This article is from the Food Preserving FAQ, by Eric Decker firstname.lastname@example.org with numerous contributions by others.
In it's most simplest form, dehydration technology is thousands of years
old. Dried meat on sticks and corn dried in the sun are two examples of
early man's ingenuity. After 1900, the need for technology to accelerate
dehydration and remove the dependence process became acute. Acceleration of
dehydration and the need to remove the dependence on sunny dry weather
where the factors that triggered invention of the Natural Draft dehydrator.
This design incorporated a fire near the bottom on a hillside. Stacks of
wooden trays filled racks. An exhaust vent in the upper porting of the
roof allowed the smoke and hot gases escape with the water vapors.
As the fire heated the air, it was carried upward providing the critical
air flow and low humidity necessary for dehydration. The Natural Draft
Dryer is generally accepted as the first commercial dryer and instituted
the use of wood frame trays and artificial heat. Unfortunately, most burned
down and today there are no known surviving examples. Ten years later, the
Natural Draft Dryer gave way to a mix of crude dryers that incorporated
small fans. Finally, between 1910 and 1920, Mr. L. N. Miller invented a box
like dryer, with artificial heat made with oil, a large fan capable of high
air velocity, humidity shutters and bleeder vents. This was the predominant
design through the 1940's and spawned many variations. In the 1960's a
group of scientists at the University of California, Davis, California,
developed the now common overhead return Tunnel Dryer. Variations of this
design are now in use throughout the USA and overseas. Commercial
Dehydrator Systems, Inc. now carries on the tradition of L.N. Miller's
dryers and the technology from UC Davis, which will keep dehydration alive
into the next centuries to come.