Solar Drying: Fundamentals,Applications and Innovations - National ...

Fadhel - Recent Advancements in Solar Drying
without any air ducts. The drying cabinet fabricated with a galvanized iron box with insulated
polystyrene walls of dimensions 1.65 x 0.60 x 1.00 m (height, width and depth)
contains six product trays each tray has an area of 0.4 m 2 with possibilities to extend to
eight product trays. The drying trays were made of a wooden frame on all four sides and
a wire mesh on the bottom to uphold the samples and/or to change the position of the
trays. The mass sample used in this experiment was 2 kg in each tray with airflow
0.0314, 0.0470 and 0.0628 m 3 /s. There was a distance of 0.12 m between trays in order
to obtain uniform air circulation. The door of the dryer was properly sealed to prevent
air leakage. In solar drying process, the auxiliary heater was used to adjust the drying
air temperature. The preliminary heated drying air by solar radiation, arrived at the inlet
of cabinet dryer was heated by electrical resistance if its temperature was less than
consign temperature; which is controlled thermostatically and then aspired by an exhaust
fan through the product to the environment. The exhaust fan of 20 cm diameter
(model KFA30, power input 40 W, running at 1400 rpm and volumetric flow at 0.325
m 3 /s) was manually controlled by a valve, allowing the choice of the desired air mass
flow. The fan was fixed below product trays at the bottom of the dryer to ensure an even
distribution of air and evacuate the humidity of the product to the surrounding. The design
and photo for the hybrid solar dryer are presented, respectively, in Figure 6.3 and
Figure 6.4 (Boughali et al., 2009).
Figure 6.3. Schematic diagram of an indirect active hybrid solar–electrical dryer
(Boughali et al., 2009)
Drying of Foods, Vegetables and Fruits 131