was used to cover the indirect
prototype solar dryer. Each dryer has six perforated galva-
nized steel trays with the dimension of 1.00 · 0.90 · 0.04 m,
and the spacing between them was 0.12 m. Each tray was
loaded with 1.2 kg of fresh whole mint, which was spread as
a single thin layer. The two prototypes were installed on the
roof of the Department of Food Science and Technology
building, Faculty of Agriculture, Cairo University, Giza (lati-
tude of 3000N and longitude of 3110E).
The experimental dataweremanually recorded every 2 h from
10 a.m. to 6 p.m. over two days, except forced convection drying
runswhichwere started at 12 noon in the first drying day.Natural
convection runs were conducted during 10–11/07/2012, while
forced convection runswere conducted during 5–6/08/2012. Both
prototypes (the direct and indirect solar dyers) were operated un-
der natural and forced convection. In the forced convection
mode, a fan (0.50 m diameter and 0.75 kW) was mounted in the
exit channel of each prototype, where the air velocity at the en-
trance channel of both solar dryers was 4.2 m s
1
as measured.
The dryerswere shut down during the night, and experimentation
was resumed the next day at 10 a.m.