Developments of solar dryers, constructing and testing of new dryers with flat and sinusoidal transpired solar collectors

Abstract

Men used solar power for drying goods for future use. They dried fish, meat, vegetables and fruits in the
same manner. Smoking for drying is also used, but it can cause cancer. Developments of different types
of agricultural solar dryers are investigated and the efficiency of solar driers for agricultural products is
tested using transpired solar collector. To increase its efficiency the absorbent area of the collector is
designed sinusoidal. These driers are designed and built in Materials and Energy Research Center and its
efficiency is measured for drying vegetable such as parsley. The experimental result of these two driers
shows an efficiency of 26.35% for the drier with sinusoidal collector and 18.82% for the drier with flat
collector, that means an increase of 7.53% in efficiency. They are also used to dry different kind of nuts in
large scale these dryers have very good efficiency. The only energy beside solar energy used in these
dryers is electrical energy to run the fan mounted behind the transpired collector to convey hot air into
dryers. Another means of energy could be used to keep the warehouse warm during the night time.
These could be heaters operated by electricity, oil, gas or stored solar energy in the form of packed bed
system using oil or water as heating fluid agent and medium size packed bed stones to store the day's
solar heat for the use at night.