Abstract: There was a scenario present day that drying of fresh
fruits and vegetables by indirect solar drying by using mechanical
device; hence, an effort was made to develop a small scale solar
tunnel dryer (STD). Drying of spinach is carried out to analyze the
performance of the dryer and to study its drying characteristics. To
evaluate the performance of dryer the independent variables were
selected as air flow rate, loading density and shade net while collector
efficiency, drying efficiency, overall efficiency and specific energy
consumption were selected as responses during performing the
experiments. The spinach was dried from initial moisture content
88.21-94.04% (w.b.) to final moisture content 3.50-5.13% (w.b.). The
drying time considerably reduced as compared to open sun drying of
spinach as sun drying took 15 h for drying. The average collector
efficiency, drying efficiency and overall efficiency were in the range
28.73-61.15%, 11.63% to 22.13%, and 7.61-14.66%, respectively.
Abstract: The study of interaction among the grain, moisture,
and the surrounding space (air) is key to understanding the graindrying
process. In Iran, rice (mostly Indica type) is dried by flat
bed type dryer until the final MC reaches to 6 to 8%. The
experiments were conducted to examine the effect of application of
discharge fan with different heights of paddy on the drying
efficiency. Experiments were designed based on two different
configurations of the drying methods; with and without discharge
fan with three different heights of paddy including; 5, 10, and 15
cm. The humid heated air will be going out immediately by the
suction of discharge fan. The drying time is established upon the
average final MC to achieve about 8%. To save energy and reduce
the drying time, the distribution of temperature between layers
should be fast and uniform with minimum difference; otherwise
the difference of MC gradient between layers will be high and will
induce grain breakage. The difference of final MC between layers
in the two methods was 48-73%. The steady state of temperature
between the two methods has saved time in the range of 10-20%,
and the efficiency of temperature distribution increased 17-26% by
the use of discharge fan.